Monday, April 4, 2022
12:00 – 12:30pm in person
Zephyr Penoyre, Columbia
Astrometric binaries in Gaia
A thousand-fold increase in the number of stars and the precision with which we can observe their motion allows us to see previously rare phenomena in great numbers and detail. Astrometric binaries are a fantastic example of this – around half of all stars are binaries and precise astrometry enables us to detect a huge number of these, with periods from months to decades. I’ll talk about the different astrometric signals binary stars produce, how we can identify them now, and how those observations will evolve and improve over the lifetime of the Gaia survey.
Marcin Marculewicz, Xiamen University via zoom
Global parameters of Weak emission-Line Quasars
Abstract: The talk concerns the analysis of one of the least known subtypes of quasars: Weak emission-Line Quasars (WLQs). The primary goal was to evaluate the global parameters such as: the black hole (BH) mass, the accretion rate of WLQs based on the continuum fit method. This method apart from the literature BH masses estimation methods does not depend on the observed FWHM of the emission line, which could be biased due to the weakness or lack of the emission lines in these quasars. Using the SED of quasars, I have fitted the geometrically thin and optically thick accretion disk model described by Novikov & Thorne equations. The literature WLQs BH masses based on FWHM of Hbeta are underestimated. I have proposed a new formula that helps calculate the proper weight of BH masses.
Bio: Marculewicz did his Ph.D. at the University of Bialystok in Poland, where he worked on global parameters of quasars with anomalous electromagnetic spectrum. From 2022 he is a postdoctoral researcher in Professor Mouyuan Sun’s group at Xiamen University. Marculewicz’s research focuses on studying quasars and supermassive black hole astrophysics.