SPITZER: Accretion in Low Mass Stars and Brown Dwarfs in the Lambda
  Orionis Cluster
SPITZER: Accretion in Low Mass Stars and Brown Dwarfs in the
Lambda Orionis Cluster
David Barrado y Navascués
Laboratorio de Astrof́ısica Espacial y F́ısica Fundamental, LAEFF-INTA, P.O. Box 50727, E-28080
Madrid, SPAIN
barrado@laeff.esa.es
John R. Stauffer
Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125
Maŕıa Morales-Calderón, Amelia Bayo
Laboratorio de Astrof́ısica Espacial y F́ısica Fundamental, LAEFF-INTA, P.O. Box 50727, E-28080
Madrid, SPAIN
Giovanni Fazzio, Tom Megeath, Lori Allen
Harvard Smithsonian Center for Astrophysics, Cambridge, MA 02138
Lee W. Hartmann, Nuria Calvet
Department of Astronomy, University of Michigan
ABSTRACT
We present multi-wavelength optical and infrared photometry of 170 previously known low
mass stars and brown dwarfs of the 5 Myr Collinder 69 cluster (Lambda Orionis). The new
photometry supports cluster membership for most of them, with less than 15% of the previous
candidates identified as probable non-members. The near infrared photometry allows us to
identify stars with IR excesses, and we find that the Class II population is very large, around
25% for stars (in the spectral range M0 - M6.5) and 40% for brown dwarfs, down to 0.04 M⊙,
despite the fact that the Hα equivalent width is low for a significant fraction of them. In addition,
there are a number of substellar objects, classified as Class III, that have optically thin disks.
The Class II members are distributed in an inhomogeneous way, lying preferentially in a filament
running toward the south-east. The IR excesses for the Collinder 69 members range from pure
Class II (flat or nearly flat spectra longward of 1 µm), to transition disks with no near-IR excess
but excesses beginning within the IRAC wavelength range, to two stars with excess only detected
at 24 µm. Collinder 69 thus appears to be at an age where it provides a natural laboratory for
the study of primordial disks and their dissipation.
Subject headings: open clusters and associations: individual (Lambda Orionis Star Forming region) –
stars: low-mass, brown dwarfs – stars: pre-main-sequence
http://arxiv.org/abs/0704.1963v1
1. Introduction
The star-formation process appears to operate
successfully over a wide range of initial conditions.
In regions like Taurus, groups of a few stars to a
few tens of stars are the norm. The molecular gas
in Taurus is arranged in a number of nearly paral-
lel filaments, possibly aligned with the local mag-
netic field, and with the small stellar groups sited
near end-points of the filaments (Hartmann 2004).
No high mass stars have been formed in the Taurus
groups, and the Initial Mass Function (hereafter,
IMF) also appears to be relatively deficient in
brown dwarfs (Briceño et al. 2003; Luhman 2004)
–but see also (Guieu et al. 2006) for an alternate
view. The Taurus groups are not gravitation-
ally bound, and will disperse into the field on
short timescales. At the other end of the mass
spectrum, regions like the Trapezium cluster and
its surrounding Orion Nebula cluster (ONC) have
produced hundreds of stars. The ONC includes
several O stars, with the earliest having spectral
type O6 and an estimated mass of order 35 M⊙.
The very high stellar density in the ONC (10,000
stars/pc3 at its center (McCaughrean & Stauffer
1994)) suggests that star-formation in the ONC
was gravity dominated rather than magnetic field
dominated. It is uncertain whether the ONC is
currently gravitationally bound or not, but it is
presumably at least regions like the ONC that are
the progenitors of long-lived open clusters like the
Pleiades. UV photoionization and ablation from
O star winds likely acts to truncate the circum-
stellar disks of low mass stars in the ONC, with
potential consequences for giant planet formation.
An interesting intermediate scale of star-
formation is represented by the Lambda Ori
association. The central cluster in the associ-
ation –normally designated as Collinder 69 or
the Lambda Orionis cluster– includes at least
one O star, the eponymous λ Ori, with spec-
tral type O8III. However, a number of lines
of evidence suggests that one of the Coll 69
1Based on observations collected Spitzer Space Tele-
scope; at the German-Spanish Astronomical Center of
Calar Alto jointly operated by the Max-Planck-Institut für
Astronomie Heidelberg and the Instituto de Astrof́ısica de
Andalućıa (CSIC); and at the WHT operated on the island
of La Palma by the Isaac Newton Group in the Spanish Ob-
servatorio del Roque de los Muchachos of the Instituto de
Astrofsica de Canarias
stars has already passed through its post-main
sequence evolution and become a supernova,
and hence indicating it was more massive than
Lambda Ori (see the complete Initial Mass Func-
tion in Barrado y Navascués, Stauffer, & Bouvier
(2005)). A census of the stars in Coll 69 by
Dolan & Mathieu (2001) –hereafter, DM– indi-
cates that the cluster is now strongly unbound.
DM argue that this is due to rapid removal of
molecular gas from the region that occurred about
1 Myr ago when the supernova exploded. They
interpreted the color-magnitude diagram of Coll
69 as indicating a significant age spread with a
maximum age of order 6 Myr; an alternative in-
terpretation is that the cluster has negligible age
spread (with age ∼6 Myr) and a significant num-
ber of binary stars. While DM identified a large
population of low mass stars in Coll 69, only four
of 72 for which they obtained spectra are clas-
sical T Tauri stars (based on their Hα emission
equivalent widths). Much younger stars, includ-
ing classical T Tauri stars, are present elsewhere
in the Lambda Ori SFR, which DM attribute to
star-formation triggered by the supernova rem-
nant shock wave impacting pre-existing molecular
cores in the region (the Barnard 30 and Barnard
35 dark clouds, in particular).
We have obtained Spitzer space telescope IRAC
and MIPS imaging of a ∼one square degree region
centered on the star λ Ori in order to (a) search
for circumstellar disks of members of the Coll 69
cluster and (b) attempt to identify new, very low
mass members of the cluster in order to determine
better the cluster IMF (in a forthcoming paper).
In §2, we describe the new observations we have
obtained; and in §3 we use those data to recon-
sider cluster membership. In §4 we use the new
candidate member list and the IR photometry to
determine the fraction of cluster members with cir-
cumstellar disks in both the stellar and substellar
domain, and we sort the stars with disks according
to their spectral slope from 1 to 24 µm.
2. The data
2.1. Optical and Near Infrared photome-
The optical and the near IR data for the bright
candidate members come from Barrado y Navascués et al.
(2004) –hereafter, Paper I. The RI –Cousins
system– data were collected with the CFHT in
1999, whereas the JHKs come from the 2MASS
All Sky Survey (Cutri et al. 2003). For cluster
members, the completeness limit is located at
I(complete,cluster) ∼ 20.2 mag, whereas 2MASS
provides near infrared data down to a limiting
magnitude of J=16.8, H=16.5, and Ks=15.7
mag. In some cases, low resolution spectroscopy
in the optical, which provides spectral types and
Hα equivalent widths, is also available. Twenty-
five objects out of the 170 CFHT1999 candidate
members are in common with Dolan & Mathieu
(1999, 2001). Those 25 stars also have Hα and
lithium equivalent widths, and radial velocities.
2.1.1. New deep Near Infrared photometry
For the objects with large error in 2MASS
JHKs, or without this type of data due to their
intrinsic faintness, we have obtained additional
measurements with the WHT (La Palma Observa-
tory, Spain) and INGRID (4.1×4.1 arcmin FOV)
in November 2002 and February 2003, and with
the Calar Alto 3.5m telescope (Almeria, Spain)
and Omega2000 in October 2005 (15.36×15.36 ar-
cmin FOV). In all cases, for each position, we took
five individual exposures of 60 seconds each, with
small offsets of a few arcseconds, thus totalling 5
minutes. In the case of the campaigns with IN-
GRID, we observed the area around the star λ
Orionis creating a grid. Essentially, we have ob-
served about 2/3 of the CFHT 1999 optical survey
region in J (in the area around the star and west of
it), with some coverage in H and K. On the other
hand, the Omega2000 observations, taken under a
Director’s Discretionary Time program, were fo-
cused on the faint candidate members. Except
for one object (LOri154), we collected observa-
tions in the J, H and Ks filters. The conditions of
the first observing run with INGRID were photo-
metric, and we calibrated the data using standard
stars from Hunt et al. (1998) observed throughout
the nights of the run. The average seeing was 0.9
arcsec. We had cloud cover during the second run
with INGRID, and the data were calibrated using
the 2MASS catalog and the stars present in each
individual image. The dispersion of this calibra-
tion is σ=0.05 magnitudes in each filter, with a
seeing of about 1.0 arcsec. Finally, no standard
stars were observed during the DDT observations
at Calar Alto. The seeing in this case was 1.2 arc-
sec. The faint Lambda Orionis candidate mem-
bers were calibrated using also 2MASS data. In
this last case, the dispersion is somewhat higher,
probably due to the worse seeing and the larger
angular pixel scale of the detector, with σ=0.1
mag. Note that this is dispersion not the error in
the calibration. These values correspond to the
FWHM of the gaussian distribution of the val-
ues zeropoint(i)=magraw(i)-mag2MASS(i), for any
star i, which also includes the photometric errors
in the 2MASS photometry and any contribution
due to the cluster stars being photometrically vari-
able. Since there is a large number of stars per
field (up to 1,000 in the Omega2000 images), the
peak of this distribution can be easily identified
and the zero points derived. A better estimate of
the error in the calibration is based on the distance
between mean, median and mode values, which
are smaller than half of the FWHM (in the case of
the mean and the median, almost identical to the
hundredth of magnitude). Therefore, the errors in
the calibration can be estimated as 0.025 and 0.05
magnitudes for the INGRID and the Omega2000
datasets, respectively.
All the data were processed and analyzed
with IRAF2, using aperture photometry. These
measurements, for 166 candidate members, are
listed in Table 1 (WHT/INGRID) and Table 3
(CAHA/Omega2000). Note that the errors listed
in the table correspond to the values produced by
the phot task with the digi.apphot package and
does not include the errors in the calibrations.
2.2. Spitzer imaging
Our Spitzer data were collected during March
15 (MIPS) and October 11 (IRAC), 2004, as part
of a GTO program. The InfraRed Array Camera
(IRAC, Fazio et al. (2004)) is a four channel cam-
era which takes images at 3.6, 4.5, 5.8, and 8.0 µm
with a field of view that covers ∼5.2×5.2 arcmin.
IRAC imaging was performed in mapping mode
with individual exposures of 12 seconds “fram-
etime” (corresponding to 10.4 second exposure
times) and three dithers at each map step. In or-
der to keep the total observation time for a given
2IRAF is distributed by National Optical Astronomy Obser-
vatories, which is operated by the Association of Universi-
ties for Research in Astronomy, Inc., under contract to the
National Science Foundation, USA
map under three hours, the Lambda Ori map was
broken into two segments, each of size 28.75×61.5
arcmin - one offset west of the star λ Ori and
the other offset to the east, with the combined
image covering an area of 57×61.5 arcmin, leav-
ing the star λ Orionis approximately at the cen-
ter. Each of the IRAC images from the Spitzer
Science Center pipeline were corrected for instru-
mental artifacts using an IDL routine developed
by S. Carey and then combined into the mosaics
at each of the four bandpasses using the MOPEX
package (Makovoz & Khan 2005). Note that the
IRAC images do not cover exactly the same FOV
in all bands, providing a slice north of the star
with data at 3.6 and 5.8 micron, and another slice
south of it with photometry at 4.5 and 8.0 microns.
The size of these strips are about 57×6.7 arcmin in
both cases. The Multiband Imaging Photometer
for Spitzer (MIPS, Rieke et al. (2004)) was used
to map the cluster with a medium rate scan mode
and 12 legs separated by 302 arcsec in the cross
scan direction. The total effective integration time
per point on the sky at 24 µm for most points in
the map was 40 seconds, and the mosaic covered
an area of 60.5×98.75 arcmin centered around the
star λ Orionis. Since there were no visible arti-
facts in the pipeline mosaics for MIPS 24 µm we
used them as our starting point to extract the pho-
tometry. We obtained MIPS 70 µm and 160 µm
imaging of the λ Ori region, but very few point
sources were detected and we do not report those
data in this paper.
The analysis of the data was done with IRAF.
First, we detected objects in each image using the
“starfind” command. Since the images in the [3.6]
and [4.5] bands are deeper than those in the [5.8]
and [8.0] bands, and since the fluxes of most ob-
jects are brighter at those wavelengths, the num-
ber of detections are much larger at the IRAC
short wavelengths than at the longer ones. Only a
relatively few objects have been detected at 24 µm
with MIPS. As a summary, 164 objects were de-
tected at at 3.6 and 4.5 micron, 145 at 5.8 micron,
139 at 8.0 micron and 13 at 24 micron.
