|
| | | | |
| | | |
| Stat |
Members: 3645
Articles: 2'501'711
Articles rated: 2609
20 April 2024 |
|
| | | | |
|
Article overview
| |
|
|
Fading hard X-ray emission from the Galactic Centre molecular cloud Sgr B2 | | R. Terrier
; G. Ponti
; G. Belanger
; A. Decourchelle
; V. Tatischeff
; A. Goldwurm
; G. Trap
; M. R. Morris
; R. Warwick
; | | Date: |
26 May 2010 | | Abstract: | The centre of our Galaxy harbours a 4 million solar mass black hole that is
unusually quiet: its present X-ray luminosity is more than 10 orders of
magnitude less than its Eddington luminosity. The observation of iron
fluorescence and hard X-ray emission from some of the massive molecular clouds
surrounding the Galactic Centre has been interpreted as an echo of a past
flare. Alternatively, low-energy cosmic rays propagating inside the clouds
might account for the observed emission, through inverse bremsstrahlung of low
energy ions or bremsstrahlung emission of low energy electrons. Here we report
the observation of a clear decay of the hard X-ray emission from the molecular
cloud Sgr B2 during the past 7 years thanks to more than 20 Ms of INTEGRAL
exposure. The measured decay time is compatible with the light crossing time of
the molecular cloud core . Such a short timescale rules out inverse
bremsstrahlung by cosmic-ray ions as the origin of the X ray emission. We also
obtained 2-100 keV broadband X-ray spectra by combining INTEGRAL and XMM-Newton
data and compared them with detailed models of X-ray emission due to
irradiation of molecular gas by (i) low-energy cosmic-ray electrons and (ii)
hard X-rays. Both models can reproduce the data equally well, but the time
variability constraints and the huge cosmic ray electron luminosity required to
explain the observed hard X-ray emission strongly favor the scenario in which
the diffuse emission of Sgr B2 is scattered and reprocessed radiation emitted
in the past by Sgr A*. Using recent parallax measurements that place Sgr B2 in
front of Sgr A*, we find that the period of intense activity of Sgr A* ended
between 75 and 155 years ago. | | Source: | arXiv, 1005.4807 | | Services: | Forum | Review | PDF | Favorites | |
|
|
No review found.
Did you like this article?
Note: answers to reviews or questions about the article must be posted in the forum section.
Authors are not allowed to review their own article. They can use the forum section.
browser Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; ClaudeBot/1.0; +claudebot@anthropic.com)
|
| |
|
|
|
|
News, job offers and information for researchers and scientists:
| |
REGISTER