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2.1. Spectroscopic Observations

Our project centers on the faintest stars in the LHS catalog. We have concentrated on stars with proper motions of yr⁻¹, but we have also obtained observations of a few LHS interlopers: stars that were originally included in Luyten’s Five‐Tenths catalog (LFT), but that proved to have lower proper motions. Those stars have LHS numbers greater than 5000.

The new observations described in this paper were obtained at a number of facilities over the last decade. Most targets were observed with the Double Spectrograph (Oke & Gunn 1982) at the Hale 200 inch (5 m) telescope between 1995 and 1999. The instrumental configuration was identical to that used in the Palomar/Michigan State University Nearby Star Spectroscopic Survey (PMSU), covering 6200–7400 Å with the red channel and 3850–5500 Å in the blue, and with a resolution of ∼3 and ∼4 Å, respectively. In many cases, the red dwarfs have low signal‐to‐noise ratio (S/N) blue spectra, which are not useful for classification purposes.

A few objects were observed with the Las Campanas Du Pont 2.5 m telescope in 1996 December, using the modular spectrograph. These spectra cover 5800–7900 Å at a resolution of ∼3 Å. We also used the LRIS spectrograph (Oke et al. 1994) on the Keck 10 m telescope to observe several of the faintest targets. Those spectra, which are comparable to those described by Kirkpatrick et al. (1999), cover 6000–10,000 Å at a resolution of ∼5 Å. Finally, LHS 2802 was observed with the Ritchey‐Chrétien spectrograph on the CTIO 4 m in 2001 May; these observations were part of our NStars program, described in Reid et al. (2004), and cover 6000–10,000 Å at a resolution of ∼3 Å.

All of the spectra were extracted and wavelength calibrated using standard IRAF routines. Flux calibrations were determined through observations of standard stars taken from Oke & Gunn (1982) and Hamuy et al. (1994). Only the LRIS spectra have been corrected for terrestrial atmospheric absorption. As a result, absorption features due to OH and the O₂ A and B bands are evident in many spectra.

2.2. Spectral Classification

We follow our previous work in measuring the TiO5, CaH1, CaH2, and CaH3 band‐strength indices defined in Table 1. Those indices are listed in Table 2 for the red dwarfs in the present sample. As discussed in PMSU1, TiO5 is linearly related to spectral type for early and mid‐M dwarfs (i.e., M0 through M6), but TiO absorption weakens for later dwarfs. The latter effect is due to dust formation (Jones & Tsuji 1997). Previously, we considered the CaH indices separately; however, the CaH2 and CaH3 indices can be combined to give good dwarf/sdM/esdM discrimination (see Lépine et al. 2004). The latter calibration is illustrated in Figure 1, using late‐type stars with trigonometric parallax data (see Table 6 and the following section).

TABLE 1 Spectroscopic Indices

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TABLE 2 Red Dwarfs

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Fig. 1.— TiO5 and CaH2+CaH3 indices for LHS stars with trigonometric parallax measurements. M dwarfs are shown as open squares, sdM as asterisks, esdM as solid triangles, and non‐M stars as crosses. The solid curve shows the position of the PMSU disk solar neighborhood (near‐solar metallicity).

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Figure 2 plots CaH1 band strengths as a function of TiO5 for all stars in the current faint LHS, while Figure 3 plots the combined CaH2+CaH3 indices against TiO5. These indices allow us to classify the stars as M dwarfs or subdwarfs. We have assigned spectral types for M dwarfs using the TiO5 relationship. TiO5 increases in strength from M0 to M6, but the trend reverses beyond M6.5 as additional absorption, mainly due to VO, depresses the continuum band; consequently, we have also visually reviewed the spectra to check for misclassified later dwarfs. The presence of detectable VO at 7400 Å (Kirkpatrick et al. 1995) distinguishes M7 dwarfs. There are no new M8 or M9 dwarfs in this sample.

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Fig. 2.— TiO5 and CaH1 indices for the LHS red dwarfs listed in Table 2; the symbols are as in Fig. 1.

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Fig. 3.— TiO5 and CaH2+CaH3 indices. Symbols as in Fig. 1.

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Metal‐poor M dwarfs show enhanced CaH and weak TiO relative to disk M dwarfs. In general, we classify metal‐poor M dwarfs as sdM or esdM, using the G97 system. We have visually reviewed these classifications, and in a few cases have reclassified objects as “ordinary” M dwarfs when their appearance is not consistent with sdM; all those objects lie within 1 σ of the cutoff between M and sdM. We note that both sdM and esdM dwarfs show a significant range in TiO5 at a given CaH band strength. Clearly, this tripartite classification system is simply a handy technique for characterizing what must be a continuous distribution of metallicity.

