The physical parameters of Markarian 501 during flaring activity |
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Authors: | W Bednarek R J Protheroe |
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Institution: | The Ohio State University, Dept. of Physics and Astronomy, 174 W. 18th Avenue, Columbus, OH 43210, USA; Department of International Education, Sun Moon University, Tangjeongmyeon, Asankun, Chung-nam, Republic of Korea, 336-840 |
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Abstract: | We analyse an N -body simulation of the Small Magellanic Cloud (SMC), that of Gardiner & Noguchi, to determine its microlensing statistics. We find that the optical depth owing to self-lensing in the simulation is low, 0.4×10−7, but still consistent (at the 90 per cent level) with that observed by the EROS and MACHO collaborations. This low optical depth is due to the relatively small line-of-sight thickness of the SMC produced in the simulation. The proper motions and time-scales of the simulation are consistent with those observed assuming a standard mass function for stars in the SMC. The time-scale distribution from the standard mass function generates a significant fraction of short time-scale events: future self-lensing events towards the SMC may have the same time-scales as events observed towards the Large Magellanic Cloud (LMC). Although some debris was stripped from the SMC during its collision with the LMC about 2×108 yr ago, the optical depth of the LMC owing to this debris is low, a few ×10−9, and thus cannot explain the measured optical depth towards the LMC. |
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Keywords: | Magellanic Clouds gravitational lensing |
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