Low mass visual binaries in the solar neighbourhood: The case of
  HD141272
Astron. Nachr. / AN Volume, No. Issue, 0 – 5 (Year of publication) / DOI DOI
Low mass visual binaries in the solar neighbourhood:
The case of HD141272⋆
T. Eisenbeiss1 ⋆⋆, A. Seifahrt1,2, M. Mugrauer1, T. O. B. Schmidt1, R. Neuhäuser1, and
T. Roell1
1 Astrophysikalisches Institut und Universitäts-Sternwarte Jena, Schillergässchen 2-3, 07745 Jena, Germany
2 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748, Garching, Germany
Received 15.08.06, accepted 29.03.07
Published online . . .
Key words binaries: visual – stars: late-type, low mass – astrometry
We search for stellar and substellar companions of young nearby stars to investigate stellar multiplicity and
formation of stellar and substellar companions. We detect common proper-motion companions of stars via
multi-epoch imaging. Their companionship is finally confirmed with photometry and spectroscopy. Here we
report the discovery of a new co-moving (13σ) stellar companion ∼ 17.8 arcsec (350AU in projected sepa-
ration) north of the nearby star HD141272 (21 pc). With EMMI/NTT optical spectroscopy we determined
the spectral type of the companion to be M3±0.5V. The derived spectral type as well as the near infrared
photometry of the companion are both fully consistent with a 0.26+0.07−0.06M⊙ dwarf located at the distance
of HD141272 (21 pc). Furthermore the photometry data rules out the pre-main sequence status, since the
system is consistent with the ZAMS of the Pleiades.
c© Year of publication WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim
1 Introduction
HD141272 is a nearby G8 dwarf with a mass of
0.83+0.07
−0.03M⊙ (Nordström et al. 2004) located in the
constellation Serpens Caput (αJ2000.0 = 15
h 48m 09.4s,
δJ2000.0 = +01
◦ 34′ 18′′). Its proper motion (µα cos δ =
−176.19 ± 1.08mas/yr, µδ = −166.72 ± 1.13mas/yr)
and parallax (π = 46.84± 1.05mas, i.e. 21 pc) are both
well determined by the European astrometry satellite
Hipparcos (Perryman et al. 1997). While Montes et al.
(2001) list HD 141272 as a member of the Local asso-
ciation with an age of ∼ 120Myr (Mart́ın et al. 2001),
Fuhrmann (2004) suggested that this star belongs to
the young Her-Lyr moving group, according to its UV-
velocities. The age of some Her-Lyr members is esti-
mated by Fuhrmann (2004) to approximately 100Myr
(e.g. HR857, HD 82443, HD113449 and HR5829) which
recently reached their main sequence position, while
others seemed to be older than ∼ 200Myr
(Fuhrmann 2004). Also Fuhrmann (2004) argued that
HD141272, with an effective temperature of Teff =
(5270±80)K, an absolute bolometric magnitudeMbol =
(5.54±0.07)mag and metallicity of [Fe/H ] = (−0.08±
0.07) dex appears slightly too bright for its main se-
quence position, indicating that it might be non single
or young.
⋆ Based on observations obtained on La Silla in ESO programs
77.C-0572(A) and Calar Alto project number F06-3.5-016.
⋆⋆ E-mail: eisen@astro.uni-jena.de
On the other hand Gaidos, Henry & Henry (2000)
measured a Fe corrected Li-equivalent width ofW6708 =
3.9 ± 1.9mÅ and a rotational velocity of
v sin i ≈ 4.0 km/s, which might be too small for a
100Myr old star. Furthermore Chen et al. (2005) ob-
served HD141272 using the infrared space telescope
Spitzer and did not find any IR-excess at 24µm and
70µm indicating that HD141272 is not surrounded by
an optically thick disk.
Finally López-Santiago et al. (2006) revised the list
of Her-Lyr members and candidates of Fuhrmann (2004)
and classified HD141272 as an doubtful member, due
to its lithium depletion.
