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Rotation periods and astrometric motions of the Luhman 16AB brown dwarfs by high-resolution lucky-imaging monitoring

Mancini, L.; Giacobbe, P.; Littlefair, S.P.; Southworth, J.; Bozza, V.; Damasso, M.; Dominik, M.; Hundertmark, M.; Jørgensen, U.G.; Juncher, D.; Popovas, A.; Rabus, M.; Rahvar, S.; Schmidt, R.W.; Skottfelt, J.; Snodgrass, C.; Sozzetti, A.; Alsubai, K.; Bramich, D.M.; Calchi Novati, S.; Ciceri, S.; D’Ago, G.; Figuera Jaimes, R.; Galianni, P.; -H. Gu, S.; Harpsøe, K.; HaugbøllE, T.; Th. Henning; Hinse, T.C.; Kains, N.; Korhonen, H.; Scarpetta, G.; Starkey, D.; Surdej, J.; -B. Wang, X.; Wertz, O.

Rotation periods and astrometric motions of the Luhman 16AB brown dwarfs by high-resolution lucky-imaging monitoring Thumbnail


Authors

L. Mancini

P. Giacobbe

S.P. Littlefair

V. Bozza

M. Damasso

M. Dominik

M. Hundertmark

U.G. Jørgensen

D. Juncher

A. Popovas

M. Rabus

S. Rahvar

R.W. Schmidt

J. Skottfelt

C. Snodgrass

A. Sozzetti

K. Alsubai

D.M. Bramich

S. Calchi Novati

S. Ciceri

G. D’Ago

R. Figuera Jaimes

P. Galianni

S. -H. Gu

K. Harpsøe

T. HaugbøllE

Th. Henning

T.C. Hinse

N. Kains

H. Korhonen

G. Scarpetta

D. Starkey

J. Surdej

X. -B. Wang

O. Wertz



Abstract

Context. Photometric monitoring of the variability of brown dwarfs can provide useful information about the structure of clouds in their cold atmospheres.The brown-dwarf binary system Luhman?16AB is an interesting target for such a study, because its components stand at the L/T transition and show high levels of variability. Luhman?16AB is also the third closest system to the solar system, which allows precise astrometric investigations with ground-based facilities.

Aims. The aim of the work is to estimate the rotation period and study the astrometric motion of both components.

Methods. We have monitored Luhman?16AB over a period of two years with the lucky-imaging camera mounted on the Danish 1.54?m telescope at La Silla, through a special i + z long-pass filter, which allowed us to clearly resolve the two brown dwarfs into single objects. An intense monitoring of the target was also performed over 16 nights, in which we observed a peak-to-peak variability of 0.20 ± 0.02?mag and 0.34 ± 0.02?mag for Luhman?16A and 16B, respectively.

Results. We used the 16-night time-series data to estimate the rotation period of the two components. We found that Luhman?16B rotates with a period of 5.1 ± 0.1?h, in very good agreement with previous measurements. For Luhman?16A, we report that it rotates more slowly than its companion, and even though we were not able to get a robust determination, our data indicate a rotation period of roughly 8?h. This implies that the rotation axes of the two components are well aligned and suggests a scenario in which the two objects underwent the same accretion process. The 2-year complete data set was used to study the astrometric motion of Luhman?16AB. We predict a motion of the system that is not consistent with a previous estimate based on two months of monitoring, but cannot confirm or refute the presence of additional planetary-mass bodies in the system.

Journal Article Type Article
Acceptance Date Oct 25, 2015
Online Publication Date Nov 30, 2015
Publication Date 2015-12
Journal Astronomy & Astrophysics
Print ISSN 0004-6361
Publisher EDP Sciences
Peer Reviewed Peer Reviewed
Volume 584
Article Number A104
DOI https://doi.org/10.1051/0004-6361/201526899
Keywords astrophysics, binaries, visual, brown dwarfs, stars, variables general, techniques photometric, image processing
Publisher URL http://dx.doi.org/10.1051/0004-6361/201526899

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