2002/07/11 by Ph. Jetzer, L. Mancini, G. Scarpetta · 2 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Event (particle physics) #Galaxies: Formation, Evolution, Phenomena #Gravitational lens #Gravitational microlensing #Large Magellanic Cloud #Lens (geology) #Optical depth #Stars #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1051/0004-6361:20021027
published as Astron.Astrophys. 393 (2002) 129-148 · To appear in A&A, 20 pages with 7 figures
arxiv created 2002/07/11 · openalex publication_date 2002/09/18 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The nature and the location of the lenses discovered in the microlensing surveys done so far towards the LMC remain unclear. Motivated by these questions we compute the optical depth and particularly the number of expected events for self-lensing for both the MACHO and EROS2 observations. We calculate these quantities also for other possible lens populations such as thin and thick disk and galactic spheroid. Moreover, we estimate for each of these components the corresponding average event duration and mean mass using the mass moment method. By comparing the theoretical quantities with the values of the observed events it is possible to put some constraints on the location and the nature of the MACHOs. Clearly, given the large uncertainties and the few events at disposal it is not possible to draw sharp conclusions, nevertheless we find that certainly at least 3-4 MACHO events are due to lenses in LMC, which are most probably low mass stars, but that hardly all events can be due to self-lensing. This conclusions is even stronger when considering the EROS2 events, due to their spatial distribution. The most plausible solution is that the events observed so far are due to lenses belonging to different intervening populations: low mass stars in the LMC, in the thick disk, in the spheroid and possibly some true MACHOs in the halo.