Discovery of a brown dwarf companion to the star HIP 64892

Cheetham, A.; Bonnefoy, M.; Desidera, S.; Langlois, M.; Vigan, A.; Schmidt, T.; Olofsson, J.; Chauvin, G.; Klahr, H.; Gratton, R.; D’Orazi, V.; Henning, T.; Janson, M.; Biller, B.; Peretti, S.; Hagelberg, J.; Ségransan, D.; Udry, S.; Mesa, D.; Sissa, E.; ... (2018). Discovery of a brown dwarf companion to the star HIP 64892. Astronomy and astrophysics, 615, A160. EDP Sciences 10.1051/0004-6361/201832650

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We report the discovery of a bright, brown dwarf companion to the star HIP 64892, imaged with VLT/SPHERE during the SHINE exoplanet survey. The host is a B9.5V member of the Lower-Centaurus-Crux subgroup of the Scorpius Centaurus OB association. The measured angular separation of the companion (1.2705±0.0023") corresponds to a projected distance of 159±12 AU. We observed the target with the dual-band imaging and long-slit spectroscopy modes of the IRDIS imager to obtain its SED and astrometry. In addition, we reprocessed archival NACO L-band data, from which we also recover the companion. Its SED is consistent with a young (<30 Myr), low surface gravity object with a spectral type of M9γ±1. From comparison with the BT-Settl atmospheric models we estimate an effective temperature of Teff=2600±100 K, and comparison of the companion photometry to the COND evolutionary models yields a mass of ~29−37 MJ at the estimated age of 16⁺¹⁵−₇ Myr for the system. HIP 64892 is a rare example of an extreme-mass ratio system (q ~ 0.01) and will be useful for testing models relating to the formation and evolution of such low-mass objects.

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