Show simple item record

dc.contributor.authorWalton, Dominicen
dc.contributor.authorFurst, Fen
dc.contributor.authorHarrison, FAen
dc.contributor.authorMiddleton, MJen
dc.contributor.authorFabian, Andrewen
dc.contributor.authorBachetti, Men
dc.contributor.authorBarret, Den
dc.contributor.authorMiller, JMen
dc.contributor.authorPtak, Aen
dc.contributor.authorRana, Ven
dc.contributor.authorStern, Den
dc.contributor.authorTao, Len
dc.date.accessioned2017-06-05T08:16:01Z
dc.date.available2017-06-05T08:16:01Z
dc.date.issued2017-04-21en
dc.identifier.issn0004-637X
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/264622
dc.description.abstractWe present results from four new broadband X-ray observations of the extreme ultraluminous X-ray source Holmberg IX X-1 (L$_{x}$ > 10$^{40}$ erg s$^{-1}$), performed by $\textit{Suzaku}$ and $\textit{Nu}$STAR in coordination. Combined with the archival data, we now have broadband observations of this remarkable source from six separate epochs. Two of these new observations probe lower fluxes than seen previously, allowing us to extend our knowledge of the broadband spectral variability exhibited. The spectra are well fit by two thermal blackbody components that dominate the emission below 10 keV, as well as a steep ($\Gamma$ $\sim$ 3.5) power-law tail that dominates above ~15 keV. Remarkably, while the 0.3–10.0 keV flux varies by a factor of ~3 between all these epochs, the 15–40 keV flux varies by only ~20%. Although the spectral variability is strongest in the ~1–10 keV band, both of the thermal components are required to vary when all epochs are considered. We also revisit the search for iron absorption features by leveraging the high-energy NuSTAR data to improve our sensitivity to extreme velocity outflows in light of the ultra-fast outflow recently detected in NGC 1313 X-1. Iron absorption from a similar outflow along our line of sight can be ruled out in this case. We discuss these results in the context of super-Eddington accretion models that invoke a funnel-like geometry for the inner flow, and propose a scenario in which we have an almost face-on view of a funnel that expands to larger radii with increasing flux, resulting in an increasing degree of geometrical collimation for the emission from intermediate-temperature regions.
dc.description.sponsorshipD.J.W. and M.J.M. acknowledge support from STFC through Ernest Rutherford fellowships, A.C.F. acknowledges support from ERC Advanced Grant 340442, and D.B. acknowledges financial support from the French Space Agency (CNES). This research has made use of data obtained with NuSTAR, a project led by Caltech, funded by NASA and managed by NASA/JPL, and has utilized the NUSTARDAS software package, jointly developed by the ASDC (Italy) and Caltech (USA). This research has also made use of data obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States, and with Suzaku, a collaborative mission between the space agencies of Japan (JAXA) and the USA (NASA).
dc.languageengen
dc.language.isoenen
dc.publisherInstitute of Physics
dc.subjectblack hole physicsen
dc.subjectX-rays: binariesen
dc.subjectX-rays: individual (Holmberg IX X-1)en
dc.titleThe Broadband Spectral Variability of Holmberg IX X-1en
dc.typeArticle
prism.issueIdentifier2en
prism.number105en
prism.publicationDate2017en
prism.publicationNameThe Astrophysical Journalen
prism.volume839en
dc.identifier.doi10.17863/CAM.10207
dcterms.dateAccepted2017-03-17en
rioxxterms.versionofrecord10.3847/1538-4357/aa683een
rioxxterms.versionVoRen
rioxxterms.licenseref.urihttp://www.rioxx.net/licenses/all-rights-reserveden
rioxxterms.licenseref.startdate2017-04-21en
dc.contributor.orcidWalton, Dominic [0000-0001-5819-3552]
dc.contributor.orcidFabian, Andrew [0000-0002-9378-4072]
dc.identifier.eissn1538-4357
rioxxterms.typeJournal Article/Reviewen
pubs.funder-project-idEuropean Research Council (340442)
pubs.funder-project-idSCIENCE & TECHNOLOGY FACILITIES COUNCIL (ST/N000927/1)


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record