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Title:
The Wide Brown Dwarf Binary Oph 1622-2405 and Discovery of a Wide, Low-Mass Binary in Ophiuchus (Oph 1623-2402): A New Class of Young Evaporating Wide Binaries?
Authors:
Close, Laird M.; Zuckerman, B.; Song, Inseok; Barman, Travis; Marois, Christian; Rice, Emily L.; Siegler, Nick; Macintosh, Bruce; Becklin, E. E.; Campbell, Randy; Lyke, James E.; Conrad, Al; Le Mignant, David
Affiliation:
AA(Steward Observatory, University of Arizona, Tucson, AZ 85721 ), AB(Department of Physics and Astronomy and NASA Astrobiology Institute, University of California, Los Angeles, CA 90095.), AC(Gemini Observatory, Hilo, HI 96720.), AD(Lowell Observatory, Flagstaff, AZ 86001.), AE(Lawrence Livermore Laboratory, Livermore, CA 94550.), AF(Department of Physics and Astronomy and NASA Astrobiology Institute, University of California, Los Angeles, CA 90095.), AG(Steward Observatory, University of Arizona, Tucson, AZ 85721 ), AH(Lawrence Livermore Laboratory, Livermore, CA 94550.), AI(Department of Physics and Astronomy and NASA Astrobiology Institute, University of California, Los Angeles, CA 90095.), AJ(W. M. Keck Observatory, Kamuela, HI 96743.), AK(W. M. Keck Observatory, Kamuela, HI 96743.), AL(W. M. Keck Observatory, Kamuela, HI 96743.), AM(W. M. Keck Observatory, Kamuela, HI 96743.)
Publication:
The Astrophysical Journal, Volume 660, Issue 2, pp. 1492-1506. (ApJ Homepage)
Publication Date:
05/2007
Origin:
UCP
Astronomy Keywords:
Stars: Binaries: General, Instrumentation: Adaptive Optics, Stars: Evolution, Stars: Formation, stars: individual (2MASS J16222521-2405139), stars: individual (2MASS J16233609-2402209), Stars: Low-Mass, Brown Dwarfs
DOI:
10.1086/513417
Bibliographic Code:
2007ApJ...660.1492C

Abstract

We imaged five objects near the star-forming clouds of Ophiuchus with the Keck Laser Guide Star AO system. We resolved sources 11 (Oph 16222-2405) and 16 (Oph 16233-2402) from Allers and coworkers into binary systems. Source 11 is resolved into a 243 AU binary, the widest known for a very low mass (VLM) binary. The binary nature of source 11 was discovered first by Allers and independently here, during which we obtained the first spatially resolved R~2000 near-infrared (J and K) spectra, mid-IR photometry, and orbital motion estimates. We estimate for 11A and 11B gravities (logg>3.75), ages (5+/-2 Myr), luminosities [log(L/Lsolar)=-2.77+/-0.10 and -2.96+/-0.10], and temperatures (Teff=2375+/-175 K and 2175+/-175 K). We find self-consistent DUSTY evolutionary model (Chabrier and coworkers) masses of 17+4-5 MJ and 14+6-5 MJ, for 11A and 11B, respectively. Our masses are higher than those previously reported (13-15 MJ and 7-8 MJ) by Jayawardhana & Ivanov. Hence, we find that the system is unlikely a ``planetary mass binary,'' as do Luhman and coworkers, but it has the second lowest mass and lowest binding energy of any known binary. Oph 11 and Oph 16 belong to a newly recognized population of wide (>~100 AU), young (<10 Myr), roughly equal mass, VLM stellar and brown dwarf binaries. We deduce that ~6%+/-3% of young (<10 Myr) VLM objects are in such wide systems. However, only 0.3%+/-0.1% of old field VLM objects are found in such wide systems. Thus, young, wide, VLM binary populations may be evaporating, due to stellar encounters in their natal clusters, leading to a field population depleted in wide VLM systems.

Based on observations made with the Keck and Gemini North telescopes.

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