2014A&A...565A..21L


C.D.S. - SIMBAD4 rel 1.7 - 2019.08.21CEST03:55:24

2014A&A...565A..21L - Astronomy and Astrophysics, volume 565A, 21-21 (2014/5-1)

Astrometric planet search around southern ultracool dwarfs. II. Astrometric reduction methods and a deep astrometric catalogue.

LAZORENKO P.F., SAHLMANN J., SEGRANSAN D., MARTIN E.L., MAYOR M., QUELOZ D. and UDRY S.

Abstract (from CDS):

We describe the astrometric reduction of images obtained with the FORS2/VLT camera in the framework of an astrometric planet search around 20M/L-transition dwarfs. We present the correction of systematic errors, the achieved astrometric performance, and a new astrometric catalogue containing the faint reference stars in 20 fields located close to the Galactic plane. Remote reference stars were used both to determine the astrometric trajectories of the nearby planet search targets and to identify and correct systematic errors. We detected three types of systematic errors in the FORS2 astrometry: the relative motion of the camera's two CCD chips, errors that are correlated in space, and an error contribution of as yet unexplained origin. The relative CCD motion probably has a thermal origin and typically is 0.001-0.010px (∼0.1-1mas), but sometimes amounts to 0.02-0.05px (3-6mas). This instability and space-correlated errors are detected and mitigated using reference stars. The third component of unknown origin has an amplitude of 0.03-0.14mas and is independent of the observing conditions. We find that a consecutive sequence of 32 images of a well-exposed star over 40-min at 0.6'' seeing results in a median rms of the epoch residuals of 0.126mas. Overall, the epoch residuals are distributed according to a normal law with a χ2 value near unity. We compiled a catalogue of 12000 stars with I-band magnitudes of 16-22 located in 20 fields, each covering ∼ 2'x2'. It contains I-band magnitudes, ICRF positions with 40-70mas precision, and relative proper motions and absolute trigonometric parallaxes with a precision of 0.1mas/yr and 0.1mas at the bright end, respectively. This work shows that an astrometric accuracy of ∼100 micro-arcseconds over two years can be achieved with a large optical telescope in a survey covering several targets and varying observing conditions.

Abstract Copyright:

Journal keyword(s): astrometry - techniques: high angular resolution - atmospheric effects - parallaxes - brown dwarfs

VizieR on-line data: <Available at CDS (J/A+A/565/A21): table1.dat cat_fors.dat>

Status in Simbad:  will not be processed

Simbad objects: 20

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Number of rows : 20

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 2MASS J06154934-0100415 BD* 06 15 49.3549619421 -01 00 41.659094164         17.00 L1.0V 11 0
2 2MASS J06300140-1840143 BD* 06 30 01.4609493271 -18 40 14.825550559         15.88 M8.5 7 0
3 2MASS J06441439-2841417 BD* 06 44 14.4139030405 -28 41 41.749065298         16.96 M9.5 7 0
4 USNO-B1.0 0644-00098276 BD* 06 52 19.7631187838 -25 34 50.466131332       19.3 15.96 M9.2V 14 0
5 2MASS J07164790-0630369 BD* 07 16 47.9039277022 -06 30 36.942708123         17.46 L1.1V 9 0
6 2MASS J07511645-2530432 BD* 07 51 16.3951502000 -25 30 43.042204212         16.53 L1.1V 16 0
7 2MASS J08051104-3158115 BD* 08 05 11.0219343546 -31 58 11.464454559         16.01 M8 5 0
8 2MASS J08123170-2444423 BD* 08 12 31.7163139884 -24 44 42.472716658       19.458 17.27 L0.9V 13 0
9 DENIS J082303.1-491201 BD* 08 23 03.1457502969 -49 12 01.265841098       20.020 17.14 L2.7V 12 0
10 SSSPM J0829-1309 BD* 08 28 34.1713208171 -13 09 19.842042734     19.1   16.07 L2 39 0
11 2MASS J10482788-5254180 BD* 10 48 27.8698669504 -52 54 18.129558996       19.965 17.25 L1.5 7 0
12 2MASS J11574809-4844428 BD* 11 57 48.0922231567 -48 44 42.844880952         17.25 M9.4V 7 0
13 2MASS J11592743-5247188 BD* 11 59 27.3607245322 -52 47 18.910528784   21 19 16.617 14.49 M9V 23 0
14 2MASS J12531092-5709248 BD* 12 53 10.9620497223 -57 09 24.848571988         16.74 L0.5 7 0
15 2MASS J15200224-4422419 BD* 15 20 02.242 -44 22 41.99       19.4 16.89 L1 20 0
16 2MASS J17054744-5441513 BD* 17 05 47.4269185940 -54 41 51.339685217       19.090 16.66 M8.5 6 0
17 2MASS J17334227-1654500 BD* 17 33 42.27 -16 54 50.0         16.82 L0.9V 8 0
18 2MASS J17453466-1640538 BD* 17 45 34.6668182094 -16 40 53.961533063         17.11 L1.3V 12 0
19 2MASS J17562963-4518224 BD* 17 56 29.63 -45 18 22.5       17.982 15.46 M9 7 0
20 2MASS J17565620-4805096 BD* 17 56 56.2079723621 -48 05 09.629197908         16.76 L0 6 0

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2019.08.21-03:55:24

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