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OGLE-2003-BLG-238: Microlensing Mass Estimate of an Isolated Star


Jiang, G and DePoy, DL and Gal-Yam, A and Gaudi, BS and Gould, A and Han, C and Lipkin, Y and Maoz, D and Ofek, EO and Park, BG and Pogge, RW and Udalski, A and Kubiak, M and Szymanski, MK and Szewczyk, O and Zebrun, K and Wyrzykowski, L and Soszynski, I and Pietrzynski, G and Albrow, MD and Beaulieu, JP and Caldwell, JAR and Cassan, A and Coutures, C and Dominik, M and Donatowicz, J and Fouque, P and Greenhill, JG and Hill, KM and Horne, K and Jorgensen, SF and Jorgensen, UG and Kane, S and Kubas, D and Martin, R and Menzies, J and Pollard, KR and Sahu, KC and Wambsganss, J and Watson, RD and Williams, A, OGLE-2003-BLG-238: Microlensing Mass Estimate of an Isolated Star, The Astrophysical Journal, 617, (2) pp. 1307-1315. ISSN 0004-637X (2004) [Refereed Article]

DOI: doi:10.1086/425678


Microlensing is the only known direct method to measure the masses of stars that lack visible companions. In terms of microlensing observables, the mass is given by M = (c 2/4G)r̃ Eθ E and so requires the measurement of both the angular Einstein radius θ E and the projected Einstein radius r̃ E. Simultaneous measurement of these two parameters is extremely rare. Here we analyze OGLE-2003-BLG-238, a spectacularly bright (I min = 10.3), high-magnification (A max = 170) microlensing event. Pronounced finite-source effects permit a measurement of θ E = 650 μas. Although the timescale of the event is only t E = 38 days, one can still obtain weak constraints on the microlens parallax: 4.4 AU < r̃ E < 18 AU at the 1 σ level. Together these two parameter measurements yield a range for the lens mass of 0.36 M ⊙ < M < 1.48 M ⊙. As was the case for MACHO-LMC-5, the only other single star (apart from the Sun) whose mass has been determined from its gravitational effects, this estimate is rather crude. It does, however, demonstrate the viability of the technique. We also discuss future prospects for single-lens mass measurements.

Item Details

Item Type:Refereed Article
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Galactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Greenhill, JG (Dr John Greenhill)
UTAS Author:Hill, KM (Dr Kym Hill)
UTAS Author:Watson, RD (Dr Bob Watson)
ID Code:30813
Year Published:2004
Web of Science® Times Cited:42
Deposited By:Physics
Deposited On:2004-08-01
Last Modified:2005-04-15

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