MOA-2010-BLG-073L: AN M-DWARF WITH A SUBSTELLAR COMPANION AT THE PLANET/BROWN DWARF BOUNDARY

Journal Article · Sun Jan 20 00:00:00 EST 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/763/1/67· OSTI ID:22167191

Street, R. A.; Tsapras, Y. ^[1]; Choi, J. -Y.; Han, C. ^[2]; Furusawa, K. ^[3]; Hundertmark, M.; Horne, K.; Dominik, M.; Browne, P.; Bajek, D. ^[4]; Gould, A. ^[5]; Sumi, T. ^[6]; Bond, I. A. ^[7]; Wouters, D. ^[8]; Zellem, R. ^[9]; Udalski, A. ^[10]; Snodgrass, C. ^[11]; Kains, N.; Bramich, D. M. ^[12]; others, and

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1. LCOGT, 6740 Cortona Drive, Suite 102, Goleta, CA 93117 (United States)
2. Department of Physics, Institute for Astrophysics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of)
3. Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan)
4. SUPA/St Andrews, Department of Physics and Astronomy, North Haugh, St. Andrews, Fife KY16 9SS (United Kingdom)
5. Department of Astronomy, Ohio State University, McPherson Laboratory, 140 West 18th Avenue, Columbus, OH 43210-1173 (United States)
6. Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043 (Japan)
7. Institute of Information and Mathematical Sciences, Massey University, Private Bag 102-904, North Shore Mail Centre, Auckland (New Zealand)
8. UPMC-CNRS, UMR 7095, Institut d'Astrophysique de Paris, 98bis boulevard Arago, F-75014 Paris (France)
9. Lunar and Planetary Laboratory, Department of Planetary Sciences, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721-0092 (United States)
10. Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland)
11. Max Planck Institute for Solar System Research, Max-Planck-Str. 2, D-37191 Katlenburg-Lindau (Germany)
12. European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Muenchen (Germany)

We present an analysis of the anomalous microlensing event, MOA-2010-BLG-073, announced by the Microlensing Observations in Astrophysics survey on 2010 March 18. This event was remarkable because the source was previously known to be photometrically variable. Analyzing the pre-event source light curve, we demonstrate that it is an irregular variable over timescales >200 days. Its dereddened color, (V - I) {sub S,0}, is 1.221 {+-} 0.051 mag, and from our lens model we derive a source radius of 14.7 {+-} 1.3 R {sub Sun }, suggesting that it is a red giant star. We initially explored a number of purely microlensing models for the event but found a residual gradient in the data taken prior to and after the event. This is likely to be due to the variability of the source rather than part of the lensing event, so we incorporated a slope parameter in our model in order to derive the true parameters of the lensing system. We find that the lensing system has a mass ratio of q = 0.0654 {+-} 0.0006. The Einstein crossing time of the event, t {sub E} = 44.3 {+-} 0.1 days, was sufficiently long that the light curve exhibited parallax effects. In addition, the source trajectory relative to the large caustic structure allowed the orbital motion of the lens system to be detected. Combining the parallax with the Einstein radius, we were able to derive the distance to the lens, D{sub L} = 2.8 {+-} 0.4 kpc, and the masses of the lensing objects. The primary of the lens is an M-dwarf with M {sub L,1} = 0.16 {+-} 0.03 M {sub Sun }, while the companion has M {sub L,2} = 11.0 {+-} 2.0 M {sub J}, putting it in the boundary zone between planets and brown dwarfs.

• OSTI ID: 22167191
• Journal Information: Astrophysical Journal, Vol. 763, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ASTRONOMY
ASTROPHYSICS
COLOR
DIAGRAMS
DISTANCE
DWARF STARS
GRAVITATIONAL LENSES
MASS
PLANETS
RED GIANT STARS
VISIBLE RADIATION