NACO-SDI imaging of known companion host stars from the AAPS and Keck planet search surveys

Jenkins, J. S. and Jones, H. R. A. and Biller, B. and O'Toole, S. J. and Pinfield, D. J. and Close, L. and Tinney, C. G. and Butler, R. P. and Wittenmyer, R. and Carter, B. and Day-Jones, A. C. (2010) NACO-SDI imaging of known companion host stars from the AAPS and Keck planet search surveys. Astronomy and Astrophysics, 515 (2). A17-28. ISSN 0004-6361

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Abstract

Direct imaging of brown dwarfs as companions to solar-type stars can provide a wealth of well-constrained data to 'benchmark' the physics of such objects, since quantities like metallicity and age can be determined from their well-studied primaries. We present results from an adaptive optics imaging program on stars drawn from the Anglo-Australian and Keck Planet Search projects, with the aim of directly imaging known cool companions. Simulations have modeled the expected contrast ratios and separations of known companions using estimates of orbital parameters available from current radial-velocity data and then a selection of the best case objects were followed-up with high contrast imaging to attempt to directly image these companions. These simulations suggest that only a very small number of radial-velocity detected exoplanets with consistent velocity fits and age estimates could potentially be directly imaged using the VLT's Simultaneous Differential Imaging system and only under favorable conditions. We also present detectability confidence limits from the radial-velocity data sets and show how these can be used to gain a better understanding of these systems when combined with the imaging data. For HD32778 and HD91204 the detectabilities help little in constraining the companion and hence almost all our knowledge is drawn from the SDI images. Therefore, we can say that these stars do not host cool methane objects, out to on-sky separations of ~2'', with contrasts less than 10-11 magnitudes. However, for HD25874, HD120780 and HD145825, the contrasts and detectabilities can rule out a number of possible solutions, particularly at low angular separations, and for the best case, down to strong methane masses of 40MJ at 1'' separation. The contrast curves constructed for these five stars show 5 sigma contrasts (Delta F1) of ~9.2-11.5 magnitudes at separations of >/=0.6'', which correspond to contrasts of ~9.7-12.0 magnitudes for companions of mid-T spectral type. Such limits allow us to reach down to 40MJ around fairly old field dwarfs that typically constitute high precision radial-velocity programs. Finally, the analysis performed here can serve as a template for future projects that will employ extreme-AO systems to directly image planets already indirectly discovered by the radial-velocity method.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Deposited in accordance with the copyright policy of the publisher.
Depositing User: Dr Brad Carter
Faculty / Department / School: Historic - Faculty of Sciences - Department of Biological and Physical Sciences
Date Deposited: 25 Nov 2010 12:18
Last Modified: 10 Jul 2014 06:42
Uncontrolled Keywords: stars; brown dwarfs; planetary systems; high angular resolution
Fields of Research (FOR2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
02 Physical Sciences > 0204 Condensed Matter Physics > 020402 Condensed Matter Imaging
08 Information and Computing Sciences > 0801 Artificial Intelligence and Image Processing > 080110 Simulation and Modelling
Socio-Economic Objective (SEO2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI: doi: 10.1051/0004-6361/200913737
URI: http://eprints.usq.edu.au/id/eprint/8221

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