Optical and X-ray properties of CAL 83 – II. An X-ray pulsation at ∼67 s★

Odendaal, Alida; Meintjes, Pieter; Charles, P. A.; Rajoelimanana, Andry

doi:10.1093/mnras/stt2111

Cited by 22 publications

(46 citation statements)

References 36 publications

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“…The greater challenge would be to explain the observed changes in period by ±3 s. Because of the large amount of inertia of a white dwarf, this drift cannot be the result of accretion-induced spin-up or -down. In addition, there is no relation with the orbital period of 1.0475 ± 0.00004 days (Schmidtke et al 2004;Odendaal et al 2014), which excludes Doppler shifts imposed by the orbital motion of the X-ray emitting plasma, for example. Furthermore, the possibility was discussed that the observed period is the beat between the rotation period of the white dwarf and the Keplerian period of the denser X-ray emitting plasma, but the required rotation period of the white dwarf would then have to be even shorter, with an estimated value of 4-12 s, which would set a new record, although this is still longer than the break-up period of 3.4 s. Finally, Odendaal et al (2014) argued that the X-ray emitting plasma must originate from an extended envelope, some two to three times the radius of the white dwarf, and if that envelope does not rotate synchronously, the spread in the 67 s oscillations can result.…”

Section: Rotation Period Of the White Dwarfmentioning

confidence: 97%

“…The long-term presence of the 67 s X-ray period in Cal 83 has led Odendaal et al (2014) to consider the possibility that the rotation period of the white dwarf is the main driver of the oscillations. While typical rotation periods of white dwarfs are much longer, the fastest rotation period in a white dwarf binary, RXJ 0648.0-4418/HD 49798, was observed to be 13.2 s (Warner et al 2003b), and a rotation period of 67 s is thus possible.…”

Section: Rotation Period Of the White Dwarfmentioning

confidence: 99%

“…While typical rotation periods of white dwarfs are much longer, the fastest rotation period in a white dwarf binary, RXJ 0648.0-4418/HD 49798, was observed to be 13.2 s (Warner et al 2003b), and a rotation period of 67 s is thus possible. Odendaal et al (2014) argued that a long mass accretion history allows the white dwarf to be sufficiently spun up. The greater challenge would be to explain the observed changes in period by ±3 s. Because of the large amount of inertia of a white dwarf, this drift cannot be the result of accretion-induced spin-up or -down.…”

Section: Rotation Period Of the White Dwarfmentioning

confidence: 99%

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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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Section: Rotation Period Of the White Dwarfmentioning

confidence: 97%

Section: Rotation Period Of the White Dwarfmentioning

confidence: 99%

Section: Rotation Period Of the White Dwarfmentioning

confidence: 99%

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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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“…A systematic search for short time-scale periodicities in all these observations revealed a ∼67 s X-ray periodicity (indicated by P(∼ 67 s)) in several of these lightcurves [10]. This periodicity is variable in nature: it disappears and reappears on time-scales of hours, and on similar time-scales the period typically varies with ∼3 s to either side of the median value of ∼67 s.…”

Section: Introductionmentioning

confidence: 90%

“…It was thus suggested that the WD rotation may be observed through a well developed envelope, the rotation of which is not quite synchronized with that of the rapidly spinning WD, resulting in a slippage of the layers on the WD surface, and a spread in the observed periodicity [10]. However, a closer investigation into the nature of this periodicity has also shown that its characteristics are remarkably similar to those of dwarf nova oscillations (DNOs) (see also the independent remarks of [13]).…”

Section: Introductionmentioning

confidence: 99%

An adapted LIMA model for the 67-s periodicity in supersoft X-ray source CAL 83

Odendaal¹,

Meintjes²

2016

Proceedings of XI Multifrequency Behaviour of High Energy Cosmic Sources Workshop — PoS(MULTIF15)

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Supersoft X-ray sources constitute a class of astronomical objects characterized by extremely high X-ray luminosities and low effective temperatures, typically 20-100 eV. The canonical model for these sources involves a white dwarf accreting from a more massive companion in a binary system at a very high rate. The high soft X-ray luminosity is derived from steady or quasisteady nuclear burning of accreted hydrogen in a shell on the white dwarf surface. CAL 83 in the Large Magellanic Cloud (LMC) is often considered to be the prototype of the SSS class. CAL 83 exhibits large-scale anti-correlated X-ray and optical variability on a superorbital time-scale of ∼450 d, which has been explained by cyclic changes of the white dwarf envelope between a contracted high-temperature and an expanded low-temperature state. A detailed periodic analysis of the XMM-Newton lightcurves of CAL 83 has revealed a variable X-ray modulation with a period of ∼67 s. This oscillation was detected in all the X-ray high state lightcurves obtained during the 2000-2009 time period, as well as in the X-ray low state lightcurve with the highest count rate. The model proposed to explain the behaviour of this oscillation is related to the low-inertia magnetic accretor (LIMA) model described in the literature to explain the observed properties of dwarf nova oscillations (DNOs). In this model, the ∼67 s modulation originates in an equatorial belt-like structure in the envelope at the boundary with the inner accretion disc, with the belt weakly coupled to the white dwarf core via a ∼10 5 G magnetic field.

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Neil Gehrels Swift Observatory studies of supersoft novae

Page

Beardmore

Osborne

2020

Advances in Space Research

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The rapid response capabilities of the Neil Gehrels Swift Observatory, together with the daily planning of its observing schedule, make it an ideal mission for following novae in the X-ray and UV bands, particularly during their early phases of rapid evolution and throughout the supersoft source interval. Many novae, both classical and recurrent, have been extensively monitored by Swift throughout their supersoft phase and later decline. We collect here results from observations of novae with outbursts which occurred between the start of 2006 and the end of 2017.

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Optical and X-ray properties of CAL 83 – II. An X-ray pulsation at ∼67 s★

Cited by 22 publications

References 36 publications

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

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

An adapted LIMA model for the 67-s periodicity in supersoft X-ray source CAL 83

Neil Gehrels Swift Observatory studies of supersoft novae

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