In our program we search for companions to Her-
Lyr members and candidates and first results are pre-
sented here. We found a co-moving companion of
HD 141272 by a combination of archival first epoch im-
ages and recent observations. We present our imaging,
the astrometric data and reduction techniques in sec-
tion 2 and 3, followed by a description of the spectro-
scopic and photometric analysis of the new companion
in section 4. The results are discussed in section 5.
2 Archival first epoch data
Astrometry is an effective method to find companions
of stars, by comparing two images taken with suffi-
ciently long epoch difference. In order to find late-type
stellar and substellar objects, we concentrate our search
c© Year of publication WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim
http://arxiv.org/abs/0704.0387v1
Astron. Nachr. / AN (Year of publication) 1
Fig. 1 POSS-I E image of HD141272 from 17 June
1950. The star is located at αJ2000.0 = 15
h 48m 09.4s,
δJ2000.0 = +01
◦ 34′ 18′′. A faint object is located in the
north of HD141272, which is hardly recognizable due
to the diffraction spikes of the primary star induced by
saturation. With a pixel size of ∼ 10microns the pixel
scale of the plate is ∼ 6.72 arcsec/pixel.
on companions of young stars. Young objects are still
in contraction and are brighter than older objects of
the same mass hence, low mass objects are easier to
detect.
We found HD141272 in three epochs of the Super-
COSMOS-Sky-Survey, namely a POSS-I (Palomar Ob-
servatory Sky Survey) plate from 1950, as well as in
UKST (United Kingdom Schmidt Telescope) infrared
and red observations from 1981 and 1992. On all three
plates we detected by eye inspection a faint object,
located approximately 18 arcsec north of HD141272,
which was not detected by the SuperCOSMOS ma-
chine due to its small angular separation to the much
brighter star and due to its overlap with the diffraction
spike (Fig. 1).
The diffraction spike of HD141272 intersects the
northern object on all three plates hence, the detec-
tion of this object would be inaccurate by means of
most common detection techniques. Nevertheless, we
obtained a position measurement of the companion can-
didate on the POSS-I plate, using the Source Extractor
package (Bertin & Arnouts 1996), included in the Star-
link application GAIA (Gray et al. 2004). The source
extractor uses thresholding and deblending of point-
spread functions hence the method is more accurate
than other detection techniques (e.g. Gaussian fitting)
under the circumstances in Fig. 1. However, an system-
atical error is possible, due to the perturbation of the
primary’s spike. This error is larger in right accession
than in declination and would affect the measurement
of the position angle rather than the separation (see
section 3, Fig. 4), due to the orientation of the system
(Fig. 1 and 3).
Due to its brightness HD141272 saturates the POSS-
I plate. Furthermore the PSF (point spread function)
is contaminated by the stray light of the companion
candidate hence, position measurement via PSF cen-
tering does not work sufficiently. We used the diffrac-
tion spikes of the saturated primary to determine its
position, since they are unaffected by the companion.
We determined the intensity center of a spike taking
∼ 30 measurements for each spike using the data re-
duction and analysis package ESO-MIDAS. The appli-
cation of a linear regression gives the position of the
star as intersection of the two spikes and leads to very
small astrometric uncertainties (∆αH = 0.047 arcsec
and ∆δH = 0.050 arcsec).
In addition to the detection on the POSS-I plate
HD 141272 and its companion-candidate are also de-
tected in 2MASS images from observing epoch 2000.
The 2MASS point source catalog (Cutri et al. 2003)
lists the position of both objects with accurate astro-
metric precision, see Tbl. 1.
Equipped with these data we determined the proper
motion of all stars in a 15 arcmin box around HD141272
which are detected at the POSS-I plate and listed in
the 2MASS point source catalog (see Fig. 2). We de-
rived the proper motion of all stars in the field by
comparing the positions of all detected objects. The
majority of sources only shows small proper motion
following a normal distribution, since these stars are
most probably at high distances. Using the Lilliefors
test for normal distribution we derived the subsample
of stars belonging to the background stars, since their
proper motion follows a normal distribution (non mov-
ing background stars). The standard deviation of the
background stars gives the statistically derived proper
motion error (σp.m., α = 8.8mas/yr, σp.m., δ = 6.8
mas/yr). Objects not belonging to the background stars
are considered as companion candidates, if they are ly-
ing within a 5-σ vicinity of HD141272 (ellipse in Fig. 2).
