---
abstract: 'We present a catalogue of H–band spectra for 85 stars of approximately solar abundance observed at a resolving power of 3000 with the KPNO Mayall 4m FTS. The atlas covers spectral types O7–M5 and luminosity classes I-V as defined on the MK system. We identify both atomic and molecular indices and line–ratios which are temperature and luminosity sensitive allowing spectral classification to be carried out in the H–band. The line ratios permit spectral classification in the presence of continuum excess emission, which is commonly found in pre–main sequence and evolved stars. We demonstrate that with spectra of $R = 1000$ obtained at $SNR > 50$ it is possible to derive spectral types within $\pm 2$ subclasses for late–type stars. These data are available electronically through the Astronomical Data Center in addition to being served on the World–Wide–Web.'
author:
- 'Michael R. Meyer'
- Suzan Edwards
- 'Kenneth H. Hinkle'
- 'Stephen E. Strom'
title: |
    Near–Infrared Classification Spectroscopy:\
    H–band Spectra of Fundamental MK Standards
---

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Introduction
============

With the recent development of large–format infrared array detectors, high quality photometric surveys are routinely conducted at wavelengths between 1–2.5 $\mu$m. Soon the completion of the 2 Micron All–Sky Survey (2MASS; Skrutskie 1997) and DENIS (Epchtein et al. 1997) will provide comprehensive catalogues of near–infrared sources with detection limits sensitive to a wide variety of stellar and non–stellar objects. Infrared spectra will be required for appropriate identification of many of these sources, and for further study of their astrophysical properties.

The pioneering study of Johnson and Mendez (1970) was the first to explore the spectra of a large sample of normal stars in the near–infrared. However many years passed before improvements in instrumentation made possible similar observations of large numbers of targets of astrophysical interest. The majority of the work done in near–infrared spectroscopy to date has been focused on the K–band, in large part because intrinsically cool or heavily obscured objects are typically brighter at K–band than in the J– or H–bands. In 1986, Kleinmann and Hall (1986; KH86) provided the first comprehensive medium resolution atlas ($R=3000$) of stellar spectra in the K-band, covering all luminosity classes, but restricted to spectral types between F8-M7. More recently, Wallace and Hinkle (1997; WH97) have extended the KH96 K–band atlas, using the same FTS spectrograph on the KPNO 4m with $R=3000$, but including stellar spectra spanning spectral types O-M and luminosity classes I-V. They also summarize the considerable body of work directed toward K–band spectroscopy in the last decade.

While in many situations, the K–band will be the wavelength selection of choice for spectroscopic studies of highly obscured or very cool objects, the presence of circumstellar dust ($T_{vap} < 2000 K$; Pollack et al. 1994) often results in significant excess continuum emission longward of $2~\mu$m. This continuum excess is commonly found in two important classes of objects: young stars with circumstellar disks (e.g. Meyer, Calvet, & Hillenbrand, 1997) and evolved stars with extensive envelopes from mass-loss (e.g. Le Bertre 1997). Near–infrared excess due to warm dust can also complicate spectroscopic studies of composite stellar systems aimed at discerning the stellar populations of other galaxies (e.g. Schinnerer et al. 1997). Continuum excess longward of $2~\mu$m will weaken or even render invisible the photospheric features in the K–band, while the photosphere will dominate at shorter wavelengths. In such a situation, near infrared spectra shortward of 2 $\mu$m will be required to see the stellar photosphere too obscured to be detected optically. To date, there has been relatively little work in the H–band (1.55–1.75 $\mu$m). Recent publications include: i) observations of 40 G, K, and M stars of luminosity class I and III at $R=1500$ by Origlia, Moorwood, and Oliva (1993); ii) the library of 56 spectra O–M of luminosity class I, II, and V at $R=500$ (Lancon & Rocca–Volmerange, 1992); iii) a library of 37 stars of luminosity classes I, III, V at $R=1500-2000$ (Dallier, Boisson, & Joly 1996) over a limited portion of the H–band; and iv) a study of 9 OB Stars at $R=570$ (Blum et al. 1997).

Here we present an H–band spectral atlas for 85 stars of nearly solar abundance with spectral types on the MK classification system ranging from 07-M5 and luminosity classes I-V. These $R=3000$ spectra were collected with the same FTS at the KPNO 4m as the K–band atlases of KH86 and WH97. In Section 2, we describe the sample selection and in Section 3 we describe the observations and calibration of the data. In Section 4 we discuss the dependence of the spectral features on temperature and luminosity and suggest a two–dimensional classification appropriate for late-type stars. In Section 5 we discuss near–IR spectral classification with regard to wavelength range/spectral resolution, and conclude with a summary of our results.

Defining the Sample
===================

In our sample selection, we chose optically visible stars which had previously been identified on the temperature and luminosity scales of the revised MK system (Keenan 1987). [^1] The majority of the stars were drawn from the following fundamental lists: i) Morgan, Abt, and Tapscott (1978) for 29 stars O6–G0; ii) Keenan and McNeil (1989) for 45 stars G0–K5; and iii) Kirkpatrick, Henry, and McCarthy (1991) for 5 late–type dwarfs K5–M3. We supplemented these primary standards with an additional 5 secondary standards from the compilation of Jaschek, Conde, and de Sierra (1964) and one late–type dwarf classified by Henry, Kirkpatrick, and Simons (1994).

In order to cover as complete a range of stellar temperature and luminosity as possible, we defined a two-dimensional grid with 26 bins of spectral type and three bins of luminosity class. Our temperature grid is binned $\times 2$ more coarsely in spectral subclass than the revised MK system, so that we typically sample only every other MK subclass. The three luminosity bins are divided into supergiants (I–II), giants (III), and subgiants/dwarf stars (IV–V). A full sampling of this grid would have resulted in 78 distinct temperature/luminosity pairs. Our atlas includes a total of 85 sources with 53 of the bins filled. Grid coverage was finer among the later spectral types, where for stars GO and later, we filled 26 of the 27 bins (9 spectral types $\times$ 3 luminosity classes). In contrast, for stars earlier than GO, only 27 of the 51 bins were covered (17 spectral types $\times$ 3 luminosity classes).

The 85 individual stars in our H–band survey are listed in Table \[sample\] along with relevent stellar properties taken from the Bright Star Catalogue (Hoffleit & Jaschek 1982). Additional restrictions on the sample selection included: i) v$sini$ $<$ 250 km s$^{-1}$ with exception of HR3982 (B7 V); ii) near-solar metallicity (avoiding those MK standards which exhibit spectral peculiarities due to enhanced or deficient metal abundance); and iii) no visual companions within the beam (separations $1-5$”). Our program was begun in advance of the K–band FTS atlas of WH97, and their sources are drawn in large measure from our sample. We note in Table \[sample\] the stars for which K–band spectra can be found in the WH97 digital atlas.

Table \[temp\] and Figure \[fig1\] provide additional insight into the temperature and luminosity coverage of our sample. In Table \[temp\], we list each of the spectral type and luminosity bins we have “filled”. For each bin in which there is at least one spectrum, we give the corresponding effective temperature. For most stars, we adopted the temperature scale of Tokunaga (1996), except for giants earlier than G0 where we adopted Schmidt–Kaler (1982) [^2]. Figure \[fig1\] provides a schematic illustrating the temperature and luminosity coverage for the 85 stars in our sample. In this illustration we have applied the same main sequence bolometric corrections to both dwarf (27) and subgiant (11) stars; as such they are indistinguishable in this diagram.