We have performed aperture photometry to de-
rive fluxes for C69 cluster members. For the IRAC
mosaics we used an aperture of 4 pixels radius,
and the sky was computed using a circular annu-
lus 4 pixels wide, starting at a radius 4 pixels away
from the center. It is necessary to apply an aper-
ture correction to our 4-pixel aperture photometry
in order to estimate the flux for a 10-pixel aper-
ture, because the latter is the aperture size used
to determine the IRAC flux calibration. In some
cases, due to the presence of nearby stars, hot pix-
els, or because of their faintness, a 2 pixel aperture
and the appropriate aperture correction were used
(see notes to Table 3). For the MIPS photome-
try at 24 µm, we used a 5.31 pixels (13 arcsec)
aperture and a sky annulus from 8.16 pixels (20
arcsec) to 13.06 pixels (32 arcsec). An aperture
correction was also applied. Table 2 provides the
zero points, aperture corrections and conversion
factors between magnitudes and Jansky, as pro-
vided by the Spitzer Science Center website.
2.2.1. Data cross-correlation
The coverage on the sky of our Spitzer/IRAC
data is an approximate square of about 1 sq.deg,
centered on the star λ Orionis. The optical data
taken with the CFHT in 1999 covers an area of
42×28 arcmin, again leaving the star in the center
of this rectangle. Therefore, the optical survey
is completely included in the Spitzer mapping,
and we have been able to look for the counterpart
of the cluster candidates presented in Paper I.
The analysis of the area covered by Spitzer but
without optical imaging in the CFHT1999 sur-
vey will be discussed in a forthcoming paper. We
have not been able to obtain reliable Spitzer pho-
tometry for some candidate members from Paper
I, especially at the faint end of the cluster se-
quence. The faintest detected object, LOri167,
depending on the isochrone and the model, would
have a mass of ∼0.017 M⊙, if it is a member
(Barrado y Navascués, Huélamo, & Morales Calderón
(2005)).
The results are listed in Table 3, where non-
members and members are included, respectively
(see next section for the discussion about the mem-
bership). In both cases, we include data corre-
sponding to the bands R and I –from CFHT–, J,
H and Ks –from 2MASS and CAHA–, [3.6], [4.5],
[5.8], and [8.0] –from IRAC– and [24] –from MIPS.
Additional near IR photometry from WHT can be
found in Table 1.
3. Color-Color and Color-Magnitude Dia-
grams and new membership assignment
Before discussing membership of the Paper I
stars based on all of the new optical and IR data,
we have made an initial selection based on the
IRAC colors. Figure 1 (see further discussion in
the next section) displays a Color-Color Diagram
with the four IRAC bands. We have found that
31 objects fall in the area defined by Allen et al.
(2004) and Megeath et al. (2004) as Class II ob-
jects (ie, TTauri stars). Another two candidate
members are located in the region correspond-
ing to Class I/II objects. We consider all these
33 objects as bona-fide members of the C69 clus-
ter. Harvey et al. (2006) have discussed the con-
fusion by extragalactic and other sources when
analysing Spitzer data (in their case, they used
Serpens, a cloud having a large extinction). We
believe that this contribution is negligible for our
Lambda Ori data, since those Class II objects de-
tected at 24 micron are in the TTauri area de-
fined by Sicilia-Aguilar et al. (2005), as displayed
in her figure 5. There can be a higher level of
contamination among the objects classiefied as
Class III. All of the objects in Figure 1 had previ-
ously been identified as cluster candidate members
based on optical CMDs –it is unlikely that a signif-
icant number of AGN would have passed both our
optical and our IR criteria (and also have been
unresolved in our optical CFHT images). More-
over, prior to our Spitzer data, only 25% candidate
members which had optical, near-IR data and op-
tical low-resolution spectroscopy turned out to be
non-members (Paper I). After adding the Spitzer
photometry, we are quite confident in the mem-
bership of the selection.
Figure 2 and Figure 3 display several color-
magnitude diagrams (CMD) using the data listed
in Tables 1 and 3. In the case of the panels of the
first figure, we present optical and IR, including
Spitzer/IRAC data; whereas in the second set of
figures only IR data are plotted. For the sake of
simplicity, we have also removed the non-members
from Figure 3.
Based on these diagrams and on the spectro-
scopic information included in Paper I, we have
reclassified the candidate members as belonging or
not to the cluster. In color-magnitude diagrams,
C69 members lie in a fairly well-defined locus, with
a lower bound that coincides approximately with
the 20 Myr isochrone in this particular set of the-
oretical models (Baraffe et al. 1998). Stars that
fall well below (or blueward) of that locus are likely
non-members; stars that fall above or redward of
that locus are retained because they could have
IR excesses or above average reddening. We com-
bine the “votes” from several CMD’s to yield a
qualitative membership determination, essentially
yes, no or maybe. In total, out of 170 candi-
dates, 19 are probable non-members, four have du-
bious membership and the rest (147 objects) seem
to be bona-fide members of the cluster. There-
fore, the ratio of non-members to initial candidate
members is 13.5 %. In any case, only additional
spectroscopy (particularly medium and high res-
olution) can be used to establish the real status.
Proper motion might be helpful, but as shown by
Bouy et al. (2007), some bona-fide member can
appear to have discrepant proper motions when
compared with the average values of the associa-
tion. Table 4 shows the results for each candidate
in the different tests used to determine its mem-
bership, the membership as in Paper I, and the
final membership based on the new photometry.
The second and last columns show the spectro-
scopic information. Note that the degree of confi-
dence in the new membership classification varies
depending on the available information and in any
event it is always a matter of probability.
As Table 3 shows, the Spitzer/IRAC data does
not match completely the limiting magnitudes
of either our optical survey with CFHT or the
2MASS JHKs data. In the case of the band [3.6],
essentially all the Lambda Orionis candidate mem-
bers should have been detected (except perhaps
the faintest ones, at about I=22 mag). Some ob-
jects in the faint end have 3.6 micron data, but
lack 2MASS NIR, although in most cases we have
supplied it with our own deep NIR survey. In the
case of the Spitzer data at 4.5 micron, some ad-
ditional candidate members fainter than I=20.9
mag were not found, due to the limiting magni-
tude of about [4.5]lim=16.3 mag. The data at 8.0
micron only reach [8.0]lim=14.0 mag, which means
that only cluster members with about I=18.6 mag
–orKs=14.9– can be detected at that wavelength.
This is important when discussing both the mem-
bership status based on color-magnitude diagrams
and the presence of infrared excesses by examin-
ing color-color diagrams. Note, however, that ob-
jects with IR excesses have fainter optical/near-IR
counterparts than predicted in the table.
Figure 4 presents another CMD with the op-
tical magnitudes from the CFHT survey (R and
I), where we display the 170 candidate members
using different symbols to distinguish their ac-
tual membership status. Small dots correspond
to non-members based on the previous discussion,
whereas plus symbols, crosses and circles denote
probable members. In the first case –in most cases
due to their faintness– they do not have a com-
plete set of IRAC magnitudes, although they can
have either a measurement at 3.6 and 4.5, or even
at 5.8 microns. In the case of the objects rep-
resented by crosses, they have been classified as
Class III objects (Weak-line TTauri stars and sub-
stellar analogs if they indeed belong to the clus-
ter) based on an IRAC color-color diagram (see
next section and Figure 1). Finally, big circles
correspond to Class II sources. The pollution
rate seems to be negligible in the magnitude range
I=12-16 (1.2–0.17 M⊙ approx, equivalent to M0
and M5, respectively), where our initial selection
based on the optical and the near infrared (2MASS
data) has worked nicely. However, for fainter can-
didates, the number of spurious members is very
large and the pollution rate amounts to about 15%
for objects with 16 < I < 19, and about 45% for
I≥19 (approximately the magnitude beyond the
reach of the 2MASS survey).
At a distance of 400 pc and for an age of 5
Myr, and according to the models by Baraffe et al.
(1998), the substellar borderline is located at
about I=17.5 mag. Table 5 lists other values
for different ages, as well other bands –J , Ks
and L′– discussed in this paper. Among our 170
CFHT candidate members, there are 25 objects
fainter than that magnitude, and which pass all
of our membership criteria which are probable
brown dwarfs. Out of these 25 objects, 12 have
low-resolution spectroscopy and seem to be bona-
fide members and, therefore, brown dwarfs. The
other 13 objects are waiting for spectral confir-
mation of their status. Assuming an age of 3 or
8 Myr would increase or decrease the number of
brown dwarf by seven in each case. In the first
case (3 Myr), five out of the seven possible BDs
have spectroscopic membership, whereas in the
second case only three were observed in Paper I.
As a summary, we have found between 18 and
32 good brown dwarfs candidates (depending on
the final age) in the Lambda Orionis cluster, and
between 17 and 9 have their nature confirmed via
low-resolution spectroscopy. Note that even this
technique does not preclude the possibility that a
few among them would actually be non-members.
Finally, the planetary mass domain starts at
about Ic=21.5, using a 5 Myr isochrone (DUSTY
models from Baraffe et al. (2002)). In that re-
gion, there is only one promising planetary mass
candidate, LOri167 (Barrado y Navascués et al .
(2007)).
4. Discussion
4.1. The Color-Color diagrams, the diag-
nostic of IR excess and the disk ratio
The Spitzer/IRAC colors are a powerful tool to
reveal the dust and, therefore, the population of
Class I and II sources in a stellar association. Fig-
ure 1 (after Allen et al. (2004) and Megeath et al.
(2004)) displays the colors derived from the mea-
surements at 3.6 minus 4.5 microns, versus those
obtained at 5.8 minus 8.0 microns. This diagram
produces an excellent diagnostic, allowing an easy
discrimination between objects with and without
disks. Note that due to the limiting magnitudes
of the IRAC bands (see the discussion in previous
section), objects fainter than about I=18.6 mag
cannot have a complete set of IRAC colors and
therefore cannot be plotted in the diagram. This
fact imposes a limit on our ability to discover mid-
IR excesses at the faint end of the cluster sequence.
For Lambda Orionis cluster members, assuming a
distance of 400 pc and an age of 5 Myr (and ac-
cording to the models by Baraffe et al. (1998)),
this limit is located at 0.040 M⊙. Figure 1 con-
tains a substantial number of objects in the region
corresponding to the Class II sources. In total,
there are 31 objects located within the solid rect-
angle out of 134 Lambda Orionis members with
data in the four IRAC bands. Among them, three
(LOri045, LOri082 and LOri092) possibly have rel-
atively large photometric errors in their 5.8 µm
flux, because inspection of their SEDs indicates
they are likely diskless. Two additional objects,
LOri038 and LOri063, have IRAC colors indicat-
ing Class I/II (actually, LOri038 is very close to
the Class II region). The SED (see below) in-
dicates that both are Class II stars. Therefore,
the fraction of cluster members that are Class II
PMS stars based on their IR excesses is ∼22–25%,
for the spectral range M0–M6.5. This is differ-
ent from what was inferred by Dolan & Mathieu
(1999, 2001) and by us (Paper I), based on the
distribution of the Hα emission and near-infrared
color-color diagrams. The Spitzer/IRAC data
clearly demonstrate that Lambda Orionis cluster
does contain a significant number of stars with
dusty circumstellar disks. No embedded objects
(Class I) seem to be present, in agreement with
the age range for the association (3-8 Myr or even
slightly larger). Note that our different IR excess
frequency compared to Dolan & Mathieu may re-
sult from their sample being primarily of higher
mass stars than ours.
Figure 5 is a blow-up of the region in Fig-
ure 1 corresponding to the Class II sources. We
have also added big minus and plus symbols, and
large squares, to indicate those objects with mea-
sured Hα equivalent widths (in low- and medium-
resolution spectrum). We have used the satura-
tion criterion by Barrado y Navascués & Mart́ın
(2003) to distinguish between objects with high
W(Hα) –plus symbols– and normal W(Hα) –
minus symbols. In principal, an object with a
W(Hα) value above the saturation criterion is ei-
ther accreting or is undergoing a flare episode.
There are two low mass stars (LOri050 and
LOri063) with an Hα line broader than 200 km/s
(Muzerolle et al. 2003), another independent indi-
cation of accretion (based on Natta et al. (2004),
they should have very large accretion rates ∼10−9
M⊙/yr). The theoretical disk models used to in-
terpret IRAC Color-Color Diagram by Allen et al.
(2004) suggest that the accretion rates increase
from the bottom-left to the top-right of the figure.
This is in agreement with our results, since most
of the accreting objects (assuming that strong Hα
is a good indicator of accretion) lie in the area
of the figure with the larger excesses (top-right).
A couple of objects with very low Hα emission
are located near the edge of the Class II area
(bottom-left), a fact that suggest that they may
have a relatively thin disk, with small or negligible
accretion. Actually these objects are surrounded
by thin disks instead of thick primordial disks (see
next section).
