HAL : hal-00402538, version 1

arXiv : 0904.0249

Code Bibliographique ADS : 2009ApJ...698L.147G

DOI : 10.1088/0004-637X/698/2/L147

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The Astrophysical Journal / The Astrophysical Journal Letters; Astrophysical Journal Letters to the Editor 698 (2009) L147-L151

The Extreme Microlensing Event OGLE-2007-BLG-224: Terrestrial Parallax Observation of a Thick-Disk Brown Dwarf

A. Gould 1, A. Udalski, B. Monard, K. Horne, Subo Dong, N. Miyake, K. Sahu, D. P. Bennett, Ł. Wyrzykowski, I. Soszyński, M. K. Szymański, M. Kubiak, G. Pietrzyński, O. Szewczyk, K. Ulaczyk, W. Allen, G. W. Christie, D. L. DePoy, B. S. Gaudi, C. Han, C.-U. Lee, J. McCormick, T. Natusch, B.-G. Park, R. W. Pogge, A. Allan, M. F. Bode 2, D. M. Bramich, M. J. Burgdorf, M. Dominik, S. N. Fraser, E. Kerins, C. Mottram, C. Snodgrass, I. A. Steele, R. Street, Y. Tsapras, F. Abe, I. A. Bond, C. S. Botzler, A. Fukui, K. Furusawa, J. B. Hearnshaw, Y. Itow, K. Kamiya, P. M. Kilmartin, A. Korpela, W. Lin, C. H. Ling, K. Masuda, Y. Matsubara, Y. Muraki, M. Nagaya, K. Ohnishi, T. Okumura, Y. C. Perrott, N. Rattenbury, To. Saito, T. Sako, L. Skuljan, D. J. Sullivan, T. Sumi, W. L. Sweatman, P. J. Tristram, P. C. M. Yock, M. Albrow, J. P. Beaulieu 3, C. Coutures 3, H. Calitz, J. Caldwell, P. Fouqué 4, R. Martin, A. Williams

(06/2009)

Parallax is the most fundamental technique for measuring distances to astronomical objects. Although terrestrial parallax was pioneered over 2000 years ago by Hipparchus (ca. 140 B.C.E.) to measure the distance to the Moon, the baseline of the Earth is so small that terrestrial parallax can generally only be applied to objects in the Solar System. However, there exists a class of extreme gravitational microlensing events in which the effects of terrestrial parallax can be readily detected and so permit the measurement of the distance, mass, and transverse velocity of the lens. Here we report observations of the first such extreme microlensing event OGLE-2007-BLG-224, from which we infer that the lens is a brown dwarf of mass M = 0.056 ± 0.004 M sun, with a distance of 525 ± 40 pc and a transverse velocity of 113 ± 21 km s–1. The velocity places the lens in the thick disk, making this the lowest-mass thick-disk brown dwarf detected so far. Follow-up observations may allow one to observe the light from the brown dwarf itself, thus serving as an important constraint for evolutionary models of these objects and potentially opening a new window on substellar objects. The low a priori probability of detecting a thick-disk brown dwarf in this event, when combined with additional evidence from other observations, suggests that old substellar objects may be more common than previously assumed.

1 :	Department of Astronomy (Ohio State University)
	Ohio State University
2 :	Astrophysics Research institute, Liverpool John Moores University (ARI, JMU)
	Liverpool John Moores University
3 :	Institut d'Astrophysique de Paris (IAP)
	CNRS : UMR7095 – INSU – Université Pierre et Marie Curie (UPMC) - Paris VI
4 :	Laboratoire Astrophysique de Toulouse-Tarbes (LATT)
	CNRS : UMR5572 – INSU – Observatoire Midi-Pyrénées – Université Paul Sabatier [UPS] - Toulouse III

Domaine

:

Planète et Univers/Astrophysique/Astrophysique stellaire et solaire Physique/Astrophysique/Astrophysique stellaire et solaire

Mots Clés : astrometry – gravitational lensing – stars: low-mass – brown dwarfs

hal-00402538, version 1

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Contributeur : Dominique Lullier <>

Soumis le : Mardi 7 Juillet 2009, 15:58:00

Dernière modification le : Mardi 7 Juillet 2009, 15:58:00