Modelling optical emission of Ultra-luminous X-ray Sources accreting above the Eddington limit

Ambrosi, E.; Zampieri, L.

doi:10.1093/mnras/sty2213

Cited by 21 publications

(15 citation statements)

References 102 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Bright optical counterparts with −8 < M V < −4 are not uncommon for ULXs, though these counterparts may have significant contribution to their optical emission from the irradiated accretion disc rather than the companion star (e.g. Grisé et al 2012;Fabrika et al 2015;Ambrosi & Zampieri 2018). We have no evidence that ULX-4 was accreting at the dates of the HST observations (although none of the observations were simultaneous with an X-ray observation so neither can we definitively rule this out).…”

Section: Super-eddington Accreting Sourcementioning

confidence: 77%

A Broadband Look at the Old and New ULXs of NGC 6946

Earnshaw

Grefenstette

Brightman

et al. 2019

ApJ

View full text Add to dashboard Cite

Two recent observations of the nearby galaxy NGC 6946 with NuSTAR, one simultaneous with an XMM-Newton observation, provide an opportunity to examine its population of bright accreting sources from a broadband perspective. We study the three known ultraluminous X-ray sources (ULXs) in the galaxy, and find that ULX-1 and ULX-2 have very steep power-law spectra with Γ = 3.6 +0.4 −0.3 in both cases. Their properties are consistent with being super-Eddington accreting sources with the majority of their hard emission obscured and down-scattered. ULX-3 (NGC 6946 X-1) is significantly detected by both XMM-Newton and NuSTAR at L X = (6.5 ± 0.1) × 10 39 erg s −1 , and has a power-law spectrum with Γ = 2.51 ± 0.05. We are unable to identify a high-energy break in its spectrum like that found in other ULXs, but the soft spectrum likely hinders our ability to detect one. We also characterise the new source, ULX-4, which is only detected in the joint XMM-Newton and NuSTAR observation, at L X = (2.27 ± 0.07) × 10 39 erg s −1 , and is absent in a Chandra observation ten days later. It has a very hard cut-off power-law spectrum with Γ = 0.7 ± 0.1 and E cut = 11 +9 −4 keV. We do not detect pulsations from ULX-4, but its transient nature can be explained either as a neutron star ULX briefly leaving the propeller regime or as a micro-tidal disruption event induced by a stellar-mass compact object.

show abstract

Section: Super-eddington Accreting Sourcementioning

confidence: 77%

A Broadband Look at the Old and New ULXs of NGC 6946

Earnshaw

Grefenstette

Brightman

et al. 2019

ApJ

View full text Add to dashboard Cite

show abstract

“…The donor stars in ULXPs obviously do not evolve in isolation, which will impact their evolution tracks (see e.g. Rappaport et al 2005;Patruno & Zampieri 2008, 2010Ambrosi & Zampieri 2018). However, comparing the possible masses and radii of the ULXP donors with those of single stars is useful to show the most plausible evolutionary stage of the donor stars in these systems.…”

Section: Limits On Donor Star Properties From X-ray Timingmentioning

confidence: 99%

“…The colors and magnitudes of the optical counterparts of ULXs can be significantly affected by irradiation of the donor star and emission from the (supercritical) accretion disc (see e.g. Copperwheat et al 2005Copperwheat et al , 2007Patruno & Zampieri 2008, 2010Ambrosi &Zampieri 2018 for theoretical work, andRoberts et al 2011;Grisé et al 2012 for observations). The theoretical work has so far mostly focused on systems with a (massive) black hole as the accretor, and shows larger effects for more massive black holes; the impact on the optical counterparts of neutron star ULXs may be less pronounced.…”

Section: Contribution From the Accretion Discmentioning

confidence: 99%

Searching for the Donor Stars of ULX Pulsars

Heida

Harrison

Brightman

et al. 2019

ApJ

View full text Add to dashboard Cite

We report on our search for the optical counterparts of two ultraluminous X-ray pulsars with known orbital periods, M82 X-2 and NGC 5907 X-1, in new and archival HST observations, in an effort to characterize the donor stars in these systems. We detect five near-infrared sources consistent with the position of M82 X-2 that are too bright to be single stars. We also detect seven sources in the WFC3/UVIS F336W image whose photometry matches that of 10 -15 M stars turning off the main sequence. Such stars have densities consistent with the properties of the donor star of M82 X-2 as inferred from X-ray timing analysis, although it is also possible that the donor is a lower mass star below our detection limit or that there is a significant contribution from the accretion disc to the optical emission. We detect three candidate counterparts to NGC 5907 X-1 in the near-infrared. All of these are too bright to be the donor star of the ULX, which based on its orbital period is a red giant. The high background at the location of NGC 5907 X-1 precludes us from detecting this expected donor star. The recently discovered NGC 5907 ULX-2 also falls within the field of view of the near-infrared imaging; we detect four sources in the error circle, with photometry that matches AGB stars. The star suggested to be the counterpart of NGC 5907 ULX-2 by Pintore et al. (2018) falls outside our 2-σ error circle.

show abstract

“…Thus, for these systems, the standard irradiation geometry will fail due to occultation by the wind. Irradiation models taking into account the presence of wind and/or a different disk structure under supercritical accretion have been proposed (Vinokurov et al 2013;Ambrosi & Zampieri 2018). These models assume a geometry in which the disk and wind are stacked at characteristic radii.…”

Section: Introductionmentioning

confidence: 99%

A Wind-disk Self-irradiation Model for Supercritical Accretion

Yao

Feng

2019

ApJL

View full text Add to dashboard Cite

Optical emission from actively accreting X-ray binaries is dominated by X-ray reprocessing on the outer disk. In the regime of supercritical accretion, strong radiation will power a massive wind that is optically thick and nearly spherical, and will occult the central hard X-rays from irradiating the outer disk. Instead, thermal emission from the wind will act as a new source of irradiation. Here, we construct a self-irradiation model, in which the inner disk (within the wind photosphere) is completely blocked by the wind, the middle part (between the wind photosphere and scattersphere) is heated by the wind directly, and the outer disk (beyond the wind scattersphere) is heated by photons leaving the scattersphere. The model can adequately fit the UV/optical SED of NGC 247 X-1, a candidate source with supercritical accretion, while the standard irradiation model fails to produce a self-consistent result. The best-fit parameters suggest that the source contains a stellar mass black hole with an accretion rate roughly 100 times the critical value. Remarkably, the UV/optical fitting predicts a wind photosphere that is well consistent with X-ray measurements, although it is an extrapolation over 3 orders of magnitude in wavelength. This implies that supercritical accretion does power a massive wind and the UV/optical data are useful in constraining the wind structure.

show abstract

Modelling optical emission of Ultra-luminous X-ray Sources accreting above the Eddington limit

Cited by 21 publications

References 102 publications

A Broadband Look at the Old and New ULXs of NGC 6946

A Broadband Look at the Old and New ULXs of NGC 6946

Searching for the Donor Stars of ULX Pulsars

A Wind-disk Self-irradiation Model for Supercritical Accretion

Contact Info

Product

Resources

About