Query : 2002A&A...389..752R

2002A&A...389..752R - Astronomy and Astrophysics, volume 389, 752-760 (2002/7-3)

RXTE view of the starburst galaxies M82 and NGC 253.


Abstract (from CDS):

The two nearby starburst galaxies M82 and NGC 253 were observed for ∼100ksec over a 10-month period in 1997. An increase of the M82 flux by a factor ∼2 was measured during the period July-November, when compared with the flux measured earlier in 1997. The flux measured in the field centered on M82 includes ∼38% of the emission from the Seyfert 1 galaxy M81. The best-fitting model for the earlier emission from M82 is thermal with kT≃6.7±0.1. In the high flux state, the emission additionally includes either an absorbed second thermal component or absorbed power-law component, with the former providing a much better fit. A likely origin for the temporal variability is a single source in M82. The flux of NGC 253, which did not vary significantly during the period of observations, can be well fit by either a thermal spectrum with kT≃3.8±0.3keV, or by a power law with photon index of 2.7±0.10. We have also attempted fitting the measurements to more realistic composite models with thermal and power-law components, such as would be expected from a dominant contribution from binary systems, or Compton scattering of (far) IR radiation by radio emitting electrons. However, the addition of any amount of a power-law component, even with cutoff at 20keV, only increases chi-square. The 90% confidence upper limit for power law emission with (photon) index 1.5 is only 2.4% of the 2-10keV flux of M82; the corresponding limit for NGC 253, with index 2.0, is 48%.

Abstract Copyright:

Journal keyword(s): galaxies: starburst - galaxies: individual: M82, NGC 253 - X-rays: galaxies - mechanisms: non-thermal radiation

Simbad objects: 4

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Number of rows : 4
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 NGC 253 SyG 00 47 33.134 -25 17 19.68   8.03   6.94 8.1 ~ 3262 2
2 M 81 Sy2 09 55 33.1726556496 +69 03 55.062505368   7.89 6.94     ~ 4360 3
3 NAME M82 ULX-1 UX? 09 55 50.01 +69 40 46.0           ~ 267 1
4 M 82 IG 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 5767 6

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