Regarding the brown dwarfs in the cluster,
several probable members (LOri126, LOri129,
LOri131, LOri132, LOri139 and LOri140) are lo-
cated within the precinct of Classical TTauri stars.
They are just at the border between stars and
substellar objects, with magnitudes in the range
I=17.52–18.21 and J=15.38–16.16 (the boundary
is located at I=17.55 and J=15.36 for 5 Myr, see
Table 5). In Paper I we presented low-resolution
spectroscopy of LOri126, LOri139 and LOri140,
which suggests they are cluster members (the
spectral types are M6.5, M6.0 and M7.0 with a Hα
equivalent width of 26.2, 19.7 and 72.8 Å, respec-
tively). In addition we have confirmed the mem-
bership of LOri129 via medium-resolution spec-
troscopy (spectral type, M6.0 with a Hα equiva-
lent width of 12.1 Å).
In total, there are 15 brown dwarf candidates
with a complete set of IRAC colors, six of which
fall in the Class II region, thus making the fraction
of brown dwarfs with IR colors indicative of cir-
cumstellar disks close to 40% (down to 0.04 M⊙),
similar to the 50% obtained by (Bouy et al. 2007)
in Upper Sco brown dwarfs, using mid-IR photom-
etry or the 50% derived by Guieu et al. (2006) in
Taurus brown dwarfs with Spitzer.
4.2. The Spectral Energy Distribution
We have plotted the SEDs of our Lambda Ori-
onis candidate members in Figures 6-8. There is
clearly a range from approximately flat spectrum,
to black-body in the near-IR but starting to show
excesses at IRAC wavelengths, to only showing ex-
cess at 24 micron. A way to study the presence of
a circumstellar disk around an object is to analyze
the shape of the SED. After Lada et al. (2006) we
have used the 3.6–8.0 µm slope for each source de-
tected in at least three IRAC bands to distinguish
between objects with optically thick, primordial
disks, objects surrounded by optically thin or ane-
mic disks and objects without disks. The results
of this test are presented in Table 4. In Figures 6-8
the SEDs are sorted in agreement with their IRAC
slope classification: diskless objects (slope index
or α<−2.56) in Figure 6, thick disks (α>−1.8)
in Figure 7, and objects surrounded by thin disks
(−1.8<α<−2.56) in Figure 8. In this last figure
we also include two low mass stars which present
an excess only at 24 micron, due to a transition
disk (see below). According to the IRAC slope
the fraction of cluster members detected in at least
three of the IRAC bands with optically thick disks
is 14%, while the total disk fraction is found to be
31% (similar to the 25% derived with the IRAC
CCD). This fraction is lower than the 50% found
by Lada et al. (2006) in IC348 (1-3 Myr) as ex-
pected due to the different age of the clusters.
Figure 9 illustrates the evolution of the disk
fraction with the age for several stellar associa-
tions (assuming that the infrared excess serves as
a proxy of the presence of a circumstellar disk).
The ratios for the different associations come from
IRAC data (Hartmann et al. 2005; Lada et al.
2006; Sicilia-Aguilar et al. 2006) in order to avoid
different results depending on the technique used
(Bouy et al. 2007). The ratio for the Lambda Ori-
onis cluster (Collinder 69) is about 30% and, as
stated before, for the objects below the substellar
borderline, the fraction of Classical TTauri objects
seems to be larger. According to its older age, the
thick disk fraction in Collinder 69 is lower than
that of IC348 (this fraction is represented by open
squares in Figure 9).
Among the objects classified as Class III sources
from Figure 1, only two (LOri043 and LOri065)
have a measurement at [24] with an unambiguous
detection. These two stars do not have excesses
at 3.6 or 4.5 micron. Therefore, they can be clas-
sified as transition objects, the evolutionary link
between the primordial disks and debris disks.
A third of the Class II sources (11 out of 33)
have measurements in the [24] band, all of them
with clear excess, as expected from their Class II
status. The lack of IR excesses at shorter wave-
lengths for LOri043 and LOri065 probably stems
from an inner disk hole or at least less inner dust
than for the Class II sources. Models of simi-
lar 24 µm-only excess sources and a discussion of
their disk-evolutionary significance can be found
in Sicilia-Aguilar et al. (2006); Muzerolle et al.
(2006); D’Alessio et al. (2006). Figure 10 shows
the same diagram as in Figure 1 but the MIPS
24 µm information is included as dashed squares.
The small circles stand for objects having optically
thin (dashed) or optically thick (solid) disks based
on their IRAC slope. The diagram shows a smooth
transition between the three types of objects: disk-
less, thin, and primordial disks. LOri103 has a
thin disk based on its 3.6–5.8 µm slope. It has
been classified as Class III due to its magnitude at
8.0 µm but we believe that it is actually a Class II
source and the faint magnitude at this bandpass
is probably due to the presence of a nebulosity.
There are some objects classified as Class III
sources by the IRAC CCD (they are outside, but
close to the Class II area in the diagram), but
have disks based on their IRAC slope. All these
objects are brown dwarfs according to the models
by Baraffe et al. (1998) (5 Myr) which pass all our
membership criteria and thus the ratio of substel-
lar objects bearing disks increases to 50 % (note
that we need detections in at least three IRAC
bands to calculate the IRAC slope).
None of our brown dwarf candidates have been
detected at 24 micron. This is probably due to the
detection limits for this band.
As a summary, of the 170 objects presented in
Paper I, 167 are discussed here (the other three
are spurious detections or the Spitzer photometry
is not reliable). Excluding the sources classified as
non-members, there are 22 which cannot be classi-
fied due to the incompleteness of the IRAC data,
95 have been classified as diskless, another two
have transition disks, 25 thin disks and 20 thick
disks. All this information has been listed in Ta-
ble 4. Note that there are nine objects classified as
Class III from color-color diagrams but which have
thin disks according to the SED slopes, and an-
other one (LOri156, a very low mass brown dwarf
candidate with a very intense Hα) which has a
thick disk based on the slope of the IRAC data.
4.3. The Spatial distribution of the mem-
We have plotted the spatial distribution of our
good candidate members in Figure 11. Four-point
stars represent B stars and λ Orionis (O8III). The
Class III members (crosses) are approximately
randomly distributed across the survey region.
Both the Class II sources and the B stars give
the impression of being concentrated into linear
grouping - with most of the B stars being aligned
vertically near RA = 83.8, and a large number
of the Class II sources being aligned in the East-
Southeast direction (plus some less well-organized
alignments running more or less north-south). It
is possible the spatial distributions are reflective
of the birth processes in C69 - with the youngest
objects (the Class II sources and B stars) tracing
the (former?) presence of dense molecular gas,
whereas the Class III sources have had time to
mix dynamically and they are no longer near the
locations where they were born.
Figure 12 shows three different views of the cen-
tral portion of the Spitzer mosaic at 3.6 microns
for the C69 region. Figures 12a and 12b (with 12b
being a blow-up of the center of 12a) emphasize
the distribution of Class II sources relative to the
cluster center; Figure 12c shows the distribution of
our brown dwarf candidates. The star λ Orionis is
at the center of each of these figures. The object
located south of the star λ Orionis is BD+09 879
C (or HD36861 C, a F8 V star), with an angular
distance of about 30 arcsec from the close binary
λ Orionis AB (the projected distance, if BD+09
879 C is a cluster member, would be 12,000 AU
from the AB pair). The apparent relative lack of
cluster candidate members within about 75 arcsec
from the star λ Orionis may be illusory, as this re-
gion was “burned out” in the optical images of the
CFHT1999 survey and is also adversely affected in
our IRAC images. There are a number of Class II
sources at about 75-90 arcsec from λ Ori, corre-
sponding to a projected separation of order 30,000
AU, so at least at that distance circumstellar disks
can survive despite the presence of a nearby O
star.
Regarding the distribution of brown dwarfs, a
significant number of them (30 %) are within the
the inner circle with a diameter of 9 arcmin (our
original optical survey covered an area of 42×28
arcmin). However, there are substellar members
at any distance from the star λ Ori (Figure 12c),
and there is no substantial evidence that the clus-
ter brown dwarfs tend to be close to the massive
central star.
We have estimated the correlation in spatial
distribution of different sets of data: Class II vs.
Class III candidates, objects with any kind of disk
(thin, thick and transition) vs. diskless objects,
and stellar vs. substellar objects (following the
substellar frontier given in Table 5 for different
ages and bands). We have computed the two-sided
Kuiper statistic (invariant Kolmogorov-Smirnov
test), and its associated probability that any of the
previously mentioned pairs of stellar groups were
drawn from the same distribution. We have calcu-
lated the two dimensional density function of each
sample considering a 4.5×3 arcmin grid-binning
in a 45×30 arcmin region centered at 05:35:08.31,
+09:56:03.6 (the star Lambda Orionis). The test
reveals that in the first case, the cumulative dis-
tribution function of Class II candidates is sig-
nificantly different from that of Class III candi-
dates, with a probability for these data sets be-
ing drawn from the same distribution of ∼ 1%.
This situation changes when comparing the set of
objects harbouring any kind of disk with that of
diskless objects, finding a probability of ∼ 50% in
this case (and hence no conclusion can be drawn,
other than that there is no strong correlation). On
the other hand, regarding a correlation with age,
the test points out a trend in the relationship be-
tween the spatial distribution of stellar and sub-
stellar objects depending on the assumed age. The
value of the probability of these two populations
sharing a common spatial distribution decreases
from a ∼ 30% when assuming an age of 3 Myr, to
∼ 0.001% for an age of 8 Myr. The value assuming
an age of 5 Myr is ∼ 1%.
The spatial distribution of objects detected at
24 micron can be seen in Figure 13. The nebulosity
immediately south of the star λ Orionis (close to
BD +09 879 C) corresponds to the HII region LBN
194.69-12.42 (see the detail in Figure 12b in the
band [3.6]). Most of the detected members are lo-
cated within the inner 9 arcmin circle, with an ap-
parent concentration in a “filament” running ap-
proximately north-south (i.e. aligned with the B
stars as illustrated in Figure 11b). Out of the clus-
ter members discovered by Dolan & Mathieu, 11
are within the MIPS [24] image (see Figure 13) and
have fluxes above the detection level. The clos-
est member to λ Orionis is D&M#33 (LOri034),
about 2 arcmin east from the central star.
The MIPS image at 24 micron suggest that
there are two bubbles centered around the λ Ori-
onis multiple star (actually, the center might be
the C component or the HII region LBN 194.69-
12.42). The first one is about 25 arcmin away,
and it is located along the North-East/South-West
axis. More conspicuous is the smaller front lo-
cated at a distance of 10.75 arcmin, again cen-
tered on the HII region and not in λ Orionis AB.
In this case, it is most visible located in the direc-
tion West/North-West, opposite to the alignment
of Class II objects and low mass members with ex-
cess at 24 micron. Similar structures can be found
at larger scales in the IRAS images of this region,
at 110 and 190 arcmin.
The star 37 Ori, a B0III, is located at the center
of the cocoon at the bottom of the image. The
source IRAS 05320+0927 is very close and it is
probably the same.
Note that while BD +09 879 C would appear
to be the source of a strong stellar wind and/or
large UV photon flux, it is not obvious that the
visible star is the UV emitter because the spectral
type for BD +09 879 C is given as F8V (Lindroos
1985). It would be useful to examine this star more
closely in order to try to resolve this mystery.
5. Conclusions
We have obtained Spitzer IRAC and MIPS data
of an area about one sq.deg around the star λ Ori-
onis, the central star of the 5 Myr Lambda Orio-
nis open cluster (Collinder 69). These data were
combined with our previous optical and near in-
frared photometry (from 2MASS). In addition, we
have obtained deep near infrared imaging. The
samples have been used to assess the member-
ship of the 170 candidate members, selected from
Barrado y Navascués et al. (2004).
By using the Spitzer/IRAC data and the crite-
ria developed by Allen et al. (2004) and Hartmann
et al. (2005), we have found 33 objects which can
be classified as Classical TTauri stars and substel-
lar analogs (Class II objects). This means that the
fraction of members with disks is 25% and 40%, for
the stellar (in the spectral range M0 - M6.5) and
substellar population (down to 0.04 M⊙). How-
ever, by combining this information with Hα emis-
sion (only a fraction of them have spectroscopy),
we find that some do not seem to be accreting.
Moreover, as expected from models, we see a
correlation in the [3.6] - [4.5] vs. [5.8] - [8.0] dia-
gram for objects with redder colors (more IR ex-
cess) to have stronger Hα emission. In addition,
following Lada et al. (2006) and the classification
based on the slope of the IRAC data, we found
that the ratio of substellar members bearing disks
(optically thin or thick) is∼ 50%, whereas is about
31% for the complete sample (14% with thick
disks). This result suggests that the timescale for
primordial disks to dissipate is longer for lower
mass stars, as suggested in Barrado y Navascués
& Mart́ın (2003).
