Multifrequency nature of the 0.75 mHz feature in the X-ray light curves of the nova V4743 Sgr

Dobrotka, A.; Ness, J. U.

doi:10.1111/j.1365-2966.2010.16654.x

Cited by 14 publications

(19 citation statements)

References 24 publications

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“…There are also several other IP candidates: V1425 Cyg, V533 Her and V842 Cen 3 , V4743 Sgr (Leibowitz et al 2006;Dobrotka & Ness 2010). Little is known how the magnetic field changes the nova evolution, it may really steer the path towards, or away from, a type Ia SN explosion in RNe.…”

Section: Discussionmentioning

confidence: 99%

SUZAKUOBSERVATION OF THE CLASSICAL NOVA V2491 Cyg IN QUIESCENCE

Zemko

Mukai

Orio

2015

ApJ

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We present Suzaku XIS observation of V2491 Cyg (Nova Cyg 2008 No. 2) obtained in quiescence, more than two years after the outburst. The nova was detected as a very luminous source in a wide spectral range from soft to hard X-rays. A very soft blackbody-like component peaking at 0.5 keV indicates that either we observe remaining, localized hydrogen burning on the surface of the white dwarf, or accretion onto a magnetized polar cap. In the second case, V2491 Cyg is a candidate "soft intermediate polar". We obtained the best fit for the X-ray spectra with several components: two of thermal plasma, a blackbody and a complex absorber. The later is typical of intermediate polars.The X-ray light-curve shows a modulation with a ∼38 min period. The amplitude of this modulation is strongly energy dependent and reaches maximum in the 0.8-2.0 keV range. We discuss the origin of the X-ray emission and pulsations, and the likelihood of the intermediate polar scenario.

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Section: Discussionmentioning

confidence: 99%

SUZAKUOBSERVATION OF THE CLASSICAL NOVA V2491 Cyg IN QUIESCENCE

Zemko

Mukai

Orio

2015

ApJ

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“…In particular we cannot explain why the signal is transient and why it is seen in such a small fraction of systems observed. If magnetic fields are needed, as in intermediate polars, the question arises why these oscillations are seen only during the SSS phase, while intermediate polars show the rotation period in optical and X-ray light curves in quiescence, for example, V4743 Sgr (Dobrotka & Ness 2010). An independent measurement of the rotation period for one of our five systems with short-period oscillations would robustly confirm or reject the possibility that the rotation period is the main driver for these oscillations.…”

Section: Rotation Period Of the White Dwarfmentioning

confidence: 99%

Short-period X-ray oscillations in super-soft novae and persistent super-soft sources

Ness

Beardmore

Osborne

et al. 2015

A&A

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Context. Transient short-period (<100 s) oscillations have been found in the X-ray light curves of three novae during their super-soft source (SSS) phase and in one persistent SSS. Aims. We pursue an observational approach to determine possible driving mechanisms and relations to fundamental system parameters such as the white dwarf mass. Methods. We performed a systematic search for short-period oscillations in all available XMM-Newton and Chandra X-ray light curves of persistent SSS and novae during their SSS phase. To study time evolution, we divided each light curve into short timesegments and computed power spectra. We then constructed a dynamic power spectrum from which we identified transient periodic signals even when only present for a short time. We base our confidence levels on simulations of false-alarm probability for the chosen oversampling rate of 16, corrected for multiple testing based on the number of time segments. From all time segments of each system, we computed fractions of time when periodic signals were detected. Results. In addition to the previously known systems with short-period oscillations, RS Oph (35 s), KT Eri (35 s), V339 Del (54 s), and Cal 83 (67 s), we found one additional system, LMC 2009a (33 s), and also confirm the 35 s period from Chandra data of KT Eri. The oscillation amplitudes are of about <15% of the respective count rates and vary without any clear dependence on the X-ray count rate. The fractions of the time when the respective periods were detected at 2σ significance (duty cycle) are 11.3%, 38.8%, 16.9%, 49.2%, and 18.7% for LMC 2009a, RS Oph, KT Eri, V339 Del, and Cal 83, respectively. The respective highest duty cycles found in a single observation are 38.1%, 74.5%, 61.4%, 67.8%, and 61.8%. Conclusions. Since fast rotation periods of the white dwarfs as origin of these transient oscillations are speculative, we concentrate on pulsation mechanisms. We present initial considerations predicting the oscillation period to scale linearly with the white dwarf radius (and thus mass), weakly with the pressure at the base, and luminosity. Estimates of the size of the white dwarf could be useful for determining whether these systems are more massive than typical white dwarfs, and thus whether they are growing from accretion over time. Signs of such mass growth may have implications for whether some of these systems are attractive as Type Ia supernova progenitors.

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“…6.7 h and ∼ 1300 s; Leibowitz et al 2006;Dobrotka & Ness 2010), V5116 Sgr (2.97 h; Sala et al 2008), CSS 081007:030559+054715 (1.77 d; Osborne et al 2009) and KT Eri (35 s; Beardmore et al 2010).…”

Section: X-ray Variability Of Nova M31n 2006-04amentioning

confidence: 99%

X-ray monitoring of classical novae in the central region of M 31

Henze

Pietsch

Haberl

et al. 2010

A&A

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Context. Classical novae (CNe) have recently been reported to represent the major class of supersoft X-ray sources (SSSs) in the central region of our neighbour galaxy M 31. Aims. We carried out a dedicated monitoring of the M 31 central region with XMM-Newton and Chandra in order to find SSS counterparts of CNe, determine the duration of their SSS phase and derive physical outburst parameters. Methods. We systematically searched our data for X-ray counterparts of CNe and determined their X-ray light curves and spectral properties. Additionally, we determined luminosity upper limits for all novae from previous studies which are not detected anymore and for all CNe in our field of view with optical outbursts between May 2005 and March 2007. Results. We detected eight X-ray counterparts of CNe in M 31, four of which were not previously known. Seven sources can be classified as SSSs, one is a candidate SSS. Two SSSs are still visible more than nine years after the nova outburst, whereas two other nova counterparts show a short SSS phase of less than 150 days. Of the latter sources, M31N 2006-04a exhibits a short-time variable X-ray light curve with an apparent period of (1.6 ± 0.3) h. This periodicity could indicate the binary period of the system. There is no X-ray detection for 23 out of 25 CNe which were within the field of view of our observations and had their outburst from about one year before the start of the monitoring until its end. From the 14 SSS nova counterparts known from previous studies, ten are not detected anymore. Additionally, we found four SSSs in our XMM-Newton data without a nova counterpart, one of which is a new source. Conclusions. Out of eleven SSSs detected in our monitoring, seven are counterparts of CNe. We therefore confirm the earlier finding that CNe are the major class of SSSs in the central region of M 31. We use the measured SSS turn-on and turn-off times to estimate the mass ejected in the nova outburst and the mass burned on the white dwarf. Classical novae with short SSS phases seem to be an important contributor to the overall population.

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Multifrequency nature of the 0.75 mHz feature in the X-ray light curves of the nova V4743 Sgr

Cited by 14 publications

References 24 publications

SUZAKUOBSERVATION OF THE CLASSICAL NOVA V2491 Cyg IN QUIESCENCE

SUZAKUOBSERVATION OF THE CLASSICAL NOVA V2491 Cyg IN QUIESCENCE

Short-period X-ray oscillations in super-soft novae and persistent super-soft sources

X-ray monitoring of classical novae in the central region of M 31

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