The X-ray-faint early-type galaxy NGC 4697

Citation
Ja. Irwin et al., The X-ray-faint early-type galaxy NGC 4697, ASTROPHYS J, 544(1), 2000, pp. 293-301
Citations number
40
Categorie Soggetti
Space Sciences
Journal title
ASTROPHYSICAL JOURNAL
ISSN journal
0004637X → ACNP
Volume
544
Issue
1
Year of publication
2000
Part
1
Pages
293 - 301
Database
ISI
SICI code
0004-637X(20001120)544:1<293:TXEGN4>2.0.ZU;2-H
Abstract
We analyze archival ROSAT HRI, ROSAT PSPC, and ASCA data of the X-ray-faint early-type galaxy NGC 4697. The joint ROSAT PSPC + ASCA spectrum is fitted by a two-component thermal model, a MEKAL model with kT(MEKAL) = 0.26(-0.0 3)(+0.04) keV with low metallicity and a bremsstrahlung model with kT(BREM) = 5.2(-1.6)(+3.0) keV. A similar model was found to fit the spectra of ano ther faint early-type galaxy (NGC 4382) and the bulge of M31. We interpret this soft emission as a combination of emission from a soft component of lo w-mass X-ray binaries (LMXBs) and from a low-temperature interstellar mediu m, although the relative contributions of the two components could not be d etermined. Twelve point sources were identified within 4 ' of NGC 4697, of which 11 are most likely LMXBs associated with the galaxy. The soft X-ray c olors of four of the LMXBs in NGC 4697 support the claim that LMXBs possess a soft spectral component. Finally, we present a simulation of what we bel ieve the Chandra data of NGC 4697 will look like.