2014A&A...568A..87L


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.05CET12:32:15

2014A&A...568A..87L - Astronomy and Astrophysics, volume 568A, 87-87 (2014/8-1)

Long-term Ks-band photometric monitoring of L dwarfs.

LOPEZ MARTI B. and ZAPATERO OSORIO M.R.

Abstract (from CDS):

Ultracool dwarfs (≲2500K) are known to display photometric variability in short timescales (hours to days), which has usually been related to rotation-modulated dust cloud patterns, or to unresolved companions. We perform photometric time-series analysis of a sample of ten early to mid-L dwarfs in the field over three years of Ks-band observations with the OMEGA2000 infrared camera of the 3.5m telescope on Calar Alto Observatory between January 2010 and December 2012. This study represents the first systematic long-term photometric monitoring of this kind of object to date. We perform Ks-band differential photometry of our targets (with typical errors of ±15-30mmag at the 1σ level) by subtracting a reference flux from each photometric measurement. This reference flux is computed using three nearby, probably constant stars in the target's field-of-view. We then construct and visually inspect the light curves to search for variability, and use four different periodogram algorithms to look for possible periods in our photometric data. Our targets do not display long-term variability over 1σ compared to other nearby stars of similar brightness, nor do the periodograms unveil any possible periodicity for these objects, with two exceptions: 2MASS J02411151-0326587 and G196-3B. In the case of 2MASS J02411151-0326587 (L0), our data suggest a tentative period of 307±21-days, at 40% confidence level, which seems to be associated with peak-to-peak variability of 44±10mmag. This object may also display variability in timescales of years, as suggested by the comparison of our Ks-band photometry with 2MASS. For G196-3B (L3), we find peak-to-peak variations of 42±10mmag, with a possible photometric period of 442±7-days, at 95% confidence level. This is roughly the double of the astrometric period reported by Zapatero Osorio et al. (2014A&A...568A...6Z). Given the significance of these results, further photometric data are required to confirm the long-term variability. Our results suggest that early- to mid-L dwarfs are fairly stable in the Ks-band within ±90mmag at the 3σ level over months to years, which covers hundreds to tens of thousands of rotation cycles. Two out of ten targets show periodic photometric variability at 2.2µm with peak-to-peak variations of about 40mmag and tentative periods of ∼300 and ∼450d.

Abstract Copyright:

Journal keyword(s): stars: low-mass - brown dwarfs - techniques: photometric - stars: general

Simbad objects: 10

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Number of rows : 10

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 2MASS J00332386-1521309 BD* 00 33 23.8720639269 -15 21 30.866646406           L4beta 22 0
2 2MASS J00452143+1634446 BD* 00 45 21.4154136422 +16 34 44.738533078           L2beta 52 0
3 2MASS J02411151-0326587 BD* 02 41 11.51904 -03 26 58.7796           L0gamma 26 0
4 2MASS J03552337+1133437 BD* 03 55 23.3772215371 +11 33 43.796763263           L5gamma 92 0
5 2MASS J05012406-0010452 BD* 05 01 24.0863586627 -00 10 45.584828608           L4gamma 45 0
6 G 196-3B BD* 10 04 20.6389184345 +50 22 59.448807780           L3beta 93 0
7 2MASS J10224821+5825453 BD* 10 22 48.2222984613 +58 25 45.394831331           L0.6V 35 0
8 2MASS J15525906+2948485 BD* 15 52 59.0621662551 +29 48 48.576310914           L0e 31 0
9 2MASSI J1726000+153819 BD* 17 26 00.07752 +15 38 19.0140           L2V 38 0
10 2MASSW J2208136+292121 BD* 22 08 13.63056 +29 21 21.5352           L3gamma 47 0

    Equat.    Gal    SGal    Ecl

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2021.03.05-12:32:15

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