2001A&A...367..218B


Query : 2001A&A...367..218B

2001A&A...367..218B - Astronomy and Astrophysics, volume 367, 218-235 (2001/2-3)

Variability in ultra cool dwarfs: evidence for the evolution of surface features.

BAILER-JONES C.A.L. and MUNDT R.

Abstract (from CDS):

We present photometric light curves for a sample of 21 ultra cool M and L dwarfs in the field and in the young open clusters σ Orionis and the Pleiades. The list of targets includes both low mass hydrogen burning stars and brown dwarfs. Evidence for variability with rms amplitudes (in the I band) of 0.01 to 0.055 magnitudes on timescales of 0.4 to 100 hours is discovered in half of these objects. Power spectral analysis using the CLEAN algorithm was performed to search for evidence of periodic variability. Some objects show strong periodicities at around a few hours, which could be due to rotational modulation of the light curve by surface features. However, several objects do not have any significant periodicities to explain their variability. The v sin i values of a similar population of objects makes it very likely that our time sampling was sensitive to the expected range of rotation periods, and simulations show that we would have detected these if they were caused by long-lived surface features. We argue that this absence of periodicity is due to the evolution of the brightness, and presumably also the physical size, of surface features on timescales of a few to a few tens of hours. This is supported in the case of 2M1145 for which two light curves have been obtained one year apart and show no common periodicity. The surface features could plausibly be photospheric dust clouds or magnetically-induced spots. The recently observed decline in chromospheric activity for late type M and L dwarfs hints towards the former explanation for at least our later-type objects. Furthermore, our sample suggests that variability is more common in objects later than M9, indicating that the variability may be related to dust formation. One light curve shows a brief, but significant, dip, which could be a short-lived feature or possibly an eclipse by a companion.

Abstract Copyright:

Journal keyword(s): methods: data analysis - stars: atmospheres - stars: low-mass, brown dwarfs - stars: rotation - stars: starspots - stars: variables: others

Errata: Erratum vol. 374, p. 1071 (2001)

Simbad objects: 22

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Number of rows : 22
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 2MASSW J0030438+313932 BD* 00 30 43.8419947723 +31 39 32.086027421           L2V 15 0
2 2MASS J03261367+2950152 BD* 03 26 13.67352 +29 50 15.2448           L3.5V 18 0
3 Cl Melotte 22 OpC 03 47 00 +24 07.0           ~ 3103 0
4 Cl* Melotte 22 BPL 132 LM* 03 47 12.0749352633 +24 28 32.057631851         19.06 M8.0 23 0
5 Cl* Melotte 22 TEIDE 1 LM* 03 47 17.9128387886 +24 22 31.730547022         19.26 M8.0 104 0
6 Cl* Melotte 22 BPL 152 LM* 03 47 39.0097758088 +24 36 22.399100742       20.17 17.91 M6.0 26 0
7 Cl* Melotte 22 BPL 172 LM* 03 48 19.0038221570 +24 25 12.993119094         18.66 M7.5 23 0
8 Cl* Melotte 22 PLIZ 12 LM* 03 51 25.5664173006 +23 45 21.481457318         19.00 M8.0 64 0
9 [BZR99] S Ori 46 * 05 36 51.7 -02 32 54           M8.5 4 0
10 [BZR99] S Ori 33 * 05 36 58.0790338638 -02 35 19.451241597         17.08 ~ 11 0
11 [BZR99] S Ori 34 * 05 37 07.2197495240 -02 32 44.242601178         17.10 ~ 5 0
12 [BZR99] S Ori 44 * 05 38 07.126 -02 43 21.05   22.29 23.54 21.54 19.64 M7 7 0
13 [BZR99] S Ori 31 Y*O 05 38 20.8779121749 -02 46 13.330061031         17.25 M4.0 23 0
14 V* V2729 Ori Or* 05 38 25.57752 -02 48 37.0224   21.09 24.40 22.07 19.54 M8.5 31 0
15 NAME sigma Orionis Cluster MGr 05 38 42 -02 36.0           ~ 505 0
16 2MASS J05395200-0059019 BD* 05 39 52.0036661257 -00 59 01.474175739           L5V 74 0
17 2MASS J09130320+1841501 BD* 09 13 03.20736 +18 41 50.1432           L3V 19 0
18 2MASSW J1145572+231730 BD* 11 45 57.1438962445 +23 17 29.652833703           L1.5V 27 0
19 2MASS J11463449+2230527 BD* 11 46 34.52016 +22 30 53.0856           L3+L4 84 0
20 2MASS J12035812+0015500 BD* 12 03 58.1325905721 +00 15 50.108788052           L5.0V 30 1
21 2MASS J13340623+1940351 BD* 13 34 06.2109918165 +19 40 35.210886869           L1.5V 18 0
22 2MASS J14392836+1929149 BD* 14 39 28.36896 +19 29 14.9820           L1V 119 0

    Equat.    Gal    SGal    Ecl

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2021.07.24-14:36:59

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