Other objects are omitted, since these are either false
detections or high-proper-motion stars moving in other
directions.
The proper motion of the nearby star HD141272
is clearly separated from the background stars. The
companion candidate clearly shares the proper motion
of HD 141272 and will be denoted HD141272B, here-
after. Fig. 2 shows with high confidence (∼ 13σ) that
HD141272A and B are co-moving over roughly 50 years.
Due the above discussed astrometric uncertainties of
HD 141272B this analysis gives a first indication of a
new nearby young double star system
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2 T. Eisenbeiss et al.: Low mass visual binaries in the solar neighbourhood: The case of HD141272
−300−250−200−150−100−50050
∆ Ra/Year [mas/yr]
standard error 
search radius 
HD141272 
companion 
candidate 
non moving background stars 
Fig. 2 Proper motion plot of HD141272 (cross) and
its companion candidate (circle) and non moving back-
ground stars (upper left). X- and Y-axis show the
change of the positions (in mas/yr). The plot is based
on POSS-I Schmidt plate (17 June 1950) and 2MASS
catalog data (29 April 2000). Error estimates are taken
as 2-σ errors from the background stars. Data points
lying outside the background stars and outside a 5-σ
vicinity of HD141272 (large ellipse) are omitted, since
these are either false detections or high proper motions
stars moving in other directions. The statistical error
of all data points is shown by the thick error cross in
the lower left. The diagram shows the common proper
motion of HD141272 and its new companion with a
confidence of ∼ 13σ.
Moreover, we used the non-moving background stars
to estimate the positional error of the detections in the
POSS-I plate. The mean of the distribution shows the
systematic error of the POSS-I measurements (∆sys, α =
−4.5mas/yr and ∆sys, δ = −4.9mas/yr as offset to
(0, 0). The whole set of data points in Fig. 2 is shifted
by that offset to correct for calibration errors between
POSS-I and 2MASS data. The standard deviation shows
the statistical measurement error (∆stat = σp.m.) hence,
can be applied as standard detection error. The total
detection error derived for the POSS-I plate is ∆α =
0.29 arcsec and ∆δ = 0.25 arcsec. The additional sys-
tematic error for the companion candidate due to the
diffraction spike of HD141272 is not included in this
error analysis.
Fig. 3 H-band image of HD 141272 and its compan-
ion candidate taken with the near infrared camera Ω-
Cass at the 3.5m telescope of the Calar Alto obser-
vatory in Spain. The separation between HD141272
and its companion candidate is ∼ 17.8 arcsec at a
position angle of ∼ 352.62◦ with a pixel scale of ∼
0.2 arcsec/pixel. Note that HD141272 is slightly satu-
rated.
3 Follow-up observations
In order to get a third epoch on our astrometric re-
sult and to detect or rule out further companions we
observed HD141272 again in April 2006 (Fig. 3). We
carried out H-band as well as narrow-band observations
(1.644µm) with the near infrared camera Ω-Cass, in-
stalled at the Cassegrain focus of the 3.5m telescope of
the Calar Alto observatory in Spain. Ω-Cass is equipped
with a 1024 × 1024 HgTeCd-detector with a pixel scale
of ∼0.2 arcsec per pixel. We always used the short-
est possible detector integration time (0.84 s) to limit
strong saturation effects due to the bright star. For
background subtraction we applied the standard jitter
technique and chose 12 jitter-positions. On each jitter
position 49 integrations (0.84 s) were co-added, yield-
ing a total integration time in the H-band of 8.2min.
All images were flatfielded with a skyflat image taken
during twilight. The whole data reduction (background
subtraction, flatfielding, and shift+add) was carried out
with the ESO data-reduction package Eclipse (Devil-
lard 2001).
