An Iron K Component to the Ultrafast Outflow in NGC 1313 X-1

Walton, D. J.; Middleton, Matthew; Pinto, C.; Fabian, A. C.; Bachetti, Matteo; Barret, D.; Brightman, Murray; Fuerst, F.; Harrison, F.; Miller, J. M.; Stern, Daniel

doi:10.3847/2041-8205/826/2/l26

Cited by 116 publications

(170 citation statements)

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“…Last, we also revisit the limits on the presence of any atomic iron absorption or emission features in light of the ultra-fast outflow (∼0.2-0.25c) recently detected in NGC 1313 X-1 Walton et al 2016b). The high-energy constraints provided by the NuSTAR data, missing in our previous line searches for Holmberg IX X-1 (Walton et al 2012(Walton et al , 2013b), mean we can now significantly improve our sensitivity to any features associated with high-velocity outflows for this source.…”

Section: Fe K Line Searchmentioning

confidence: 90%

“…Considering the XMM-Newton, Suzaku, and NuSTAR databases, the majority of the archival exposure available for Holmberg IX X-1 covers states similar to epoch 1, so we focus on these data in order to maximize the S/N while considering only observations with similar spectra. Following Walton et al (2016b), we also only consider XMMNewton observations in which Holmberg IX X-1 was placed on-axis in order to avoid increased background emission from copper lines at ∼8 keV seen in the EPIC-pn detector away from the optical axis (Carter & Read 2007), which fall in the energy range of interest. Therefore, in addition to the data from epochs 1, 3, and 6, we also include archival data from anotherlong Suzaku exposure (OBSID 707019010)and two short XMMNewton exposures (ODSIDs 0112521001 and 0112521101).…”

Section: Fe K Line Searchmentioning

confidence: 99%

“…We also include the two neutral absorption components included in our primary spectral analysis (Galactic and intrinsic to Holmberg IX), with the latter fixed to =Ń 1.5 10 H,int 21 cm −2 based on the results above (see also Miller et al 2013) 1 . To search for atomic features, we follow a similar approach to our previouswork on ULX outflows (e.g., Walton et al 2013bWalton et al , 2016b. The reader is referred to Walton et al (2012) for more details, but in brief, we slide a narrow (σ=10 eV) Gaussian across the energy range of interest in steps of 40 eV (oversampling the Suzaku energy resolution by a factor ∼4).…”

Section: Fe K Line Searchmentioning

confidence: 99%

“…Indeed, we now know that at least three of this population of extreme ULXs are actually highly super-Eddington neutron stars Fürst et al 2016;Israel et al 2017aIsrael et al , 2017b. Furthermore, in the case of NGC 1313 X-1, anotherL 10 X 40 erg s −1 ULX, discrete absorption features from a massive outflow have now finally been detected Walton et al 2016b), following an initial suggestion that low-energy (∼1 keV) residuals could be related to such a wind (Middleton et al 2014. Large outflows from the accretion flow are broadly expected from superEddington accretion theory (e.g., Poutanen et al 2007).…”

Section: Introductionmentioning

confidence: 98%

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The Broadband Spectral Variability of Holmberg IX X-1

Walton

Fürst

Harrison

et al. 2017

ApJ

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We present results from four new broadband X-ray observations of the extreme ultraluminous X-ray source Holmberg IX X-1 ( > L 10 X 40 erg s −1 ), performed by Suzaku and NuSTAR 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 (G~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 superEddington 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.

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Section: Fe K Line Searchmentioning

confidence: 90%

Section: Fe K Line Searchmentioning

confidence: 99%

Section: Fe K Line Searchmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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The Broadband Spectral Variability of Holmberg IX X-1

Walton

Fürst

Harrison

et al. 2017

ApJ

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“…From Figure 4 it is clear that the strongest spectral change is observed in p. At super-Eddington accretion rates, it is expected that the accretion disk is flared up due to radiation pressure, i.e., itbecomes geometrically thick and increases in size with radius. In addition, a strong wind is launched, which is also largely optically thick (Poutanen et al 2007;Dotan & Shaviv 2011) and for which observational evidence has recently been found in NGC 1313X-1 and NGC 5408X-1 (Pinto et al 2016;Walton et al 2016b). The observed temperature profile, therefore, depends on which parts and with what angle we observe the accretion disk.…”

Section: Connection Between the Super-orbital Period And Spectral Chamentioning

confidence: 99%

Spectral Changes in the Hyperluminous Pulsar in NGC 5907 as a Function of Super-Orbital Phase

Fürst

Walton

Stern

et al. 2017

ApJ

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103

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We present broadband, multi-epoch X-ray spectroscopy of the pulsating ultra-luminous X-ray source (ULX) in NGC 5907. Simultaneous XMM-Newton and NuSTAR data from 2014 are best described by a multicolor blackbody model with a temperature gradient as a function of accretion disk radius significantly flatter than expected for a standard thin accretion disk ( µ -T r r p ( ) , with = -+ p 0.608 0.012 0.014 ). Additionally, we detect a hard power-law tail at energies above 10 keV, which we interpret as being due to Comptonization. We compare this observation to archival XMM-Newton, Chandra, and NuSTAR data from 2003, 2012, and 2013, and investigate possible spectral changes as a function of phase over the 78-daysuper-orbital period of this source. We find that observations taken around phases 0.3-0.4 show very similar temperature profiles, even though the observed flux varies significantly, while one observation taken around phase 0 has a significantly steeper profile. We discuss these findings in light of the recent discovery that the compact object is a neutron star and show that precession of the accretion disk or the neutron star can self-consistently explain most observed phenomena.

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Ultrafast outflows in ultraluminous X‐ray sources

Pinto¹,

Fabian²,

Middleton

et al. 2017

Astron Nachr

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Ultraluminous X-ray sources (ULXs) are bright extragalactic sources with X-ray luminosities above 10 39 erg/s powered by accretion onto compact objects. According to the first studies performed with XMM-Newton ULXs seemed to be excellent candidates to host intermediate-mass black holes (10 2−4 M⊙). However, in the last years the interpretation of super-Eddington accretion onto stellar-mass black holes or neutron stars for most ULXs has gained a strong consensus. One critical missing piece to confirm the super-Eddington scenario was the direct detection of the massive, radiativelydriven winds expected as atomic emission/absorption lines in ULX spectra. The first evidence for winds was found as residuals in the soft X-ray spectra of ULXs. Most recently we have been able to resolve these residuals into rest-frame emission and blueshifted (∼ 0.2c) absorption lines arising from highly ionized gas in the deep high-resolution XMMNewton spectra of two ultraluminous X-ray sources. The compact object is therefore surrounded by powerful ultrafast winds as predicted by models of hyper-Eddington accretion. Here we discuss the relevance of these discoveries and the importance of further, deep, XMM-Newton observations of powerful winds in many other ultraluminous X-ray sources to estimate the energetics of the wind, the geometry of the system, and the masses of the central accretors.

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An Iron K Component to the Ultrafast Outflow in NGC 1313 X-1

Cited by 116 publications

References 50 publications

The Broadband Spectral Variability of Holmberg IX X-1

The Broadband Spectral Variability of Holmberg IX X-1

Spectral Changes in the Hyperluminous Pulsar in NGC 5907 as a Function of Super-Orbital Phase

Ultrafast outflows in ultraluminous X‐ray sources

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