Multiwavelength modelling the SED of supersoft X-ray sources I. The method and examples

Skopal, A.

doi:10.1016/j.newast.2013.10.009

Cited by 16 publications

(28 citation statements)

References 59 publications

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“…where the error correspond to the statistical error of the [Fe ] 6374 Å line luminosity. The so obtained value of the WD colour temperature is close to the temperatures ℎ = (2.275 ± 0.3) × 10 5 K and ℎ = (2.50 ± 0.1) × 10 5 K derived previously by Kahabka & Haberl (2006) and Skopal (2015), respectively. In addition, this temperature is in agreement with the simple formula of Iĳima (1981) used to estimate the effective temperature of a central source from the nebular emission line fluxes:…”

Section: Colour Temperature Of the White Dwarfsupporting

confidence: 89%

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LIN 358: a symbiotic binary accreting above the steady hydrogen fusion limit

Kuuttila

Gilfanov

Woods

et al. 2020

Monthly Notices of the Royal Astronomical Society

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Symbiotic binaries are long-period interacting binaries consisting of a white dwarf (WD) accreting material from a cool evolved giant star via stellar winds. In this paper, we study the symbiotic binary LIN 358 located in the Small Magellanic Cloud. We have observed LIN 358 with the integral field spectrograph WiFeS and obtained its line emission spectrum. With the help of the plasma simulation and spectral synthesis code cloudy, we have constructed a 2D photoionization model of LIN 358. From comparison with the observations, we have determined the colour temperature of the WD in LIN 358 to be 19 eV, its bolometric luminosity L = (1.02 ± 0.15) × 1038 erg s−1, and the mass-loss rate from the donor star to be 1.2 × 10−6 M⊙ yr−1. Assuming a solar H to He ratio in the wind material, a lower limit to the accreted mass fraction in LIN 358 is 0.31. The high mass accretion efficiency of a wind Roche lobe overflow implies that the WD is accreting above the upper boundary of stable hydrogen fusion and thus growing in mass with the maximal rate of ≈4 × 10−7 M⊙ yr−1. This causes the WD photosphere to expand, which explains its low colour temperature. Our calculations show that the circumstellar material in LIN 358 is nearly completely ionized except for a narrow cone around the donor star, and that the WD emission is freely escaping the system. However, due to its low colour temperature, this emission can be easily attenuated by even moderate amounts of neutral interstellar medium. We speculate that other symbiotic systems may be operating in a similar regime, thus explaining the paucity of observed systems.

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Section: Colour Temperature Of the White Dwarfsupporting

confidence: 89%

“…This is possible due to the fact that in the near-IR the emission from the AGB star dominates over the emission from both the WD, which peaks in the UV, and the ionized nebula, which is most prominent in the optical lines (Skopal 2005). Using these parameters Skopal (2015) classified the giant star in LIN 358 to be a type K5 Ib supergiant.…”

Section: Introductionmentioning

confidence: 99%

LIN 358: a symbiotic binary accreting above the steady hydrogen fusion limit

Kuuttila

Gilfanov

Woods

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…The main simplification of the calculations presented in this paper is the assumption of blackbody spectrum for the post-nova SSSs. This assumption is commonly made in SSS studies; it is motivated, at least partly, by the fact that the observed spectral energy distribution (SED) of the continuum emission in SSSs can be often represented by the simple blackbody spectrum (e.g, Skopal 2015). However, it is obvious that spectral formation in SSSs is much more complex.…”

Section: Discussionmentioning

confidence: 99%

Population of post-nova supersoft X-ray sources

Soraisam

Gilfanov

Wolf

et al. 2015

Mon. Not. R. Astron. Soc.

