The recent direct detection of gravitational waves has triggered the interest in gravitational wave sources. Some sources are potentially observable only with space based interferometers, such as the forthcoming LISA scheduled for launch after 2030. Cataclysmic variables are binary sources whose emission is in the sensititivity band of LISA. The paper presents an estimation of the gravitational wave emission of about five hundreds cataclysmic variables. The most promising sources are AM CVn systems.
{"title":"Cataclysmic variables as gravitational wave sources","authors":"R. Poggiani","doi":"10.22323/1.315.0008","DOIUrl":"https://doi.org/10.22323/1.315.0008","url":null,"abstract":"The recent direct detection of gravitational waves has triggered the interest in gravitational wave sources. Some sources are potentially observable only with space based interferometers, such as the forthcoming LISA scheduled for launch after 2030. Cataclysmic variables are binary sources whose emission is in the sensititivity band of LISA. The paper presents an estimation of the gravitational wave emission of about five hundreds cataclysmic variables. The most promising sources are AM CVn systems.","PeriodicalId":71342,"journal":{"name":"黄金时代","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90185580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Suzaku satellite observed dozens of WD binaries and gave us various findings and knowledge. In this paper, four topics are picked up. (1) From a nova outburst of V2491 Cyg, a very hard non-thermal component with Γ= 0.1 $pm$0.2 was found. Mass accretion seemed to be rekindled 30 days after the nova and its X-ray spectrum is similar to that of intermediate polars. (2) In a nova outburst of a symbiotic Mira star V407 Cyg, a non-equilibrium ionization (NEI) plasma emission was found, which shows asymmetry in the environment encountered by the nova ejecta. The coincidental GeV γ-ray decline/X-ray rise can be explained by the stalling of the shock front because of the ejecta running into the red giant photosphere. (3) X-ray spectra of five symbiotic stars (CD-28 3719, Hen 3-1591, Hen 3-461, EG And and 4 Dra) have hot thermal plasma of $T_{rm max}$ > 3 keV. To reproduce thetemperature, X-ray energy source should be ascribed to release of the gravitational potential in boundary layers. (4) X-ray spectrum of γ Cas can be reproduced by a single-temperature thermal plasma model of 15 keV. X-ray dips of order of 10$^4$ s can be explained by partial covering absorption. A WD binary is more likely for γ Cas identity because of its spectrum without power-law component and consistency of the covering fractions of absorbers and dip duration.
{"title":"The impact of SUZAKU on the knowledge of The Physics of CVs","authors":"T. Hayashi","doi":"10.22323/1.315.0009","DOIUrl":"https://doi.org/10.22323/1.315.0009","url":null,"abstract":"Suzaku satellite observed dozens of WD binaries and gave us various findings and knowledge. In this paper, four topics are picked up. (1) From a nova outburst of V2491 Cyg, a very hard non-thermal component with Γ= 0.1 $pm$0.2 was found. Mass accretion seemed to be rekindled 30 days after the nova and its X-ray spectrum is similar to that of intermediate polars. (2) In a nova outburst of a symbiotic Mira star V407 Cyg, a non-equilibrium ionization (NEI) plasma emission was found, which shows asymmetry in the environment encountered by the nova ejecta. The coincidental GeV γ-ray decline/X-ray rise can be explained by the stalling of the shock front because of the ejecta running into the red giant photosphere. (3) X-ray spectra of five symbiotic stars (CD-28 3719, Hen 3-1591, Hen 3-461, EG And and 4 Dra) have hot thermal plasma of $T_{rm max}$ > 3 keV. To reproduce thetemperature, X-ray energy source should be ascribed to release of the gravitational potential in boundary layers. (4) X-ray spectrum of γ Cas can be reproduced by a single-temperature thermal plasma model of 15 keV. \u0000X-ray dips of order of 10$^4$ s can be explained by partial covering absorption. A WD binary is more likely for γ Cas identity because of its spectrum without power-law component and consistency of the covering fractions of absorbers and dip duration.","PeriodicalId":71342,"journal":{"name":"黄金时代","volume":"55 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78036667","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The eruptions of novae are among the brightest explosions on the Universe. I present a review of the recent observations of galactic and extragalactic novae, with a focus on the results of the new facilities for high cadence optical observations and of X-ray and gamma ray observatories.
