Close stars and an inactive accretion disc in Sgr A* : eclipses and flares

  title={Close stars and an inactive accretion disc in Sgr A* : eclipses and flares},
  author={S Nayakshin and R. Sunyaev Harvard-Smithsonian Center for Astrophysics and Iki and Moscow and Russia.},
  journal={Monthly Notices of the Royal Astronomical Society},
A cold neutral and extremely dim accretion disc may be present as a remnant of past vigorous activity around the black hole at our Galactic Centre (GC). Here we discuss ways to detect such a disc through its interaction with numerous stars present in the central 0.01 pc of the Galaxy. The first major effect expected is X-ray and near-infrared (NIR) flares arising when stars pass through the disc. The second is eclipses of the stars by the disc. We point out conditions under which the properties… 
Using close stars as probes of hot accretion flow in Sgr A
The extremely hot and tenuous accretion flow in the immediate vicinity of Sgr A ∗ is believed to be invisible (too dim) in the X-ray band, except for short X-ray flares. Here we point out that during
Close stars and accretion in low-luminosity active galactic nuclei
It is found that, despite 'low' luminosities of LLAGNs, unrealistically high stellar densities are required to make a sizable radiative contribution to the Hubble Space Telescope optical/ultraviolet spectra of these galactic nuclei.
Low angular momentum accretion flow model of Sgr A* activity
Sgr A* is a source of strongly variable emission in several energy bands. It is generally agreed that this emission comes from the material surrounding the black hole which is either falling in or
On highly eccentric stellar trajectories interacting with a self-gravitating disc in Sgr A
We propose that Kozai's phenomenon is responsible for the long-term evolution of stellar orbits near a supermassive black hole. We pursue the idea that this process may be driven by a fossil
Enhanced activity of massive black holes by stellar capture assisted by a self-gravitating accretion disc
Aims. We study the probability of close encounters between stars from a nuclear cluster and a massive black hole (10 4 MM• 10 8 M� ). The gravitational field of the system is dominated by the black
Stellar Processes Near the Massive Black Hole in the Galactic Center
A massive black hole resides in the center of most, perhaps all galaxies. The one in the center of our home galaxy, the Milky Way, provides a uniquely accessible laboratory for studying in detail the
X-ray flares reveal mass and angular momentum of the Galactic Center black hole
We have analysed the light curve of the two brightest X-ray flares from the Galactic Center black hole, one flare observed by XMM-Newton on October 3, 2002 (Porquet et al. \cite{P2003}), and the
Impulsive Electromagnetic Emission near a Black Hole
The electromagnetic signature of a point explosion near a Kerr black hole (BH) is evaluated. The first repetitions produced by gravitational lensing are not periodic in time; periodicity emerges only
Radio Variability of the Sagittarius $ {\rm A^*}$ due to an Orbiting Star
Recently, unprecedentedly accurate data on the orbital motion of stars in the vicinity of the Sagittarius $ {\rm A^*}$ have been available. Such information can be used not only to constrain the mass
The extreme luminosity states of Sagittarius A
We discuss mm-wavelength radio, 2.2–11.8 μm NIR and 2–10 keV X-ray light curves of the super massive black hole (SMBH) counterpart of Sagittarius A* (SgrA*) near its lowest and highest observed


A star in a 15.2-year orbit around the supermassive black hole at the centre of the Milky Way
Ten years of high-resolution astrometric imaging allow us to trace two-thirds of the orbit of the star currently closest to the compact radio source (and massive black-hole candidate) Sagittarius A* and show that the star is on a bound, highly elliptical keplerian orbit around Sgr A*.
Rapid X-ray flaring from the direction of the supermassive black hole at the Galactic Centre
The discovery of rapid X-ray flaring from the direction of Sagittarius A* provides compelling evidence that the emission is coming from the accretion of gas onto a supermassive black hole at the Galactic Centre.
A new X-ray flare from the galactic nucleus detected with the XMM-Newton photon imaging cameras
Sgr A*, the compact radio source believed to be the counterpart of the massive black hole at the Galactic nucleus, was observed to undergo rapid and intense flaring activity in X-rays with Chandra in
Evidence for a black hole from high rotation velocities in a sub-parsec region of NGC4258
MANY galaxies are thought to contain massive black holes— exceeding ten million solar masses—at their centres1,2, but firm observational evidence has proved to be surprisingly elusive. The best
The First Measurement of Spectral Lines in a Short-Period Star Bound to the Galaxy’s Central Black Hole: A Paradox of Youth
We have obtained the first detection of spectral absorption lines in one of the high-velocity stars in the vicinity of the Galaxy's central supermassive black hole. Both Brγ (2.1661 μm) and He I
Limits on the Short-Term Variability of Sagittarius A* in the Near-Infrared
The recent detection of a 3 hr X-ray flare by the Chandra X-Ray Observatory has raised the possibility of enhanced emission over a broad range of wavelengths from Sagittarius A*, the suspected 2.6 ×
Star–disc interactions near a massive black hole
We examine the possibility that stars in the nuclei of galaxies could be ground down into short-period orbits, by interaction with a disc around a central massive black hole. A star on a highly
The Proper Motion of Sagittarius A*. I. First VLBA Results
We observed Sgr A* and two extragalactic radio sources nearby in angle with the VLBA over a period of 2 yr and measured relative positions with an accuracy approaching 0.1 mas. The apparent proper
Possible Evidence for Truncated Thin Disks in the Low-Luminosity Active Galactic Nuclei M81 and NGC 4579.
M81 and NGC 4579 are two of the few low-luminosity active galactic nuclei that have an estimated mass for the central black hole, detected hard X-ray emission, and detected optical/UV emission. In
The Spectral Energy Distributions of Low-Luminosity Active Galactic Nuclei
As a step toward elucidating the physical conditions in nearby active galaxies, this paper presents spectral energy distributions (SEDs) of a sample of seven low-luminosity active galactic nuclei