سمینار این هفته را خانم دکتر صدیقه سجادیان از پژوهشکده نجوم پژوهشگاه دانشهای بنیادی IPM برگزار خواهند کرد. عنوان و چکیدهٔ سمینار ایشان به شرح زیر است:
Title:
همبستگی بین قطبش و حرکت اخترسنجی ستاره ی چشمه
در رویداد های ریزهمگرایی گرانشی
(Correlation between astrometric shift and polarization in gravitational microlensing )
Abstract:
Gravitational microlensing as a mathematical map from the source to the lens plane breaks the circular symmetry of a source by producing distorted images at the either sides of the source position. This property causes some relevant phenomena such as polarization and light centroid shift of source star images. In this talk, I show that the polarization orientation is parallel and correlated with the centroid shift vector of a circular source star in a simple Paczynski microlensing event as well as binary lensing near the fold singularities and on the symmetry axis of cusp. Comparing the polarization and astrometric shift orientations helps to distinguish the source trajectory with respect to the caustic line. Moreover, anomalies over the source surface such as star spots break this unidirectional relation. Owing to this unidirectional relation, the polarimetric measurements uniquely determine the source star trajectory by resolving u_0 degeneracy in the same way as the astrometric observations.
این سمینار در روز یکشنبه ۲۱ اردیبهشت ماه ۱۳۹۳، ساعت ۱۵در اتاق شورا در طبقهٔ پنجم دانشکدهٔ فیزیک برگزار خواهد شد.