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Record 1 of 1248
The ULX Population in the Starburst Galaxy NGC 253
Author and Affiliation:
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)
Abstract: Optimism 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 .
Publication Date: Jan 01, 2004
Document ID:
20040171431
(Acquired Nov 30, 2004)
Subject Category: ASTRONOMY
Document Type: Preprint
Meeting Information: AAS Conference; 30 May - 3 Jun. 2004; Denver, CO; United States
Meeting Sponsor: American Astronomical Society; United States
Financial Sponsor: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Organization Source: NASA Goddard Space Flight Center; Greenbelt, MD, United States
Description: 1p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: No Copyright
NASA Terms: BLACK HOLES (ASTRONOMY); STARBURST GALAXIES; STELLAR MASS; MASS SPECTRA; X RAY SOURCES; A STARS; NEUTRON STARS; MATHEMATICAL MODELS; POINT SOURCES; STELLAR EVOLUTION
Availability Source: Other Sources
Availability Notes: Abstract Only
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