The nature of donors in ultraluminous X-ray binaries powered by neutron stars

Karino, Shotaro

doi:10.1093/mnras/stx2998

Cited by 5 publications

(3 citation statements)

References 47 publications

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“…In this attempt, observational campaigns have been carried out (Ptak et al 2006;Tao et al 2011;Grisé et al 2012;Gladstone et al 2013;Heida et al 2014;López et al 2017). Theoretical arguments have been made to constrain the donor star but they often presuppose a RLOF mass transfer and thus might not hold for ULXs in general (Karino 2017). If the stellar mass-loss rate is too low or the source too bright (typically, hyperluminous X-ray sources), wind-RLOF cannot channel enough matter, but otherwise, when the wind is slow enough, it is a fully viable scenario to enhance the mass-transfer rate.…”

Section: Discussionmentioning

confidence: 99%

Wind Roche lobe overflow in high-mass X-ray binaries

Mellah

Sundqvist

Keppens

2019

A&A

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Ultraluminous X-ray sources (ULXs) have such high X-ray luminosities that they were long thought to be accreting intermediate-mass black holes. Yet, some ULXs have been shown to display periodic modulations and coherent pulsations suggestive of a neutron star in orbit around a stellar companion and accreting at super-Eddington rates. In this Letter, we propose that the mass transfer in ULXs could be qualitatively the same as in supergiant X-ray binaries (SgXBs), with a wind from the donor star highly beamed towards the compact object. Since the star does not fill its Roche lobe, this mass transfer mechanism known as “wind Roche lobe overflow” can remain stable even for large donor-star-to-accretor mass ratios. Based on realistic acceleration profiles derived from spectral observations and modeling of the stellar wind, we compute the bulk motion of the wind to evaluate the fraction of the stellar mass outflow entering the region of gravitational predominance of the compact object. The density enhancement towards the accretor leads to mass-transfer rates systematically much larger than the mass-accretion rates derived by the Bondi-Hoyle-Lyttleton formula. We identify orbital and stellar conditions for a SgXBs to transfer mass at rates necessary to reach the ULX luminosity level. These results indicate that Roche-lobe overflow is not the only way to funnel large quantities of material into the Roche lobe of the accretor. With the stellar mass-loss rates and parameters of M101 ULX-1 and NGC 7793 P13, wind Roche-lobe overflow can reproduce mass-transfer rates that qualify an object as an ULX.

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Section: Discussionmentioning

confidence: 99%

Wind Roche lobe overflow in high-mass X-ray binaries

Mellah

Sundqvist

Keppens

2019

A&A

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“…Typical ULXs have X-ray luminosities in excess of 10 39 erg s −1 (Swartz et al 2004;Walton et al 2011). Although the ULXs are believed to be powered mostly by Roche lobe overflow (Karino 2018;El Mellah et al 2019), the wind accretion remains a viable option at least for some of these sources (Miller et al 2014;Wiktorowicz et al 2021).…”

Section: Implications For Ulxsmentioning

confidence: 99%

X-ray irradiation of the stellar wind in HMXBs with B supergiants: Implications for ULXs

Krtička

Kubát

Krtičková

2022

A&A

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Wind-fed high-mass X-ray binaries are powered by accretion of the radiatively driven wind of the luminous component on the compact star. Accretion-generated X-rays alter the ionization state of the wind. Because higher ionization states drive the wind less effectively, X-ray ionization may brake acceleration of the wind. This causes a decrease in the wind terminal velocity and mass flux in the direction toward the X-ray source. Here we study the effect of X-ray ionization on the stellar wind of B supergiants. We determine the binary parameters for which the X-ray irradiation significantly influences the stellar wind. This can be conveniently studied in diagrams that plot the optical depth parameter versus the X-ray luminosity. For low optical depths or for high X-ray luminosities, X-ray ionization leads to a disruption in the wind aimed toward the X-ray source. Observational parameters of high-mass X-ray binaries with B-supergiant components appear outside the wind disruption zone. The X-ray feedback determines the resulting X-ray luminosity. We recognize two states with a different level of feedback. For low X-ray luminosities, ionization is weak, and the wind is not disrupted by X-rays and flows at large velocities, consequently the accretion rate is relatively low. On the other hand, for high X-ray luminosities, the X-ray ionization disrupts the flow braking the acceleration, the wind velocity is low, and the accretion rate becomes high. These effects determine the X-ray luminosity of individual binaries. Accounting for the X-ray feedback, estimated X-ray luminosities reasonably agree with observational values. We study the effect of small-scale wind inhomogeneities (clumping), showing that clumping weakens the effect of X-ray ionization by increasing recombination and the mass-loss rate. This effect is particularly important in the region of the so-called bistability jump. We show that ultraluminous X-ray binaries with LX ≲ 1040 erg s−1 may be powered by accretion of a B-supergiant wind on a massive black hole.

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“…High magnetic field NSs are short-lived (Thompson & Duncan 1995) and associated with supernova remnants and recent star formation (e.g., Kaspi & Beloborodov 2017). In addition, the masses of companion stars to NS ULXs are observed or inferred to be over 5 M (e.g., Karino 2018). Located in an old environment, M86 tULX-1 is unlikely to be an accreting NS.…”

Section: Accretor Type and Massmentioning

confidence: 99%

Discovery of a transient ultraluminous X-ray source in the elliptical galaxy M86

Haaften

Maccarone

Rhode

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We report the discovery of the transient ultraluminous X-ray source (ULX) CXOU J122602.3+125951 (hereafter M86 tULX-1), located 3 52 (19 kpc) northwest of the centre of the giant elliptical galaxy M86 (NGC 4406) in the Virgo Cluster. The spectrum of M86 tULX-1 can be fit by a power law plus multicolour disc model with a 1.0 +0.8 −2.6 index and a 0.66 +0.17 −0.11 keV inner disc temperature, or by a power law with a 1.86 ± 0.10 index. For an isotropically emitting source at the distance of M86, the luminosity based on the superposition of spectral models is (5 ± 1) × 10 39 erg s −1 . Its relatively hard spectrum places M86 tULX-1 in a hitherto unpopulated region in the luminosity-disc temperature diagram, between other ULXs and the (sub-Eddington) black-hole X-ray binaries. We discovered M86 tULX-1 in an archival 148-ks 2013 July Chandra observation, and it was not detected in a 20-ks 2016 May Chandra observation, meaning it faded by a factor of at least 30 in three years. Based on our analysis of deep optical imaging of M86, it is probably not located in a globular cluster. It is the brightest ULX found in an old field environment unaffected by recent galaxy interaction. We conclude that M86 tULX-1 may be a stellar-mass black hole of ∼30 − 100 M with a low-mass giant companion, or a transitional object in a state between the normal stellar-mass black holes and the ultraluminous state.

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The nature of donors in ultraluminous X-ray binaries powered by neutron stars

Cited by 5 publications

References 47 publications

Wind Roche lobe overflow in high-mass X-ray binaries

Wind Roche lobe overflow in high-mass X-ray binaries

X-ray irradiation of the stellar wind in HMXBs with B supergiants: Implications for ULXs

Discovery of a transient ultraluminous X-ray source in the elliptical galaxy M86

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