Theoretical Astrophysics Research Group

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Dr Sergei Nayakshin

CV (PDF)

Primary Research Interests:
Accretion discs in AGN, Galactic Centre: recent star formation, wind fed accretion, AGN -- galaxy connection, star formation in general

Contact Address:
Department of Physics and Astronomy
University of Leicester
University Road
Leicester LE1 7RH
U.K.

Tel: +44 116 252 2454
Fax: +44 116 252 2070
email: Sergei.Nayakshin at astro.le.ac.uk

Summary of what I do in Leicester

I have been in Leicester since 2005, and I really enjoy working here. Besides research expanded on below, I teach two classes (the 1st year core class PA113 "Electricity and Magnetism", and the 3rd year option class PA 3631 "Extreme Stars"). I am also the Department's PhD Admissions tutor since 2007.

Brief Description of current research.
    Currently, there is no real understanding of how super-massive black holes grow. We understand that gaseous material must lose most of its angular momentum before it might accrete onto the black hole. The usual engine of angular momentum transfer -- an accretion disc -- appears to be too cold to drive the material inwards on astrophysically relevant time scales from the distance of a fraction of a parsec into the AGN. Worse still, when material is this cold, it is predicted to be unstable to self-gravitational collapse, which could in principle form stars. This basic theoretical scenario has been recently dramatically confirmed with discovery of several tens of massive young stars near Sgr A*, the super-massive black hole in the centre of our Galaxy. Apparently, these stars "stole" about 10,000 solar masses of gas that Sgr A* managed to lure into the inner parsec. This theft of food is one of the reasons why Sgr A* is so dim by super-massive blackhole standards now.
    In the past several years I concentrated on understanding these youngs stars in the Galactic Centre, both analytically and numerically. I am also trying to use the observations of these young stars to constrain theories of massive star formation in general, as the conditions in Sgr A* are absolutely extreme. Other topics I pursued recently are stellar wind accretion onto Sgr A*, possible existence of a cold gaseous disc, and ways to constrain the number of isolated stellar mass black holes and neutron stars in the inner parsec of the GC.
    The ultimate goal of this research is much broader than Sgr A*. Using this (closest to us) supermassive black hole as a test case, I would like to understand how exactly AGN and quasars receive their fuel, and what happens in the inner few parsecs of AGN.
    Finally, I continue to be interested in the physics of accretion flows on very small scales, very close to the last stable orbit around the black hole, frequently collaborating with Chris Done (Durham).

Selected talks:

Seminar in IoA, Cambridge (10/2006)
Invited talk at an AGN conference in Xian, China, 10/2006. "Stellar processes near AGN" Powerpoint, BIG file (~ 30 Mb) Proceedings article in PDF
Conference summary talk jointly with Mark Morris, Bad Honef, Germany, April 2006. A reasonably complete summary of what was hot in the Galactic Centre research in 2006. PDF file
Invited talk at a conference in IKI, Moscow, 2005 (PDF; Never late to learn Russian!!!)
"Theory of Iron K-alpha lines from AGN disks". Invited, KITP, Santa Barbara, 2002 Presentation

Chandra press release (2005)
The only "observational" paper I ever wrote caught the eye of Chadra press release officers, who arranged a press release on this work. The paper (Nayakshin & Sunyaev 2005) points out observational evidence that star formation in the inner parsec of the Galaxy must have been in situ and that the stars created there were unusually massive. The following link has text and an artist created movie illustrating star formation near Sgr A*.

Recent PhDs, current students, and their projects:

Jorge Cuadra, now a postdoc with M. Begelman, JILA, Boulder, CO, USA. Jorge worked on the topics below. For more info go to his own webpage and check his publications on ADS.

stellar wind accretion onto Sgr A*, the supermassive blackhole in the centre of the Galaxy
star formation in an accretion disc around Sgr A*
enigmatic X-ray/near-infrared flares from Sgr A*

Alex Hobbs, 2nd year PhD student. SPH simulations of star formation in the central parsec of Sgr A*, formation of accretion discs from collisions of molecular clouds.

PhD studentship opportunities:

- We are also interested in PhD studentship applications. Due to STFC rules, unfortunately, only UK students or students from EU that reside in the UK are fully supported by the research council. However, there might be specific scholarships, so please follow this link for more info, or contact me by email.

- I personally will be interested in supervising a PhD student that would start in ~ October 2008. Depending on the student's abilities and interests, the projects could be either (semi)analytical or purely numerical.

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