The galactic centre

1979 ◽  
Vol 366 (1726) ◽  
pp. 345-355 ◽  
Keyword(s):  
Extended Period ◽  
Galactic Centre ◽  
X Ray ◽  
Coded Mask

While the Uhuru satellite detected an extended or multiple X-ray source located in the direction of the galactic centre, and while transient and burst sources have been found there by Ariel 5 and SAS-3, there has not so far been any detailed description of this important source. By using results from a coded mask telescope flown in 1976 on a Skylark rocket (the first successful application of such a device in astronomy) and from an extended period of observations with Ariel 5, a number of burst and ir­regular variable X-ray sources have now been discovered. In particular, the region within a few degrees of the galactic centre is evidently one of continual but irregular X-ray activity.

scholarly journals TTM Observations of X1755-338

1995 ◽  
Vol 151 ◽  
pp. 334-335
Author(s):  
H.C. Pan ◽  
G.K. Skinner ◽  
R.A. Sunyaev ◽  
K.N. Borozdin
Keyword(s):  
Black Hole ◽  
Energy Resolution ◽  
Space Station ◽  
Galactic Centre ◽  
Imaging Spectrometer ◽  
X Ray ◽  
Black Hole Candidate ◽  
Coded Mask

X1755-338 is an X-ray binary source which displays X-ray dips with a 4.4 hour period (White et al. 1984). It was previously noted as an unusually soft X-ray source by Jones (1977) and was suggested later as a black-hole candidate (BHC) by White & Marshall (1984), and White et al. (1984), based on the similarity of its location in an X-ray colour-colour diagram to that of a group of BHCs.The TTM is a coded-mask imaging spectrometer on board the KVANT module of the MIR space station. It is capable of producing images in the 2 – 30 keV band with an energy resolution of about 18% at 6 keV. The instrumental details are given in Brinkman et al. (1985).We observed X1755-338 in 1989 March-September during the period of the TTM Galactic Centre Survey.

scholarly journals Exploring a New Population of Compact Objects: X-ray and IR Observations of the Galactic Centre

2008 ◽  
Author(s):  
Reba M. Bandyopadhyay ◽  
Andrew J. Gosling ◽  
Stephen E. Eikenberry ◽  
Michael P. Muno ◽  
Katherine M. Blundell ◽  
...  
Keyword(s):  
Compact Objects ◽  
Galactic Centre ◽  
X Ray

scholarly journals A Multi-Wavelength View of the XMM-Newton Galactic Plane

2014 ◽  
Vol 1 (1) ◽  
pp. 123-126
Author(s):  
Ada Nebot Gómez-Morán ◽  
Christian Motch
Keyword(s):  
Surface Density ◽  
Binary Systems ◽  
Galactic Plane ◽  
Galactic Centre ◽  
Galactic Latitude ◽  
X Ray ◽  
Model Predictions ◽  
Science Centre ◽  
Multi Wavelength ◽  
Galactic Longitude

We present an X-ray survey of the Galactic Plane conducted by the Survey Science Centre of the XMM-Newton satellite. The survey contains more than 1300 X-ray detections at low and intermediate Galactic latitudes and covering 4 deg<sup>2</sup> well spread in Galactic longitude. From a multi-wavelength analysis, using optical spectra and helped by optical and infrared photometry we identify and classify about a fourth of the sources. The observed surface density of soft X-ray (&lt;2 keV) sources decreases with Galactic latitude and although compatible with model predictions at first glance, presents an excess of stars, likely due to giants in binary systems. In the hard band (&gt;2 keV) the surface density of sources presents an excess with respect to the expected extragalactic contribution. This excess highly concentrates towards the direction of the Galactic Centre and is compatible with previous results from Chandra observations around the Galactic Centre. The nature of these sources is still unknown.

scholarly journals Flares from Galactic Centre pulsars: a new class of X-ray transients?

2016 ◽  
Vol 459 (1) ◽  
pp. L95-L99 ◽  
Author(s):  
Dimitrios Giannios ◽  
Duncan R. Lorimer
Keyword(s):  
Galactic Centre ◽  
X Ray ◽  
New Class

Two years of successful operations of the coded-mask telescope SIGMA for hard X-ray and soft γ-ray astronomy

1993 ◽  
Vol 30 ◽  
pp. 261-269
Author(s):  
Jacques Paul ◽  
François Lebrun ◽  
Pierre Mandrou ◽  
Jean-Pierre Roques
Keyword(s):  
X Ray ◽  
Γ Ray ◽  
Coded Mask

The Observation of X-Rays from the Galactic Centre and Centaurus Regions

1968 ◽  
Vol 1 (4) ◽  
pp. 168-169 ◽  
Author(s):  
G. Buselli
Keyword(s):  
Galactic Centre ◽  
X Rays ◽  
Experimental Equipment ◽  
X Ray ◽  
Preliminary Results

This paper reports results from a graded shield X-ray telescope experiment flown from Mildura, Australia on 29 February 1968. The experimental equipment also included the actively collimated telescope previously described. Certain preliminary results from this flight have been described elsewhere.

scholarly journals Non-equilibrium chemistry and destruction of CO by X-ray flares

2019 ◽  
Vol 486 (1) ◽  
pp. 1094-1122 ◽  
Author(s):  
Jonathan Mackey ◽  
Stefanie Walch ◽  
Daniel Seifried ◽  
Simon C O Glover ◽  
Richard Wünsch ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Thermal Evolution ◽  
Galactic Nuclei ◽  
Galactic Centre ◽  
X Rays ◽  
X Ray ◽  
Uv Emission ◽  
Sgr A ◽  
X Ray Binaries ◽  
Fractal Cloud

