Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-03-24
Astron.Astrophys. 432 (2005) 501
Astronomy and Astrophysics
Astrophysics
Appeared on A&A 432, 501, 2005. Low resolution black and white figures
Scientific paper
10.1051/0004-6361:20041355
Pixel lensing is the gravitational microlensing of light from unresolved stars contributing to the luminosity flux collected by a single pixel. A star must be sufficiently magnified, that is, the lens impact parameter must be less than a threshold value $u_T$ if the excess photon flux in a pixel is to be detected over the background. Assuming the parameters of the Isaac Newton Telescope and typical observing conditions, we present maps in the sky plane towards M31 of threshold impact parameter, optical depth, event number and event time scale, analyzing in particular how these quantities depend on $u_T$ in pixel lensing searches. We use an analytical approach consisting of averaging on $u_T$ and the star column density the optical depth, microlensing rate and event duration time scale. An overall decrease in the expected optical depth and event number with respect to the classical microlensing results is found, particularly towards the high luminosity M31 inner regions. As expected, pixel lensing events towards the inner region of M31 are mostly due to self-lensing, while in the outer region dark events dominate even for a 20% MACHO halo fraction. We also find a far-disk/near-disk asymmetry in the expected event number, smaller than that found by \cite{Kerins04}. Both for self and dark lensing events, the pixel lensing time scale we obtain is $\simeq 1 - 7$ days, dark events lasting roughly twice as long as self-lensing events. The shortest events are found to occur towards the M31 South Semisphere. We also note that the pixel lensing results depend on $
de Paolis Francesco
Ingrosso Gabriele
Nucita Achille A.
Zakharov Aleksandr F.
No associations
LandOfFree
Influence of magnification threshold on pixel lensing optical depth, event rate and time scale distributions towards M31 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Influence of magnification threshold on pixel lensing optical depth, event rate and time scale distributions towards M31, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Influence of magnification threshold on pixel lensing optical depth, event rate and time scale distributions towards M31 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-587228