We calibrated our Ω-Cass image for relative astrom-
etry, using the well known binary systems HIP 63322
and HIP 82817, which we observed during the same
night and with the same instrumentation as our sci-
ence image. Using the Hipparcos astrometry (Perry-
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Astron. Nachr. / AN (Year of publication) 3
Table 1 Separation and position angle of the co-moving companion HD141272B relative to its primary
HD141272A for all observing epochs. We also show the expected change of separation and position angle in
case that the companion is a non-moving background source, derived with the well known proper and parallactic
motion of the primary.
epoch telescope/ pixel scale band sepobs. sepifback PAobs. PAifback
[dd/mm/yyy] catalogs [arcsec] [arcsec] [arcsec] [◦] [◦]
17/07/1950 POSS-I 1.0 E (6442Å) 17.85±0.31 − 353.6±1.1 −
29/04/2000 2MASS 0.7 JHKS 17.83±0.150 26.92±0.33 352.42±0.48 14.61±0.75
20/04/2006 3.5m CA 0.2 H 17.851±0.041 28.12±0.31 352.62±0.18 16.48±0.68
man et al. 1997) and considering the maximal orbital
motion of the calibration binaries we estimated the
pixel scale (192 ± 0.43mas/pixel) and the orientation
(−1.86±0.18 ◦) of the Ω-Cass images. This yields to the
relative astrometric parameters of the system (Tbl. 1).
For the detection of both objects we used the Gaussian
centroiding technique, implemented in ESO-MIDAS.
Further co-moving companions could be ruled out
around HD141272 within an angular separation of ∼ 5
to 73 arcsec (1500AU of projected separation) with H-
band magnitudes down to 18.3mag (S/N= 3).
HD 141272A and B are separated by ∼ 17.8 arcsec
(Fig. 3), hence the projected separation of the system
is approximately 380AU and its orbital period can be
estimated with Kepler’s third law to be roughly 7000
years (we use 0.83M⊙ for HD 141272A and 0.26M⊙
for B). During 56 years of epoch difference between
the POSS-I and our H-band observation, this yields
maximal orbital motion as large as ∼0.5 arcsec in sep-
aration (edge-on orbit assumed) or ∼3◦ in position an-
gle (face-on orbit assumed). Therefore, we derived the
separation and the position angle of the companion for
all three observing epochs which are summarized in
Tab. 1. These results are also visualized in Fig. 4. Note
that absolute calibrated astrometric data, derived for
the POSS-I image as described in section 2, as well as
catalog data from the 2MASS catalog is used in Fig. 4,
while the third epoch data is based on relative astrom-
etry, hence the uncertainties of that data point are sig-
nificantly smaller.
While the separation between HD141272A and B
did not change during 56 years, we found a slight de-
crease of its position angle. This effect is most likely
due to the perturbation of the companions PSF by the
diffraction spike of the primary (see section 2 and Fig.
1). Nevertheless Fig. 4 ensures the companionship of
HD 141272B, since all data points are lying within the
given error bars of the first epoch.
4 Photometry and Spectroscopy
The infrared colors of both components of the new bi-
nary system HD141272AB are listed in the 2MASS
point source catalog, i.e. accurate J, H, and KS band
2.43 2.44 2.45 2.46
JD−2400000.5
2.43 2.44 2.45 2.46
JD−2400000.5
Fig. 4 Separation (sep) and position angle (PA) for
HD 141272A and B from 1950 to 2006 (three data
points). Upper lines show the changes of the proper-
ties under the assumption HD141272B was a back-
ground star (including parallactic motion of A) while
the straight, opening lines give the range of the bi-
nary movement, considering maximal orbital move-
ment. While the separation stays approximately con-
stant there is a change in the position angle, caused
by the perturbation of the companions PSF due to the
diffraction spikes of the primary.
Table 2 2MASS Photometry of HD141272A and B
Comp. J H KS
[mag] [mag] [mag]
A 5.991±0.021 5.610±0.027 5.501±0.018
B 9.298±0.020 8.725±0.055 8.456±0.023
photometry is available for the primary and its co-
moving companion, which is summarized in Tab. 2. Ad-
ditionally the I-band magnitude of both components
(mI = 8.59 ± 0.02mag for A and mI = 10.572 ±
0.02mag for B) is measured in the second release of the
DENIS database, while the accuracy for HD141272A
is limited due to saturation effects, hence the given er-
ror is probably underestimated.