Spectra of M dwarfs in the current sample are shown in Figure 4, the sdM in Figure 5, and the esdM in Figure 6. (Note that for logistical reasons, LHS 2255 [sdM1.5] is plotted in Fig. 4a.) As noted above, most stars have low S/N data in the blue. However, there are relatively few examples of such data in the literature, particularly for subdwarfs; exceptions are Ake & Greenstein (1980), Bessell (1982, 1993), and Reid et al. (2000). Consequently, Figure 7 uses representative stars to illustrate the M, sdM, and esdM sequences at these wavelengths.

Fig. 4a.—M2–M4. – 4g.—M6.5–M9.

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Fig. 4.— LHS stars classified as M dwarfs, sorted by spectral type: (a) M2 to M4, (b) M4 to M4.5, (c) M4.5 to M5, (d) M5 to M5.5, (e) M5.5, (f) M5.5 to M6.5, (g) M6.5 to M9.

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Fig. 5a.—sdM0–sdM3. – 5c.—sdM4–sdM7.

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Fig. 5.— LHS stars classified as sdM subdwarfs, sorted by spectral type: (a) sdM0 to sdM3, (b) sdM3 to sdM4, (c) sdM4 to sdM7.

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Fig. 6a.—esdK7–esdM2.5. – 6c.—esdM4–esdM6.

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Fig. 6.— LHS stars classified as esdM subdwarfs, sorted by spectral type: (a) esdK7 to esdM2.5, (b) esdM2.5 to esdM4, (c) esdM4 to esdM6.

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Fig. 7.— (a) Blue‐channel Hale DBSP spectra of a representative subset of disk dwarfs. The principal molecular bands are marked; note that LHS 1595, VB 8, and VB 10 all show Hβ emission. (b) Blue‐channel Hale DBSP spectra of a representative subset of sdM and esdM subdwarfs. The principal molecular bands are identified.

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Only a few objects show Hα emission. We report measured equivalent widths for Hα, and when blue spectra were also obtained, simultaneous Hβ (Table 3). We can detect and measure emission stronger than 1 Å; we cannot reliably characterize weaker emission (such as in LHS 3611; Fig. 4c).

TABLE 3 Equivalent Widths

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Finally, Figure 8 shows spectra of the white dwarfs in the sample. Several of these stars, identified in Table 4, have previous observations. We have assigned approximate classifications to the remaining stars, based on comparison with the standard sequences in Wesemael et al. (1993). In general, the low S/N of the blue spectra precludes precise classification. Many stars are DC dwarfs, with featureless spectra. As noted above, most spectra have not been corrected for terrestrial absorption, so the O₂ A and B bands, together with OH absorption at 7200 Å, are prominent in many spectra. Moreover, the apparent absorption feature at ∼4400 Å in LHS 1625A (Fig. 8a) is an artifact introduced by an ill‐placed cosmic‐ray event. As discussed further below, the high proportion of DC white dwarfs is not unexpected, given that these are the faintest (coolest) degenerates in the LHS catalog.

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Fig. 8.— (a‐c) LHS stars classified as white dwarfs.

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TABLE 4 White Dwarfs

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2.3. 2MASS Near‐Infrared Photometry

Most LHS stars lack accurate photometry. Bakos et al. (2002) have published revised positions for stars in the LHS catalog, and we have used those data to cross‐reference our targets against the 2MASS Point Source Catalog1 to obtain J, H, and photometry. Table 2 gives results for M dwarfs and subdwarfs, while Table 4 lists photometry of white dwarfs.

In some cases, no 2MASS counterpart of the LHS star was found at the Bakos et al. (2002) position. All of these stars are faint white dwarfs, for which it is reasonable to believe that the source is too faint to be detected by 2MASS. In a few cases, the published positions in the revised LHS catalog are incorrect, but we were able to recover the appropriate star through visual inspection of the Digitized Sky Survey images.

2.4. Other LHS Stars

A total of 91 LHS stars meet our magnitude criterion, , but are not included in the current set of observations. We have cross‐referenced those stars against the 2MASS database, and Table 5 presents the near‐infrared photometry. Most have previous photometric or spectroscopic observations, and for those that lack such data, we have used the optical/near‐infrared colors to separate dwarfs/subdwarfs and degenerate stars. As noted above, at least eight LHS sources are definitely spurious; a further two sources, LHS 1833 and LHS 2867, may well prove to be erroneous.