We have also found that the distribution of
Collinder members is very inhomogeneous, specif-
ically for the Class II objects. Most of them are
located in a filament which goes from the central
star λ Orionis to the south-east, more or less to-
wards the dark cloud Barnard 35. In addition,
there are several Class II stars close to the central
stars. If the (previously) highest mass member
of C69 has already evolved off the main sequence
and become a supernova, either the disks of these
Class II stars survived that episode or they formed
subsequent to the supernova.
We have also derived the fluxes at 24 micron
from Spitzer/MIPS imaging. Only a handful –
13– of the low mass stars were detected (no brown
dwarfs). Most of them are Class II objects. In
the case of the two Class III members with 24
micron excess, it seems that they correspond to
transitions disks, already evolving toward the pro-
toplanetary phase.
We thank Calar Alto Observatory for allocation
of director’s discretionary time to this programme.
This research has been funded by Spanish grants
MEC/ESP2004-01049,MEC/Consolider-CSD2006-
0070, and CAM/PRICIT-S-0505/ESP/0361.
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Table 1
Additional near infrared photometry for the candidate members of the Lambda Orionis
cluster (WHT/INGRID).
Name I error J error H error Ks error
LOri006 12.752 11.67 0.01 10.90 0.01 10.94 0.01
LOri007 12.779 11.65 0.01 – – – –
LOri008 12.789 11.53 0.01 10.85 0.01 10.62 0.01
LOri009 12.953 11.79 0.01 – – – –
LOri011 13.006 11.59 0.01 – – – –
LOri015 13.045 11.90 0.01 – – – –
LOri016 13.181 12.00 0.01 11.41 0.01 11.27 0.01
LOri020 13.313 11.95 0.01 – – – –
LOri021 13.376 12.26 0.01 – – – –
LOri022 13.382 12.20 0.01 11.44 0.01 11.22 0.01
LOri024 13.451 12.35 0.01 – – – –
LOri026 13.472 12.00 0.01 – – – –
LOri027 13.498 12.51 0.01 – – – –
LOri030 13.742 12.44 0.01 11.81 0.01 11.64 0.01
LOri031 13.750 12.34 0.01 – – – –
LOri034 13.973 12.43 0.01 – – – –
LOri035 13.974 12.56 0.01 – – – –
LOri036 13.985 12.53 0.01 – – – –
LOri037 13.988 13.43 0.01 – – – –
LOri048 14.409 12.78 0.01 12.17 0.01 12.00 0.01
LOri049 14.501 13.13 0.01 – – – –
LOri050 14.541 13.17 0.01 – – – –
LOri053 14.716 13.17 0.01 – – – –
LOri055 14.763 13.24 0.01 – – – –
LOri056 14.870 13.33 0.01 – – – –
LOri057 15.044 13.43 0.01 – – – –
LOri060 15.144 13.60 0.01 – – – –
LOri061 15.146 13.38 0.01 12.74 0.01 12.54 0.01
LOri062 15.163 13.60 0.01 – – – –
LOri063 15.340 13.72 0.01 13.02 0.01 12.69 0.01
LOri065 15.366 13.66 0.01 13.04 0.01 12.85 0.01
LOri068 15.200 13.73 0.01 – – – –
LOri069 15.203 13.28 0.01 – – – –
LOri071 15.449 13.72 0.01 – – – –
LOri073 15.277 13.68 0.01 – – – –
LOri076 15.812 14.12 0.01 13.51 0.01 13.28 0.01
LOri077 15.891 14.11 0.01 – – – –
LOri082 16.022 14.18 0.01 13.64 0.01 13.35 0.01
LOri083 16.025 14.22 0.01 13.63 0.01 13.32 0.01
LOri085 16.043 14.21 0.01 13.58 0.01 13.26 0.01
LOri087 16.091 14.44 0.01 – – – –
LOri088 16.100 14.14 0.01 – – – –
LOri089 16.146 14.43 0.01 – – – –
LOri093 16.207 14.47 0.01 – – – –
LOri094 16.282 14.37 0.01 – – – –
LOri096 16.366 14.59 0.01 13.98 0.01 13.72 0.01
LOri099 16.416 14.62 0.01 – – – –
LOri100 16.426 14.83 0.01 – – – –
LOri102 16.505 14.57 0.01 14.05 0.01 13.78 0.01
LOri104 16.710 14.90 0.01 – – – –
LOri105 16.745 14.84 0.01 – – – –
LOri107 16.776 14.91 0.01 14.35 0.01 14.05 0.01
LOri115 17.077 15.35 0.01 – – – –
LOri116 17.165 15.31 0.01 – – – –
LOri120 17.339 15.36 0.01 – – – –
LOri130 17.634 15.76 0.01 – – – –
LOri131 17.783 15.29 0.01 14.83 0.01 14.41 0.01
LOri132 17.822 15.77 0.01 – – – –
LOri134 17.902 15.72 0.01 15.17 0.01 14.82 0.01
LOri135 17.904 15.63 0.01 15.14 0.01 14.79 0.01
LOri136 17.924 15.53 0.01 – – – –
Table 2
Zero points, aperture corrections and conversion factors between the magnitudes and
the fluxes in Jansky.
Channel Ap. correction ap=4px (mag) Ap. correction ap=2px (mag) Zero Point (mag)a Flux mag=0 (Jy)
[3.6] 0.090 0.210 17.26 280.9b
[4.5] 0.102 0.228 16.78 179.7b
[5.8] 0.101 0.349 16.29 115.0b
[8.0] 0.121 0.499 15.62 64.1b
[24] 0.168d 11.76 7.14c
aZero Points for aperture photometry performed with IRAF on the BCD data.
bReach et al. (2005)
cEngelbracht et al. (2006)
dThe aperture used for MIPS [24] was always 5.31 pixels.
Table 3
Candidate members of the Lambda Orionis cluster (Collinder 69)
Name R error I error J error H error Ks error [3.6] error [4.5] error [5.8] error [8.0] error [24] error Mem1
LOri001 13.21 0.00 12.52 0.00 11.297 0.022 10.595 0.022 10.426 0.021 10.228 0.003 10.255 0.004 10.214 0.009 10.206 0.010 – – Y
LOri002 13.44 0.00 12.64 0.00 11.230 0.024 10.329 0.023 10.088 0.019 9.935 0.003 10.042 0.003 9.930 0.009 9.880 0.008 – – Y
LOri003 13.39 0.00 12.65 0.00 11.416 0.023 10.725 0.022 10.524 0.023 10.262 0.003 10.318 0.004 10.239 0.010 10.171 0.010 – – Y
LOri004 13.71 0.00 12.65 0.00 11.359 0.022 10.780 0.023 10.548 0.021 10.287 0.003 10.249 0.004 10.185 0.009 10.127 0.009 – – Y
LOri005 13.38 0.00 12.67 0.00 11.378 0.022 10.549 0.022 10.354 0.023 10.204 0.003 10.321 0.004 10.218 0.009 10.158 0.009 – – Y
LOri006 13.55 0.00 12.75 0.00 11.542 0.026 10.859 0.026 10.648 0.021 10.454 0.003 10.454 0.004 10.399 0.011 10.319 0.010 – – Y
LOri007 13.72 0.00 12.78 0.00 11.698 0.027 11.101 0.024 10.895 0.030 10.668 0.004 10.636 0.004 10.615 0.012 10.482 0.013 – – Y
LOri008 13.60 0.00 12.79 0.00 11.548 0.029 10.859 0.023 10.651 0.024 10.498 0.003 10.495 0.004 10.440 0.011 10.256 0.012 – – Y
LOri009 13.70 0.00 12.95 0.00 11.843 0.024 11.109 0.024 10.923 0.023 10.834 0.004 10.873 0.005 10.788 0.012 10.743 0.014 – – Y
LOri010 13.70 0.00 12.96 0.00 11.880 0.026 11.219 0.026 11.041 0.023 10.916 0.004 10.953 0.005 10.733 0.012 10.839 0.016 – – Y
LOri011 13.84 0.00 13.01 0.00 11.604 0.026 10.784 0.024 10.554 0.024 10.378 0.003 10.521 0.004 10.444 0.011 10.326 0.011 – – Y
LOri012 13.80 0.00 13.03 0.00 11.816 0.026 10.971 0.024 10.795 0.023 10.619 0.003 10.758 0.005 10.627 0.012 10.543 0.012 – – Y
LOri013 14.21 0.00 13.03 0.00 11.656 0.022 10.918 0.022 10.719 0.023 10.511 0.003 10.480 0.004 10.467 0.011 10.344 0.012 – – Y
LOri014 13.84 0.00 13.03 0.00 11.941 0.024 11.278 0.027 11.092 0.023 10.902 0.004 10.904 0.005 10.839 0.014 10.797 0.014 – – Y
LOri015 13.83 0.00 13.05 0.00 11.870 0.024 11.127 0.024 10.912 0.019 10.808 0.004 10.886 0.005 10.824 0.013 10.882 0.015 – – Y
LOri016 14.07 0.00 13.18 0.00 11.958 0.024 11.284 0.027 11.053 0.024 10.833 0.004 10.817 0.006 10.378 0.011 10.700 0.014 – – Y
LOri017 13.99 0.00 13.19 0.00 12.188 0.024 11.482 0.023 11.323 0.021 11.165 0.005 11.206 0.006 11.173 0.017 11.072 0.019 – – Y
LOri018 14.21 0.00 13.26 0.00 11.991 0.024 11.284 0.022 11.090 0.023 10.804 0.004 10.798 0.005 10.722 0.012 10.636 0.014 – – Y
LOri019 14.33 0.00 13.31 0.00 12.019 0.026 11.316 0.024 11.067 0.021 10.880 0.004 10.866 0.005 10.767 0.013 10.788 0.018 – – Y
LOri020 14.65 0.00 13.31 0.00 11.856 0.028 11.214 0.026 11.025 0.027 10.676 0.003 10.609 0.004 10.573 0.012 10.485 0.012 – – Y
LOri021 14.26 0.00 13.38 0.00 12.258 0.027 11.560 0.026 11.296 0.021 11.129 0.004 11.107 0.005 11.081 0.016 11.065 0.019 – – Y
LOri022 14.41 0.00 13.38 0.00 12.102 0.023 11.411 0.022 11.156 0.019 11.010 0.004 10.985 0.005 10.895 0.014 10.683 0.014 – – Y
LOri023 14.43 0.00 13.44 0.00 12.221 0.027 11.471 0.022 11.290 0.024 11.090 0.004 11.114 0.005 11.071 0.015 10.928 0.018 – – Y
LOri024 14.43 0.00 13.45 0.00 12.139 0.030 11.446 0.026 11.223 0.028 11.018 0.004 11.019 0.005 10.972 0.015 10.877 0.016 – – Y
LOri025 14.36 0.00 13.45 0.00 12.163 0.044 11.409 0.051 11.090 0.033 10.668 0.003 10.674 0.004 10.613 0.012 10.576 0.012 – – Y
LOri026 14.57 0.00 13.47 0.00 12.046 0.028 11.324 0.024 11.092 0.025 10.882 0.004 10.833 0.005 10.811 0.014 10.742 0.013 – – Y
LOri027 14.49 0.00 13.50 0.00 12.378 0.026 11.718 0.023 11.503 0.021 11.305 0.005 11.306 0.006 11.237 0.016 11.179 0.025 – – Y
LOri028 14.86 0.00 13.65 0.00 12.488 0.024 11.872 0.022 11.687 0.021 11.439 0.005 11.417 0.006 11.348 0.017 11.297 0.021 – – Y
LOri029 14.89 0.00 13.69 0.00 12.210 0.026 11.460 0.027 11.071 0.019 10.259 0.003 9.830 0.003 9.321 0.006 8.416 0.003 5.684 0.007 Y
LOri030 14.95 0.00 13.74 0.00 12.427 0.027 11.686 0.026 11.428 0.021 11.208 0.007 11.157 0.007 11.119 0.019 10.997 0.023 – – Y
LOri031 14.90 0.00 13.75 0.00 12.412 0.028 11.654 0.023 11.442 0.028 11.206 0.004 11.188 0.006 11.150 0.015 11.079 0.016 – – Y
