On the nature of the ultraluminous X-ray source Holmberg II X-1

Abstract

We present a comprehensive spectral analysis of the ultraluminous X-ray source Holmberg II X-1 using broadband and high-resolution X-ray spectra taken with the XMM-Newton satellite over a period of 19 years benefiting from a recent campaign. We tested several models for the broadband spectra among which a double thermal component provided a reasonable description for the continuum between 0.3-10 keV and enabled us to constrain the properties of the accretion disc. The Luminosity-Temperature trends of the inner and outer disc components broadly agree with the expectations for a thin disc, although the exact values of the slopes are slightly sensitive to the adopted model. However, all tested models show L-T trends which deviate from a power law above a bolometric luminosity of about 5 $\times 10^{39}$erg/s, particularly for the hot thermal component associated to the inner accretion flow. Assuming that such deviations are due to the accretion rate exceeding its Eddington limit or, most likely, the super-critical rate, a compact object with a mass 16-36 Msun, i.e. a stellar-mass black hole, is inferred. The time-averaged (2021) high resolution spectra present narrow emission lines at 1 keV primarily from Ne IX-X and a very strong at 0.5 keV from N VII, which indicate Ne-N-rich gas with non-Solar abundances. This favours a nitrogen-rich donor star, such as a blue/red supergiant, which has escaped from its native stellar cluster characterised by a low-metallicity environment.

arXiv comment16 pages, 15 figures, accepted for publication in Astronomy & Astrophysics

References in corpus (62)

• Modelling the behaviour of accretion flows in X-ray binaries
• An Ultraluminous X-ray Source Powered by An Accreting Neutron Star
• Super-critically accreting stellar-mass black holes as ultraluminous X-ray sources
• Optimal binning of X-ray spectra and response matrix design
• An accreting pulsar with extreme properties drives an ultraluminous x-ray source in NGC 5907
• The Ultraluminous State
• Discovery of coherent pulsations from the Ultraluminous X-ray Source NGC 7793 P13
• The Nature of SS433 and the Ultraluminous X-ray Sources
• The ultraluminous state revisited: fractional variability and spectral shape as diagnostics of super-Eddington accretion
• Resolved atomic lines reveal outflows in two ultraluminous X-ray sources
• A spectral-timing model for ULXs in the super-critical regime
• High Resolution Imaging of the HeII lambda 4686 Emission Line Nebula Associated with the Ultraluminous X-Ray Source in Holmberg II
• Radio Detections During Two State Transitions of the Intermediate Mass Black Hole HLX-1
• Ultraluminous X-ray sources
• Discovery of a 2.8 s pulsar in a 2 d orbit High-Mass X-ray Binary powering the Ultraluminous X-ray source ULX-7 in M51
• Evidence for Pulsar-like Emission Components in the Broadband ULX Sample
• Clumpy Outflow from Supercritical Accretion Flows
• Evidence for a Variable Ultrafast Outflow in the Newly Discovered Ultraluminous Pulsar NGC 300 ULX-1
• From ultraluminous X-ray sources to ultraluminous supersoft sources: NGC 55 ULX, the missing link
• Revealing a Cool Accretion Disk in the Ultraluminous X-ray Source M81 X-9 (Holmberg IX X-1): Evidence for an Intermediate Mass Black Hole
• Diagnosing the accretion flow in ultraluminous X-ray sources using soft X-ray atomic features
• Broad absorption features in wind-dominated ULXs?
• Optically thick outflows in ultraluminous supersoft sources
• Measuring Black Hole Spin via the X-ray Continuum Fitting Method: Beyond the Thermal Dominant State
• An Iron K Component to the Ultrafast Outflow in NGC 1313 X-1
• Searching for Outflows in Ultraluminous X-ray Sources Through High-Resolution X-ray Spectroscopy
• XMM-Newton campaign on the ultraluminous X-ray source NGC 247 ULX-1: outflows
• A deep XMM-Newton observation of the ultraluminous X-ray source HoII X-1 : the case against a 1000 solar mass black hole
• Puffy accretion disks: sub-Eddington, optically thick, and stable
• Long-term X-ray spectral evolution of Ultraluminous X-ray sources: implications on the accretion flow geometry and the nature of the accretor
• Pulsing and Non-Pulsing ULXs: the Iceberg Emerges
• Unveiling recurrent jets of the ULX Holmberg II X-1: evidence for a massive stellar-mass black hole?
• A dipping black-hole X-ray binary candidate in NGC 55
• Keck/MOSFIRE spectroscopy of five ULX counterparts
• NuSTAR, XMM-Newton and Suzaku Observations of the Ultraluminous X-ray Source Holmberg II X-1
• The Unusual Broadband X-ray Spectral Variability of NGC 1313 X-1 seen with XMM$-$Newton, Chandra and NuSTAR
• XMM-Newton Campaign On Ultraluminous X-ray Source NGC 1313 X-1: Wind vs. State Variability
• Revisiting Putative Cool Accretion Disks in Ultraluminous X-ray Sources
• More nitrogen rich B-type stars in the SMC cluster, NGC 330
• Ionised Emission and Absorption in a Large Sample of Ultraluminous X-ray Sources
• The Lense-Thirring timing-accretion plane for ULXs
• Thermal stability of winds driven by radiation pressure in super-Eddington accretion disks
• Evidence for precession due to supercritical accretion in ultraluminous X-ray sources
• The Nature of the UV/optical Emission of the Ultraluminous X-Ray Source in Holmberg II
• Discovery of a recurrent spectral evolutionary cycle in the ultra-luminous X-ray sources Holmberg II X-1 and NGC 5204 X-1
• Uncovering Red and Dusty Ultraluminous X-ray Sources with Spitzer
• Modelling the disk atmosphere of the low mass X-ray binary EXO 0748-676
• Discovery of a large population of Nitrogen-Enhanced stars in the Magellanic Clouds
• Quasi-periodic dipping in the ultraluminous X-ray source, NGC 247 ULX-1
• Slim Disk: Viscosity Prescriptions and Observational Implications
• Thermally driven winds in ULXs
• Spectral variability in Swift and Chandra observations of the Ultraluminous source NGC 55 ULX1
• The X-ray properties of the dwarf Magellanic-type galaxy NGC 55
• The ultraluminous X-ray source HoII X-1: kinematic evidence of its escape from the cluster
• The chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1
• Testing the relativistic Doppler boost hypothesis for supermassive binary black holes candidates via broad emission line profiles
• Unveiling the disc structure in ultraluminous X-ray source NGC 55 ULX-1
• Propeller states in locally super-critical ULXs
• Unveiling the nitrogen-rich massive star in the metal-poor galaxy NGC 4068
• Ultra-luminous X-ray sources: extreme accretion and feedback
• Spectral calculations of 3D RMHD simulations of super-Eddington accretion onto a stellar-mass black hole
• High-Resolution Spectroscopy of X-ray Binaries

Cited by in corpus (6)

• Euclid: Early Release Observations -- Deep anatomy of nearby galaxies
• A new pulsating neutron star in the Ultraluminous X-ray source NGC 4559 X7?
• 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
• The hunt for new pulsating ultraluminous X-ray sources: a clustering approach
• XMM-Newton multi-year campaign on NGC 55 ULX-1: Resolving the wind and its variability with RGS
• A high-resolution X-ray view of the ultra-fast outflow in MAXI J1810-222