TABLE 5 Faint LHS Stars Not Observed in this Program

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Of the remaining 81 stars, 44 have near‐infrared/optical colors consistent with M dwarfs or subdwarfs, while 37 are white dwarfs. Only eight hydrogen‐burning stars (LHS 1480, 1660a, 1709, 1829, 1845a, 2309, 2480, and 2676) and nine degenerates (LHS 1132, 1200, 1341, 1402, 1542, 1938, 1974, 2618, and 3811) lack published photometry or spectroscopy; the remaining stars have sufficient observations to allow an assessment of their likely properties. Several stars have trigonometric parallax measurements (Monet et al. 1992; Tinney 1996), while others have distance estimates from the PMSU survey (PMSU1).

3.1. Distances

The high proper motion of LHS stars renders them obvious nearby star candidates. Many have been targeted in trigonometric parallax programs, including a number of stars in the present sample. Table 6 lists trigonometric parallax data, 2MASS photometry, and spectral types for those stars, together with data for other late‐type subdwarfs from the compilation by Gizis (1997). The majority of the parallax measurements are from either Harrington & Dahn (1980) or Monet et al. (1992).

TABLE 6 Parallax Stars

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Most stars in the current sample, however, lack direct distance measurements. In the case of disk dwarfs listed in Table 2, we can use the ( , TiO5) and ( , CaH2) relations derived by Cruz & Reid (2002) to calculate spectroscopic parallaxes for spectral types earlier than M7; we have averaged the results to give the values listed in Table 2. These indices are not calibrated reliably for either ultracool disk dwarfs (spectral type ≥M7) or for subdwarfs. Moreover, a number of stars listed in Table 5 lack the requisite band‐strength indices. For those stars, we must estimate distances using spectral‐type/ relations.

Lépine et al. (2003a) have computed spectral‐type/ calibrations for disk dwarfs, sdM subdwarfs, and esdM subdwarfs. Figure 9 compares their derived relations against data for stars with reliable trigonometric parallaxes from both Table 6 and the 8 pc sample (Reid et al. 2003). While the Lépine et al. subdwarf calibrations are in broad agreement with the data, it is clear that the spectral‐type/ relation derived for disk dwarfs overestimates absolute magnitudes for spectral types earlier than M3. Our calibrating data set includes additional subdwarfs, so we have recomputed all three calibrations, fitting linear relations. For esdM dwarfs, we derive where spectral type (SpT) = −1 at esdK7, 0 at esdM0, etc. For sdM dwarfs, we have Both the sdM and esdM relations are very close to those computed by Lépine et al. For disk M dwarfs, the calibration has to take into account the well‐documented break in the main sequence between spectral types M3 and M4 (see Reid & Cruz 2002 for further discussion; we note that this feature still lacks any thorough theoretical exploration). Consequently, we divide the disk calibration into three segments: and As Figure 9 shows, this segmented calibration is very close to the Lépine et al. relation for spectral types later than M3. Moreover, the sdM and M dwarf calibrations are almost identical for spectral types later than M4. We have used these relations to derive distances for the sdM and esdM dwarfs, and for disk dwarfs with only spectral type measurements.

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Fig. 9.— HR diagram for parallax stars. Stars from the present sample of LHS stars are plotted using the same symbols as in Fig. 1, and disk dwarfs from the 8 pc sample are plotted as crosses. The solid lines mark the spectral‐type/ calibrations from Lépine et al. (2002); the dashed lines are the relations adopted in this paper.

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Tables Table 2 and 5 list distance estimates for the hydrogen‐burning stars in the faint LHS sample (with the exception of the 8 M dwarfs lacking even spectral types cited in § 2.4). We have not attempted to estimate absolute magnitudes and distances for the degenerate stars, since in most cases our spectra are insufficient to allow reliable temperature estimates. For consistency with our continuing survey of the stellar populations in the immediate solar neighborhood (Cruz et al. 2003; Reid et al. 2004), we also give the corresponding J‐band absolute magnitude for each star.

The distance distributions of the M‐type LHS stars are shown in Figure 10, combining data from Tables 2 and 5. As expected, the higher velocity halo subdwarfs span a much larger range of distance: the M dwarfs have an average distance of 51.5 pc and a median distance of 36.5 pc; for sdM dwarfs, the parameters are pc and pc; for esdM dwarfs, pc and pc. There are 26 stars with formal distance estimates less than 20 pc (14 from Table 2 and 12 from 5); all save one (LHS 3841, see below) are disk dwarfs with spectral types M5.5 or later.