Observations and Data Calibration
=================================

Observations of our 85 sample stars were obtained at the Mayall 4m telescope at Kitt Peak National Observatory during four separate observing runs from 1993–1994 (Table \[ftslog\]). We used the Fourier Transform Spectrometer (FTS) dual–output interferometer (Hall et al. 1979). The FTS was ideal for this program for several reasons. First, the wavelength coverage of the FTS is limited only by the bandpass of the blocking filters, independent of the spectral resolution. This gave us complete coverage in the J– and H–bands which would have been difficult to obtain with available grating spectrographs. For example, our H–band spectral range is a factor of two greater than the spectra of Dallier et al. (1996). Secondly, the spectral resolution is fixed by the path difference scanned with the interferometer so we were able to chose the highest resolution possible and achieve S/N in excess of 75 for the majority of our sources. [^3] Finally, because of the novel background subtraction algorithm of the 4m FTS described below, we were able to observe the brightest stars in our sample ($H < 3.0^m$) during good daytime conditions (typically mornings). Combining daytime observations with targeted nighttime observations of key faint sources, the FTS provided a uniform set of high quality spectra for a large sample of spectral standards.

Our observing program included simultaneous spectral coverage in both the J–band and the H–band. However, the J–band data presented difficulties which made it expeditious to focus our initial effort on the H–band. The primary problems with the J-band spectra were; i) the inherent difficulty in data reduction due to rapid temporal variations in telluric water vapor absorption; and ii) and the relative paucity of strong features which would allow spectral classification over the full range of stellar temperature and luminosity. We defer discussion of the J–band spectra to a future contribution.

Spectra were collected simultaneously in the J– and H–bands with the use of a dichroic beamsplitter to separate the wavelengths longward and shortward of 1.5 $\mu$m. Each star was centered within an input aperture of 3.8 arcsec while sky background was measured through an identical aperture 50.0 arcsec away. The interferogram was scanned at a rate of 1 kHz as the path difference was varied continuously from 0.0–0.75 cm providing an unapodized resolution of 0.8 cm$^{-1}$. Data were obtained as separate scan pairs, with the path difference varied first in one direction and then the other. A forward–backward scan pair was treated as an “observation” and observations were repeated in beam–switching mode (A–B–B–A). Because the sky background from each aperture produces an interferogram shifted in phase by 180$^{\circ}$ at each set of detectors, source spectra are background subtracted in fourier space as they are collected. This permits observations of bright stars to be obtained during good daytime conditions. These beam–switched observations were repeated and scans were averaged until adequate signal–to–noise ratio (SNR) was achieved. The interferograms were transformed at Kitt Peak National Observatory yielding spectra in units of relative flux versus wavenumber ($\sigma$ in cm$^{-1}$). The transformed spectra were converted into fits format images and all data reduction was performed using the IRAF software package [^4]. The spectra were then convolved with a gaussian filter of half–width $\delta = 1.2$ cm$^{-1}$. This procedure, commonly referred to as apodization, eliminates “ringing” observed in the FTS spectra due to the finite scan path of the interferometer. The resulting apodized resolution (Rayleigh criterion) was $\delta \sigma = 2.1$ cm$^{-1}$ giving a mean resolving power of $R=3000$ in the H–band. At this stage the J– and H–band spectra were separated for ease of reduction. The slope of the continuum was normalized to 1.0 using a four–segment spline fitting function. Care was taken to keep the residuals from this fit to within 1 %.

Next we corrected the spectra for telluric absorption features present in the spectra which varied with zenith angle. We attempted to construct an opacity map for the earth’s atmosphere by dividing normalized spectra obtained of the A0 star standards at different airmass. Because of the simplicity of the A0 star spectra, showing primarily hydrogen lines in absorption, it was relatively easy to monitor the degree to which this procedure was successful. In dividing two normalized spectra of the same star taken at different airmass, all stellar photospheric absorption features should directly cancel, leaving only those absorption features due to the earth’s atmosphere. If we assume that the opacity of the telluric absorption is directly proportional to airmass we derive: $$\tau(\sigma,X = 1.0) = \frac{1}{(X_{high}-X_{low})} \times ln[ \frac{I(\sigma,X_{low})}{I(\sigma,X_{high})}]$$ where $\tau$ is the atmospheric opacity, $X_{low}$ is the low airmass value, and $X_{high}$ is the high airmass value. A typical opacity map derived in this way for the H–band is shown in Figure \[fig2\]. Several of the features in this map identified with known constituents of the earth’s atmosphere such as water vapor, methane, and carbon dioxide, are denoted in Figure \[fig2\]. Again if the atmospheric opacity varies linearly with airmass we can simply scale the opacity for each star so that $\tau(\sigma,X) = X \times \tau(\sigma,X=1.0)$. Using this technique we corrected the spectra to zero–airmass; $$I(\sigma,X=0.0) = I(\sigma,X) \times e^{\tau(\sigma,X)}$$ We used the highest signal–to–noise A0 standard star spectra ($SNR > 100$) with the largest $\Delta X$ to define the opacity. We found some residual telluric absorptions, possibly due to water vapor which do not vary strictly with airmass. Such features severely complicate the reduction of the J–band spectra.

Finally, the forward and backward scans of each star were averaged and residuals of the differenced spectra were calculated in order to evaluate the average SNR. The observations were obtained with the goal of achieving SNR of 75 or greater. In most cases this was achieved with the highest quality spectra reaching values of several hundreds. The average SNR for each stellar spectrum is included in Table \[ftshewsup\] –Table \[ftshewdw\] below.

Line Identification and Dependence on Temperature and Luminosity
================================================================

Representative H–band spectra are shown in Figures \[fig3\]– \[fig6\] for luminosity classes I–II, III, IV, and V, with prominent atomic and molecular features identified. Line identifications were made for the strongest lines from comparison with the solar photospheric and umbral near infrared atlases (Livingston & Wallace 1991 (LW91); Wallace & Livingston 1992 (WL92)). However, at our moderate spectral resolution many features are blended and we found the model atmosphere calculations of Oliva, Moorwood, and Origlia (1993) to be useful in identifying the dominant contributors to a blend in late–type stars.

Visual inspection of the features in Figures \[fig3\]– \[fig6\] reveals that $R=3000$ H–band spectra contain sufficent temperature and luminosity sensitive features to enable spectral classes to be distinguished. Beginning with the early type stars, the dominant spectral features are HeI 5882 cm$^{-1}$ (1.700 $\mu$m) and the Brackett series of hydrogen from lines 4-10 (1.736 $\mu$m) to 4-16 (1.556 $\mu$m). The He I line exceeds the strength of the Brackett lines in the very earliest stars (06 to B0), with a maximum equivalent width of $\sim 0.83$ cm$^{-1}$ (HR1903; B0 Ia), and recedes to undetectable levels ($\sim 0.10$ cm$^{-1}$) by spectral type B8. From the late B to early F stars, the Brackett series dominates the spectrum, after which lines of neutral atomic metals begin to take prominence. The strongest metallic lines include MgI, SiI, CaI, AlI, and FeI, which increase in strength toward the K stars. Finally molecular features of OH and CO dominate the spectra of the latest–type stars from K5–M5. The most striking luminosity-sensitive feature is the second–overtone CO bandhead $[v, v^{'} = 6, 3]$ at 6177 cm$^{-1}$ (1.619 $\mu$m), which is found in the spectra of the K and M stars. This feature is signficantly stronger in stars of lower surface gravity at equivalent spectral type.

