NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
The ULX Population in the Starburst Galaxy NGC 253Optimism is mounting for the existence of intermediate mass black holes (IMBH), which occupy the mass spectrum somewhere between the stellar-mass and supermassive varieties. IMBH are naturally predicted by theoretical stellar and black hole evolution models, but the strong attention to them began only recently with the discovery of ultraluminous x-ray sources (ULX). If isotropic and accreting normally, ULX have luminosities tens to thousands of times greater than the Eddington luminosity of a neutron star or stellar-mass black hole. A standard interpretation of their x-ray flux implies that they are powered by IMBH. On the other hand, they may be stellar-mass black holes that are beamed or emit anisotropically. Therefore, the exact nature of ULX is highly controversial. ULX are common in starburst galaxies. At a distance of only 3 Mpc, NGC 253 is bright, nearby, and one of the best-studied starburst galaxies. Approximately 50 distinct x-ray point sources are detected in or near the plane of the galaxy. At least six of these are ULX, with luminosities greater than 10 times that expected for a stellar-mass, accreting compact object. We present new Chandra data from an 80 ksec observation of NGC 253 obtained in 2003 that provides high quality spectra of these sources. Comparing the 1999 and 2003 Chandra observations, the sources have varied significantly over the course of four years, with one of the ULX disappearing completely. The ULX spectra are similar to black-hole XRBs and at least one appears to possess an iron K line. We will discuss what insight these data provide for the nature of ULX in NGC 253 .
Document ID
20040171431
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Weaver, K. A.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Heckman, T. M.
(Johns Hopkins Univ. United States)
Strickland, D. K.
(Johns Hopkins Univ. United States)
Date Acquired
August 22, 2013
Publication Date
January 1, 2004
Subject Category
Astronomy
Meeting Information
Meeting: AAS Conference
Location: Denver, CO
Country: United States
Start Date: May 30, 2004
End Date: June 3, 2004
Sponsors: American Astronomical Society
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