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Fig. 10.— Distance distribution of the M‐type LHS stars in Tables 2 and 5. We have separated M dwarfs, sdM subdwarfs, and esdM subdwarfs, and the dashed line in each panel marks the average distance, while the dotted line shows the median distance.

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3.2. Velocities

Our spectra are not suitable for deriving reliable radial velocities: the dispersion is relatively low, and many stars lack adjacent wavelength‐calibration data. As a result, we cannot determine space motions for the LHS stars. However, we can estimate tangential velocities for the M dwarfs and subdwarfs in the sample.

Figure 11 shows the tangential velocity distributions for M dwarfs, sdM subdwarfs, and esdM subdwarfs. The samples include stars from Table 5 with distance estimates. As in Figure 10, we have marked both the mean and median values in each distribution. The average velocities are 172, 356, and 341 km s⁻¹ for M, sdM, and esdM dwarfs, while the median values are 116, 340, and 331 km s⁻¹, respectively.

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Fig. 11.— Tangential velocity distribution of the M‐type LHS stars in Tables 2 and 5. As in Fig. 10, we have separated M dwarfs, sdM subdwarfs, and esdM subdwarfs, and the short‐dashed vertical line in each histogram panel marks the average distance, while the dotted line shows the median distance. The long‐dashed line outlines the expected distribution of tangential velocities, based on the disk and halo kinematics described in the text. The right‐hand panels plot the velocity/spectral type distributions for each data set.

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We also show the distribution of with spectral type. In all three cases, the highest velocity stars have early spectral types. This is to be expected, since the magnitude selection criterion, , requires that more luminous earlier type stars lie at larger distances than later type dwarfs. Coupled with the LHS selection criterion, yr⁻¹, this ensures high tangential velocities. There are seven stars that formally have tangential velocities in excess of 500 km s⁻¹: LHS 1342 (M2.5, km s⁻¹), LHS 3958 (sdM4, 510 km s⁻¹), LHS 3322 (sdM1, 512 km s⁻¹), LHS 2172 (sdM3.5, 516 km s⁻¹), LHS 2519 (sdM1, 543 km s⁻¹), LHS 2818 (sdM0, 746 km s⁻¹), and LHS 2533 (esdM1.5, 611 km s⁻¹). We note that the sdM absolute magnitude calibration has significant dispersion, particularly for early‐type dwarfs. Nonetheless, the local Galactic escape speed is usually estimated as between 450 and 650 km s⁻¹ (Leonard & Tremaine 1990), so it is important to obtain more reliable distance estimates (and radial velocities) for these stars.

We have used Monte Carlo simulations to compare the observed velocity distributions against the expected results, based on current determinations of the kinematics of the Galactic disk and halo. The M dwarf sample includes contributions from at least the disk and thick disk, since only a small subset of stars in the latter component have abundances (see Reid 2005 for further discussion). We adopt kinematics from the PMSU survey for the disk ( , , ; , , km s⁻¹) and take the thick disk kinematics from Strömgren (1987; −5, −40, −17; 65, 54, 38), with the local thick disk density normalized to 10% that of the disk. For the halo, we use the two‐component model from Sommer‐Larsen & Zhen (1990): Halo I (−20, −150, −4; 140, 100, 70), the flattened component; and Halo II (−7, −180, −5; 155, 110, 110).

The results of these simulations are plotted as long‐dashed lines in the left‐hand panels of Figure 11. Both halo components are consistent with the observed sdM and esdM distributions, with km s⁻¹ for Halo I and 330 km s⁻¹ for Halo II. However, there is poorer agreement between the composite disk model and the observed M dwarf velocity distribution. In particular, the model predicts an average tangential velocity of km s⁻¹ and significantly fewer stars at high velocities ( km s⁻¹).

There are at least three factors that are likely to contribute to the M‐dwarf discrepancy. First, the kinematically selected LHS sample certainly includes a significant number of mildly metal‐poor M dwarfs, notably thick disk stars. Our M‐dwarf absolute magnitude calibrations tend to overestimate the luminosities, distances, and velocities of those stars. Second, the mildly metal‐poor M dwarfs may include metal‐rich halo subdwarfs, with and intrinsically higher velocities relative to the Sun. Finally, a number of recent studies have suggested that the local disk population includes more high‐velocity stars than predicted by simple kinematic models. The high‐velocity M dwarfs in this sample could be the lower mass counterparts of the high‐velocity white dwarfs that have attracted attention over the last decade (see Reid 2005 for a more extensive review of this issue).