To further enable spectral classification in the H–band, we have identified a set of 9 features which are prominent in stars of spectral type A-M. These include a relatively isolated Brackett line (H4-11), 5 neutral metals, and 3 molecular bands. In Table \[ftshband\], we define 9 narrow band indices with bandpasses ranging from 10 to 50 cm$^{-1}$, which include each of these features. The variable widths of the bandpasses were selected to minimize line blending, contamination from residual telluric absorption, and sensitivity to radial velocity shifts. Table \[ftshband\] also identifies the wavenumber of the dominant contributor and the lower state energy level, the central wavenumber and passband of the index, and additional species which may contribute to the index strength. The equivalent widths of these 9 indices were evaluated from the normalized spectra of our 85 survey stars, and are tabulated in Tables  \[ftshewsup\] to  \[ftshewdw\] in units of cm$^{-1}$ [^5]. Uncertainties in these equivalent widths depend on the SNR of the spectrum in question and the bandpass/strength of the feature. Errors range from $\sigma_{EW} = 0.02-0.1$ cm$^{-1}$ exceeding this upper limit in very few cases. Multiple observations of several sources are listed for comparison.

The temperature and luminosity dependence for four representative indices is illustrated in Figure \[fig7\]. The 4–11 Brackett line (HI5950) behaves as expected, with a rapid rise to a maximum (at a peak equivalent width of $\sim$ 3 cm$^{-1}$) as $T_{eff}$ approaches 10000 K, and a slower decline toward higher temperatures. The behavior of the index is similar in both the dwarfs and the giants, although the luminosity class I/II sources show a larger scatter, presumably due to intrinsic variability (e.g. Kaufer et al. 1996). The general behavior of the neutral atomic features is illustrated by the Mg6345 index. In luminosity classes IV–V, this index reaches a maximum strength between 5000-6000 K, with a peak equivalent width of $\sim$ 2.5 cm$^{-1}$. In contrast, the maximum strength of this index in the lower surface gravity objects (also $\sim$ 2.5 cm$^{-1}$) is found in the coolest stars in our sample, monotonically decreasing toward higher temperatures; as expected given the behavior of ionization state as a function of surface gravity. The two SiI indices exhibit similar behavior, but the AlI index, (not shown) turns over at much lower temperatures in our dwarf stars because of its lower ionization potential. Note that we have chosen not to form an index based on the strongest SiI line at 6292 cm$^{-1}$ (1.5892 $\mu$m) because it is coincident with the 4–14 Brackett line of HI at 6297 cm$^{-1}$ (1.5881 $\mu$m).

The behavior of the molecular features is illustrated for both the second–overtone $^{12}$CO (6,3) and the OH ($\Delta v = 2$) indices. Both indices exhibit a similar behavior with temperature and luminosity, becoming detectable around $T_{eff}$ = 5000, with a strength in the giants approximately twice that in the dwarfs. Similar behavior was noted by KH86 in the first–overtone CO features in the K–band. In dwarf stars the second–overtone CO index reaches a maximum before M5, and displays a turnover toward the coolest stars. This may be due in part to features of CaI and FeI which contaminate the index for intermediate spectral types (F5–K3). Ali et al. (1995) find that the relationship between T$_{eff}$ and equivalent widths of the first–overtone CO bandheads flatten out between 3500–5000 K in dwarf stars. From high resolution ($R > 45,000$) FTS spectra, Wallace & Hinkle (1996) observed that the 2 $\mu$m continuum in late–type dwarf stars is suppressed by numerous water vapor features which are blended at intermediate to low resolution. Predicting the equivalent widths of features where the apparent continuum is subject to temperature and luminosity effects is not straight–forward. In contrast, both the CO and OH indices continue to rise at the coolest temperatures for stars of higher luminosity. However, the magnitude (and temperature) of the maximum in the dwarf stars differs between the CO and OH indices, which we use in the next section to define a two-dimensional classification scheme for late–type stars. We note that the OH index begins to include a contribution from the stark–broadened 4-11 Brackett line at 5949 cm$^{-1}$ creating a secondary maxiumum in the strength of this index around 10,000 K in the dwarf stars.

While the temperature and luminosity dependence of the atomic features is readily understood through application of the Saha and Boltzman equations governing the population of the ionization states and energy levels respectively, the explanation behind the behavior of the molecular features is more subtle. Two possibilities for the factor of two enhancement in the molecular bands in the giants over the dwarfs have been explored in the literature. One attributes the luminosity dependence in the molecular features to differing microturbulence in the atmospheres of dwarfs and giants. The expectation is that larger microturbulence in the lower surface gravity giants effectively broadens the opacity of the feature over a larger frequency interval in these saturated features, thereby enhancing the equivalent width (McWilliams & Lambert 1984). Another possible contributor is the differing depth of the line formation region in the dwarfs versus the giants, which is fixed by the H$^{-}$ opacity. As described by Gray (1992) higher surface gravity results in a higher electron pressure (and thus H$^-$ column density). This brings the CO line formation region closer to the stellar surface reducing $N_{CO}$ according to the following proportionality: $$P_e \sim g^{1/3} \sim N_{H^-} \sim 1/N_{CO}$$ In any case, this luminosity dependence of the band strength gives an excellent empirical discriminant between giants and dwarfs, which we exploit below to develop a two dimensional spectral index.

To discern surface gravity effects between the super–giants and giants or between sub–giants and dwarf stars requires more careful study. A detailed examination of line strengths as a function of surface gravity at a fixed temperature reveal the expected trends. However, this behavior does not reveal itself in the coarse analysis afforded by our narrow–band indices.

While the temperature and luminosity sensitivities outlined above can provide good spectral classification in many instances, discriminants which do not rely on absolute line strength are required when a star is subject to near-infrared continuum veiling. In this case line ratio diagnostics are to be preferred, since absorption features will appear shallower in the presence of continuum excess but line ratios will be preserved as long as the excess is not strongly wavelength dependent. We have identified one diagnostic based on line ratios which can be used to evaluate both temperature and luminosity for stars from K3-M5 in the presence of continuum veiling. This two–dimensional spectral index is defined as:

$$\frac{EW[OH5920]}{EW[Mg6345]} \ vs. 
\ \frac{EW[CO6018+CO6170]}{EW[Mg6345]}$$

where EW is the equivalent width in cm$^{-1}$ for the indices identified in Table \[ftshband\] and listed in Tables \[ftshewsup\]– \[ftshewdw\]. The temperature and luminosity dependence of this diagnostic is illustrated in Figure \[fig8\]. In this diagnostic, the ratio of the OH5920 to Mg6345 indices is temperature sensitive, with distinct temperature dependences for dwarfs and giants. Specifically we find

$$T_{eff} (V) = 4640 \pm 250 - (2610 \pm 110) \frac{EW[OH5920]}{EW[Mg6345]}$$

and

$$T_{eff} (III) = 5100 \pm 180 - (2730 \pm 80)\times \frac{EW[OH5920]}{EW[Mg6345]}$$

The comparison of this temperature sensitive ratio with the sum of the two $^{12}$CO indices, also normalized to Mg6345, then provides an excellent means of identifying both the temperature and luminosity class of late–type stars. Formal errors in the equivalent width suggest that spectral types can be evaluated to within $\pm 2$ subclasses ($\pm$ 300 K) from K3–M5 using spectra with $SNR > 50$ based on these indices alone.

Discussion and Summary
======================

Spectral classification in the near-infrared will become increasingly important in the next decade, as the 2MASS and DENIS near-infrared sky surveys reveal unprecented numbers of stars which are optically–invisible. Because the 1–2.5 $\mu$m region is on the Rayleigh–Jeans tail of most stellar SEDs, it is not an ideal wavelength regime to pursue spectral classification. Yet, there are sufficient features in both the H– and the K–bands to allow most stellar photospheres to be classified. For heavily reddened sources, the K–band will be the wavelength of choice. However, continuum emission from circumstellar dust with temperatures less than 2000 K can heavily veil stellar photospheres at wavelengths greater than 2.0 $\mu$m. In this case, shorter wavelength spectra are required in order to identify the underlying star.

