The First Detection of (O IV) from an Ultraluminous X-Ray Source with Spitzer. 2. Evidence for High Luminosity in Holmberg II ULX
Abstract
This is the second of two papers examining Spitzer Infrared Spectrograph observations of the ultraluminous X-ray source (ULX) in Holmberg II. Here, we perform detailed photoionization modeling of the infrared lines. Our analysis suggests that the luminosity and morphology of the [Oiv] 25.89 micronmeters emission line is consistent with photoionization by the soft X-ray and far ultraviolet (FUV) radiation from the accretion disk of the binary system and inconsistent with narrow beaming. We show that the emission nebula is matter bounded both in the line-of-sight direction and to the east, and probably radiation-bounded to the west. A bolometric luminosity in excess of 10(exp 40) erg s(exp -1) would be needed to produce the measured [O iv] flux. We use modeling and previously published studies to conclude that shocks likely contribute very little, if at all,to the high-ionization line fluxes observed in the Holmberg II ULX. Additionally, we find that the spectral type of the companion star has a surprisingly strong effect on the predicted strength of the [O iv] emission. This finding could explain the origin of [O iv] in some starburst systems containing black hole binaries.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2010
- Accession Number
- ADA539638
Entities
People
- Ciprian T. Berghea
- K. A. Weaver
- R. P. Dudik
- T. R. Kallman
Organizations
- United States Naval Observatory