Publikace ÚTF


Freeman, M.; Philpott, L. C.; Abe, F.; Albrow, M. D.; Bennett, D. P.; Bond, I. A.; Botzler, C. S.; Bray, J. C.; Cherrie, J. M.; Christie, G. W.; Dionnet, Z.; Gould, A.; Han, C.; Heyrovsk´y, D.; McCormick, J. M.; Moorhouse, D. M.; Muraki, Y.; Natusch, T.; Rattenbury, N. J.; Skowron, J.; Sumi, T.; Suzuki, D.; Tan, T. -G.; Tristram, P. J.; Yock, P. C. M.

Recently Sumi et al. reported evidence for a large population of planetary-mass objects (PMOs) that are either
unbound or orbit host stars in orbits 10 AU. Their result was deduced from the statistical distribution of durations
of gravitational microlensing events observed by the MOA collaboration during 2006 and 2007. Here we study
the feasibility of measuring the mass of an individual PMO through microlensing by examining a particular event,
MOA-2011-BLG-274. This event was unusual as the duration was short, the magnification high, the source-size
effect large, and the angular Einstein radius small. Also, it was intensively monitored from widely separated
locations under clear skies at low air masses. Choi et al. concluded that the lens of the event may have been a PMO
but they did not attempt a measurement of its mass. We report here a re-analysis of the event using re-reduced
data. We confirm the results of Choi et al. and attempt a measurement of the mass and distance of the lens using
the terrestrial parallax effect. Evidence for terrestrial parallax is found at a 3σ level of confidence. The best fit to
the data yields the mass and distance of the lens as 0.80± 0.30 MJ and 0.80 ± 0.25 kpc respectively. We exclude
a host star to the lens out to a separation ∼40 AU. Drawing on our analysis of MOA-2011-BLG-274 we propose
observational strategies for future microlensing surveys to yield sharper results on PMOs including those down to
super-Earth mass.
journal:The Astrophysical Journal
pages:181 (12pp)
apj799_181.pdf (1172.36 kB)

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