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Multiepoch VLBI of L Dwarf Binary 2MASS J0746+2000AB: Precise Mass Measurements and Confirmation of Radio Emission from Both Components

Zhang, Qicheng and Hallinan, Gregg and Brisken, Walter and Bourke, Stephen and Golden, Aaron (2020) Multiepoch VLBI of L Dwarf Binary 2MASS J0746+2000AB: Precise Mass Measurements and Confirmation of Radio Emission from Both Components. Astrophysical Journal, 897 (1). Art. No. 11. ISSN 1538-4357. https://resolver.caltech.edu/CaltechAUTHORS:20200604-151505163

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Abstract

Surveys have shown that up to 1/10th of all ultracool dwarfs (UCDs) are appreciable radio emitters, with their emission attributed to a combination of gyrosynchrotron radiation and the electron cyclotron maser instability. 2M J0746+2000AB is a close stellar binary comprised of an L0 and L1.5 dwarf that was previously identified as a source of 5 GHz radio emission. We used Very Long Baseline Interferometry (VLBI) to precisely track the radio emission over seven epochs in 2010–2017, and found both components to be radio emitters—the first such system identified—with the secondary component as the dominant source of emission in all epochs. The previously identified 2.07 hr periodic bursts were confirmed to originate from the secondary component, although an isolated burst was also identified from the primary component. We additionally fitted the VLBI absolute astrometric positions jointly with existing relative orbital astrometry derived from optical/infrared observations with Markov Chain Monte Carlo methods to determine the orbital parameters of the two components. We found the masses of the primary and secondary optical components to be 0.0795 ± 0.0003 M⊙, and 0.0756 ± 0.0003 M⊙, respectively, representing the most precise mass estimates of any UCDs to date. Finally, we place a 3σ upper limit of 0.9 M_(jup) au on the mass and separation of planets orbiting either of the two components.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-4357/ab9177DOIArticle
https://arxiv.org/abs/2005.03657arXivDiscussion Paper
ORCID:
AuthorORCID
Zhang, Qicheng0000-0002-6702-191X
Hallinan, Gregg0000-0002-7083-4049
Golden, Aaron0000-0002-8599-2031
Alternate Title:Multi-Epoch VLBI of L Dwarf Binary 2MASS J0746+2000AB: Precise Mass Measurements and Confirmation of Radio Emission from Both Components
Additional Information:© 2020 The American Astronomical Society. Received 2019 December 2; revised 2020 April 30; accepted 2020 May 6; published 2020 June 26. This material is based in part upon work supported by the National Science Foundation under Grant AST-1654815. We thank M. C. Liu for help isolating a systematic rotation in the existing relative astrometry, and both M. C. Liu and T. J. Dupuy, as well as an anonymous referee for reading this manuscript and providing valuable feedback. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work made use of the Swinburne University of Technology software correlator, developed as part of the Australian Major National Research Facilities Programme and operated under licence (Deller et al. 2011). The Green Bank Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. The European VLBI Network is a joint facility of independent European, African, Asian, and North American radio astronomy institutes. Scientific results from data presented in this publication are derived from the following EVN project code(s): GH009. Facilities: EVN - European VLBI Network, GBT - , VLBA. - Software: AIPS (Greisen 1990), Astropy (Astropy Collaboration et al. 2013), CASA (Jaeger 2008), corner.py (Foreman-Mackey 2016), emcee (Foreman-Mackey et al. 2013), matplotlib (Hunter 2007), Python (van Rossum 1995).
Group:Astronomy Department
Funders:
Funding AgencyGrant Number
NSFAST-1654815
Subject Keywords:Radio astrometry ; Close binary stars ; Stellar magnetic fields ; Low mass stars
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Radio astrometry (1337); Close binary stars (254); Stellar magnetic fields (1610); Low mass stars (2050)
Record Number:CaltechAUTHORS:20200604-151505163
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200604-151505163
Official Citation:Qicheng Zhang et al 2020 ApJ 897 11
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103718
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:05 Jun 2020 14:15
Last Modified:29 Jun 2020 20:35

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