LOri032 15.04 0.00 13.80 0.00 12.410 0.029 11.714 0.023 11.493 0.021 11.252 0.004 11.215 0.006 11.178 0.016 11.080 0.019 – – Y
LOri033 14.82 0.00 13.81 0.00 12.455 0.033 11.800 0.042 11.502 0.027 11.146 0.004 11.149 0.005 11.060 0.015 11.020 0.019 – – Y
LOri034 15.10 0.00 13.97 0.00 12.442 0.026 11.639 0.026 11.184 0.023 10.068 0.003 9.734 0.003 9.314 0.007 8.325 0.003 5.738 0.007 Y
LOri035 15.25 0.00 13.97 0.00 12.546 0.024 11.842 0.027 11.609 0.019 11.371 0.005 11.349 0.006 11.283 0.017 11.259 0.021 – – Y
LOri036 15.47 0.00 13.98 0.00 12.576 0.024 11.936 0.023 11.706 0.021 11.395 0.005 11.378 0.006 11.287 0.018 11.260 0.019 – – Y
LOri037 15.17 0.00 13.99 0.00 12.459 0.024 11.727 0.026 11.492 0.021 11.302 0.005 11.309 0.006 11.198 0.016 11.180 0.018 – – Y
LOri038 15.10 0.00 14.01 0.00 12.684 0.030 11.954 0.029 – – 11.455 0.005 11.320 0.006 10.970 0.014 9.857 0.008 6.211 0.010 Y
LOri039 15.25 0.00 14.02 0.00 12.755 0.030 12.004 0.023 11.775 0.023 11.523 0.005 11.534 0.007 11.434 0.018 11.373 0.025 – – Y
LOri040 15.38 0.00 14.06 0.00 12.553 0.024 11.877 0.022 11.594 0.024 11.364 0.005 11.319 0.006 11.231 0.017 11.218 0.025 – – Y
LOri041 15.55 0.00 14.10 0.00 12.500 0.024 11.856 0.023 11.587 0.027 11.255 0.004 11.187 0.006 11.131 0.015 11.123 0.021 – – Y
LOri042 15.31 0.00 14.14 0.00 12.813 0.027 12.099 0.026 11.853 0.023 11.604 0.005 11.633 0.007 11.546 0.019 11.479 0.025 – – Y
LOri043 15.46 0.00 14.16 0.00 12.707 0.024 12.021 0.026 11.741 0.024 11.512 0.005 11.496 0.007 11.408 0.019 11.393 0.024 8.479 0.102 Y
LOri044 15.39 0.00 14.17 0.00 12.924 0.024 12.318 0.024 12.065 0.023 11.837 0.006 11.804 0.007 11.751 0.023 11.674 0.024 – – Y
LOri045 15.56 0.00 14.23 0.00 12.768 0.023 12.102 0.026 11.844 0.023 11.602 0.005 11.596 0.007 12.023 0.039 11.474 0.026 – – Y
LOri046 15.64 0.00 14.36 0.00 13.033 0.023 12.478 0.026 12.252 0.026 11.906 0.006 11.852 0.008 11.787 0.024 11.763 0.032 – – Y
LOri047 15.91 0.00 14.38 0.00 12.732 0.026 12.097 0.031 11.827 0.026 11.474 0.005 11.400 0.006 11.303 0.017 11.342 0.025 – – Y
LOri048 15.78 0.00 14.41 0.00 12.887 0.027 12.196 0.029 11.932 0.026 11.612 0.006 11.521 0.008 11.448 0.020 10.920 0.018 8.119 0.087 Y
Table 3—Continued
Name R error I error J error H error Ks error [3.6] error [4.5] error [5.8] error [8.0] error [24] error Mem1
LOri049 15.77 0.00 14.50 0.00 13.173 0.027 12.592 0.029 12.253 0.023 12.004 0.006 11.992 0.009 12.043 0.027 12.427 0.057 – – Y
LOri050 15.90 0.00 14.54 0.00 12.877 0.027 12.236 0.027 11.955 0.031 11.471 0.005 11.089 0.005 10.529 0.011 9.537 0.007 7.268 0.029 Y
LOri051 15.91 0.00 14.60 0.00 13.266 0.024 12.559 0.022 12.285 0.021 12.017 0.006 11.995 0.008 11.969 0.024 11.919 0.035 – – Y
LOri052 15.93 0.00 14.63 0.00 13.117 0.023 12.454 0.024 12.192 0.019 11.917 0.006 11.863 0.008 11.764 0.022 11.791 0.029 – – Y
LOri053 16.08 0.00 14.72 0.00 13.173 0.032 12.521 0.023 12.278 0.027 11.995 0.006 11.954 0.008 11.886 0.022 11.862 0.034 – – Y
LOri054 16.19 0.00 14.73 0.00 13.189 0.024 12.509 0.022 12.271 0.027 11.974 0.006 11.948 0.009 11.805 0.025 11.862 0.038 – – Y
LOri055 16.12 0.00 14.76 0.00 13.184 0.026 12.477 0.026 12.253 0.026 12.044 0.006 12.038 0.009 12.015 0.029 11.902 0.038 – – Y
LOri056 16.43 0.00 14.87 0.00 13.211 0.029 12.567 0.026 12.267 0.029 12.011 0.004211.906 0.005211.913 0.019211.853 0.0322– – Y
LOri057 16.63 0.00 15.04 0.00 13.412 0.024 12.773 0.023 12.487 0.030 12.177 0.007 12.078 0.009 11.988 0.030 11.992 0.033 – – Y
LOri058 16.57 0.00 15.06 0.00 13.521 0.024 12.935 0.022 12.643 0.027 12.332 0.007 12.269 0.010 12.172 0.032 12.637 0.072 – – Y
LOri059 16.57 0.00 15.10 0.00 13.574 0.026 12.884 0.026 12.682 0.032 12.317 0.007 12.270 0.009 12.218 0.030 12.679 0.066 – – Y
LOri060 16.56 0.00 15.14 0.00 13.598 0.030 12.961 0.030 12.663 0.029 12.423 0.008 12.418 0.011 12.408 0.041 12.377 0.051 – – Y
LOri061 16.58 0.00 15.15 0.00 13.533 0.023 12.833 0.026 12.525 0.027 12.052 0.006 11.851 0.008 11.519 0.019 10.730 0.015 8.047 0.046 Y
LOri062 16.62 0.00 15.16 0.00 13.634 0.029 13.005 0.030 12.725 0.027 12.370 0.007 12.246 0.009 12.153 0.030 11.306 0.021 7.834 0.035 Y
LOri063 16.80 0.01 15.34 0.00 13.756 0.029 13.066 0.029 12.663 0.030 11.666 0.006 11.368 0.007 11.768 0.028 10.397 0.014 6.055 0.010 Y
LOri064 16.78 0.01 15.34 0.00 13.782 0.026 13.098 0.025 12.846 0.029 12.486 0.008 12.489 0.011 12.378 0.034 12.245 0.053 – – Y
LOri065 16.89 0.01 15.37 0.00 13.820 0.024 13.123 0.029 12.843 0.027 12.526 0.008 12.504 0.011 12.494 0.032 12.641 0.063 8.424 0.075 Y
LOri066 17.12 0.01 15.40 0.00 13.506 0.024 12.901 0.026 12.654 0.029 12.221 0.007 12.170 0.010 12.196 0.039 12.578 0.072 – – Y
LOri067 17.05 0.01 15.53 0.00 14.000 0.033 13.356 0.027 13.102 0.036 12.794 0.010 12.727 0.014 12.702 0.046 12.786 0.071 – – Y
LOri068 16.76 0.01 15.20 0.00 13.521 0.027 12.902 0.026 12.628 0.027 12.348 0.005212.246 0.006212.029 0.016212.145 0.0362– – Y
LOri069 16.89 0.01 15.20 0.00 13.384 0.027 12.774 0.027 12.425 0.027 12.089 0.006 12.015 0.008 12.034 0.026 11.903 0.042 – – Y
LOri070 17.18 0.01 15.61 0.00 14.042 0.032 13.405 0.029 13.067 0.031 12.809 0.009 12.779 0.013 12.799 0.041 12.559 0.060 – – Y
LOri071 17.13 0.00 15.63 0.00 13.749 0.030 13.129 0.024 12.839 0.031 12.470 0.008 12.382 0.010 12.276 0.031 12.250 0.044 – – Y
LOri072 17.00 0.00 15.35 0.00 13.554 0.026 12.944 0.032 12.631 0.027 11.993 0.006 11.860 0.008 11.836 0.026 11.718 0.037 – – Y
LOri073 16.84 0.01 15.28 0.00 13.644 0.028 12.992 0.023 12.715 0.027 12.376 0.007 12.274 0.009 12.187 0.029 12.162 0.031 – – Y
LOri074 17.03 0.01 15.39 0.00 13.663 0.026 13.088 0.025 12.720 0.024 12.312 0.007 12.310 0.010 12.290 0.030 12.259 0.046 – – Y
LOri075 16.95 0.01 15.23 0.00 13.396 0.026 12.794 0.026 12.526 0.024 12.089 0.006 11.990 0.008 11.924 0.026 11.936 0.038 – – Y
LOri076 17.39 0.01 15.81 0.00 14.216 0.027 13.527 0.027 13.201 0.032 12.916 0.010 12.843 0.014 12.669 0.048 12.754 0.072 – – Y
LOri077 17.45 0.00 15.89 0.00 14.031 0.027 13.416 0.027 13.109 0.035 12.761 0.009 12.717 0.012 12.700 0.046 12.650 0.073 – – Y
LOri078 17.35 0.00 15.92 0.00 14.227 0.041 13.593 0.053 13.286 0.040 12.766 0.009 12.844 0.014 12.789 0.046 12.554 0.069 – – Y
LOri079 17.51 0.00 16.00 0.00 14.221 0.032 13.536 0.032 13.338 0.039 13.002 0.006212.970 0.008212.876 0.078212.724 0.0482– – Y
LOri080 17.51 0.00 16.01 0.00 13.804 0.023 13.196 0.022 12.891 0.033 12.504 0.008 12.424 0.010 12.597 0.041 12.190 0.031 – – Y
LOri081 17.61 0.00 16.02 0.00 14.669 0.032 13.692 0.032 13.209 0.037 12.620 0.008 12.360 0.010 12.050 0.030 11.632 0.028 8.062 0.056 Y
LOri082 17.57 0.00 16.02 0.00 14.200 0.033 13.570 0.025 13.281 0.033 13.008 0.011 12.954 0.015 13.586 0.100 12.830 0.100 – – Y
LOri083 17.56 0.00 16.02 0.00 14.265 0.030 13.638 0.035 13.375 0.040 13.012 0.010 12.946 0.013 12.947 0.057 13.017 0.074 – – Y
LOri084 17.48 0.00 16.03 0.00 14.077 0.024 13.448 0.027 13.188 0.034 12.888 0.010 12.800 0.013 12.863 0.061 12.745 0.067 – – Y
LOri085 17.65 0.01 16.04 0.00 14.189 0.026 13.622 0.037 13.233 0.027 12.584 0.008 12.315 0.010 12.090 0.028 11.510 0.029 8.089 0.056 Y
LOri086 17.59 0.00 16.09 0.00 14.482 0.032 13.867 0.032 13.503 0.040 13.251 0.011 13.205 0.016 13.160 0.057 13.277 0.098 – – Y
LOri087 17.54 0.00 16.09 0.00 14.186 0.039 13.601 0.030 13.279 0.035 12.978 0.010 12.894 0.013 13.002 0.064 12.669 0.060 – – Y
LOri088 17.78 0.00 16.10 0.00 14.140 0.031 13.543 0.037 13.228 0.039 12.923 0.009 12.853 0.013 12.865 0.040 12.676 0.051 – – Y
LOri089 17.79 0.00 16.15 0.00 14.380 0.032 13.839 0.035 13.512 0.039 13.156 0.011 13.123 0.015 13.682 0.086 12.877 0.081 – – Y
LOri090 17.77 0.00 16.17 0.00 14.515 0.041 13.881 0.023 13.651 0.051 13.226 0.011 13.116 0.015 12.930 0.047 13.126 0.100 – – Y
LOri091 18.01 0.00 16.18 0.00 14.184 0.032 13.556 0.032 13.289 0.031 12.868 0.009 12.803 0.013 13.087 0.062 12.462 0.054 – – Y
LOri092 17.84 0.00 16.19 0.00 14.441 0.030 13.841 0.038 13.537 0.040 13.158 0.011 13.053 0.014 13.517 0.087 12.992 0.089 – – Y
LOri093 17.82 0.00 16.21 0.00 14.462 0.030 13.836 0.039 13.604 0.052 13.169 0.011 13.104 0.015 13.256 0.073 12.982 0.098 – – Y
LOri094 18.03 0.00 16.28 0.00 14.404 0.034 13.802 0.030 13.425 0.038 12.955 0.009 12.994 0.014 13.184 0.058 12.894 0.085 – – Y
LOri095 17.96 0.00 16.35 0.00 14.564 0.033 13.913 0.029 13.613 0.048 13.247 0.012 13.278 0.017 13.176 0.067 13.340 0.138 – – Y