The early-type stars are probably the most challenging for spectral classification in the near–infrared. We find that a rough classification from 07-B8 can be made in the H–band by the relative strengths of HeI 5882 cm$^{-1}$ and the Brackett series (see also Blum et al. 1997). Hanson, Conti, and Rieke (1995) have established a classification scheme in the K–band for O–B stars relying on lines of helium as well as higher ionization species obtained at $R > 1000$. For stars A through early K, the H–band may be superior to the K band in providing a large number of intermediate ionization potential species with strong features such as MgI, SiI, and FeI in addition to the numerous Brackett series features. Stars K3–M5 are probably best classified in the K–band (KH86; Ali et al. 1995; WH97) using atomic features of MgI, CaI, and NaI as well as the first–overtone CO bandheads observed at $R \sim 1000$. However we have found that these stars also have strong temperature and luminosity sensitive features in the H–band such as MgI, AlI, OH, and the second–overtone CO bandheads. The very latest–type stars ($> M5$) have very strong, broad, molecular features which can be identified at resolutions as low as $R \sim 300$. Kirkpatrick et al. 1993 (see also Jones et al. 1996) have classified stars in the I– or the J–band employing features due to VO, TiO, and FeH. In addition, broad water vapor bands observed throughout the 1–2.5 $\mu$m region (Jones et al. 1995) are an important opacity source in the atmospheres of the coolest stars as well as brown dwarfs (Allard & Hauschildt 1995). While the I– or J–bands are probably the best spectral regions to classify extremely cool stars (as they lie on the Wien side of the Planck function for these objects) more heavily obscured objects can still be profitably observed at low resolution in the J– and H–bands (e.g. NICMOS on HST) or in the K–band (Wilking, Greene, & Meyer 1998) in search of these water vapor absorptions.

The H–band spectral atlas we have presented is comprised of moderate resolution spectra with $R \sim 3000$. In contrast, most spectral classification is typically carried out with $R \sim 500-1000$. The strongest and broadest features in the H–band are the CO(6-3) bands and the Brackett lines. These features could be identified with much lower spectral resolution than our survey, at $R \sim 500$. The most crowded region in the H–band spectra is that in the vicinity of the HI line at 5948.50 cm$^{-1}$ (1.68110 $\mu$m), the AlI triplet at 5964–5980 cm$^{-1}$ (1.677–1.672 $\mu$m), and the SiI line at 5993.29 cm$^{-1}$ (1.66853 $\mu$m). In order to properly separate these important features from each other, a resolving power of $R \sim 1000$ is required. At this resolution, one can also obtain measurements of the HeI line at 5882 cm$^{-1}$ (1.700 $\mu$m). At $R = 3000$ one can resolve individual components of the AlI triplet, the Mg I doublet, and the CO bandheads, as well as the stark–broadened Brackett lines in the early–type dwarf stars (Table \[ftshband\]). An additional issue in the near–infrared is the significant contribution to shot-noise from air-glow lines. In the H–band air–glow from OH is sufficently bright and variable that they compromise $R=1000$ H–band spectral classification for very faint sources. Spectral resolution as high as $R \sim 5000$ will be required to resolve the bulk of these air–glow features and to obtain adequate SNR spectra of faint objects [^6].

In summary, we present an H–band spectral atlas at a resolving power of $R = 3000$ that spans a wide range in stellar temperature (O7-M5) and luminosity class (I-V). This spectral region contains a number of temperature and/or luminosity sensitive atomic and molecular features which will allow spectral classification to be carried out in the H-band. As an example of the efficacy of this spectral range for distinguishing stellar spectral types, we define a set of narrow–band indices which, with $ SNR \sim 50$, permit classification of late–type stars on the MK system within $\pm 2$ subclasses. It appears however, that for most applications obtaining H–band spectra at $R \sim 1000$ will be sufficient for classification.

Appendix A: Electronic Availability of the Data
===============================================

The final reduced averaged spectra as well as the difference of the forward and backward scan pairs (see Section 3 for description of the reduction procedure) are available through the Astronomical Data Center (ADC) for each observation listed in this paper. The ADC can be contacted directly: i) by post at Astronomical Data Center, NASA Goddard Space Flight Center, Code 631, Greenbelt, MD 20771; or ii) by telephone at (301) 286–8310; or iii) by fax at (301) 286–1771; or iv) via the internet at http://adc.gsfc.nasa.gov. The data are in fits format with pertinent header information included for each image. These fits format files, useful plotting routines, and other relevent information are also available on the World Wide Web at http://donald.phast.umass.edu. The raw FTS data are also available directly from NOAO (contact KHH for details).

We would like to thank Lori Allen, Ed Chang, Lynne Hillenbrand, Susan Kleinmann, Michael Skrutskie, and Lloyd Wallace for helpful discussions. Special thanks to John Carpenter for assisting in the initial compilation of the standard star lists, and to Karen Strom and Stephen Friedman for their assistance in making the data available electronically. Antonella Romano provided assistance in preparing the tables and figures for publication. Support for MRM during the final stages of this work was provided by NASA through Hubble Fellowship grant \# HF–01098.01–97A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under contract NAS 5–26555. SE acknowledges support from the National Science Foundation’s Faculty Award for Women Program. This work was supported in part through a grant from the National Science Foundation (\# AST–9114863) to SES.

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Lancon, A., & Rocca-Volmerange, B. 1992, A&AS, 96, 593

Le Bertre, T. 1997, A&A, 324, 1059

Litzen, U. 1964, Ark. Fys., 28, 239

Livingston, W., & Wallace, L. 1991, Solar Atlas 1–5 $\mu$m, Kitt Peak Observatory Bulletin (LW91)

McWilliam, A., & Lamber, D.L. 1984, PASP, 96, 882

Meyer, M.R., Calvet, N., & Hillenbrand, L.A. 1997, AJ, 114, 288

Morgan, W., Abt, H., & Tabscott, J. 1978, Revised MK Spectral Atlas for Stars Ealier than the Sun, Yerkes and Kitt Peak Observatories

Origlia, L., Moorwood, A., & Oliva, E. 1993, A&A, 280, 536

Pollack, J.B., Hollenbach, D., Beckwith, S.V.W., Damon, P., Rousch, T., & Fong, W. 1994, ApJ, 421, 615.

Risberg, G. 1965, Ark. Fys., 28, 381

Schinnerer, E., Eckart, A., Quirrenbach, A., Boker, T., Tacconi–Garman, L.E., Downes, D. 1997, ApJ, 488, 174

Skrutskie, M.F. 1997, Impact of Large Scale Near-IR Sky Surveys, eds. Gorzon, F., Epchtein, N., Omont, A., Burton, B., & Persi, P. (Kluwer: Amsterdam, Netherlands)

Schmidt–Kaler, T.H. 1982, Physical Parameters of Stars, Landolt-Bornstein New Series, Vol. 2b, Astronomy and Astrophysics, Stars and Star Clusters, ed. K. Shaifers & H. H. Voigt, (Springer–Verlag: New York)

Tokunaga, A., 1996, Astrophysical Quantities, submitted

Wallace, L., & Livingston, W. 1992, Atlas of Dark Sunspot Spectrum 1–5 $\mu$m, Kitt Peak Observatory Bulletin (WL92)

Wallace, L. & Hinkle, K. 1996, APJS, 107, 312

Wallace, L. & Hinkle, K. 1997, APJS, 111, 445 (WH97)