In order to obtain also unsaturated images of the
primary we observed the binary system with Ω-Cass
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4 T. Eisenbeiss et al.: Low mass visual binaries in the solar neighbourhood: The case of HD141272
in the FeII (1.644µm) narrow-band filter. Thereby, we
used again the 12 point jitter pattern but co-added 15
integrations (4 s) per jitter position, yielding a total in-
tegration time of 12min. The bright primary as well as
its fainter co-moving companion are both well detected
in this narrow-band image and their fluxes did not ex-
ceed the linearity level of the Ω-Cass detector. Hence,
we could use this image to derive the magnitude differ-
ence between the primary star and its companion and
obtained ∆HFeII = 3.166± 0.005mag, fully consistent
with the magnitude difference derived from the 2MASS
data in H-band (∆H = 3.115± 0.061mag.)
Furthermore we acquired a low-resolution optical
spectrum with EMMI at the NTT on La Silla to de-
termine the spectral type of HD141272B and prove its
common distance with HD141272A. The spectrum was
taken in RILD and REMD mode covering a wavelength
of 400-900nm with a resolution of R ≈ 3000 at 600nm.
The data reduction followed the standard procedure for
low-resolution optical spectra: After bias subtraction,
flat fielding and wavelength calibration with a HeAr arc
spectrum we corrected for the instrumental response
and for telluric features using a spectrum of HR5501
taken at the same airmass as HD141272B.
We determined the spectral type by comparing our
spectrum with a standard sequence of M dwarfs in the
same spectral range and with comparable spectral res-
olution (Bochanski et al. 2006), see Fig. 5. The best
fit resulted in a spectral type of M3.25 ± 0.25 which
is consistent with a spectral type of M3.0± 0.5 deter-
mined from the TiO5 spectral index of 0.49 following
Cruz & Reid (2002).
Adopting the latter spectral type as final we derived
a spectrophotometric distance of 24.4±4.2 pc from the
MJ relation given in Cruz & Reid (2002) and the J
magnitude from 2MASS, assuming that the companion
is on the Main sequence. The determined distance is in
excellent agreement with the HIPPARCOS measured
distance of 21.35±0.48 pc for HD 141272A, confirming
their common distance. Hence, we call the companion
HD141272B.
5 Conclusions
With the astrometric data reduction and analysis tech-
niques presented in this work, we could verify the com-
mon proper motion of both components of the binary
system HD141272AB during 56 years of epoch differ-
ence between the first successful observation of this sys-
tem on the POSS-I plates taken in July 1950 and our
H-band imaging obtained with Ω-Cass in April 2006.
Furthermore we obtained an optical spectrum of the
companion and derived its spectral type to range be-
tween M2.5V and M3.5V. The infrared apparent mag-
nitudes of the co-moving companion are fully consis-
tent with a M3 dwarf which is located at the distance
400 500 600 700 800 900
HD 141272 B
Wavelength [nm]
Fig. 5 Relative flux of the spectral sequence from
M1 to M5 (Bochanski et al. 2006) in comparison to the
EMMI spectrum of HD141272B, ranging from 400 to
900 nm. The resolutions are comparable (R ∼ 3000 for
the EMMI spectrum and R ∼ 6000 for the standard
spectra at 600 nm). HD 141272B shows good agree-
ment with an M3 star.
of HD141272A which finally confirms the companion-
ship of this new binary system. The companion is an
addition to the Catalog of Nearby Stars within 25 pc
(Gliese & Jahreiß 1991).
In order to get an estimation of the system age we
compared the infrared photometry of HD 141272A and
B with ≈ 1300 members of the Pleiades cluster which
are listed in the WEBDA database (Mermilliod 1998).
