2004A&A...419..703B


Query : 2004A&A...419..703B

2004A&A...419..703B - Astronomy and Astrophysics, volume 419, 703-712 (2004/5-4)

Spectroscopic rotation velocities of L dwarfs from VLT/UVES and their comparison with periods from photometric monitoring.

BAILER-JONES C.A.L.

Abstract (from CDS):

The variability and rotation of ultra cool dwarfs (UCDs) provide important information on the atmospheres and evolution of these very low mass stars and brown dwarfs. As part of an ongoing program to investigate this, the projected rotation velocities, vsini, derived from high resolution VLT/UVES spectroscopy via cross correlation are presented for 16 field UCDs (M9V-L7.5V). This doubles the number of L dwarfs for which vsin i has been measured. All targets are found to have vsin i between 10 and 40km/s confirming that L dwarfs are rapid rotators. Radial velocities have also been measured to a precision of 1-2km/s. From the random distribution of the rotation axes, i, and theoretically predicted radii, one-sided confidence intervals are placed on the rotation periods of individual objects. These are compared with published period data obtained from photometric monitoring programs. From this, the period of 31h for the L0.5 dwarf 2M0746+2000 published by Gelino et al. (2002, Ph.D. Thesis, New Mexico State University) may be ruled out as the rotation period. The period of 11.2±0.8h for the L1.5 dwarf 2M1145+2317 obtained by Bailer-Jones & Mundt (2001A&A...367..218B) is consistent with the present vsin i results so is plausibly the true rotation period. The inclination of the rotation axis is constrained to be i=62°-90° with an expectation value of 76°. Alternatively the data set a lower limit on the radius of 0.1R, which is within the range of radii predicted by models for brown dwarfs older than 0.5Gyr. Similarly, the period of 2.7±0.1h detected by the same authors for 2M1334+1940 is also confirmed as the likely rotation period; the inclination is i=27°-44°(<i≥34°). Where no variability or period was detected by the monitoring programs the likely reason is low contrast modulating surface features. However, in three cases variability but no period was detected, even though the likely rotation period range inferred from vsin i lies within the timescale to which the monitoring was sensitive. This reinforces the ``masking hypothesis'' of Bailer-Jones & Mundt (2001A&A...367..218B), the idea that the evolution of photospheric features on timescales shorter than the rotation period obscure the regular modulation of the light curve. As has been previously discussed, a likely candidate for such features is inhomogeneous dust clouds.

Abstract Copyright:

Journal keyword(s): techniques: spectroscopic - stars: low-mass, brown dwarfs - stars: variables: general - stars: rotation

Simbad objects: 21

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Number of rows : 21
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 V* DY Psc BY* 00 24 24.6343271916 -01 58 19.968960103     19.42 17.301 15.022 M9.5V 194 1
2 LP 944-20 LM* 03 39 35.2525168530 -35 25 43.628465433     18.69 16.39 13.288 M9.5Ve 269 0
3 LSPM J0746+2000 BD* 07 46 42.50553 +20 00 31.9757       17.9 15.034 L0+L1.5 174 1
4 2MASSI J0825196+211552 BD* 08 25 19.6171008398 +21 15 51.565129705       21.97 19.22 L7.5V 107 0
5 2MASS J09130320+1841501 BD* 09 13 03.20736 +18 41 50.1432           L3V 19 0
6 2MASSI J1029216+162652 BD* 10 29 21.7025023848 +16 26 51.888202233       19.588 17.600 L2.5 29 0
7 DENIS J104731.1-181558 BD* 10 47 31.0598687732 -18 15 57.451257015           L0.3V 24 0
8 2MASSW J1145572+231730 BD* 11 45 57.1438962445 +23 17 29.652833703           L1.5V 27 0
9 2MASS J11463449+2230527 BD* 11 46 34.52016 +22 30 53.0856           L3+L4 84 0
10 2MASS J11593850+0057268 BD* 11 59 38.4887250057 +00 57 26.694904747           L0.4V 25 0
11 2MASS J12035812+0015500 BD* 12 03 58.1325905721 +00 15 50.108788052           L5.0V 30 1
12 DENIS J122815.2-154733 BD* 12 28 15.23184 -15 47 34.2312       20.187 18.163 L5.5+L5.5 137 0
13 NAME Kelu-1 BD* 13 05 40.1737206066 -25 41 05.830344467         16.85 L2+L3.5 241 0
14 2MASS J13340623+1940351 BD* 13 34 06.2109918165 +19 40 35.210886869           L1.5V 18 0
15 2MASSW J1412244+163312 BD* 14 12 24.4909214617 +16 33 11.741214448       19.449 17.258 L0.5V 24 0
16 DENIS J1431.0-1953 * 14 31 01.26288 -19 53 48.9768           ~ 8 0
17 2MASS J14392836+1929149 BD* 14 39 28.36896 +19 29 14.9820           L1V 119 0
18 DENIS J144137.2-094558 BD* 14 41 37.1670168475 -09 45 59.155474431       20.030 17.234 L1+L1 48 0
19 2MASSW J1507476-162738 BD* 15 07 47.6756748763 -16 27 40.118410414     22.136 18.928 16.579 L5V 176 0
20 2MASSW J1615441+355900 BD* 16 15 44.1549648987 +35 58 59.562297891           L3V 28 0
21 2MASSW J2224438-015852 BD* 22 24 43.8550503291 -01 58 53.265872547           L4.5V 110 0

    Equat.    Gal    SGal    Ecl

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2021.07.27-10:10:15

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