Wilking, B.A., Greene, T.P., & Meyer, M.R. 1998, AJ, submitted

[lllllll]{} & & & & & &\
1903 & \*46 $\epsilon$ Ori & 2.4 & B0 & Ia & 26SB & 87\
1203 & 44 $\zeta$ Per & 3.4 & B1 & Ib & 20SB & 59\
2827 & 31 $\eta$ CMa & 2.5 & B5 & Ia & 41V & 45\
1713 & \*19 $\beta$ Ori & 0.1 & B8 & Ia & 21SB & 33\
3975 & \*30 $\eta$ Leo & 3.3 & A0 & Ib & 3V & 20\
7924 & \*50 $\alpha$ Cyg & 1.0 & A2 & Ia & -5SBO & 21\
1865 & 11 $\alpha$ Lep & 2.0 & F0 & Ib & 24 & 13\
1017 & \*33 $\alpha$ Per & 0.9 & F5 & Ib & -2V & 18\
7796 & \*37 $\gamma$ Cyg & 1.1 & F8 & Ib & -8V & 20\
8232 & \*22 $\beta$ Aqr & 1.5 & G0 & Ib & 7V? & 18\
7479 & 5 $\alpha$ Sge & 2.4 & G1 & II & 2V? & 0\
7063 & $\beta$ Sct & 2.2 & G4 & IIa & -22SB10 & 10\
8752 & \*- & 3.6 & G4v & $>I$ & -58V? & 35\
7314 & \*21 $\theta$ Lyr & 2.1 & K0 & +II & -31V & $<$19\
6713 & 93 Her & 2.4 & K0.5 & IIb & -24 & $<$17\
8465 & \*21 $\zeta$ Cep & 1.1 & K1.5 & Ib & -18SB & $<$17\
6498 & 49 $\sigma$ Oph & 1.9 & K2 & II & -27 & $<$19\
603 & 57 $\gamma^1$ And & -0.5 & K3 & -IIb & -12SB & $<$17\
8089 & \*63 Cyg & 1.5 & K4 & Ib-IIa & -26V & –\
8079 & \*62 $\xi$ Cyg & 0.5 & K4.5 & Ib-II & -20SB & $<$17\
2061 & 58 $\alpha$ Ori & -2.? & M1-2 & Ia-Iab & 21SB & –\
1155 & \*– & 0.5 & M2 & +IIab & -3V & –\
921 & 25 $\rho$ Per & -1.7 & M4 & II & 28 & –\
7009 & \*– & 0.6 & M4.5-M5 & +II & -19 & –\
6406 & \*64 $\alpha^1$ Her & -2.4 & M5 & Ib-II & -33V & 21\
1899 & 44 $\iota$ Ori & 3.5 & O9 & III & 22SB2O & 130\
1552 & 3 $\pi^4$ Ori & 4.1 & B2+B2 & III & 23SBO & 40\
5291 & \*11 $\alpha$ Dra & 3.5 & A0 & III & -13SBO & 18\
403 & \*37 $\delta$ Cas & 2.3 & A5 & III-IV & 7SB & 113\
1412 & \*78 $\theta^2$ Tau & 2.9 & A7 & III & 40SB1O & 78\
4031 & \*36 $\zeta$ Leo & 2.8 & F0 & III & -16SB & 84\
21 & \* 11 $\beta$ Cas & 1.6 & F2 & III–IV & 12SB & 70\
5017 & \*20 CVn & 3.9 & F3 & III & 8V? & 17\
2706 & 48 Gem & 5.0 & F5 & III-IV & 13V & 74\
8905 & \*68 $\upsilon$ Peg & 3.3 & F8 & III & -11 & 79\
4883 & \*31 Com & 3.0 & G0 & III & -1V? & 77\
4716 & 5 CVn & 2.8 & G6 & III & -12SB & $<$17\
7328 & 1 $\kappa$ Cyg & 1.6 & G9 & III & -29SB & $<$17\
7949 & 53 $\epsilon$ Cyg & 0.2 & K0 & -III & -11SB? & $<$17\
8317 & \*11 Cep & 2.3 & K1 & III & -37 & $<$17\
6299 & \*27 $\kappa$ Oph & 0.8 & K2 & III & -56V & $<$17\
165 & 31 $\delta$ And & 0.5 & K3 & III & -7SB1O & $<$17\
6705 & \*33 $\gamma$ Dra & -1.2 & K5 & III & -28 & $<$17\
152 & – & 1.7 & K5-M0 & III & -33V & $<$17\
4517 & \*3 $\nu$ Vir & 0.3 & M1 & IIIab & 51V? & –\
6242 & – & 0.4 & M4 & +III-IIIa & -7V? & –\
7886 & \*– & -0.6 & M6 & III & -66V? & –\

\[sample\]

[lllllll]{} & & & & & &\
6588 & 85 $\iota$ Her & 4.3 & B3 & IV & -20SB1O & 11\
4033 & \*33 $\lambda$ UMa & 3.3 & A2 & IV & 18V & 48\
1351 & 57 Tau & 4.9 & F0 & IV & 42SB1? & 109\
5235 & 8 $\eta$ Boo & 1.5 & G0 & IV & 0SB1O & 13\
5409 & 105 $\phi$ Vir & 2.8 & G2 & IV & -10SB & 0\
6623 & 86 $\mu$ Her & 1.4 & G5 & IV & -16V & 20\
995 & 59 Ari & 3.9 & G6 & IV & 0V & –\
7602 & 60 $\beta$ Aql & 1.7 & G8 & IV & -40V & $<$ 16\
7957 & \*3 $\eta$ Cep & 1.2 & K0 & IV & -87 & $<$17\
5901 & 11 $\kappa$ CrB & 2.5 & K1 & IVa & -24 & $<$17\
6014 & – & 3.6 & K1.5 & IV & -4V & –\
2456 & \*15 Mon & 5.5 & O7 & V(e) & 33SB & 63\
5191 & \*85 $\eta$ UMa & 2.4 & B3 & V & -11SB? & 205\
3982 & \*32 $\alpha$ Leo & 1.6 & B7 & V & 6SB & 329\
7001 & \* $\alpha$ Lyr & 0.0 & A0 & V & -14V & 15\
2491 & \*9 $\alpha$ CMa & -1.5 & A1 & Vm & -8SBO & 13\
4534 & \*94 $\beta$ Leo & 2.0 & A3 & V & 0V & 121\
4357 & \*68 $\delta$ Leo & 2.3 & A4 & V & -20V & 181\
4931 & 78 UMa & 4.1 & F2 & V & -10V? & 92\
1279 & – & 5.1 & F3 & V & 36SB1? & 25\
2943 & \*10 $\alpha$ CMi & -0.6 & F5 & IV-V & -3SBO & 6\
1538 & 59 Eri & 2.3 & F6 & V & 35 & –\
4375 & \*53 $\xi$ UMa & 3.0 & G0 & V & -16SB1O & 1\
4983 & 43 $\beta$ Com & 3.1 & F9.5 & V & 6SB? & 6\
483 & \*– & 3.7 & G1.5 & V & 4V? & 2\
4374 & 53 $\xi$ UMa & 3.5 & G0 & V & -16SB1O & 3\
5072 & 70 Vir & 3.6 & G4 & V & 5V & 1\
4496 & \*61 UMa & 3.8 & G8 & V & -5V & $<$17\
7462 & \*61 $\sigma$ Dra & 3.0 & K0 & V & 27V & $<$17\
1084 & \*18 $\epsilon$ Eri & 1.6 & K2 & V & 15V? & $<$17\
8832 & \*– & 3.2 & K3 & V & -18V & –\
– & GL570A & 3.0 & K4 & V & - & -\
8085 & \*61 Cyg & 2.4 & K5 & V & -64V & $<$17\
8086 & 61 Cyg & 3.1 & K7 & V & -64V? & =$<$25\
– & GL338A & 4.5 & M0 & V & - & -\
– & GL526 & 4.5 & M1.5 & V & - & -\
– & \*GL411 & 3.6 & M2 & V & - & -\
– & \*GL725A & 4.7 & M3 & V & - & -\

