J/A+A/584/A104 Luhman 16AB Lucky imaging photometry & astrometry (Mancini+ 2015)
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., Jorgensen 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., Gu S.-H., Harpsoe K.,
Haugbolle T., Henning T., Hinse T.C., Kains N., Korhonen H., Scarpetta G.,
Starkey D., Surdej J., Wang X.-B., Wertz O.
<Astron. Astrophys. 584, A104 (2015)>
=2015A&A...584A.104M 2015A&A...584A.104M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple
Keywords: binaries: visual - brown dwarfs - stars: variables: general -
techniques: photometric - techniques: image processing
Abstract:
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, as 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, allowing precise
astrometric investigations with ground-based facilities.
The aim of the work is to estimate the rotation period and study the
astrometric motion of both components.
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 0.20mag and 0.34mag for
Luhman 16A and 16B, respectively.
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-hr, in very good agreement with previous measurements. For
Luhman 16A, we report that it rotates slower than its companion and,
even though we were not able to get a robust determination, our data
indicate a rotation period of roughly 8-hr. 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 dataset was used to study the astrometric
motion of Luhman16AB. 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.
Description:
Photometric light curves and astrometric motion curves of Luhman 16A
and Luhman 16B.
Objects:
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RA (2000) DE Designation(s)
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10 49 19.0 -53 19 10 Luhman 16A = ** LUH 16A
10 49 18.9 -53 19 09 Luhman 16B = ** LUH 16B
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
astrom.dat 119 24 Astrometry of Luhman 16A and Luhman 16B
luh16a.dat 39 708 Photometric light curves of Luhman 16A
luh16b.dat 39 708 Photometric light curves of Luhman 16B
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Byte-by-byte Description of file: astrom.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 d JD Julian Date (JD-2456000.0)
11- 22 F12.10 deg Xi16A Measured Xi standard coordinate of Luhman 16A (1)
24- 36 F13.10 deg Eta16A Measured Eta standard coordinate of Luhman 16A (1)
38- 50 E13.8 deg e_Xi16A Uncertainty on Xi16A
52- 64 E13.8 deg e_Eta16A Uncertainty Eta16A
66- 77 F12.10 deg Xi16B Measured Xi standard coordinate of Luhman 16B (1)
79- 91 F13.10 deg Eta16B Measured Eta standard coordinate of Luhman 16B (1)
93-105 E13.8 deg e_Xi16B Uncertainty on Xi16B
107-119 E13.8 deg e_Eta16B Uncertainty Eta16B
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Note (1): see equations in Sec 3.2.
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Byte-by-byte Description of file: luh16a.dat luh16b.dat
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Bytes Format Units Label Explanations
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3- 15 F13.7 d BJD Barycentric JD for the midpoint of observation
(TDB, BJD-2400000)
18- 27 F10.7 mag izmag PSF photometry i+z mag of Luhman 16 A
31- 39 F9.7 mag e_izmag Measurement error of the i+z band magnitude
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Acknowledgements:
Luigi Mancini, mancini(at)mpia.de
History:
* 30-Nov-2015: First on-line version
* 16-Feb-2016: Astrometric table added (from author)
(End) Luigi Mancini [MPIA, Germany], Patricia Vannier [CDS] 27-Oct-2015