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New Masses and Ages for the Planetary Mass Binary Candidate Ophiuchus #11 (2MASS J16222521-2405139) and the Discovery of Another Very Wide, Low-Mass, Binary in Ophiuchus (2MASS J16233609-2402209) | | Laird M. Close
; Ben Zuckerman
; Inseok Song
; Travis Barman
; Christian Marois
; Emily L. Rice
; Nick Siegler
; Bruce Macintosh
; Eric E. Becklin
; Randy Campbell
; James E. Lyke
; Al Conrad
; David Le Mignant
; | | Date: |
27 Aug 2006 | | Abstract: | We imaged five objects considered by Allers et al. (2006) to be of low-mass and associated with the young star-forming clouds in Ophiuchus. We resolved their #11 (2MASS J16222521-2405139) and #16 (2MASS J16233609-2402209) into binaries. The #16 binary is an unusually wide (212 AU), very low-mass (VLM), binary composed of a ~100 Mjup primary (16A) and a ~73 MJup (16B) secondary. The #11 object is even more unusual. The binary nature of 11 was independently discovered by Jayawardhana & Ivanov (2006b) who call it Oph 162225-240515. The Oph #11 projected separation, 243 AU, is the largest known for a VLM binary and an order of magnitude larger than that of older field VLM binaries. We have obtained the first spatially resolved near-infrared (J & K) spectra and Mid-IR photometry. We estimate for 11A and 11B gravities (log(g)>3.75), ages (5+/-2 Myr), luminosities (log(L)=-2.77+/-0.10 and -2.96+/-0.10), and temperatures (Teff=2375+/-175 and 2175+/-175 K). We find self-consistent DUSTY evolutionary model (Chabrier et al. 2000) masses of 17.5+/-2.5 MJup and 15.5+/-2.5 MJup, respectively. Our masses are higher than the previously reported 13-15 MJup and 7-8 MJup masses for 11A and 11B (Jayawardhana & Ivanov 2006b). Hence, we find the system is unlikely a ``planetary mass binary’’, but it is the second lowest mass binary known. Moreover, due to its large separation, Oph 11 appears to have a binding energy lower than any other known binary. The formation (and survival) of such a weakly bound system with Vesc~0.5 km/s may pose a serious challenge to brown dwarf/star formation theories. Oph #11 and Oph #16 belong to a new population of wide (>200 AU), young, roughly equal mass, VLM stellar and brown dwarf binaries that may become unbound over time. | | Source: | arXiv, astro-ph/0608574 | | Services: | Forum | Review | PDF | Favorites | |
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