LOri096 18.02 0.02 16.37 0.00 14.627 0.038 13.965 0.037 13.638 0.047 13.039 0.010 12.732 0.013 12.527 0.045 12.029 0.039 – – Y
Table 3—Continued
Name R error I error J error H error Ks error [3.6] error [4.5] error [5.8] error [8.0] error [24] error Mem1
LOri098 18.12 0.00 16.40 0.00 14.647 0.037 13.985 0.045 13.682 0.039 13.393 0.012 13.301 0.016 13.284 0.075 13.182 0.115 – – Y
LOri099 18.14 0.00 16.42 0.00 14.709 0.034 14.074 0.035 13.676 0.043 13.421 0.013 13.335 0.018 13.211 0.069 13.352 0.124 – – Y
LOri100 18.08 0.00 16.43 0.00 14.768 0.044 14.044 0.042 13.821 0.044 13.446 0.012 13.325 0.017 13.163 0.066 13.318 0.123 – – Y
LOri101 18.14 0.00 16.48 0.00 15.019 0.038 14.372 0.044 14.110 0.066 13.763 0.015 13.627 0.021 13.860 0.105 13.475 0.153 – – N
LOri102 18.24 0.00 16.50 0.00 14.634 0.047 14.083 0.050 13.809 0.057 13.296 0.012 13.213 0.015 13.275 0.073 13.101 0.108 – – Y
LOri103 18.30 0.00 16.55 0.00 14.643 0.029 14.126 0.029 13.833 0.055 13.425 0.013 13.387 0.018 13.140 0.067 13.628 0.151 – – Y
LOri104 18.48 0.03 16.71 0.01 14.667 0.030 14.136 0.036 13.721 0.042 13.143 0.011 12.877 0.014 12.694 0.055 11.762 0.035 – – Y
LOri105 18.58 0.00 16.75 0.00 14.922 0.040 14.340 0.052 13.993 0.053 13.621 0.016 13.593 0.021 13.601 0.093 13.536 0.159 – – Y
LOri106 18.48 0.00 16.76 0.00 14.776 0.043 14.161 0.057 13.743 0.045 13.295 0.012 12.967 0.014 12.558 0.045 11.832 0.034 8.849 0.151 Y
LOri107 18.85 0.00 16.78 0.00 14.656 0.036 13.987 0.035 13.621 0.052 13.213 0.017 13.152 0.019 13.215 0.082 13.046 0.160 – – Y
LOri108 18.64 0.00 16.80 0.00 14.840 0.033 14.256 0.048 13.918 0.050 13.498 0.013 13.464 0.018 13.387 0.073 13.303 0.124 – – Y
LOri109 18.67 0.00 16.81 0.00 14.96 0.01 14.47 0.01 14.18 0.01 13.699 0.015 13.654 0.022 13.519 0.077 13.708 0.190 – – Y
LOri110 18.54 0.00 16.82 0.00 15.043 0.051 14.475 0.056 14.144 0.060 13.798 0.016 13.796 0.026 14.017 0.130 13.454 0.177 – – Y
LOri111 18.88 0.00 16.86 0.00 14.801 0.038 14.165 0.043 13.786 0.051 13.419 0.012 13.330 0.017 13.601 0.082 13.664 0.185 – – Y
LOri112 18.72 0.00 16.87 0.00 14.991 0.042 14.358 0.048 14.148 0.062 13.412 0.013 13.335 0.017 13.334 0.079 13.299 0.145 – – Y
LOri113 18.71 0.00 16.99 0.00 15.18 0.01 14.62 0.01 14.30 0.01 13.723 0.017 13.579 0.021 13.263 0.070 12.448 0.054 – – Y
LOri114 18.99 0.00 17.06 0.00 15.092 0.044 14.389 0.053 14.006 0.064 13.502 0.015 13.414 0.020 13.525 0.096 13.051 0.108 – – Y
LOri115 18.80 0.00 17.08 0.00 15.449 0.047 14.821 0.068 14.594 0.104 14.083 0.017 14.012 0.030 13.942 0.119 13.346 0.131 – – Y
LOri116 19.05 0.01 17.17 0.00 15.343 0.057 14.573 0.055 14.411 0.082 13.977 0.017 13.847 0.024 14.340 0.190 13.614 0.141 – – Y
LOri117 19.24 0.01 17.21 0.00 15.10 0.01 14.36 0.01 14.17 0.01 13.418 0.018 13.102 0.024 13.063 0.105 – – – – Y
LOri118 19.10 0.01 17.23 0.00 15.269 0.044 14.686 0.064 14.181 0.057 13.430 0.013 13.251 0.016 12.844 0.045 12.178 0.043 – – Y
LOri119 19.11 0.00 17.30 0.00 15.26 0.01 14.74 0.01 14.41 0.01 13.568 0.014 13.492 0.019 13.408 0.088 13.590 0.170 – – Y
LOri120 19.23 0.00 17.34 0.00 15.335 0.050 14.770 0.059 14.337 0.087 13.878 0.015 13.688 0.020 13.458 0.086 12.783 0.070 – – Y
LOri121 19.12 0.00 17.37 0.00 15.533 0.060 15.093 0.086 14.748 0.099 14.336 0.019 14.310 0.031 14.053 0.144 – – – – Y
LOri122 19.31 0.00 17.38 0.00 15.428 0.066 14.852 0.060 14.462 0.080 14.096 0.018 13.973 0.027 14.315 0.190 13.659 0.174 – – Y
LOri124 19.30 0.00 17.45 0.00 15.661 0.073 15.059 0.082 14.778 0.112 14.353 0.012214.235 0.018214.303 0.086213.976 0.1262– – Y
LOri125 19.29 0.04 17.51 0.01 15.661 0.073 15.059 0.082 14.778 0.112 14.353 0.012214.235 0.018214.303 0.086213.976 0.1262– – Y
LOri126 19.52 0.01 17.52 0.00 15.62 0.01 15.04 0.01 14.67 0.01 13.709 0.014 13.577 0.021 13.118 0.063 12.352 0.049 – – Y
LOri127 19.87 0.10 17.53 0.01 13.016 0.023 12.606 0.027 12.468 0.024 12.401 0.007 12.348 0.010 12.301 0.033 12.352 0.037 – – N
LOri128 19.53 0.01 17.58 0.00 15.624 0.077 15.099 0.087 14.769 0.109 14.150 0.021 14.115 0.031 14.327 0.254 13.956 0.209 – – Y
LOri129 19.51 0.01 17.59 0.00 15.383 0.056 14.816 0.072 14.526 0.102 13.625 0.014 13.317 0.016 13.194 0.058 12.598 0.057 – – Y
LOri130 19.44 0.01 17.63 0.00 15.731 0.059 15.265 0.092 14.735 0.110 14.408 0.013214.382 0.020214.041 0.077214.348 0.2562– – Y
LOri131 19.79 0.01 17.78 0.00 15.429 0.054 14.900 0.063 14.380 0.090 13.991 0.017 13.909 0.025 13.865 0.119 13.344 0.106 – – Y
LOri132 19.99 0.01 17.82 0.00 15.583 0.067 14.962 0.078 14.913 0.145 14.173 0.019 14.087 0.025 14.076 0.140 13.630 0.129 – – Y
LOri133 19.68 0.01 17.83 0.00 16.290 0.101 15.900 0.167 15.378 0.203 15.066 0.032 14.941 0.041 15.077 0.312 – – – – N
LOri134 19.91 0.01 17.90 0.00 15.543 0.057 14.937 0.074 14.666 0.107 14.321 0.020 14.071 0.027 13.880 0.113 13.884 0.154 – – Y
LOri135 19.91 0.01 17.90 0.00 15.671 0.072 15.082 0.087 14.908 0.138 14.334 0.014214.166 0.018214.171 0.113213.871 0.1082– – Y
LOri136 20.06 0.12 17.92 0.01 15.560 0.085 14.828 0.090 14.576 0.108 14.139 0.016214.224 0.023213.948 0.083213.607 0.1072– – Y
LOri137 19.89 0.08 17.96 0.09 – – – – – – 16.454 0.073 16.789 0.270 – – – – – – N
LOri138 20.01 0.01 17.96 0.00 15.821 0.078 15.204 0.083 14.971 0.133 14.527 0.022 14.469 0.035 14.150 0.123 – – – – Y
LOri139 20.04 0.01 18.16 0.00 16.16 0.01 15.53 0.01 15.06 0.01 14.054 0.017 13.658 0.019 13.151 0.056 12.663 0.062 – – Y
LOri140 20.34 0.01 18.21 0.00 15.981 0.078 15.224 0.089 14.750 0.113 14.030 0.017 13.704 0.023 13.299 0.066 12.786 0.078 – – Y
LOri141 20.44 0.01 18.25 0.00 16.61 0.01 15.89 0.01 15.68 0.02 15.100 0.034 15.668 0.089 – – – – – – N
LOri142 20.34 0.01 18.27 0.00 16.25 0.01 15.58 0.01 15.26 0.01 14.705 0.028 14.674 0.041 – – – – – – Y
LOri143 20.32 0.01 18.30 0.00 16.11 0.01 15.61 0.02 15.23 0.01 14.835 0.015 14.896 0.023 14.765 0.089 14.553 0.126 – – Y
LOri144 20.24 0.11 18.30 0.11 17.69 0.02 16.90 0.02 16.55 0.03 16.476 0.094 16.424 0.184 – – – – – – N?
LOri146 20.88 0.26 18.60 0.02 16.230 0.107 15.470 0.110 14.936 0.128 14.404 0.022214.199 0.035213.836 0.103213.614 0.1752– – Y
LOri147 20.54 0.01 18.60 0.00 16.58 0.02 15.93 0.02 15.62 0.02 15.348 0.023215.675 0.048215.128 0.2242– – – – Y?
Table 3—Continued
Name R error I error J error H error Ks error [3.6] error [4.5] error [5.8] error [8.0] error [24] error Mem1
LOri148 20.77 0.02 18.62 0.00 16.39 0.01 16.12 0.01 15.98 0.02 14.869 0.030 14.989 0.051 14.530 0.210 – – – – Y?
LOri149 21.07 0.02 18.95 0.00 99.99 0.00 88.88 0.00 16.97 0.02 17.135 0.132216.829 0.0992– – – – – – N
LOri150 21.29 0.03 19.00 0.00 16.656 0.152 16.134 0.197 15.560 0.214 15.015 0.032 15.133 0.070 14.942 0.390 – – – – Y
LOri151 20.98 0.02 19.00 0.00 17.40 0.02 16.76 0.02 16.52 0.04 15.801 0.056 15.716 0.103 – – – – – – N
LOri152 21.43 0.04 19.05 0.00 16.773 0.173 16.657 0.295 15.870 0.285 16.313 0.086 16.316 0.158 – – – – – – N?
LOri153 21.30 0.03 19.17 0.00 17.09 0.01 16.37 0.01 16.09 0.03 15.223 0.036 15.139 0.072 – – – – – – Y
LOri154 21.79 0.05 19.31 0.00 16.804 0.169 16.143 0.192 15.513 0.219 15.071 0.035 15.953 0.141 – – – – – – Y
LOri155 21.87 0.06 19.36 0.00 16.97 0.01 16.30 0.01 15.84 0.02 15.085 0.019215.412 0.045214.878 0.163214.517 0.1832– – Y
LOri156 22.05 0.06 19.59 0.01 17.06 0.02 16.34 0.02 15.89 0.02 14.942 0.029 14.688 0.038 14.127 0.148 13.870 0.146 – – Y
LOri157 22.09 0.06 19.63 0.01 18.08 0.03 17.42 0.03 17.00 0.04 16.907 0.103 16.719 0.161 – – – – – – N
LOri158 22.07 0.05 19.67 0.01 18.59 0.03 17.86 0.05 17.61 0.08 17.627 0.123217.565 0.2452– – – – – – N?
LOri159 22.25 0.06 20.01 0.01 18.21 0.02 17.62 0.05 17.47 0.09 16.422 0.089 16.627 0.207 – – – – – – N?
LOri160 22.82 0.13 20.29 0.02 18.11 0.03 17.14 0.02 16.38 0.03 15.669 0.052 15.384 0.079 – – – – – – Y
LOri161 23.09 0.19 20.34 0.01 17.71 0.02 16.90 0.02 16.51 0.03 16.361 0.122 16.451 0.249 – – – – – – Y
LOri162 23.22 0.51 20.42 0.02 17.64 0.03 16.90 0.09 16.52 0.04 15.675 0.062 15.733 0.112 – – – – – – Y
LOri163 22.96 0.24 20.42 0.02 17.86 0.04 17.02 0.08 16.76 0.05 15.666 0.062 15.904 0.119 – – – – – – Y
LOri164 23.11 0.17 20.44 0.01 18.75 0.04 18.17 0.05 18.31 0.13 – – – – – – – – – – N
LOri165 23.12 0.22 20.73 0.02 18.77 0.08 18.11 0.16 17.90 0.09 16.377 0.112 16.130 0.189 – – – – – – N?
LOri166 23.33 0.18 20.75 0.02 18.26 0.03 88.88 0.00 17.38 0.04 16.655 0.055217.232 0.2372– – – – – – Y?
