First simultaneous microlensing observations by two space telescopes: Spitzer & Swift reveal a brown dwarf in event OGLE-2015-BLG-1319

Creators: Shvartzvald, Y.; Calchi Novati, S.; Beichman, C.; Carey, S.; Spitzer Team; RoboNet Collaboration; OGLE Group; MOA Group; MINDSTEP Consortium; Swift Collaboration

Abstract

Simultaneous observations of microlensing events from multiple locations allow for the breaking of degeneracies between the physical properties of the lensing system, specifically by exploring different regions of the lens plane and by directly measuring the "microlens parallax". We report the discovery of a 30-55M_J brown dwarf orbiting a K dwarf in microlensing event OGLE-2015-BLG-1319. The system is located at a distance of ∼5 kpc toward the Galactic bulge. The event was observed by several ground-based groups as well as by Spitzer and Swift, allowing the measurement of the physical properties. However, the event is still subject to an 8-fold degeneracy, in particular the well-known close-wide degeneracy, and thus the projected separation between the two lens components is either ∼0.25 AU or ∼45 AU. This is the first microlensing event observed by Swift, with the UVOT camera. We study the region of microlensing parameter space to which Swift is sensitive, finding that while for this event Swift could not measure the microlens parallax with respect to ground-based observations, it can be important for other events. Specifically, for detecting nearby brown dwarfs and free-floating planets in high magnification events.

Additional Information

© 2016 American Astronomical Society. Received 2016 June 7; revised 2016 August 24; accepted 2016 August 24; published 2016 November 7. We thank T. Meshkat and R. Patel for fruitful discussions about directly imaging free-floating planets. Work by YS and CBH was supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, administered by Universities Space Research Association through a contract with NASA. This work makes use of observations from the LCOGT network, which includes three SUPAscopes owned by the University of St Andrews. The RoboNet programme is an LCOGT Key Project using time allocations from the University of St Andrews, LCOGT and the University of Heidelberg together with time on the Liverpool Telescope through the Science and Technology Facilities Council (STFC), UK. This research has made use of the LCOGT Archive, which is operated by the California Institute of Technology, under contract with the Las Cumbres Observatory. The OGLE project has received funding from the National Science Centre, Poland, grant MAESTRO 2014/14/A/ST9/00121 to AU. OGLE Team thanks Profs. M. Kubiak and G. Pietrzyński, former members of the OGLE team, for their contribution to the collection of the OGLE photometric data over the past years. TS acknowledges the financial support from the JSPS, JSPS23103002, JSPS24253004 and JSPS26247023. The MOA project is supported by the grant JSPS25103508 and 23340064. Work by AG and SC was supported by JPL grant 1500811. Work by AG and WZ was supported by NSF grant AST-15168. Work by JCY was performed under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. The Spitzer Team thanks Christopher S. Kochanek for graciously trading us his allocated observing time on the CTIO 1.3m during the Spitzer campaign. We thank the Swift operations team for approving and implementing the Target of Opportunity request. This publication was made possible by NPRP grant #X-019-1-006 from the Qatar National Research Fund (a member of Qatar Foundation). Work by SM has been supported by the Strategic Priority Research Program "The Emergence of Cosmological Structures" of the Chinese Academy of Sciences Grant No. XDB09000000, and by the National Natural Science Foundation of China (NSFC) under grant numbers 11333003 and 11390372. M.P.G.H. acknowledges support from the Villum Foundation. NP acknowledges funding by the Portuguese FCT - Foundation for Science and Technology and the European Social Fund (ref: SFRH/BGCT/113686/2015) and the Gemini-Conicyt Fund, allocated to project #32120036. CITEUC is funded by National Funds through FCT - Foundation for Science and Technology (project: UID/Multi/00611/2013) and FEDER - European Regional Development Fund through COMPETE 2020 Operational Programme Competitiveness and Internationalisation (project: POCI-01-0145-FEDER-006922). GD acknowledges Regione Campania for support from POR-FSE Campania 2014-2020. Based on data collected by MiNDSTEp with the Danish 1.54 m telescope at the ESO La Silla observatory.

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Submitted - 1606.02292v1.pdf

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