{"title":"Galactic and Extragalactic Novae – An Updated Review","authors":"R. Poggiani","doi":"10.22323/1.315.0048","DOIUrl":"https://doi.org/10.22323/1.315.0048","url":null,"abstract":"The eruptions of novae are among the brightest explosions on the Universe. I present a review of the recent observations of galactic and extragalactic novae, with a focus on the results of the new facilities for high cadence optical observations and of X-ray and gamma ray observatories.","PeriodicalId":71342,"journal":{"name":"黄金时代","volume":"32 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72454422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The symbiotic binary AG Dra regularly undergoes quiescent and active stages which consist of several outbursts repeating with about 360d 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$_{beta}$ absorption component on their equivalent widths as well as consequences of the approximations used in our previous works.
{"title":"Recent outburst activity of the symbiotic binary AG Draconis","authors":"J. Merc, R. G'alis, L. Leedjarv","doi":"10.22323/1.315.0060","DOIUrl":"https://doi.org/10.22323/1.315.0060","url":null,"abstract":"The symbiotic binary AG Dra regularly undergoes quiescent and active stages which consist of several outbursts repeating with about 360d 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$_{beta}$ absorption component on their equivalent widths as well as consequences of the approximations used in our previous works.","PeriodicalId":71342,"journal":{"name":"黄金时代","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88168044","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Kononov, C. Lacy, V. Puzin, V. P. Kozhevnikov, A. Sytov, A. P. Lyaptsev
We present the results of simultaneous spectroscopic and photometric observations of the cataclysmic variable star (hereafter CVs) V455 Andromedae, belonging to the WZ Sge sub-class, in quiescence. Using the spectroscopic data we computed time-resolved Doppler tomograms of the system demonstrating its behavior at different orbital phases. In the tomograms one can see the periodic brightening of different regions within one orbital cycle. We interpret this brightening as being due to the interaction of four phase-locked shock waves in the disk with a specific internal precessing density wave that develops inside the disk, because of the tidal influence of the secondary star, and this density wave propagates up to the disk's outer regions. When the outer part of the density wave in its precessional motion reaches a shock wave the local density grows, which amplifies the shock (by increasing $rho V^{2}/2$). This results in an additional energy release in the shock and can be observed as a brightening. Analysis of the tomographic results and the photometric data shows that two main sources contribute to the light curves of the system: the radiation of the "hot line" and the bow-shock gives us two major orbital humps, located approximately at the orbital phases $phi=0.25$ and $phi=0.75$; the amplification of the four shock waves may give us up to four "superhumps" shifting over the light curve with the precessional period. These two effects, when overlapping, change the shape of the light curves, shift the hump maxima, and they sometimes produce more than two humps in the light curve. We should emphasize that when saying "superhumps" we imply an effect that is observed in quiescent light curves of WZ Sge stars, as opposed to "classical" superhumps usually observed in outbursts.
{"title":"On the nature of quiescent light curves demonstrated by WZ Sge stars","authors":"D. Kononov, C. Lacy, V. Puzin, V. P. Kozhevnikov, A. Sytov, A. P. Lyaptsev","doi":"10.22323/1.315.0031","DOIUrl":"https://doi.org/10.22323/1.315.0031","url":null,"abstract":"We present the results of simultaneous spectroscopic and photometric observations of the cataclysmic variable star (hereafter CVs) V455 Andromedae, belonging to the WZ Sge sub-class, in quiescence. Using the spectroscopic data we computed time-resolved Doppler tomograms of the system demonstrating its behavior at different orbital phases. In the tomograms one can see the periodic brightening of different regions within one orbital cycle. We interpret this brightening as being due to the interaction of four phase-locked shock waves in the disk with a specific internal precessing density wave that develops inside the disk, because of the tidal influence of the secondary star, and this density wave propagates up to the disk's outer regions. When the outer part of the density wave in its precessional motion reaches a shock wave the local density grows, which amplifies the shock (by increasing $rho V^{2}/2$). This results in an additional energy release in the shock and can be observed as a brightening. Analysis of the tomographic results and the photometric data shows that two main sources contribute to the light curves of the system: the radiation of the \"hot line\" and the bow-shock gives us two major orbital humps, located approximately at the orbital phases $phi=0.25$ and $phi=0.75$; the amplification of the four shock waves may give us up to four \"superhumps\" shifting over the light curve with the precessional period. These two effects, when overlapping, change the shape of the light curves, shift the hump maxima, and they sometimes produce more than two humps in the light curve. We should emphasize that when saying \"superhumps\" we imply an effect that is observed in quiescent light curves of WZ Sge stars, as opposed to \"classical\" superhumps usually observed in outbursts.","PeriodicalId":71342,"journal":{"name":"黄金时代","volume":"133 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2016-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75695703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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