LOri167 23.86 0.64 20.90 0.02 18.01 0.03 17.17 0.07 16.83 0.09 15.935 0.063 16.060 0.129 – – – – – – Y
LOri168 24.15 0.62 21.54 0.04 19.39 0.09 18.58 0.08 18.70 0.25 – – – – – – – – – – N?
LOri169 24.83 1.10 21.88 0.05 20.10 0.10 19.47 0.15 018.93 0.42 – – – – – – – – – – Y?
LOri170 25.41 2.61 22.06 0.07 20.35 0.20 19.20 0.20 019.39 0.46 – – – – – – – – – – N?
1Final membership.
22-pixel aperture radius used for the photometry due to the presence of nearby objects or hot pixels.
∗LOri097 and LOri145 are artifacts. LOri123 is a non member and has uncertainties in its photometry.
Table 4
Candidate members of the Lambda Orionis cluster (Collinder 69)
Name SpT Phot.Mem1 Mem2 Mem3 IRAC classification4 SED slope5 Disk type Comment6
LOri001 – Y Y Y Y Y Y Y Mem Y III -2.8 Diskless Ha- WHa(DM)=2.51 DM#01
LOri002 – Y Y Y Y Y Y Y NM- Y III -2.74 Diskless –
LOri003 – Y Y Y Y Y Y Y Mem Y III -2.71 Diskless Ha- WHa(DM)=3.35 DM#46
LOri004 – Y Y Y Y Y Y Y Mem Y III -2.65 Diskless –
LOri005 – Y Y Y Y Y Y Y NM- Y III -2.75 Diskless –
LOri006 – Y Y Y Y Y Y Y Mem Y III -2.68 Diskless –
LOri007 – Y Y Y Y Y Y Y Mem Y III -2.63 Diskless –
LOri008 – Y Y Y Y Y Y Y Mem Y III -2.56 Diskless Ha- WHa(DM)=1.65 DM#51
LOri009 – Y Y Y Y Y Y Y Mem Y III -2.71 Diskless –
LOri010 – Y Y Y Y Y Y Y Mem Y III -2.69 Diskless –
LOri011 – Y Y Y Y Y Y Y NM- Y III -2.70 Diskless –
LOri012 – Y Y Y Y Y Y Y NM- Y III -2.70 Diskless –
LOri013 – Y Y Y Y Y Y Y Mem Y III -2.66 Diskless Ha- WHa(DM)=4.41 DM#04
LOri014 – Y Y Y Y Y Y Y Mem Y III -2.71 Diskless Ha- WHa(DM)=1.45 DM#58
LOri015 – Y Y Y Y Y Y Y Mem Y III -2.89 Diskless –
LOri016 – Y Y Y Y Y Y Y Mem Y III -2.58 Diskless –
LOri017 – Y Y Y Y Y Y Y Mem Y III -2.72 Diskless Ha- WHa(DM)=0.80 DM#60
LOri018 – Y Y Y Y Y Y Y Mem Y III -2.63 Diskless Ha- WHa(DM)=2.02 DM#56
LOri019 – Y Y Y Y Y Y Y Mem Y III -2.71 Diskless –
LOri020 – Y Y Y Y Y Y Y Mem Y III -2.63 Diskless –
LOri021 – Y Y Y Y Y Y Y Mem Y III -2.76 Diskless Ha- WHa(DM)=1.47 DM#25
LOri022 – Y Y Y Y Y Y Y Mem Y III -2.65 Diskless Ha- WHa(DM)=4.39 DM#44
LOri023 – Y Y Y Y Y Y Y Mem Y III -2.65 Diskless Ha- WHa(DM)=1.95 DM#50
LOri024 – Y Y Y Y Y Y Y Mem Y III -2.67 Diskless –
LOri025 – Y Y Y Y Y Y Y Mem? Y III -2.72 Diskless Ha- WHa(DM)=3.95 DM#59
LOri026 – Y Y Y Y Y Y Y Mem Y III -2.69 Diskless Ha- WHa(DM)=6.07 DM#12
LOri027 – Y Y Y Y Y Y Y Mem Y III -2.68 Diskless –
LOri028 – Y Y Y Y Y Y Y Mem? Y III -2.67 Diskless –
LOri029 – Y Y Y Y Y Y Y NM- Y II -0.72 Thick Ha+ WHa(DM)=30.00 DM#36
LOri030 – Y Y Y Y Y Y Y Mem Y III -2.60 Diskless –
LOri031 M4.0 Y Y Y Y Y Y Y Mem Y III -2.69 Diskless Ha- WHa=3.8 DM#20 WHa(DM)= 3.45
LOri032 – Y Y Y Y Y Y Y Mem Y III -2.64 Diskless Ha- WHa(DM)=6.83 DM#55
LOri033 – Y Y Y Y Y Y Y Mem Y III -2.68 Diskless Ha- WHa(DM)=3.14 DM#39
LOri034 – Y Y Y Y Y Y Y NM- Y II -0.85 Thick Ha+ WHa(DM)=10.92 DM#33
LOri035 – Y Y Y Y Y Y Y Mem Y III -2.70 Diskless Ha- WHa(DM)=4.13 DM#29
LOri036 – Y Y Y Y Y Y Y Mem Y III -2.67 Diskless –
LOri037 – Y Y Y Y Y Y Y Mem Y III -2.67 Diskless Ha- WHa(DM)=3.63 DM#11
LOri038 – Y – Y Y Y – – Mem Y I/II -1.00 Thick Ha+ WHa(DM)=24.95 DM#02
LOri039 – Y Y Y Y Y Y Y Mem Y III -2.65 Diskless Ha- WHa(DM)=3.59 DM#49
LOri040 – Y Y Y Y Y Y Y Mem Y III -2.66 Diskless Ha- WHa(DM)=3.90 DM#41
LOri041 – Y Y Y Y Y Y Y Mem Y III -2.69 Diskless Ha- WHa(DM)=8.20 DM#38
LOri042 M4.0 Y Y Y Y Y Y Y Mem Y III -2.67 Diskless Ha- WHa=4.3 DM#54 WHa(DM)= 4.22
LOri043 – Y Y Y Y Y Y Y Mem Y III -2.69 Transition –
LOri044 – Y Y Y Y Y Y Y Mem Y III -2.65 Diskless –
LOri045 – Y Y Y Y Y Y Y Mem Y II7 -2.68 Diskless –
LOri046 – Y Y Y Y Y Y Y Mem? Y III -2.67 Diskless –
LOri047 – Y Y Y Y Y Y Y Mem Y III -2.68 Diskless Ha- WHa(DM)=8.65 DM#47
LOri048 – Y Y Y Y Y Y Y Mem Y II -2.07 Thin –
LOri049 – Y Y Y Y Y Y Y Mem Y III -3.32 Diskless –
LOri050 M4.5 Y Y Y Y Y Y Y Mem Y II -0.60 Thick 200km WHa=15.6
LOri051 – Y Y Y Y Y Y Y Mem Y III -2.73 Diskless –
LOri052 – Y Y Y Y Y Y Y Mem Y III -2.68 Diskless –
LOri053 – Y Y Y Y Y Y Y Mem Y III -2.68 Diskless –
LOri054 – Y Y Y Y Y Y Y Mem Y III -2.68 Diskless –
LOri055 M4.5: Y Y Y Y Y Y Y Mem Y III -2.68 Diskless Ha- WHa=8.2
LOri056 M4.5: Y Y Y Y Y Y Y Mem Y III -2.68 Diskless Ha- WHa=7.2
LOri057 M5.5 Y Y Y Y Y Y Y Mem Y III -2.62 Diskless Ha- WHa=8.4
LOri058 M4.5: Y Y Y Y Y Y Y Mem Y III -3.16 Diskless Ha- WHa=7.3
LOri059 M4.5 Y Y Y Y Y Y Y Mem Y III -3.23 Diskless Ha- WHa=8.7
LOri060 M4.5: Y Y Y Y Y Y Y Mem Y III -2.79 Diskless Ha- WHa=4.1
LOri061 – Y Y Y Y Y Y Y Mem Y II -1.32 Thick –
LOri062 – Y Y Y Y Y Y Y Mem Y II -1.66 Thick –
LOri063 M4.5: Y Y Y Y Y Y Y Mem? Y I/II -1.58 Thick Ha+FL WHa=12.8
LOri064 – Y Y Y Y Y Y Y Mem Y III -2.54 Thin –
Table 4—Continued
Name SpT Phot.Mem1 Mem2 Mem3 IRAC classification4 SED slope5 Disk type Comment6
LOri065 – Y Y Y Y Y Y Y Mem Y III -2.97 Transition –
LOri066 – Y Y Y Y Y Y Y Mem Y III -3.25 Diskless –
LOri067 – Y Y Y Y Y Y Y Mem Y III -2.83 Diskless –
LOri068 M5.0 Y Y Y Y Y Y Y Mem? Y III -2.57 Diskless Ha+ WHa=16.6
LOri069 – Y Y Y Y Y Y Y Mem? Y III -2.65 Diskless –
LOri070 – Y Y Y Y Y Y Y Mem Y III -2.57 Diskless –
LOri071 M5.0 Y Y Y Y Y Y Y Mem Y III -2.58 Diskless Ha- WHa=8.0
LOri072 – Y Y Y Y Y Y Y Mem? Y III -2.55 Thin –
LOri073 M5.0 Y Y Y Y Y Y Y Mem? Y III -2.59 Diskless Ha+? WHa=12.0
LOri074 – Y Y Y Y Y Y Y Mem? Y III -2.78 Diskless –
LOri075 M5.5 Y Y Y Y Y Y Y Mem? Y III -2.67 Diskless Ha- WHa=9.4 WHa=9.4
LOri076 – Y Y Y Y Y Y Y Mem Y III -2.62 Diskless –
LOri077 M5.0 Y Y Y Y Y Y Y Mem Y III -2.72 Diskless Ha- WHa=8.8
LOri078 – Y Y Y Y Y Y Y Mem Y III -2.58 Diskless –
LOri079 – Y Y Y Y Y Y Y Mem? Y III -2.51 Thin –
LOri080 M5.5 Y Y Y Y Y Y Y Mem Y II -2.55 Thin Ha+? WHa=14.3
LOri081 M5.5 N Y Y Y Y Y Y Mem+ Y II -1.70 Thick Ha- WHa=4.2
LOri082 M4.5 Y Y Y Y Y Y Y Mem+ Y II7 -2.82 Diskless Ha- WHa=8.6
LOri083 – Y Y Y Y Y Y Y Mem Y III -2.85 Diskless –
LOri084 – Y Y Y Y Y Y Y Mem Y III -2.71 Diskless –
LOri085 – Y Y Y Y Y Y Y Mem Y II -1.63 Thick –
LOri086 – Y Y Y Y Y Y Y Mem Y III -2.86 Diskless –
LOri087 M4.5 Y Y Y Y Y Y Y Mem+ Y III -2.54 Thin Ha- WHa=6.7
LOri088 – Y Y Y Y Y Y Y Mem Y III -2.58 Diskless –
LOri089 M5.0 Y Y Y Y Y Y Y Mem Y II -2.50 Thin Ha- WHa=5.1
LOri090 – Y Y Y Y Y Y Y Mem Y III -2.69 Diskless –
LOri091 M5.5 Y Y Y Y Y Y Y Mem Y II -2.48 Thin Ha+? WHa=14.7
LOri092 – Y Y Y Y Y Y Y Mem Y II -2.79 Diskless –
LOri093 – Y Y Y Y Y Y Y Mem Y III -2.68 Diskless –
LOri094 M5.5 Y Y Y Y Y Y Y Mem Y III -2.82 Diskless Ha- WHa=10.4
LOri095 M6.0 Y Y Y Y Y Y Y Mem+ Y III -2.91 Diskless Ha- WHa=7.3
LOri096 – Y Y Y Y Y Y Y Mem Y II -1.71 Thick –
LOri098 M5.0 Y Y Y Y Y Y Y Mem+ Y III -2.61 Diskless Ha- WHa=12.9
LOri099 M5.25 Y Y Y Y Y Y Y Mem Y III -2.74 Diskless Ha- WHa=6.6
LOri100 M5.5 Y Y Y Y Y Y Y Mem Y III -2.67 Diskless Ha+? WHa=13.1
LOri101 – N N ? ? Y Y Y Mem? N III -2.6 Diskless –
LOri102 – Y Y Y Y Y Y Y Mem? Y III -2.65 Diskless –
LOri103 – Y Y Y Y Y Y Y Mem? Y III8 -2.31 Thin –
LOri104 – Y Y Y Y Y Y Y Mem Y II -1.30 Thick –
LOri105 – Y Y Y Y Y Y Y Mem Y III -2.75 Diskless –
LOri106 M5.5 Y Y Y Y Y Y Y Mem Y II -1.16 Thick Ha+ WHa=54.0
LOri107 M6.0 Y Y Y Y Y Y Y Mem+ Y III -2.68 Diskless Ha- WHa=11.7
LOri108 – Y Y Y Y Y Y Y Mem Y III -2.61 Diskless –
LOri109 M5.5 Y Y Y Y Y Y Y Mem Y III -2.82 Diskless Ha- WHa=10.1
LOri110 M5.5 Y Y Y Y Y Y Y Mem Y II -2.52 Thin Ha- WHa=9.1
LOri111 – Y Y Y Y Y Y Y Mem Y III -3.19 Diskless –
LOri112 – Y Y Y Y Y Y Y NM- Y III -2.72 Diskless –
LOri113 M5.5 Y Y Y Y Y Y Y Mem Y II -1.37 Thick Ha+ WHa=22.0
LOri114 M6.5 Y Y Y Y Y Y Y Mem+ Y II -2.38 Thin Ha- WHa=10.9
LOri115 M5.0 Y Y Y Y Y Y Y NM+ Y II -2.02 Thin Ha- WHa=8.5
LOri116 M5.5 Y Y Y Y Y Y Y Mem+ Y II -2.43 Thin Ha- WHa=11.1
LOri117 M6.0 Y Y Y Y Y Y Y Mem Y – -2.20 Thin Ha+? WHa=22.9
LOri118 M5.5 Y Y Y Y Y Y Y Mem+ Y II -1.37 Thick Ha- WHa=10.1
LOri119 M5.5 Y Y Y Y Y Y Y NM? Y III -2.85 Diskless Ha+? WHa=12.7
LOri120 M5.5 Y Y Y Y Y Y Y Mem+ Y II -1.59 Thick Ha- WHa=7.4
LOri121 – Y Y Y Y ? Y Y NM- Y – -2.31 Thin –
LOri122 – Y Y Y Y Y Y Y Mem Y II -2.46 Thin –
LOri124 M5.5 Y Y Y Y Y Y Y Mem? Y III -2.56 Diskless Ha- WHa=8.4
LOri125 – Y Y Y Y Y Y Y NM- Y III -2.56 Diskless –
LOri126 M6.5 Y Y Y Y Y Y Y Mem+ Y II -1.24 Thick Ha+? WHa=26.2
LOri127 – N N N N N N N NM- N III -2.78 Diskless –
LOri128 – Y Y Y Y Y Y Y Mem? Y III -2.69 Diskless –
LOri129 M6.0 Y Y Y Y Y Y Y Mem? Y II -1.71 Thick Ha+? WHa=12.1
LOri130 M5.5 Y Y Y Y Y ? Y Mem+ Y III -2.69 Diskless Ha- WHa=8.7
Table 4—Continued
Name SpT Phot.Mem1 Mem2 Mem3 IRAC classification4 SED slope5 Disk type Comment6