All objects are plotted in a J-K vs. MH color-magnitude
diagram (Fig. 6). The colors of all objects are obtained
from the 2MASS catalog and we derived the absolute
H-Band magnitudes of all comparison stars using their
2MASS H-band photometry and a mean distance mod-
ule of the Pleiades of 5.97mag (WEBDA database).
The expected distance uncertainty of the cluster mem-
bers which results in an uncertainty of their absolute H-
band magnitudes was approximated with the angular
diameter of the Pleiades cluster on the sky, assuming a
similar extension of the cluster also in the radial direc-
tion. The absolute H-band magnitudes of HD141272A
and B are derived with 2MASS photometry and the
Hipparcos parallax of the binary system. Compared to
the Pleiades of the same J-K color HD141272A and
B appear a little fainter, indicating that the system is
already on the ZAMS, which is similar to the results of
earlier works (Gaidos 1998; Wright et al. 2004).
If we assume that both components of the binary
system have already reached the ZAMS we can deter-
mine the mass of the secondary using equation (11)
from Kirkpatrick & McCarthy (1994) with the given
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Astron. Nachr. / AN (Year of publication) 5
−0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
J−K [mag]
0.75 0.8 0.85 0.9 0.95 1
J−K [mag]
HD 141272 A 
HD 141272 B 
Fig. 6 J-K vs. MH diagram for the Pleiades and
HD141272A and B (rectangles symbolize the error
boxes). The inserted plot shows HD141272B and the
surrounding Pleiades stars drawn to a larger scale. The
main sequence of the cluster can be seen although there
are some outliers due to the mean distance module
(5.97mag for Pleiades) applied. The mean error of the
Pleiades is shown by the error cross in the lower left.
HD 141272A and B appear a little fainter than Pleiades
stars of the same J-K color. This indicates, that the
system already reached the ZAMS.
errors for the constants a and b and the range of the
spectral type. We derived a mass of
M∗ = 0.26
+0.07
−0.06M⊙.
Future work should ascertain the age of the system
and derive more properties of the M dwarf, which en-
larges the list of nearby low mass stars bound in binary
systems.
Acknowledgements. We would like to thank the technical
staff of the ESO NTT at La Silla as well as of the Centro
Astronómico Hispano Alemán (CAHA) at Calar Alto for all
their help and assistance in carrying out the observations.
In addition we would like to thank John Bochanski, An-
drew West, Suzanne Hawley and Kevin Covey for providing
the electronic sequence of M-stars composite spectra.
T.O.B. Schmidt acknowledges support from a Thur-
ingian State Scholarship and from a Scholarship of the Evan-
gelisches Studienwerk e.V. Villigst.
This publication makes use of data products from the
Two Micron All Sky Survey, which is a joint project of
the University of Massachusetts and the Infrared Process-
ing and Analysis Center/California Institute of Technology,
funded by the National Aeronautics and Space Administra-
tion and the National Science Foundation.
We use imaging data from the SuperCOSMOS Sky Sur-
vey, prepared and hosted by the Wide Field Astronomy
Unit, Institute for Astronomy, University of Edinburgh,
which is funded by the UK Particle Physics and Astron-
omy Research Council.
This research has made use of the VizieR catalogue
access tool and the Simbad database, both operated at
the Observatoire Strasbourg, as well as of the WEBDA
database, operated at the Institute for Astronomy of the
University of Vienna.
The DENIS project has been partly funded by the SCI-
ENCE and the HCM plans of the European Commission
under grants CT920791 and CT940627. It is supported by
INSU, MEN and CNRS in France, by the State of Baden-
Württemberg in Germany, by DGICYT in Spain, by CNR
in Italy, by FFwFBWF in Austria, by FAPESP in Brazil,
by OTKA grants F-4239 and F-013990 in Hungary, and by
the ESO C&EE grant A-04-046.
Jean Claude Renault from IAP was the Project man-
ager. Observations were carried out thanks to the contri-
bution of numerous students and young scientists from all
involved institutes, under the supervision of P. Fouqué, sur-
vey astronomer resident in Chile.
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	Introduction
	Archival first epoch data
	Follow-up observations
	Photometry and Spectroscopy
	Conclusions