ABSTRACT Sources of X-rays such as active galactic nuclei and X-ray binaries are often variable by orders of magnitude in luminosity over time-scales of years. During and after these flares the surrounding gas is out of chemical and thermal equilibrium. We introduce a new implementation of X-ray radiative transfer coupled to a time-dependent chemical network for use in 3D magnetohydrodynamical simulations. A static fractal molecular cloud is irradiated with X-rays of different intensity, and the chemical and thermal evolution of the cloud are studied. For a simulated $10^5\, \mathrm{M}_\odot$ fractal cloud, an X-ray flux &lt;0.01 erg cm−2 s−1 allows the cloud to remain molecular, whereas most of the CO and H2 are destroyed for a flux of ≥1 erg cm−2 s−1. The effects of an X-ray flare, which suddenly increases the X-ray flux by 105×, are then studied. A cloud exposed to a bright flare has 99 per cent of its CO destroyed in 10–20 yr, whereas it takes &gt;103 yr for 99 per cent of the H2 to be destroyed. CO is primarily destroyed by locally generated far-UV emission from collisions between non-thermal electrons and H2; He+ only becomes an important destruction agent when the CO abundance is already very small. After the flare is over, CO re-forms and approaches its equilibrium abundance after 103–105 yr. This implies that molecular clouds close to Sgr A⋆ in the Galactic Centre may still be out of chemical equilibrium, and we predict the existence of clouds near flaring X-ray sources in which CO has been mostly destroyed but H is fully molecular.

scholarly journals The Swift Bulge Survey: optical and near-IR follow-up featuring a likely symbiotic X-ray binary and a focused wind CV

2020 ◽  
Vol 492 (3) ◽  
pp. 4344-4360 ◽  
Author(s):  
A W Shaw ◽  
C O Heinke ◽  
T J Maccarone ◽  
G R Sivakoff ◽  
J Strader ◽  
...  
Keyword(s):  
White Dwarf ◽  
Near Infrared ◽  
Substantial Contribution ◽  
Galactic Centre ◽  
First Year ◽  
X Ray ◽  
Giant Stars ◽  
Near Ir ◽  
Star Binary

ABSTRACT The nature of very faint X-ray transients (VFXTs) – transient X-ray sources that peak at luminosities $L_X\lesssim 10^{36} {\rm \, erg \, s^{-1}}$ – is poorly understood. The faint and often short-lived outbursts make characterizing VFXTs and their multiwavelength counterparts difficult. In 2017 April we initiated the Swift Bulge Survey, a shallow X-ray survey of ∼16 square degrees around the Galactic centre with the Neil Gehrels Swift Observatory. The survey has been designed to detect new and known VFXTs, with follow-up programmes arranged to study their multiwavelength counterparts. Here we detail the optical and near-infrared follow-up of four sources detected in the first year of the Swift Bulge Survey. The known neutron star binary IGR J17445-2747 has a K4III donor, indicating a potential symbiotic X-ray binary nature and the first such source to show X-ray bursts. We also find one nearby M-dwarf (1SXPS J174215.0-291453) and one system without a clear near-IR counterpart (Swift J175233.9-290952). Finally, 3XMM J174417.2-293944 has a subgiant donor, an 8.7 d orbital period, and a likely white dwarf accretor; we argue that this is the first detection of a white dwarf accreting from a gravitationally focused wind. A key finding of our follow-up campaign is that binaries containing (sub)giant stars may make a substantial contribution to the VFXT population.

scholarly journals Colliding winds in and around the stellar group IRS 13E at the galactic centre

2019 ◽  
Vol 492 (2) ◽  
pp. 2481-2496 ◽  
Author(s):  
Q Daniel Wang ◽  
Jun Li ◽  
Christopher M P Russell ◽  
Jorge Cuadra
Keyword(s):  
Thermal Emission ◽  
Ambient Medium ◽  
Velocity Spread ◽  
Galactic Centre ◽  
X Ray ◽  
Stellar Group ◽  
Cool Gas ◽  
Sgr A ◽  
Colliding Winds ◽  
Projected Distance

ABSTRACT IRS 13E is an enigmatic compact group of massive stars located in projection only 3.6 arcsec away from Sgr A*. This group has been suggested to be bounded by an intermediate-mass black hole (IMBH). We present a multiwavelength study of the group and its interplay with the environment. Based on Chandra observations, we find the X-ray spectrum of IRS 13E can be well characterized by an optically thin thermal plasma. The emission peaks between two strongly mass-losing Wolf–Rayet stars of the group. These properties can be reasonably well reproduced by simulated colliding winds of these two stars. However, this scenario underpredicts the X-ray intensity in outer regions. The residual emission likely results from the ram-pressure confinement of the IRS 13E group wind by the ambient medium and is apparently associated with a shell-like warm gas structure seen in Pa α and in ALMA observations. These latter observations also show strongly peaked thermal emission with unusually large velocity spread between the two stars. These results indicate that the group is colliding with the bar of the dense cool gas mini-spiral around Sgr A*. The extended X-ray morphology of IRS 13E and its association with the bar further suggest that the group is physically much farther away than the projected distance from Sgr A*. The presence of an IMBH, while favourable to keep the stars bound together, is not necessary to explain the observed stellar and gas properties of IRS 13E.

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