Book review

Greiner, Thomas M.

doi:10.1002/ajpa.20498

Cited by 5 publications

(8 citation statements)

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“…Photometric variations of AG Dra during quiescence stages are the most pronounced in the U filter with the amplitude around 0.5 mag and they decrease towards longer wavelengths. The contribution of the WD radiation should be not more than about 10% in the U filter (0.1 mag) during quiescence according to the temperatures and radii indicated by the results of Mikołajewska et al (1995) and Greiner et al (1997) based on analysis of ultraviolet and X-ray observations, respectively. It seems from these results and from the fact that quiescence variations in the U filter are periodical with the orbital period that these variations can be explained by varying visibility of an ionised gaseous region, which is, in fact, the partially optically thick wind from the giant ionised by the WD in AG Dra Skopal, 2008).…”

Section: Orbital Dependence Of the He II And H β Ratiomentioning

confidence: 87%

Recent outburst activity of the symbiotic binary AG Draconis

Merc¹,

Gális²,

Leedjärv³

2018

Proceedings of the Golden Age of Cataclysmic Variables and Related Objects IV — PoS(GOLDEN 2017)

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The symbiotic binary AG Dra regularly undergoes quiescent and active stages which consist of several outbursts repeating with about 360 d interval. The recent outburst activity of AG Dra started by the minor outburst in the late spring of 2015 and was definitely confirmed by the outbursts in April 2016 and May 2017. In the presented work, the photometric and spectroscopic behaviour of the recent outburst activity of AG Dra is presented in detail. Moreover, the temperature of the white dwarf in AG Dra is studied based on the behaviour of the prominent emission lines. We show that a disentanglement of particular effects in the observed changes of the emission lines is crucial to investigate the intrinsic white dwarf temperature variations related to outburst activity of this strongly interacting binary. We also report the effects of the low excitation lines orbital variations and of the H β absorption component on their equivalent widths as well as consequences of the approximations used in our previous works.

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Section: Orbital Dependence Of the He II And H β Ratiomentioning

confidence: 87%

Recent outburst activity of the symbiotic binary AG Draconis

Merc¹,

Gális²,

Leedjärv³

2018

Proceedings of the Golden Age of Cataclysmic Variables and Related Objects IV — PoS(GOLDEN 2017)

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“…The reddening has been estimated to be E(B-V) = 0.05 (Mikolawjewska et al 1995), however, reddening values as high as E(B-V) = 0.10 have not been ruled out (Young et al 1995). AG Dra has been classified as a supersoft X-ray source (Greiner et al 1997). It has been established that the X-ray/FUV flux level of AG Dra is anti-correlated with the optical maxima (Greiner et al 1997).…”

Section: Introductionmentioning

confidence: 99%

“…AG Dra has been classified as a supersoft X-ray source (Greiner et al 1997). It has been established that the X-ray/FUV flux level of AG Dra is anti-correlated with the optical maxima (Greiner et al 1997).…”

Section: Introductionmentioning

confidence: 99%

On the Nature of the Hot Component in the Symbiotic, Supersoft X-Ray Binary Ag Draconis

Sion

Moreno

Godon

et al. 2012

The Astronomical Journal

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AG Dra is a symbiotic variable consisting of a metal poor, yellow giant mass donor under-filling its Roche lobe, and a hot accreting white dwarf, possibly surrounded by an optically thick, bright accretion disk which could be present from wind accretion. We constructed NLTE synthetic spectral models for white dwarf spectra and optically thick accretion disk spectra to model a FUSE spectrum of AG Dra, obtained when the hot component is viewed in front of the yellow giant. The spectrum has been de-reddened (E(B-V) = 0.05) and the model fitting carried out, with the distance regarded as a free parameter, but required to 1 Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer (FUSE) was operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985.2 Visiting at the Henry Rowland Department of Physics, The Johns Hopkins University, Baltimore, MD.-2 -be larger than the Hipparcos lower limit of 1 kpc. We find that the best-fitting model is a bare accreting white dwarf with M wd = 0.4M ⊙ , T ef f = 80,000K and a model-derived distance of 1543 pc. Higher temperatures are ruled out due to excess flux at the shortest wavelengths while a lower temperature decreases the distance below 1 kpc. Any accretion disk which might be present is a only a minor contributor to the FUV flux. This raises the possibility that the soft X-rays originate from a very hot boundary layer between a putative accretion disk and the accreting star.

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“…In LMC S154, X-rays were detected only near the maximum of outburst and have not been detected since then ). The opposite is expected in the case of Z-And-type outbursts, where the X-ray flux is lowest during outburst and highest during quiescence (Greiner et al 1997).…”

Section: Symbiotic Nova Classificationmentioning

confidence: 90%

LMC S154: the first Magellanic symbiotic recurrent nova

Iłkiewicz

Mikołajewska

Miszalski

et al. 2019

A&A

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Classical nova outburst has been suggested for a number of extragalactic symbiotic stars, but in none of the systems has it been proven. In this work we study the nature of one of these systems, LMC S154. We gathered archival photometric observations in order to determine the timescales and nature of variability in this system. Additionally we carried out photometric and spectroscopic monitoring of the system and fitted synthetic spectra to the observations. Carbon abundance in the photosphere of the red giant is significantly higher than that derived for the nebula, which confirms pollution of the circumbinary material by the ejecta from nova outburst. The photometric and spectroscopic data show that the system reached quiescence in 2009, which means that for the first time all of the phases of a nova outburst were observed in an extragalactic symbiotic star. The data indicate that most probably there were three outbursts observed in LMC S154, which would make this system a member of a rare class of symbiotic recurrent novae. The recurrent nature of the system is supported by the discovery of coronal lines in the spectra, which are observed only in symbiotic stars with massive white dwarfs and with short-recurrence-time outbursts. Gathered evidence is sufficient to classify LMC S154 as the first bona fide extragalactic symbiotic nova, which is likely a recurrent nova. It is also the first nova with a carbon-rich donor.

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Book review

Cited by 5 publications

References 0 publications

Recent outburst activity of the symbiotic binary AG Draconis

Recent outburst activity of the symbiotic binary AG Draconis

On the Nature of the Hot Component in the Symbiotic, Supersoft X-Ray Binary Ag Draconis

LMC S154: the first Magellanic symbiotic recurrent nova

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