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The Orbit of the L dwarf + T dwarf Spectral Binary SDSS J080531.84+481233.0

Burgasser, Adam J. and Blake, Cullen H. and Gelino, Christopher R. and Sahlmann, Johannes and Bardalez Gagliuffi, Daniella (2016) The Orbit of the L dwarf + T dwarf Spectral Binary SDSS J080531.84+481233.0. Astrophysical Journal, 827 (1). Art. No. 25. ISSN 0004-637X.

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SDSS J080531.84+481233.0 is a closely separated, very-low-mass (VLM) binary identified through combined-light spectroscopy and confirmed as an astrometric variable. Here we report four years of radial velocity monitoring observations of the system that reveal significant and periodic variability, confirming the binary nature of the source. We infer an orbital period of 2.02 ± 0.03 years, a semimajor axis of 0.76_(-0.06)^(+0.05) au, and an eccenticity of 0.46 ± 0.05, consistent with the amplitude of astrometric variability and prior attempts to resolve the system. Folding in constraints based on the spectral types of the components (L4 ± 0.7 and T5.5 ± 1.1), corresponding effective temperatures, and brown dwarf evolutionary models, we further constrain the orbital inclination of this system to be nearly edge-on (90° ± 19°), and deduce a large system mass ratio (M_2/M_1 = 0.86_(-0.12)^(+0.10)), substellar components (M_1 = 0.057_(-0.014)^(+0.016 M_☉, M_2 = 0.048_(-0.010)^(+0.008) M_☉), and a relatively old system age (minimum age = 4.0_(-1.2)^(+1.9) Gyr). The measured projected rotational velocity of the primary (V_(rot) sin i = 34.1 ± 0.7 km s^(−1)) implies that this inactive source is a rapid rotator (period ≾ 3 hr) and a viable system for testing spin–orbit alignment in VLM multiples. Robust model-independent constraints on the component masses may be possible through measurement of the reflex motion of the secondary at wavelengths in which it contributes a greater proportion of the combined luminence, while the system may also be resolvable through sparse-aperature mask interferometry with adaptive optics. The combination of well-determined component atmospheric properties and masses near and/or below the hydrogen minimum mass make SDSS J0805+4812AB an important system for future tests of brown dwarf evolutionary models.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Burgasser, Adam J.0000-0002-6523-9536
Sahlmann, Johannes0000-0001-9525-3673
Bardalez Gagliuffi, Daniella0000-0001-8170-7072
Additional Information:© 2016 American Astronomical Society. Received 2016 March 26; revised 2016 May 17; accepted 2016 May 17; published 2016 August 3. The authors thank Joel Aycock, Scott Dahm, Randy Campbell, Greg Doppman, Heather Hershey, Carolyn Jordan, Marc Kassis, Jim Lyke, Gary Punawai, Julie Rivera, Terry Stickel, Hien Tran, and Cynthia Wilburn at Keck Observatory, and Christine Nichols and Melisa Tallis at UCSD, for their assistance with the NIRSPEC observations. AJB acknowledges funding support from the National Science Foundation under award No. AST-1517177. The material is based upon work supported by the National Aeronautics and Space Administration under Grant No. NNX15AI75G. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France; NASA's Astrophysics Data System Bibliographic Services; the M, L, T, and Y dwarf compendium housed at; and the SpeX Prism Libraries at We thank our anonymous referee for her/his/their prompt and helpful review of the original manuscript. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate and grateful to have the opportunity to conduct observations from this mountain.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Subject Keywords:binaries: spectroscopic; brown dwarfs; stars: individual (SDSS J080531.84+481233.0) ; stars: low-mass
Issue or Number:1
Record Number:CaltechAUTHORS:20160805-092645027
Persistent URL:
Official Citation:Adam J. Burgasser et al 2016 ApJ 827 25
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69464
Deposited By: Ruth Sustaita
Deposited On:05 Aug 2016 17:13
Last Modified:09 Mar 2020 13:19

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