2006ApJ...645.1485B


Query : 2006ApJ...645.1485B

2006ApJ...645.1485B - Astrophys. J., 645, 1485-1497 (2006/July-2)

Discovery of the coolest extreme subdwarf.

BURGASSER A.J. and KIRKPATRICK J.D.

Abstract (from CDS):

We report the discovery of LEHPM 2-59 as the coolest extreme M subdwarf (esdM) found to date. Optical and near-infrared spectroscopy demonstrate that this source is of later spectral type than the esdM7 APMPM J0559-2903, with the presence of strong alkali lines (including Rb I), VO absorption at 7400 Å, and H2O absorption at 1.4 µm. Current optical classification schemes yield a spectral type of esdM8, making LEHPM 2-59 one of only two ultracool esdMs known. The substantial space velocity of this object (Vgalactic~-180 km/s) identifies it as a halo star. Spectral model fits to the optical and near-infrared spectral data for this and four other late-type esdMs indicate that LEHPM 2-59 is the coolest esdM currently known, with Teff=2800-3000 K and -1.5≲[M/H]≲-2.0. Comparison of Teffdeterminations for M dwarfs and esdMs based on spectral model fits from this study and the literature demonstrate a divergence in Teffscales beyond spectral types ∼M5/esdM5, as large as 600-800 K by types M8/esdM8. While this divergence is likely an artifact of the underlying classification scheme, it may lead to systematic errors in the derived properties of intermediate metallicity subdwarfs. We comment on the future of ultracool subdwarf classification and suggest several ideas for addressing shortcomings in current (largely extrapolated) schemes.

Abstract Copyright:

Journal keyword(s): Stars: Chemically Peculiar - stars: individual (LEHPM 2-59) - stars: individual (APMPM J0559-2903) - Stars: Low-Mass, Brown Dwarfs - Stars: Subdwarfs

CDS comments: In table 1 and text : LSR 0822-1700 is a misprint for LSR 0822+1700 (= LSR J0822+1700)

Simbad objects: 12

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Number of rows : 12
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 LP 589-7 PM* 01 57 27.9251685894 +01 16 43.632827839   20.5   19.1   ~ 9 0
2 HD 13936 * 02 15 28.3109874216 -09 27 59.497762932   6.537 6.549     A0V 57 0
3 LEHPM 2-59 LM* 04 52 09.9531022259 -22 45 09.344928797       18.82 17.22 esdM8.5 12 0
4 SSSPM J0500-5406 PM* 05 00 15.7731573616 -54 06 27.523111287           esdM6 12 0
5 HD 32855 * 05 05 17.3007074424 -21 15 30.560875452   7.83 7.79     A0V 15 0
6 APMPM J0559-2903 LM* 05 58 58.9230621580 -29 03 26.708741813       18.12 16.32 esdM7.5 24 0
7 HD 41473 * 06 04 07.2167998056 -29 20 20.527470060   7.77 7.80     A0V 14 0
8 HD 58383 * 07 26 02.4187924008 +14 06 10.604821356   7.32 7.41     A0V 17 0
9 LSR J0822+1700 LM* 08 22 33.7512747281 +17 00 18.928058113       18.7   usdM7.5 17 0
10 SSSPM J1013-1356 LM* 10 13 07.3464466893 -13 56 21.261502194       18.73 16.01 sdM9.5 40 1
11 LSR J1610-0040 LM* 16 10 28.9498230750 -00 40 53.964223684       17.51 14.81 sdM6.5 52 0
12 SSSPM J1930-4311 PM* 19 29 41.0053369204 -43 10 36.265058294       18.42 16.32 sdM7 9 1

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