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dc.contributor.authorMezcua, M.
dc.contributor.authorFabbiano, G.
dc.contributor.authorGladstone, J.
dc.contributor.authorFarrell, S.
dc.contributor.authorSoria, Roberto
dc.identifier.citationMezcua, M and Fabbiano, G. and Gladstone, J and Farrell, Sean and Soria, Roberto. 2014. Revealing the nature of the ULX and X-ray population of the spiral galaxy NGC 4088. Astrophysical Journal. 785 (2): pp. 1-9.

We present the first Chandra and Swift X-ray study of the spiral galaxy NGC 4088 and its ultraluminous X-ray source (ULX N4088-X1). We also report very long baseline interferometry (VLBI) observations at 1.6 and 5 GHz performed quasi-simultaneously with the Swift and Chandra observations, respectively. Fifteen X-ray sources are detected by Chandra within the D25 ellipse of NGC 4088, from which we derive the X-ray luminosity function (XLF) of this galaxy. We find the XLF is very similar to those of star-forming galaxies and estimate a star-formation rate of 4.5 M☉ yr–1. The Chandra detection of the ULX yields its most accurate X-ray position, which is spatially coincident with compact radio emission at 1.6 GHz. The ULX Chandra X-ray luminosity, L 0.2-10.0 keV = 3.4 × 1039 erg s–1, indicates that N4088-X1 could be located at the high-luminosity end of the high-mass X-ray binary (HMXB) population of NGC 4088. The estimates of the black hole (BH) mass and ratio of radio to X-ray luminosity of N4088-X1 rule out a supermassive BH nature. The Swift X-ray spectrum of N4088-X1 is best described by a thermal Comptonization model and presents a statistically significant high-energy cutoff. We conclude that N4088-X1 is most likely a stellar remnant BH in an HMXB, probably fed by Roche lobe overflow, residing in a super-Eddington ultraluminous state. The 1.6 GHz VLBI source is consistent with radio emission from possible ballistic jet ejections in this state.

dc.publisherInstitute of Physics Publishing
dc.subjectradio continuum: general
dc.subjectaccretion disks
dc.subjectblack hole physics
dc.subjectX-rays: binaries
dc.subjectISM: jets and outflows
dc.titleRevealing the nature of the ULX and X-ray population of the spiral galaxy NGC 4088
dc.typeJournal Article
dcterms.source.titleAstrophysical Journal

Copyright © 2014 - American Astronomical Society

curtin.accessStatusOpen access

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