The First Detection of [O IV] from an Ultraluminous X-ray Source with Spitzer. II. Evidence for High Luminosity in Holmberg II ULX

Abstract

This is the second of two papers examining Spitzer Infrared Spectrograph (IRS) 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 [O IV] 25.89 $\mu$m 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${}^{40}$ erg s${}^{-1}$ 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.

Accepted by ApJ

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Cited by in corpus (28)

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• Ultraluminous X-ray sources
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• NuSTAR, XMM-Newton and Suzaku Observations of the Ultraluminous X-ray Source Holmberg II X-1
• NuSTAR and XMM-Newton observations of the extreme ultraluminous X-ray source NGC 5907 ULX1: A Vanishing Act
• On rapid binary mass transfer -- I. Physical model
• Can nebular HeII emission be explained by ultra-luminous X-ray sources?
• X-ray spectral state is not correlated with luminosity in Holmberg II X-1
• Comparing Spectral Models for ULXs with NGC 4517 ULX1
• Searching for Massive Outflows in Holmberg IX X-1 and NGC 1313 X-1: The Iron K Band
• The Nature of the UV/optical Emission of the Ultraluminous X-Ray Source in Holmberg II
• Uncovering Red and Dusty Ultraluminous X-ray Sources with Spitzer
• MUSE spectroscopy of the ULX NGC 1313 X-1: a shock-ionised bubble, an X-ray photoionised nebula, and two supernova remnants
• Evolution of the spectral curvature in the ULX Holmberg II X-1
• Statistical study of a large and cleaned sample of ultraluminous and hyperluminous X-ray sources
• Ultrafast outflows in ultraluminous X-ray sources
• Spitzer Observations of MF 16 Nebula and the associated Ultraluminous X-ray Source
• Black Holes and Neutron Stars in Nearby Galaxies: Insights from NuSTAR
• The ultraluminous X-ray source HoII X-1: kinematic evidence of its escape from the cluster
• Detection of a Radio Bubble around the Ultraluminous X-ray Source Holmberg IX X-1
• The Local Environment of Ultraluminous X-ray Sources Viewed by XMM Newton's Optical Monitor
• First Detection of Mid-Infrared Variability from an Ultraluminous X-Ray Source Holmberg II X-1
• The Binary Black Hole Merger Rate from Ultraluminous X-ray Source Progenitors
• Spitzer IRAC observations of IR excess in Holmberg IX X-1: A circumbinary disk or a variable jet?
• Impact of ultraluminous X-ray sources on photoabsorption in the first galaxies
• Mid-Infrared and X-ray luminosity correlations of X-ray point sources in NGC 1399
• Multi-wavelength spectroscopic analysis of the ULX Holmberg II X-1 and its nebula suggests the presence of a heavy black hole accreting from a B-type donor