[rlll]{} & & &\
O6-O8– & & 37000 & 38000\
O9– & 32500 & 32000 & 33200\
O9.5– & & & 31450\
B0– & 26000 & 29000 & 29700\
B1– & 20700 & 24000 & 25600\
B2– & 17800 & 20300 & 22300\
B3– & 15600 & 17100 & 19000\
B4 & 13900 & & 17200\
B5– & 13400 & 15000 & 15400\
B6 & 12700 & 14100 & 14100\
B7– & 12000 & 13200 & 13000\
B8– & 11200 & 12400 & 11800\
B9– & 10500 & 11000 & 10700\
A0– & 9730 & 10100 & 9480\
A1– & 9230 & 9480 &\
A2 & 9080 & 9000 & 8810\
A5– & 8510 & 8100 & 8160\
A7– & & 7650 & 7930\
F0– & 7700 & 7150 & 7020\
F2– & 7170 & 6870 & 6750\
F5– & 6640 & 6470 & 6530\
F7– & & & 6240\
F8– & 6100 & 6150 &\
G0– & 5510 & 5910 & 5930\
G2 & & & 5830\
G3 & 4980 & &\
G4 & & 5190 & 5740\
G6 & & 5050 & 5620\
G8– & 4590 & 4960 &\
K0– & 4420 & 4810 & 5240\
K1– & 4330 & 4610 &\
K2– & 4260 & 4500 & 5010\
K3– & 4130 & 4320 &\
K4– & & 4080 & 4560\
K5– & 3850 & 3980 & 4340\
K7 & & & 4040\
M0– & 3650 & 3820 & 3800\
M1– & 3550 & 3780 & 3680\
M2– & 3450 & 3710 & 3530\
M3– & 3200 & 3630 & 3380\
M4– & 2980 & 3560 & 3180\
M5– & & 3420 & 3030\
M6– & & 3250 & 2850\

\[temp\]

[lll]{} & &\
March 9–10, 1993 & Day & 17\
April 1–3, 1993 & Day/Night & 30\
May 18–19, 1993 & Day & 10\
January 30–31, 1994 & Day/Night & 42\

\[ftslog\]

[lllllll]{} & & & & & &\
MgI(4s–4p) & 5.39 & 5843.41 & 1.71133 & 5844 & 10 & CO, Fe, Ni, OH\
OH($\Delta v = 2$) & 0.76 & 5920: & 1.689 & 5920 & 20 & C, CO, Fe, Ni\
HI(4-11) & 12.75 & 5948.50 & 1.68110 & 5950 & 20 & CO, Fe, Ni, Si\
AlI(4p–4d tr) & 4.09 & 5963.76 & 1.67679 & 5972.5 & 25 & CO, Fe, Ni, OH\
& & 5968.31 & 1.67552 & & &\
& & 5979.60 & 1.67235 & & &\
SiI(4p–3d) & 5.98 & 5993.29 & 1.66853 & 5993 & 10 & CO, Fe, Ni, OH\
$^{12}$CO(8,5)bh & 1.55 & 6018 & 1.662 & 6017.5 & 15 & Fe, OH, S\
$^{12}$CO(6,3)bh & 1.05 & 6177 & 1.619 & 6170 & 50 & Ca, Fe, Ni, OH, Si\
SiI(4p–5s) & 5.98 & 6263.92 & 1.59644 & 6264 & 10 & Fe, Mg, Ni, OH\
MgI(4s–4p tr) & 5.93 & 6341.10 & 1.57701 & 6345 & 20 & CN, CO, Fe, H$_2$O, Ni, OH\
& & 6347.88 & 1.57533 & & &\
& & 6351.22 & 1.57450 & & &\

\[ftshband\]

[llllllllllll]{} & & & & & & & & & & &\
HR1903 & 26000 & 203 & -0.03 & 0.09 & 0.75 & 0.17 & -0.02 & 0.11 & 0.27 & 0.11 & 0.47\
HR1903 & 26000 & 167 & 0.01 & 0.07 & 0.73 & 0.11 & -0.00 & 0.09 & 0.19 & 0.12 & 0.32\
HR1203 & 20700 & 160 & -0.01 & 0.12 & 0.80 & 0.18 & 0.01 & 0.11 & 0.23 & 0.11 & 0.56\
HR2827 & 13400 & 045 & -0.05 & -0.02 & 1.06 & -0.04 & 0.20 & -0.04 & 0.01 & -0.05 & 0.08\
HR1713 & 11200 & 218 & 0.04 & 0.06 & 1.27 & 0.23 & 0.05 & 0.09 & 0.19 & 0.17 & 0.50\
HR3975 & 9730 & 068 & -0.08 & 0.11 & 2.12 & 0.23 & 0.12 & -0.09 & 0.33 & 0.20 & 0.58\
HR7924 & 9080 & 225 & -0.05 & 0.00 & 1.40 & 0.20 & -0.02 & 0.03 & -0.14 & 0.08 & 0.08\
HR1865 & 7700 & 196 & -0.01 & 0.22 & 2.21 & 0.32 & 0.14 & -0.13 & 0.30 & 0.25 & 0.52\
HR1017 & 6640 & 248 & 0.08 & 0.25 & 1.88 & 0.43 & 0.06 & -0.02 & 0.53 & 0.41 & 1.05\
HR7796 & 6100 & 324 & 0.10 & 0.29 & 1.58 & 0.69 & 0.14 & 0.03 & 0.79 & 0.60 & 0.94\
HR8232 & 5510 & 290 & 0.09 & 0.37 & 1.28 & 0.67 & 0.17 & 0.03 & 1.18 & 0.67 & 1.19\
HR8752 & 5510 & 084 & -0.13 & 0.34 & 1.16 & 0.14 & 0.07 & 0.02 & 0.16 & 0.16 & 0.41\
HR7479 & 5333 & 096 & 0.15 & 0.13 & 1.13 & 0.70 & 0.10 & 0.00 & 0.92 & 0.41 & 0.69\
HR7479 & 5333 & 109 & 0.10 & 0.22 & 1.07 & 0.49 & 0.11 & 0.02 & 0.76 & 0.54 & 1.04\
HR7479 & 5333 & 182 & 0.13 & 0.12 & 1.08 & 0.56 & 0.05 & 0.07 & 0.94 & 0.49 & 1.06\
HR7479 & 5333 & 093 & 0.06 & -0.02 & 1.20 & 0.53 & 0.03 & 0.14 & 1.05 & 0.54 & 0.93\
HR7063 & 4902 & 260 & 0.17 & 0.12 & 0.94 & 0.84 & 0.14 & 0.25 & 1.66 & 0.76 & 1.06\
HR7314 & 4420 & 193 & 0.23 & 0.15 & 0.84 & 0.88 & 0.15 & 0.46 & 2.25 & 1.00 & 1.60\
HR7314 & 4420 & 257 & 0.15 & 0.17 & 0.67 & 0.59 & 0.10 & 0.37 & 1.91 & 0.86 & 1.36\
HR6713 & 4375 & 265 & 0.22 & 0.19 & 0.81 & 0.80 & 0.16 & 0.40 & 1.86 & 0.79 & 1.25\
HR8465 & 4295 & 308 & 0.13 & 0.28 & 0.68 & 0.70 & 0.19 & 0.63 & 2.35 & 1.02 & 1.79\
HR6498 & 4260 & 247 & 0.24 & 0.30 & 0.84 & 1.00 & 0.21 & 0.83 & 2.75 & 1.11 & 1.84\
HR603 & 4130 & 453 & 0.24 & 0.34 & 0.69 & 0.61 & 0.19 & 0.49 & 2.09 & 0.87 & 1.46\
HR8089 & 3990 & 202 & 0.21 & 0.45 & 0.50 & 0.67 & 0.14 & 0.68 & 2.26 & 0.94 & 1.59\
HR8079 & 3920 & 445 & 0.24 & 0.67 & 0.62 & 0.80 & 0.24 & 1.05 & 2.70 & 1.05 & 1.72\
HR2061 & 3550 & 327 & 0.54 & 1.08 & 0.36 & 1.39 & 0.23 & 1.46 & 3.92 & 0.89 & 2.22\
HR1155 & 3450 & 237 & 0.46 & 1.31 & 0.58 & 1.12 & 0.38 & 1.37 & 3.35 & 1.12 & 2.03\
HR921 & 2980 & 225 & 0.77 & 1.41 & 0.29 & 1.27 & 0.37 & 1.10 & 4.08 & 0.67 & 1.52\
HR7009 & 2925 & 292 & 0.63 & 1.43 & 0.79 & 1.55 & 0.54 & 1.79 & 4.68 & 1.26 & 2.21\
HR6406 & 2800 & 319 & 0.59 & 1.41 & 0.80 & 1.66 & 0.54 & 1.85 & 4.98 & 1.31 & 2.31\

\[ftshewsup\]