4.1. The Hydrogen‐Burning Stars

Figure 12 plots the spectral type distribution of the faintest M‐type stars in the LHS catalog, including stars from both Tables 2 and 5. Approximately 80% of the faint LHS stars are on the main sequence; ∼30% are subdwarfs, with a ∼55:45 split between types sdM and esdM. The high proportion of metal‐poor stars is a direct consequence of the proper‐motion selection: as Figure 11 emphasizes, halo stars generally have high velocities with respect to the Sun and therefore have a larger sampling volume in proper‐motion surveys than the lower velocity disk population. The scarcity of early‐type M dwarfs is a consequence of the apparent magnitude selection limit, . In order for such stars (which have ) to enter the current LHS sample, their tangential velocities would have to substantially exceed the Galactic escape speed. The LHS catalog does include many early‐type M dwarfs, but at brighter apparent magnitudes.

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Fig. 12.— Spectral type distribution of the faintest M‐type stars in the LHS catalog. The sample includes stars from both Tables 2 and 5, encompassing 95% of the hydrogen‐burning LHS stars with .

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We note that despite the large numbers of sdM and esdM stars detected, we do not identify any that rival the coolest subdwarf stars known: esdM7 (Schweitzer et al. 1999), sdM8 (Lépine et al. 2003b), or sdL (Lépine et al. 2003d; Burgasser et al. 2003). We attribute this to both incompleteness in the LHS catalog at magnitudes fainter than (Lépine et al. 2003d), and to the likely scarcity of such objects.

On the other hand, one would expect very low mass stars from the low‐metallicity tail of the halo to be present in the LHS catalog. Leggett et al. (2000), for example, suggest that LHS 451 is an extremely metal‐poor esdM, based on multiwaveband photometry. In Gizis (1997) and Gizis & Reid (1997), several esdM stars with particularly weak TiO bands were identified as potentially having metallicities . LHS 1826, the coolest esdM dwarf in the LHS catalog, stands out in particular, classified as esdM6 based on the CaH band strengths, but with negligible TiO absorption ( ). This star lies well away from the pack in Figures 2 and 3, but a number of other esdM dwarfs have TiO5 band strengths that are almost as weak. At earlier spectral types (CaH type ≲3), TiO absorption is not strong even in solar‐abundance dwarfs, and the most extreme subdwarfs are likely to have esdK spectral types. Any such stars in the LHS catalog can be expected to be brighter than . At later types, the lowest abundance esdM dwarfs are LHS 453, 3178, and 4028 (all esdM3), LHS 3555 (esdM3.5), and LHS 1625 (esdM4.5).

4.2. Activity

It is well known that the fraction of M dwarfs with chromospheric emission (dMe stars) rises toward later spectral types (e.g., Hawley et al. 1996). We have used our Hα observation to calculate the activity fraction as a function of spectral type for the faint LHS M dwarfs; those statistics are given in Table 7. The observed fractions at spectral types M5 to M7 are significantly lower than the statistics for all M dwarfs within 25 pc (Hawley et al. 1996); at M5 and M6, our data find lower fractions than those measured for M dwarfs at moderate distances above the Galactic plane (West et al. 2004). We attribute this to the proper‐motion selection that defines our sample; by selecting stars with higher tangential motions, we are also selecting the oldest, least active stars in the solar neighborhood.

TABLE 7 Fraction of dMe Stars

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None of the subdwarfs (sdM or esdM) shows activity. We conclude that the spin‐down timescale of these very low mass M subdwarfs is less than the age of the halo (10–12 Gyr); this is consistent with the properties of their higher metallicity M‐dwarf counterparts. We know from two binary sdMe systems in Gizis (1998) that it is possible for rapidly rotating sdM dwarfs to show emission. Combining the present sample with previous surveys gives a total of 50 esdM dwarfs; none of those stars shows Hα emission, implying that ≲4% are close, tidally locked binaries.

What is the threshold rotational velocity for activity? Bopp & Fekel (1977) found that an equatorial velocity of 5 km s⁻¹ was required for significant Hα emission in BY Dra variables in the disk population. These stars are early‐type M dwarfs with radiative cores, where the standard solar dynamo model is applicable, rather than fully convective late‐type M dwarfs, where a shear dynamo is a more likely source of magnetic activity. If the solar model holds for late‐type subdwarfs, then the 5 km s⁻¹ threshold corresponds approximately to rotation periods less than 5 days, and for low‐mass subdwarf binaries, orbital semimajor axes between 0.035 and 0.05 AU.

