2008ApJ...672.1153R


C.D.S. - SIMBAD4 rel 1.7 - 2020.10.31CET12:29:19

2008ApJ...672.1153R - Astrophys. J., 672, 1153-1158 (2008/January-2)

Hubble Space Telescope search for M subdwarf binaries.

RIAZ B., GIZIS J.E. and SAMADDAR D.

Abstract (from CDS):

We present HST ACS observations of 19 nearby M subdwarfs in a search for binary systems. Other than the wide common proper-motion pair LHS 2140/2139, none of our sdM and esdM targets are found to be binaries. Our survey is sensitive to equal-luminosity companions at close (2-8 AU) separations, while substellar secondaries could have been detected at separations in the range of 6-30 AU. To check for wide binaries, we have compared the POSS I and II images in a field of view as large as 10'x10', but could not detect a single comoving star for any of the targets. Combining our results with those from Gizis & Reid, we have a binary fraction of 3% (1/28). Detection of a small number of M subdwarf binaries reported in the literature suggests a higher fraction than the one obtained here, probably comparable to that found for the more massive solar-type stars in the halo (13%-15%). Comparison with the disk M dwarf fraction (∼25%), however, suggests multiplicity to be rare among the lowest mass halo stars, implying the two populations formed under different initial conditions. The low binary fraction in our survey could be explained by selection biases. A decrease in multiplicity has been observed in the disk for masses below 0.1 M, the peak in the disk mass function (MF). The globular cluster MF is found to peak at about 0.33 M, with a decrease in the number of stars per unit mass below the peak mass. Our sample being composed of stars with masses between ∼0.2 and 0.085 M suggests that a decrease in multiplicity similar to the disk may also be true for the halo stars, but perhaps below a mass of ∼0.3 M. A higher M subdwarf binary fraction may be obtained if the selected primaries have masses near or higher than the peak in the MF.

Abstract Copyright:

Journal keyword(s): Stars: Binaries: General - Galaxy: Halo - Stars: Low-Mass, Brown Dwarfs - Stars: Population II - Stars: Subdwarfs

Simbad objects: 30

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Number of rows : 30

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 LP 524-26 PM* 00 11 00.7862750117 +04 20 25.138497035   19.6   17.0   usdM4 13 0
2 LP 824-198 PM* 00 11 42.1533041999 -20 57 12.876085368   20.5       M6V 11 0
3 WISEA J001441.67+654648.6 PM* 00 14 40.1567522154 +65 46 44.727847559   17.6   15.6 14.5 sdM4.5 5 0
4 LP 645-78 PM* 00 25 51.2102376823 -07 48 07.973319514   20.6       sdM6 17 0
5 LP 405-55 PM* 00 43 31.4336335200 +20 54 31.191413096   20.3   18.3   M7.0V 16 0
6 2MASS J01574055+5308134 PM* 01 57 40.6327791748 +53 08 13.395791750   13.8       sdM3.5 7 0
7 G 76-39 LM* 02 52 45.5138666139 +01 55 50.575567957   16.27 14.73 13.5 12.73 esdM2 33 0
8 Wolf 134 LM* 03 13 24.2289034679 +18 49 37.659907109   15.567 14.117 13.219 12.435 esdK7 55 0
9 Ross 585 PM* 03 30 44.80608 +34 01 07.3524   14.0   12.26   sdM0 36 0
10 LSR J0519+4213 PM* 05 19 13.6513304799 +42 13 48.953018714   18.3   16.1   esdM3.5 7 0
11 LP 251-35 PM* 05 22 05.3054965945 +38 14 14.636995453   16.6 16.25 14.6   usdM3 17 0
12 LSR J0609+2319 PM* 06 09 52.4366472758 +23 19 12.661939778   18.4   16.0   sdM5.0 9 0
13 G 105-23 LM* 06 14 01.5850193519 +15 09 54.296864871   16.23   13.6   sdM2.0 24 0
14 LP 258-28 LM* 08 30 51.6486055998 +36 12 56.811125640   19.7   16.6   esdM6 15 0
15 G 46-40 PM* 09 25 31.0851825602 +00 18 17.681141916   16.61   14.0   sdM0.5 17 0
16 G 11-35 LM* 12 02 33.6593915754 +08 25 50.731714280   15.58   13.2   sdM2.0 27 0
17 G 165-47 LM* 14 06 55.5868589230 +38 36 56.042322347   16.24   13.7   usdM1 41 0
18 LSPM J1425+7102 LM* 14 25 05.0227940507 +71 02 09.678947111   20.8   18.61 16.21 sdM8 29 0
19 LP 857-48 LM* 14 31 38.2546329151 -25 25 32.851042214   16.8 15.68     esdM4 28 0
20 LP 440-52 LM* 14 39 00.3087274496 +18 39 38.704121134   19.6 18.39 17.3 14.64 sdM7 58 0
21 LP 803-27 LM* 15 45 40.2078778816 -20 36 16.697685091     16.57     sdM5.0 20 0
22 LP 625-2 PM* 16 20 14.7820440635 -01 16 39.670264899   18.3 17.18     sdM2 11 0
23 LP 141-1 LM* 18 45 52.2452564851 +52 27 40.623179319   16.72 14.96 14.67   d/sdM4 43 0
24 G 210-19 LM* 20 27 29.0848219064 +35 59 24.806448054   16.39   14.0   sdM1.5 31 0
25 LSPM J2036+5100 LM* 20 36 21.6141972503 +51 00 04.698980889       17.46 15.26 sdM7.5 24 1
26 LSPM J2122+3656 LM* 21 22 56.3507924065 +36 56 00.289932207   18.7   16.0   esdM5 9 0
27 APMPM J2126-4454 PM* 21 26 23.9279561949 -44 53 33.795962974           sdM0 5 0
28 Wolf 1037 LM* 22 28 49.052208 +05 48 12.69000   15.63   13.77   usdK7 33 0
29 G 128-34 LM* 23 08 26.0376000260 +31 40 23.802925570   16.19   13.8   esdM0.5 26 0
30 VB 12 PM* 23 17 06.0292131972 -13 50 52.312428216   19.29 16.96 16.67   esdM3 25 1

    Equat.    Gal    SGal    Ecl

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2020.10.31-12:29:19

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