NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Chandra Discovery of Luminous Supersoft X-Ray Sources in M81A Chandra ACIS-S imaging observation of the nearby galaxy M81 (NGC 3031) reveals 9 luminous soft X-ray sources. The local environments, X-ray spectral properties, and X-ray light curves of the sources are presented and discussed in the context of prevailing physical models for supersoft sources. It is shown that the sample falls within expectations based on population synthesis models taken from the literature though the high observed luminosities (L approx.2e36 to approx.3e38 ergs in the 0.2--2.0-keV band) and equivalent blackbody temperatures (T approx.40 to 80 eV) place the brightest detected M81 objects at the high luminosity end of the class of supersoft sources defined by previous ROSAT and Einstein studies of nearby galaxies. This is interpreted as a natural consequence of the higher sensitivity of Chandra to hotter and more luminous systems. Most of the sources can be explained as canonical supersoft sources, secreting white dwarfs powered by steady surface nuclear burning, with X-ray spectra well-fit by hot white dwarf local thermodynamic equilibrium atmosphere models. An exceptionally bright source is scrutinized in greater detail as its estimated barometric luminosity, L approx. 1.5e39 ergs, greatly exceeds theoretical estimates for supersoft sources. This source may be beyond the stability limit and undergoing a phase of mass outflow under extreme conditions. Alternatively, a model in which the observed X-ray spectrum arises from an accretion disk around a blacklists of mass approx.1200/sqrt(cosi) solar masses (viewed at an inclination angle 1) cannot be excluded.
Document ID
20020050611
Acquisition Source
Marshall Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Swartz, Douglas A.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Ghosh, Kajal K.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Sulimanov, Valery
(NASA Marshall Space Flight Center Huntsville, AL United States)
Tennant, Allyn F.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Wu, Kinwah
(NASA Marshall Space Flight Center Huntsville, AL United States)
Six, N. Frank
Date Acquired
August 20, 2013
Publication Date
January 1, 2002
Subject Category
Astronomy
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Available Downloads

There are no available downloads for this record.
No Preview Available