A transition to a low/soft state in the ultra-luminous compact X-ray source Holmberg II X-1

Details A transition to a low/soft state in the ultra-luminous compact X-ray source Holmberg II X-1 A transition to a low/soft state in the ultra-luminous compact X-ray source Holmberg II X-1

2004-01-12

arxiv.org/abs/astro-ph/0401223v2

Astrophys.J. 608 (2004) L57-L60

Astronomy and Astrophysics

Astrophysics

Revised and shortened version, To appear in ApJ Letters

Scientific paper

10.1086/422338

We present three XMM-Newton observations of the ultra-luminous compact X-ray source Holmberg II X-1 in its historical brightest and faintest states. The source was in its brightest state in April 2002 with an isotropic X-ray luminosity of 2e40 erg/s but changed to a peculiar low/soft state in September 2002 in which the X-ray flux dropped by a factor of four and the spectrum softened. In all cases, a soft excess component, which can be described by a simple or multicolor disk blackbody (MCD; kT = 120-170 eV), is statistically required in addition to a power-law continuum (Gamma = 2.4 - 2.9). Both the spectral components became weaker and softer in the low/soft state, however, the dramatic variability is seen in the power-law component. This spectral transition is opposite to the `canonical' high/soft -- low/hard transitions seen in many Galactic black hole binaries. There is possible contribution from an optically thin thermal plasma. When this component is taken into account, the spectral transition appears to be normal -- a drop of the power-law flux and slightly softer blackbody component in the low state.

Affiliated with

Also associated with

No associations

Rating

A transition to a low/soft state in the ultra-luminous compact X-ray source Holmberg II X-1 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with A transition to a low/soft state in the ultra-luminous compact X-ray source Holmberg II X-1, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A transition to a low/soft state in the ultra-luminous compact X-ray source Holmberg II X-1 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-266023