4.3. The White Dwarfs

Almost 20% of the faintest LHS stars are degenerates; most are spectral type DC. As noted above, this is to be expected: selection by proper motion biases a sample to nearby stars; hence, degenerates with intrinsically low luminosities are found preferentially among the faintest stars in a proper‐motion catalog. These stars play an important role in understanding the formation history of the Milky Way, since they define the lower limit of the white dwarf luminosity function and set constraints on the age of the oldest stars in the Galactic disk (Bergeron et al. 1997; Reid 2005).

Four white dwarfs in the present sample are among the cool white dwarfs analyzed by Bergeron et al. (1997, 2001): LHS 1405, K, with a He‐rich atmosphere; LHS 2364, K, with a H‐rich atmosphere; LHS 2673, another H‐rich star, has K; and LHS 3151, K, with a H‐rich atmosphere. These temperatures are consistent with cooling times from 6 to 9 Gyr.

Eight stars in Table 4 have been identified as high‐velocity white dwarfs: LHS 1433, 1739, 1898, 3779, and 3821 were selected from the New Luyten Two‐Tenths (NLTT) catalog by Kawka et al. (2004); and LHS 1274, 4033, and 4042 are included in the sample of cool, high proper motion white dwarfs identified by Oppenheimer et al. (2001, hereafter OHDHS). All three of the OHDHS stars also have spectroscopy by Salim et al. (2004). While LHS 1274 and 4042 are probably relatively old degenerates, LHS 4033 has been shown to be a high‐mass white dwarf (∼1.32 ; Dahn et al. 2004). LHS 4033 is significantly hotter than other high‐velocity white dwarfs, with K and a likely cooling time of ∼1 Gyr. Finally, LHS 3250 is one of the coolest white dwarfs known, with strong pressure‐induced H₂ absorption, and is one of the few known degenerates that may prove to be a member of the (Population II) Galactic halo (Harris et al. 1999).

In addition to the cool DC white dwarfs, the faint LHS stars in the present sample include five DQ (carbon) dwarfs, of which three are new identifications; the most unusual, LHS 1737, is discussed further below. There are also two magnetic white dwarfs. LHS 2273 was originally identified as a magnetic white dwarf by Schmidt & Smith (1995) and shows clear evidence for Zeeman splitting of the hydrogen lines. LHS 2534 is more unusual; the strongest features in the spectrum are due to Na, Mg, and Ca, all of which show clear Zeeman splitting (Reid et al. 2001). Half of the stars in Table 2 (and at least nine stars in Table 5) still lack high‐S/N spectra and/or accurate optical photometry. More detailed observations of those stars are clearly desirable.

4.4. Individual Stars of Interest

LHS 1035, 1135, 1669, 2236, 2419.—These five stars were classified as sdM dwarfs in Gizis & Reid (1997). All lie near the M/sdM boundary, and all five are classified as disk dwarfs in the present reanalysis.

LHS 1317.—We classify this star as M7 on the basis of the strong TiO and obvious VO. It has no detectable emission and is also quite blue, with . The most likely explanation is that this star has an older age and a lower metallicity than most nearby M7 dwarfs. Based on the location in the CaH/TiO band‐strength diagrams, we estimate a metallicity ; i.e., at the lower range of disk metallicities but above the lower limit of the sdM class.

LHS 1737.—This white dwarf has broad absorption features centered at ∼4900 and ∼4500 Å. These wavelengths could match He i lines, but in that case the white dwarf would have a temperature exceeding ∼20,000 K, , and a distance exceeding 160 pc; the optical/near‐infrared colors are inconsistent with such a high temperature. The more likely alternative is that LHS 1737 is similar to ESO 439−162 and LHS 1126, which have strong absorption features at these wavelengths, attributed to shifted and broadened C₂ lines (Wesemael et al. 1993).

LHS 2167.—This star was listed as an M5.5 dwarf in Gizis & Reid (1997), but is clearly a DC white dwarf. In fact, the band‐strength indices listed in Table 4 of that paper are from an observation of LHS 2179, an M5.5 dwarf.

LHS 3841.—This esdM2 is very bright. The implied distance, assuming it is single, is only 19 pc. It should be a high‐priority target for trigonometric parallax programs.