SHAO Astrophysics Colloquium

Title: Supersoft AGNs: signature of super Eddington accretion, IMBH, TDE or new AGN spectral state?

Speaker: Xinwen Shu (Anhui Normal University)

Time: 3 pm, April 26 (Thursday)

Location: Lecture Hall, 3rd floor

Abstract:

Supersoft AGNs are a special class of AGNs which lack significant hard X-ray emission above ~2 keV. They may host intermediate mass black holes (IMBH) accreting in a poorly explored regime of parameter space, such as super Eddingtong accretion and extreme coronal condition. Their X-ray spectra are dominated by a soft thermal component, a form similar to disk blackbody emission in stellar-mass BHs in their high/soft state. Though only three supersoft AGNs are reported to date, they show distinct X-ray variability behavior, some of them could be associated with TDEs.  In this talk, I will present the multi-wavelength characteristics of RX J1301.9+2746, the most distinct source of this kind. In particular, I will show our follow-up JVLA observations which reveal fast intraday radio variability, confining its origin likely from a compact jet. This is further supported by the unresolved radio emission observed with our VLBA observations. Such the unexpected presence of compact jet in a supersoft AGN challenges canonical theories of jet formation, but may have implications on the origin of radio emission in radio-quiet AGNs. All the results suggest that this AGN is an ideal laboratory for studying the universality of accretion/ejection coupling in BH accreting systems.

Group meetings

Black hole Accretion and High-energy Astrophysics /Black Hole Feedback and Cosmic Ray Astrophysics Seminar

Location: 1608

Time: 14:00-16:00, Wednesday (Apr 25th)

Speaker: Maochun Wu

Revisiting the Cooling Flow Problem in Galaxies, Groups, and Clusters of Galaxies

http://adsabs.harvard.edu/abs/2018arXiv180304972M

Speaker: Can Cui 

https://arxiv.org/pdf/1802.10306.pdf

http://adsabs.harvard.edu/abs/2018NatAs...2..198H

Seminar talk

Time:  4pm on Fri (Apr 27th)

Location: The lecture room on 17th floor

Speaker: Jerry Sellwood

Title: Two-body scattering and relaxation in disk systems
Abstract: The formula for the rate of relaxation in a gravitating system of point mass particles that is given in standard text books implicitly assumes that system is roughly spherical. I will derive a modified expression for rotationally-supported disks, and discuss its implications for real galaxy disks and for simulations.

Ref: http://adsabs.harvard.edu/abs/2013ApJ...769L..24S