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Novae undergo a supersoft X-ray phase of varying duration after the optical outburst. Such transient post-nova supersoft X-ray sources (SSSs) are the majority of the observed SSSs in M31. In this paper, we use the post-nova evolutionary models of Wolf et al. to compute the expected population of post-nova SSSs in M31. We predict that depending on the assumptions about the WD mass distribution in novae, at any instant there are about 250 -600 post-nova SSSs in M31 with (unabsorbed) 0.2-1.0 keV luminosity L x 10 36 erg/s. Their combined unabsorbed luminosity is of the order of ∼ 10 39 erg/s. Their luminosity distribution shows significant steepening around log(L x ) ∼ 37.7 -38 and becomes zero at L x ≈ 2 × 10 38 erg/s, the maximum L x achieved in the post-nova evolutionary tracks. Their effective temperature distribution has a roughly power law shape with differential slope of ≈ 4-6 up to the maximum temperature of T eff ≈ 1.5 × 10 6 K.We compare our predictions with the results of the XMM-Newton monitoring of the central field of M31 between 2006 and 2009. The predicted number of post-nova SSSs exceed the observed number by a factor of ≈ 2-5, depending on the assumed WD mass distribution in novae. This is good agreement, considering the number and magnitude of uncertainties involved in calculations of the post-nova evolutionary models and their X-ray output. Furthermore, only a moderate circumstellar absorption, with hydrogen column density of the order of ∼ 10 21 cm −2 , will remove the discrepancy.

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“…(9) of Skopal 2015). Angular radius of the giant, θ g , can be obtained from its observed bolometric flux,…”

Section: Modelling the Sedmentioning

confidence: 99%

New outburst of the symbiotic nova AG Pegasi after 165 yr

Skopal

Shugarov

Sekeráš

et al. 2017

A&A

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Context. AG Peg is known as the slowest symbiotic nova, which experienced its nova-like outburst around 1850. After 165 years, during June of 2015, it erupted again showing characteristics of the Z And-type outburst. Aims. The primary objective is to determine basic characteristics, the nature and type of the 2015 outburst of AG Peg. Methods. We achieved this aim by modelling the spectral energy distribution using low-resolution spectroscopy (330-750 nm; R = 500-1000), medium-resolution spectroscopy (420-720 nm; R ∼ 11000), and U BVR C I C photometry covering the 2015 outburst with a high cadence. Optical observations were complemented with the archival HST and FUSE spectra from the preceding quiescence. Results. During the outburst, the luminosity of the hot component was in the range of 2-11×10 37 (d/0.8 kpc) 2 erg s −1 , being in correlation with the light curve (LC) profile. To generate the maximum luminosity by the hydrogen burning, the white dwarf (WD) had to accrete at ∼ 3 × 10 −7 M ⊙ yr −1 , which exceeds the stable-burning limit and thus led to blowing optically thick wind from the WD. We determined its mass-loss rate to a few ×10 −6 M ⊙ yr −1 . At the high temperature of the ionising source, 1.5 − 2.3 × 10 5 K, the wind converted a fraction of the WD's photospheric radiation into the nebular emission that dominated the optical. A one order of magnitude increase of the emission measure, from a few ×10 59 (d/0.8 kpc) 2 cm −3 during quiescence, to a few ×10 60 (d/0.8 kpc) 2 cm −3 during the outburst, caused a 2 mag brightening in the LC, which is classified as the Z And-type of the outburst. Conclusions. The very high nebular emission and the presence of a disk-like H i region encompassing the WD, as indicated by a significant broadening and high flux of the Raman-scattered O vi 6825 Å line during the outburst, is consistent with the ionisation structure of hot components in symbiotic stars during active phases.

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Multiwavelength modelling the SED of supersoft X-ray sources I. The method and examples

Cited by 16 publications

References 59 publications

LIN 358: a symbiotic binary accreting above the steady hydrogen fusion limit

LIN 358: a symbiotic binary accreting above the steady hydrogen fusion limit

Population of post-nova supersoft X-ray sources

New outburst of the symbiotic nova AG Pegasi after 165 yr

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