J/A+A/556/A133 Astrometric orbit of DENIS-P J082303.1-49120 (Sahlmann+, 2013)
Astrometric orbit of a low-mass companion to an ultracool dwarf.
Sahlmann J., Lazorenko P.F., Segransan D., Martin E.L., Queloz D., Mayor M.,
Udry S.
<Astron. Astrophys. 556, A133 (2013)>
=2013A&A...556A.133S 2013A&A...556A.133S
ADC_Keywords: Positional data ; Binaries, orbits ; Parallaxes, trigonometric ;
Proper motions
Keywords: stars: low-mass - binaries: close - brown dwarfs - planetary systems -
astrometry - parallaxes
Abstract:
Little is known about the existence of extrasolar planets around
ultracool dwarfs. Furthermore, binary stars with Sun-like primaries
and very low-mass binaries composed of ultracool dwarfs show
differences in the distributions of mass ratio and orbital separation
that can be indicative of distinct formation mechanisms. Using
FORS2/VLT optical imaging for high precision astrometry we are
searching for planets and substellar objects around ultracool dwarfs
to investigate their multiplicity properties for very low companion
masses. Here we report astrometric measurements with an accuracy of
one tenth of a milli-arcsecond over two years that reveal orbital
motion of the L1.5 dwarf DENIS-P J082303.1-491201 (having 7.5±1% of
the Sun's mass) caused by a companion with a mass of 28±2 Jupiter
masses that revolves about its host on an eccentric orbit in
246.4±1.4days. This new system is nearby at 20.77±0.08pc and has
the smallest mass ratio (0.36±0.02) of known very low-mass binaries
with a characterised orbit. With this discovery we demonstrate 100
micro-arcsecond astrometry over an arc-minute field and over several
years that is sufficient to discover sub-Jupiter mass planets around
ultracool dwarfs. We also show that the achieved parallax accuracy of
<0.4% makes it possible to remove distance as a dominant source of
uncertainty in the modelling of ultracool dwarfs.
Description:
Reduced data used in this publication: Relative astrometry. The data
can be modelled with Eq. 1 of the paper are plotted in Fig.3 and
Fig.4. They were obtained from optical imaging with the FORS2 camera
at the Very Large Telescope.
Objects:
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RA (2000) DE Designation(s)
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08 23 03.13 -49 12 01.3 DENIS-P J082303.1-491201 = 2MASS J08230313-4912012
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 105 281 Relative astrometry of DENIS-P J082303.1-491201
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See also:
J/AJ/133/971 : Low-mass stars and brown dwarfs wide companions (Allen+, 2007)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- EpNr [1/14] Epoch number of the observation
4- 16 F13.5 d JD [2455540/2456299] Julian Date of the observation
18- 25 F8.3 mas dRA Relative Right Ascension*cos(Declination)
27- 31 F5.3 mas e_dRA Standard uncertainty of dRA
33- 39 F7.3 mas dDE Relative Declination
41- 45 F5.3 mas e_dDE Standard uncertainty of dDE
47- 54 F8.5 --- PRA Parallax factor in Right Ascension Πα
56- 63 F8.5 --- PDE Parallax factor in Declination Πδ
65- 72 F8.5 --- fx1 Chromatic refraction factor Nr.1 (section 3)
74- 81 F8.5 --- fx2 Chromatic refraction factor Nr.2 (section 3)
83- 90 F8.5 --- fy1 Chromatic refraction factor Nr.3 (section 3)
92- 99 F8.5 --- fy2 Chromatic refraction factor Nr.4 (section 3)
101-105 F5.3 mas Cov Covariance
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Acknowledgements:
Johannes Sahlmann, Johannes.Sahlmann(at)unige.ch
(End) Patricia Vannier [CDS] 07-Jun-2013