[llllllllllll]{} & & & & & & & & & & &\
HR1899 & 32000 & 164 & -0.03 & 0.17 & 0.54 & 0.15 & -0.04 & 0.03 & 0.18 & 0.10 & 0.49\
HR1899 & 32000 & 182 & -0.04 & 0.20 & 0.62 & 0.11 & 0.05 & -0.03 & 0.07 & -0.00 & 0.07\
HR1552 & 20300 & 115 & -0.07 & 0.13 & 1.29 & 0.31 & 0.10 & -0.09 & 0.12 & -0.01 & 0.09\
HR5291 & 10100 & 159 & -0.07 & 0.19 & 2.65 & 0.78 & 0.02 & 0.05 & 0.28 & 0.11 & 0.41\
HR403 & 8100 & 202 & -0.02 & 0.39 & 2.79 & 0.77 & 0.09 & -0.13 & 0.25 & 0.08 & 0.54\
HR1412 & 7650 & 186 & -0.02 & 0.43 & 2.70 & 0.71 & 0.05 & -0.10 & 0.60 & 0.25 & 0.91\
HR4031 & 7150 & 193 & 0.02 & 0.29 & 2.30 & 0.54 & 0.12 & -0.09 & 0.25 & 0.13 & 0.48\
HR21 & 6870 & 245 & 0.03 & 0.32 & 1.99 & 0.55 & 0.04 & -0.11 & 0.20 & 0.22 & 0.82\
HR21 & 6870 & 179 & 0.01 & 0.25 & 2.21 & 0.63 & 0.13 & -0.14 & 0.46 & 0.24 & 0.69\
HR5017 & 6700 & 174 & 0.04 & 0.28 & 2.58 & 0.83 & 0.07 & -0.03 & 0.43 & 0.36 & 0.96\
HR2706 & 6470 & 086 & 0.01 & 0.39 & 2.08 & 0.47 & 0.16 & -0.10 & 0.13 & 0.20 & 0.64\
HR8905 & 6270 & 059 & 0.06 & 0.13 & 1.06 & 0.45 & -0.01 & -0.16 & 0.30 & 0.28 & 1.02\
HR4883 & 5910 & 280 & 0.15 & 0.20 & 1.07 & 0.52 & 0.09 & 0.04 & 0.90 & 0.43 & 1.02\
HR4716 & 5050 & 133 & 0.17 & 0.10 & 0.97 & 0.47 & 0.13 & 0.07 & 1.29 & 0.54 & 0.92\
HR7328 & 4885 & 281 & 0.19 & 0.20 & 0.78 & 0.57 & 0.11 & 0.11 & 1.33 & 0.67 & 1.35\
HR7949 & 4810 & 369 & 0.21 & 0.24 & 0.77 & 0.59 & 0.13 & 0.18 & 1.39 & 0.67 & 1.38\
HR8317 & 4710 & 191 & 0.29 & 0.14 & 0.63 & 0.58 & 0.08 & 0.26 & 1.79 & 0.83 & 1.64\
HR6299 & 4500 & 532 & 0.26 & 0.09 & 0.77 & 0.81 & 0.10 & 0.44 & 1.92 & 0.76 & 1.40\
HR165 & 4320 & 266 & 0.34 & 0.24 & 0.64 & 0.58 & 0.18 & 0.41 & 1.98 & 0.89 & 1.45\
HR6705 & 3990 & 298 & 0.39 & 0.60 & 0.77 & 1.12 & 0.26 & 0.96 & 3.05 & 1.12 & 1.75\
HR6705 & 3990 & 694 & 0.41 & 0.61 & 0.76 & 1.07 & 0.25 & 0.89 & 2.87 & 1.06 & 1.66\
HR152 & 3956 & 270 & 0.37 & 0.86 & 0.58 & 0.92 & 0.34 & 0.87 & 2.59 & 0.78 & 1.40\
HR4517 & 3780 & 673 & 0.66 & 1.06 & 0.33 & 1.07 & 0.21 & 0.89 & 3.14 & 0.70 & 1.93\
HR6242 & 3560 & 458 & 0.52 & 1.12 & 0.57 & 1.18 & 0.39 & 1.45 & 3.93 & 1.16 & 1.96\
HR7886 & 3250 & 574 & 0.61 & 1.54 & 0.89 & 1.71 & 0.64 & 2.25 & 5.69 & 1.41 & 2.42\

\[ftshewgn\]

[llllllllllll]{} & & & & & & & & & & &\
HR6588 & 19000 & 162 & -0.03 & 0.10 & 1.65 & 0.48 & -0.03 & 0.02 & 0.17 & 0.07 & 0.40\
HR4033 & 8810 & 146 & -0.00 & 0.33 & 2.62 & 0.73 & 0.06 & 0.02 & 0.27 & 0.13 & 0.35\
HR1351 & 7020 & 094 & -0.06 & 0.40 & 2.18 & 0.62 & 0.19 & -0.19 & -0.01 & 0.10 & 0.24\
HR5235 & 5930 & 341 & 0.16 & 0.12 & 1.21 & 0.83 & 0.11 & 0.03 & 1.30 & 0.64 & 1.14\
HR5235 & 5930 & 263 & 0.17 & 0.26 & 1.26 & 0.68 & 0.18 & -0.01 & 0.97 & 0.50 & 1.03\
HR5409 & 5830 & 158 & 0.16 & 0.16 & 1.02 & 0.51 & 0.12 & -0.03 & 0.91 & 0.44 & 0.95\
HR6623 & 5680 & 211 & 0.33 & 0.12 & 0.87 & 0.87 & 0.09 & 0.09 & 1.21 & 0.69 & 1.38\
HR995 & 5620 & 143 & 0.22 & 0.08 & 0.80 & 0.61 & 0.23 & 0.03 & 1.09 & 0.48 & 1.14\
HR7602 & 5430 & 056 & 0.46 & 0.15 & 0.71 & 0.86 & 0.01 & 0.17 & 1.40 & 0.57 & 1.49\
HR7957 & 5240 & 189 & 0.22 & 0.09 & 0.68 & 0.70 & 0.07 & 0.15 & 1.04 & 0.46 & 0.99\
HR7957 & 5240 & 192 & 0.09 & 0.18 & 0.56 & 0.52 & -0.01 & 0.09 & 0.75 & 0.40 & 1.17\
HR5901 & 5125 & 395 & 0.37 & 0.13 & 0.55 & 0.62 & 0.08 & 0.21 & 1.61 & 0.74 & 1.60\
HR5901 & 5125 & 153 & 0.37 & 0.09 & 0.75 & 0.93 & 0.15 & 0.30 & 1.54 & 0.71 & 1.13\
HR6014 & 5068 & 072 & 0.31 & -0.12 & 0.39 & 0.59 & 0.14 & 0.05 & 1.10 & 0.70 & 1.40\
HR6014 & 5068 & 133 & 0.42 & 0.11 & 0.58 & 0.55 & 0.18 & 0.09 & 1.48 & 0.65 & 1.24\

\[ftshewsub\]

