High-precision astrometry on the VLT/FORS1  at time scales of few 
days

Lazorenko, P. F.; Mayor, M.; Dominik, M.; Pepe, F.; Ségransan, D.; Udry, S.

doi:10.1051/0004-6361:20077149

Cited by 16 publications

(21 citation statements)

References 29 publications

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“…For earlier runs of the MCMC analysis, we placed much wider constraints of ±200 mas on CDAR parameters ρ FORS2 and d FORS2 , finding the two parameters to be tightly correlated (see Figure 3 from Lazorenko et al (2007), which uses different units). This linear relationship between ρ FORS2 and d FORS2 is shown in our Figure 7.…”

Section: Resultsmentioning

confidence: 99%

Individual, Model-independent Masses of the Closest Known Brown Dwarf Binary to the Sun

Garcia

Ammons

Salama

et al. 2017

ApJ

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At a distance of ∼ 2 pc, our nearest brown dwarf neighbor, Luhman 16 AB, has been extensively studied since its discovery 3 years ago, yet its most fundamental parameter -the masses of the individual dwarfs -has not been constrained with precision. In this work we present the full astrometric orbit and barycentric motion of Luhman 16 AB and the first precision measurements of the individual component masses. We draw upon archival observations spanning 31 years from the European Southern Observatory (ESO) Schmidt Telescope, the Deep Near-Infrared Survey of the Southern Sky (DENIS), public FORS2 data on the Very Large Telescope (VLT), and new astrometry from the Gemini South Multiconjugate Adaptive Optics System (GeMS). Finally, we include three radial velocity measurements of the two components from VLT/CRIRES, spanning one year. With this new data sampling a full period of the orbit, we use a Markov Chain Monte Carlo algorithm to fit a 16-parameter model incorporating mutual orbit and barycentric motion parameters and constrain the individual masses to be 27.9

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Section: Resultsmentioning

confidence: 99%

Individual, Model-independent Masses of the Closest Known Brown Dwarf Binary to the Sun

Garcia

Ammons

Salama

et al. 2017

ApJ

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“…The total telescope time used over two years was ∼15 nights including overheads. The data reduction methods used to extract the target's astrometry from the raw images are described in Lazorenko (2006) and Lazorenko et al (2011Lazorenko et al ( , 2009Lazorenko et al ( , 2007) (see also JS13 and Sahlmann 2012). However, because of the large amount of collected data in the present programme, it was possible to significantly improve the reduction, in particular the mitigation of systematic errors.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Astrometric planet search around southern ultracool dwarfs

Lazorenko

Ségransan

Martín

et al. 2014

A&A

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Context. Extrasolar-planet searches that target very low-mass stars and brown dwarfs are hampered by intrinsic or instrumental limitations. Time series of astrometric measurements with precisions better than one milli-arcsecond can yield new evidence on the planet occurrence around these objects. Aims. We present first results of an astrometric search for planets around 20 nearby dwarf stars with spectral types M8-L2. Methods. Over a time-span of two years, we obtained I-band images of the target fields with the FORS2 camera at the Very Large Telescope. Using background stars as references, we monitored the targets' astrometric trajectories, which allowed us to measure parallax and proper motions, set limits on the presence of planets, and to discover the orbital motions of two binary systems. Results. We determined trigonometric parallaxes with an average accuracy of 0.09 mas ( 0.2%), which resulted in a reference sample for the study of ultracool dwarfs at the M/L transition, whose members are located at distances of 9.5-40 pc. This sample contains two newly discovered tight binaries (DE0630−18 and DE0823−49) and one previously known wide binary (DE1520−44). Only one target shows I-band variability >5 mmag rms. We derived planet exclusion limits that set an upper limit of 9% on the occurrence of giant planets with masses 5 M J in intermediate-separation (0.01-0.8 AU) orbits around M8-L2 dwarfs. Conclusions. We demonstrate that astrometric observations with an accuracy of 120 µas over two years are feasible from the ground and can be used for a planet-search survey. The detection of two tight very low-mass binaries shows that our search strategy is efficient and may lead to the detection of planetary-mass companions through follow-up observations.

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“…Reductions were based on the method previously applied to FORS1/2 observations (Lazorenko et al 2007(Lazorenko et al , 2009. The method was shown to efficiently mitigate atmospheric image motion, geometric field distortion, DCR, and other effects, thus ensuring stable precision over time scales of a few days to a few years.…”

Section: Astrometric Modelmentioning

confidence: 99%

Astrometric search for a planet around VB 10

Lazorenko

Ségransan

Figueira

et al. 2011

A&A

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We observed VB 10 in August and September 2009 using the FORS2 camera of the VLT with the aim of measuring its astrometric motion and of probing for the presence of the announced planet VB 10b. We used the published STEPS astrometric positions of VB 10 over a timespan of 9 years, which allowed us to compare the expected motion of VB 10 due to parallax and proper motion with the observed motion and to compute precise deviations. The single-epoch precisions of our observations are about 0.1 mas, and the data showed no significant residual trend, while the presence of the planet should have induced an apparent proper motion greater than 10 mas yr −1 . Subtraction of the predicted orbital motion from the observed data produces a strong trend in position residuals of VB 10. We estimated the probability that this trend is caused by random noise. After taking all the uncertainties into account and using Monte-Carlo resampling of the data, we are able to reject the existence of VB 10b with the announced mass of 6.4 M J with a false alarm probability of only 5 × 10 −4 . A 3.2 M J planet is also rejected with a false alarm probability of 0.023.

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High-precision astrometry on the VLT/FORS1 at time scales of few days

Cited by 16 publications

References 29 publications

Individual, Model-independent Masses of the Closest Known Brown Dwarf Binary to the Sun

Individual, Model-independent Masses of the Closest Known Brown Dwarf Binary to the Sun

Astrometric planet search around southern ultracool dwarfs

Astrometric search for a planet around VB 10

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