Speaker
Description
Abstract
Polarization of the microlensing events offers a distinctive prospect to investigate the characteristics of the lensing matter and the fundamental matter distribution of the gravitationally lensed systems. The idea behind this research is to investigate the possibility to use polarization measurements to better characterize gravitational lensing via microlensing by analyzing the polarization variation caused by light bending around a compact body (star or black hole).
By following the model by Simmons et al. (2002) to compute the polarization as due to the photon scattering on dust grains in the stellar wind we can explore how polarization varies with lens parameters and the geometry of the lensing system.
Polarization measurements on ongoing microlensing events can be very useful for further characterizing them, therefore the detection of a variable polarization leads to an independent measure of the angular Einstein radius R_E of the lens, the position angle of the lens and the velocity direction in the sky (Yoshida 2006).
Also, since a survey telescope can not measure the polarization accurately, alert systems are needed that allow larger telescopes to perform polarimetric observations in the event of a microlensing. (G. Ingrosso et al.(2012))
These polarization signals allow us to better understand the gravitational lensing process, which fine-tunes our models, and ultimately enables us to better constrain the nature of dark matter and compact objects in the universe.
References
G. Ingrosso et al., "Polarization in microlensing events towards the Galactic bulge," in Monthly Notices of the Royal Astronomical Society, vol. 426, no. 2, pp. 1496-1506, Oct. 2012, doi: 10.1111/j.1365-2966.2012.21820.x
Hiroshi Yoshida, Finite source effect on the polarization degree induced by a single microlens, Monthly Notices of the Royal Astronomical Society, Volume 369, Issue 2, 21 June 2006, Pages 997–1008
J. F. L. Simmons, J. E. Bjorkman, R. Ignace, I. J. Coleman, Polarization from microlensing of spherical circumstellar envelopes by a point lens, Monthly Notices of the Royal Astronomical Society, Volume 336, Issue 2, October 2002, Pages 501–510,
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