[llllllllllll]{} & & & & & & & & & & &\
HR2456 & 38000 & 053 & -0.03 & 0.36 & 0.39 & 0.26 & 0.16 & 0.12 & -0.32 & 0.11 & 0.31\
HR2456 & 38000 & 073 & -0.12 & 0.18 & 0.48 & 0.10 & 0.06 & -0.15 & 0.15 & 0.03 & 0.10\
HR5191 & 19000 & 282 & -0.05 & 0.19 & 1.71 & 0.57 & 0.08 & -0.07 & 0.22 & 0.07 & 0.24\
HR3982 & 13000 & 241 & -0.08 & 0.13 & 2.22 & 0.47 & 0.04 & -0.09 & 0.28 & 0.03 & 0.15\
HR3982 & 13000 & 241 & -0.07 & 0.09 & 2.14 & 0.51 & 0.06 & -0.09 & 0.32 & 0.12 & 0.26\
HR7001 & 9480 & 678 & -0.05 & 0.36 & 2.83 & 1.06 & 0.03 & -0.03 & 0.41 & 0.15 & 0.52\
HR7001 & 9480 & 146 & -0.10 & 0.38 & 2.81 & 1.02 & 0.10 & -0.05 & 0.43 & 0.17 & 0.41\
HR2491 & 9145 & 111 & -0.07 & 0.36 & 2.71 & 0.83 & 0.16 & -0.14 & 0.37 & -0.08 & 0.10\
HR2491 & 9145 & 148 & -0.14 & 0.40 & 2.67 & 0.93 & 0.12 & -0.13 & 0.39 & 0.05 & 0.20\
HR4534 & 8593 & 205 & -0.04 & 0.45 & 2.67 & 1.01 & 0.11 & -0.12 & 0.30 & 0.07 & 0.34\
HR4357 & 8377 & 192 & -0.05 & 0.40 & 2.83 & 0.96 & 0.09 & -0.12 & 0.24 & 0.06 & 0.38\
HR4931 & 6750 & 119 & 0.04 & 0.24 & 1.47 & 0.62 & -0.01 & -0.06 & 0.09 & 0.09 & 0.86\
HR1279 & 6677 & 080 & 0.10 & 0.32 & 1.62 & 0.67 & 0.15 & -0.09 & 0.26 & 0.12 & 0.64\
HR2943 & 6530 & 327 & 0.04 & 0.33 & 1.60 & 0.57 & 0.15 & -0.14 & 0.54 & 0.27 & 0.74\
HR1538 & 6385 & 281 & 0.06 & 0.34 & 1.26 & 0.53 & 0.18 & -0.11 & 0.51 & 0.22 & 0.90\
HR4375 & 6085 & 254 & 0.26 & 0.15 & 0.63 & 0.56 & 0.15 & -0.06 & 0.68 & 0.37 & 1.09\
HR4983 & 5930 & 123 & 0.21 & 0.16 & 0.75 & 0.66 & 0.09 & 0.04 & 0.71 & 0.45 & 1.20\
HR4983 & 5930 & 173 & 0.19 & 0.21 & 0.90 & 0.52 & 0.19 & -0.06 & 0.87 & 0.47 & 0.96\
HR483 & 5855 & 059 & 0.24 & 0.02 & 0.68 & 0.29 & 0.04 & -0.17 & 0.18 & 0.37 & 1.09\
HR483 & 5855 & 079 & 0.24 & 0.19 & 0.90 & 0.46 & 0.19 & -0.11 & 0.67 & 0.48 & 1.30\
HR4374 & 5830 & 250 & 0.28 & 0.20 & 0.62 & 0.63 & 0.10 & -0.01 & 0.90 & 0.47 & 1.35\
HR5072 & 5740 & 197 & 0.26 & 0.15 & 0.74 & 0.53 & 0.16 & -0.04 & 0.99 & 0.53 & 1.28\
HR4496 & 5430 & 105 & 0.35 & 0.17 & 0.59 & 0.59 & 0.21 & -0.08 & 1.12 & 0.61 & 1.45\
HR4496 & 5430 & 090 & 0.31 & 0.16 & 0.39 & 0.50 & 0.13 & -0.04 & 0.69 & 0.43 & 1.08\
HR7462 & 5240 & 131 & 0.52 & 0.04 & 0.38 & 0.72 & 0.09 & 0.09 & 1.20 & 0.62 & 1.89\
HR7462 & 5240 & 095 & 0.51 & 0.07 & 0.37 & 0.69 & 0.13 & 0.06 & 1.16 & 0.72 & 2.05\
HR1084 & 5010 & 223 & 0.61 & 0.19 & 0.44 & 0.74 & 0.24 & -0.01 & 1.59 & 0.76 & 2.00\
HR8832 & 4785 & 111 & 0.88 & 0.14 & 0.29 & 1.06 & 0.17 & 0.18 & 1.88 & 0.90 & 2.50\
GL570A & 4560 & 120 & 0.90 & 0.22 & 0.37 & 1.13 & 0.28 & 0.04 & 2.02 & 0.90 & 2.29\
HR8085 & 4340 & 125 & 0.65 & 0.18 & 0.01 & 1.15 & 0.11 & 0.15 & 1.59 & 0.60 & 2.38\
HR8086 & 4040 & 170 & 0.72 & 0.39 & 0.06 & 1.46 & 0.14 & 0.11 & 1.78 & 0.50 & 2.07\
HR8086 & 4040 & 181 & 0.72 & 0.32 & 0.07 & 1.48 & 0.15 & 0.12 & 1.86 & 0.52 & 2.18\
GL338A & 3800 & 072 & 0.98 & 0.37 & 0.08 & 1.36 & 0.13 & 0.02 & 1.51 & 0.34 & 1.80\
GL526 & 3605 & 068 & 0.62 & 0.42 & -0.13 & 1.32 & 0.16 & 0.10 & 1.04 & 0.04 & 0.92\
GL411 & 3530 & 202 & 0.48 & 0.53 & -0.04 & 1.29 & 0.16 & 0.01 & 1.17 & 0.10 & 1.19\
GL411 & 3530 & 189 & 0.47 & 0.55 & -0.07 & 1.29 & 0.18 & 0.06 & 1.21 & 0.12 & 1.23\
GL725A & 3380 & 083 & 0.52 & 0.57 & -0.10 & 1.15 & 0.06 & 0.03 & 0.93 & -0.00 & 0.99\
GL725A & 3380 & 107 & 0.54 & 0.56 & -0.12 & 1.25 & 0.02 & 0.08 & 1.20 & -0.02 & 1.09\

\[ftshewdw\]

[^1]: For a detailed listing of spectral types and luminosity classes in the revised MK system see Keenan (1985).

[^2]: Recent work by Bessell, Castelli, and Plez (1998) provides updated temperatures, colors, and bolometric corrections for a wide range of spectral types and luminosity classes.

[^3]: For details concerning the advantages and disadvantages of fourier transform spectroscopy, see Bell (1974).

[^4]: IRAF is distributed by the National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy, Inc., under contract to the National Science Foundation.

[^5]: The conversion to angstroms is $EW(\AA) = [EW(cm^{-1})/ \sigma^2] \times 10^8$

[^6]: See Herbst (1994) for a comprehensive discussion of OH airglow background supression strategies.