LOri131 – Y Y Y Y Y Y Y Mem? Y II -2.12 Thin –
LOri132 – Y Y Y Y Y Y N NM- Y II -2.25 Thin –
LOri133 M4.5 N N N ? ? N Y NM+ N – -2.91 Diskless –
LOri134 M5.0 Y Y Y Y ? ? Y NM+ Y III -2.34 Thin –
LOri135 M7.0 Y Y Y Y Y Y ? Mem? Y III -2.56 Diskless Ha- WHa=15.5
LOri136 – Y Y Y Y Y Y Y Mem? Y III -2.17 Thin –
LOri137 – – – N N – – – ? N – – – –
LOri138 – Y Y Y Y Y Y Y NM- Y – -2.13 Thin –
LOri139 M6.0 Y Y Y Y Y Y Y Mem+ Y II -1.22 Thick Ha+? WHa=19.7
LOri140 M7.0 Y Y Y Y Y Y Y Mem+ Y II -1.40 Thick Ha+ WHa=72.8
LOri141 M4.5 N N ? N Y Y Y NM+ N – -5.35 Diskless –
LOri142 – Y Y Y Y Y Y Y Mem? Y – – – –
LOri143 M6.5 Y Y Y Y Y Y Y Mem+ Y III -2.59 Diskless Ha+ WHa=35.7
LOri144 – N N N N N N Y ? N? – – – –
LOri146 – Y Y Y Y Y Y Y Mem Y III -1.90 Thin –
LOri147 M5.5 Y Y ? N ? N Y NM+ Y? – -2.41 Thin –
LOri148 – Y N Y Y Y Y N NM- Y? – -2.19 Thin –
LOri149 – – N N N – N – ? N – – – –
LOri150 M8.0 Y Y Y Y Y Y Y Mem+ Y – -2.72 Diskless Ha- WHa=15.6
LOri151 M5.5 N N N ? Y Y Y NM? N – – – –
LOri152 – Y Y N N N N Y NM- N? – – – –
LOri153 – ? Y Y Y Y Y Y ? Y – – – –
LOri154 M8.0 Y Y Y ? Y Y Y Mem+ Y – – – Ha- WHa=16.9
LOri155 M8.0 Y Y Y Y Y Y Y Mem+ Y III -2.03 Thin Ha+? WHa=38.0
LOri156 M8.0 Y Y Y Y Y Y Y Mem+ Y III -1.54 Thick Ha+ WHa=101.7
LOri157 – N N N N N N Y ? N – – – –
LOri158 – N N N N N N Y ? N? – – – –
LOri159 – N N N N Y Y N ? N? – – – –
LOri160 – N Y Y Y Y Y Y ? Y – – – –
LOri161 M8.5 Y Y Y Y Y Y Y Mem+ Y – – – Ha+ WHa=123
LOri162 – Y Y Y Y Y Y Y ? Y – – – –
LOri163 – Y Y Y Y Y Y Y ? Y – – – –
LOri164 – N N – – – – N ? N – – – –
LOri165 M7.5 N N Y Y Y Y ? NM? N? – – – –
LOri166 – ? ? Y N Y Y ? ? Y? – – – –
LOri167 – Y Y Y Y Y Y Y ? Y – – – –
LOri168 – N N – – – – Y ? N? – – – –
LOri169 – N N – – – – – ? Y? – – – –
LOri170 – N N – – – – – ? N? – – – –
1Membership is Ivs(I-J); Ivs(I-K); Ivs(I-3.6); Ivs(I-4.5); Jvs(J-3.6);Kvs(K-3.6); Jvs(J-K).
2Membership as in Paper I.
3Final membership.
4Classification as measured in the IRAC CCD –[3.6]-[4.5] versus [5.8]-[8.0]. Class III stands for diskless
members and Class II are Classical TTauri stars or substellar analogs.
5IRAC slope. Lada et al. (2006) classified the objects according to their IRAC slope: α <-2.56 for a diskless
object, -2.56< α <-1.80 for a transition object, and α >-1.80 for objects bearing optically thick disks
6Ha+ = W(Halpha) above the saturation criterion.
Ha- = W(Halpha) below the saturation criterion.
200km = width of Halpha equal or larger than this value.
WHa(DM) = from Dolan & Mathieu
Probably diskless objects. The different results on IRAC CCD and IRAC slope are probably
due to an uncertain measure at 5.8 µm.
Probably a class II source with an uncertain measure at 8.0 µm.
Table 5
Location of the substellar frontier, using models by Baraffe et al. (1998) and a distance
of 400 pc. Values such as 340 or 450 pc would modify the listed magnitudes by −0.35 and
+0.26, respectively. We have included an interstellar reddening of E(B − V )=0.12,
equivalent to AI=0.223, AJ=0.106, AK=0.042, AL=0.022
Age (Myr) Ic J Ks L′
1 16.72 14.35 13.32 12.88
3 17.18 14.87 13.84 13.40
5 17.55 15.36 14.35 13.92
8 17.92 15.80 14.80 14.36
10 18.13 16.01 15.01 14.57
16 18.52 16.40 15.40 14.96
20 18.71 16.59 15.60 15.15
Fig. 1.— Spitzer/IRAC CCD. Class I/II (big empty circles, magenta), Class II (big empty circles, red) and
Class III –or not members– (crosses) have been classified using this diagram (After Allen et al. (2004) and
Hartmann et al. (2005)).
Fig. 2.— Optical/IR Color-Magnitude Diagram. Non-members appear as dots. Class II sources (Classical
TTauri stars and substellar analogs) have been included as big (red) circles, whereas Class III (Weak-line
TTauri) objects appear as crosses, and other Lambda Orionis members lacking the complete set of IRAC
photometry are displayed with the plus symbol. The figure includes 1, 3, 5, 10, 20, 50, and 100 Myr isocrones
from Baraffe et al. (1998) as solid lines, as well as 5 Myr isochrones corresponding to dusty and COND
models (Chabrier et al. 2000; Baraffe et al. 2002), as dotted and dashed lines.
Fig. 3.— Near-IR and Spitzer Color-Magnitude Diagram. Class II sources (Classical TTauri stars and
substellar analogs) have been included as big (red) circles, whereas Class III (Weak-line TTauri) objects
appear as crosses, and other Lambda Orionis members lacking the complete set of IRAC photometry are
displayed with the plus symbol. The figure includes 1, 5, 10, 20, and 100 Myr isochrones from Baraffe et al.
(1998) as solid lines, as well as 5 Myr isochrones corresponding to dusty and COND models (Chabrier et al.
2000; Baraffe et al. 2002), as dotted and dashed lines. Note that in the last panel we have the the L and M
data for the NextGen models, since Spitzer photometry has not been computed for this set of models.
Fig. 4.— Optical Color-Magnitude Diagram with the CFHT magnitudes and our new membership classifi-
cation. Symbols as in previous figures.
Fig. 5.— Spitzer/IRAC CCD for Class II objects. We have included information regarding the Hα emission.
Fig. 6.— Spectral Energy Distributions for some stellar members of the Lambda Orionis cluster sorted
according to their IRAC slope: simple photosphere spectra. Objects lacking IRAC slope or being in the
boundary between two types have been classified after visual inspection.
Fig. 7.— Spectral Energy distribution for some stellar members of the Lambda Orionis cluster sorted
according to their IRAC slope: flat, or sloping IR spectra with the excess starting in the near-IR (thick
disks).
Fig. 8.— Spectral Energy distribution for some stellar members of the Lambda Orionis cluster sorted
according to their IRAC slope: spectra with excesses begining in the IRAC or MIPS range (thin disks and
transition objects). LOri043 and LOri065 were classified as diskless objects but have been sorted as objects
bearing thin disks due to their excess at MIPS [24].
Fig. 9.— The fraction of Class II stars and massive brown dwarfs in several SFRs and young clusters (filled
squares). Open squares stand for thick disk fractions of IC348 and C69.
Fig. 10.— Spitzer/IRAC CCD. We show with different symbols (see key) cluster members with different
types of disks.
Fig. 11.— a) Spatial distribution of our sample. IRAS contour levels at 100 microns also have have been
included as solid (magenta) lines. The big, thick-line rectangle corresponds to the CFHT survey (Paper I).
Class II sources (Classical TTauri stars and substellar analogs) have been included as big (red) circles,
whereas Class III (Weak-line TTauri) objects appear as crosses, and other Lambda Orionis members lacking
the complete set of IRAC photometry are displayed with the plus symbol. b) Spatial distribution of the
low mass stars from Dolan & Mathieu (1999, 2001). OB stars appear as four-point (blue) stars, with size
related to magnitude (the bigger, the brighter). The overplotted thick triangles indicates those stars whose
Hα equivalent width is larger than the saturation criterion defined by Barrado y Navascués & Mart́ın (2003),
thus suggesting the presence of active accretion. Based on Hα alone, the fraction of accreting stars would
be 11%.
Fig. 12.— Spitzer/IRAC image at 3.6 micron centered around the star λ Orionis. a) The size is about
9×9 arcmin, equivalent to 192,000 AU. The double circle indicates the presence of a Class II object, whereas
squares indicate the location of cluster members from Dolan & Mathieu (1999;2001). The intensity of the
image is in logarithmic scale. b) Detail around the star λ Orionis. The size is about 3.3×3.3 arcmin,
equivalent to 80,000 AU. c) Distribution of bona-fide brown dwarfs. The size of the image is 45×30 arcmin.
North is up, East is left.
Fig. 13.— Spitzer/MIPS image at 24 microns which includes the members of the Lambda Orionis cluster
visible at this wavelength, including those cluster members by Dolan & Mathieu (1999, 2001) as big circles
and CFHT member as small circles detected at this wavelength. The size is about 60.5×60.5 arcmin. North
is up, East is left. The figure is centered on the star λ Ori AB.
	Introduction
	The data
	Optical and Near Infrared photometry
	New deep Near Infrared photometry
	Spitzer imaging
	Data cross-correlation
	Color-Color and Color-Magnitude Diagrams and new membership assignment
	Discussion
	The Color-Color diagrams, the diagnostic of IR excess and the disk ratio
	The Spectral Energy Distribution
	The Spatial distribution of the members
	Conclusions
