Accretion disk coronae of intermediate polar cataclysmic variables

Barbera, Enrico; Orlando, S.; Peres, G.

doi:10.1051/0004-6361/201630285

Cited by 8 publications

(9 citation statements)

References 58 publications

(73 reference statements)

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“…J0508 exhibits variability on timescales of hours, as seen in the form of flaring behaviour in the XMM-Newton observation. Intermediate polars are known to exhibit flaring behaviour on short timescales, which may arise in the turbulent inner region of the accretion disk or from bright spots on the surface of the WD (Barbera et al 2017;Hellier 2001). The largest flux variations on long-term timescales, by about a factor of six, were also seen from J0508 (Fig.…”

Section: Discussionmentioning

confidence: 99%

Discovery of four super-soft X-ray sources in XMM-Newton observations of the Large Magellanic Cloud

Maitra

Haberl

2021

A&A

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Context. Super-soft X-ray sources were established as a heterogeneous class of objects from observations of the Large Magellanic Cloud (LMC). Aims. We have searched for new sources of this class in the X-ray images obtained from the XMM-Newton survey of the LMC and additional archival observations. Methods. We first selected candidates by visual inspection of the image and screened out the artefacts that can mimic super-soft X-ray sources as well as the bright foreground stars that create optical loading in the detectors. We obtained four new super-soft X-ray sources for which we performed detailed X-ray timing and spectral analyses and searched for possible optical counterparts to identify their nature. We also looked at archival ROSAT and Swift observations to investigate the long-term behaviour of the sources. Results. XMMU J050452.0−683909 is identified as the central star of the planetary nebula SMP LMC 21 in the LMC. We suggest XMMU J051854.8−695601 and XMMU J050815.1−691832 as new soft intermediate polars based on the nature of their X-ray spectrum. Their estimated absorption-corrected luminosities and the blackbody radii indicate that they are located in our Galaxy, rather than the LMC. We discovered coherent pulsations of 497 s from XMMU J044626.6-692011, which indicates a magnetic cataclysmic variable nature of the source. The location of XMMU J044626.6−692011 in the LMC or our Galaxy is less clear. It could either be a white dwarf in the LMC with nuclear burning on its surface near the Eddington limit or another soft intermediate polar in our Galaxy. Conclusions. The discovery of new super-soft X-ray sources makes a significant contribution to the known population in our Galaxy. An observed higher density of sources in the direction of the Magellanic Clouds can likely be explained by the relatively low Galactic column density in their direction as well as a large number of existing observations sensitive at low X-ray energies.

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Section: Discussionmentioning

confidence: 99%

Discovery of four super-soft X-ray sources in XMM-Newton observations of the Large Magellanic Cloud

Maitra

Haberl

2021

A&A

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“…J0508 exhibits variability on timescales of hours as seen in form of flaring behaviour in the XMM-Newton observation. IPs are known to exhibit flaring behaviour on short timescales, which may arise in the turbulent inner region of the accretion disk, or from bright spots on the surface of the white dwarf (Barbera et al 2017;Hellier 2001). The largest flux variations on long-term timescales by about a factor of 6 were also seen from J0508 (Fig.…”

Section: Discussionmentioning

confidence: 99%

Discovery of four super-soft X-ray sources in XMM-Newton observations of the Large Magellanic Cloud

Maitra,

Haberl

2021

Preprint

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Context. Super-soft X-ray sources were established as a heterogeneous class of objects from observations of the Large Magellanic Cloud (LMC). Aims. We have searched for new sources of this class in the X-ray images obtained from the XMM-Newton survey of the LMC and additional archival observations. Methods. We first selected candidates by visual inspection of the image, and screened out artefacts which can mimic super-soft X-ray sources as well as bright foreground stars which create optical loading on the CCD image. We finally obtained 4 new super-soft X-ray sources for which we performed detailed X-ray timing and spectral analysis and searched for possible optical counterparts to identify their nature. We also looked at archival ROSAT and Swift observations to investigate the long-term behaviour of the sources. Results. XMMU J050452.0−683909 is identified as the central star of the planetary nebula SMP LMC 21 in the LMC. We suggest XMMU J051854.8−695601 and XMMU J050815.1−691832 as new soft intermediate polars from the nature of their X-ray spectrum. Their estimated absorption-corrected luminosities and the blackbody radii indicate that they are located in our Galaxy, rather than the LMC. We discovered coherent pulsations of 497 s from XMMU J044626.6−692011 which indicates a magnetic cataclysmic variable nature of the source. The location of XMMU J044626.6−692011 in the LMC or our Galaxy is less clear. It could either be a white dwarf in the LMC with nuclear burning on its surface near the Eddington limit, or another soft intermediate polar in our Galaxy. Conclusions. The discovery of new super-soft X-ray sources makes a significant contribution to the known population in our own Galaxy. An observed higher density of sources in the direction of the Magellanic Clouds can likely be explained by the relatively low Galactic column density in their direction as well as a large number of existing observations sensitive at low X-ray energies.

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“…In order to compare to the astrophysical case however, we now consider solely the post-shock or downstream region. The β ram value (the ratio of thermal to magnetic pressure in a shocked system) is β ram ~ 10 −2 –10 −4 for the case of polars 10 compared to for intermediate polars 34 . The huge magnetic field associated with polars means that strict Alfven similarity criteria cannot feasibly be met in a scaled laboratory experiment.…”

Section: Discussionmentioning

confidence: 99%

Laboratory study of stationary accretion shock relevant to astrophysical systems

Mabey

Albertazzi

Falize

et al. 2019

Sci Rep

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Accretion processes play a crucial role in a wide variety of astrophysical systems. Of particular interest are magnetic cataclysmic variables, where, plasma flow is directed along the star’s magnetic field lines onto its poles. A stationary shock is formed, several hundred kilometres above the stellar surface; a distance far too small to be resolved with today’s telescopes. Here, we report the results of an analogous laboratory experiment which recreates this astrophysical system. The dynamics of the laboratory system are strongly influenced by the interplay of material, thermal, magnetic and radiative effects, allowing a steady shock to form at a constant distance from a stationary obstacle. Our results demonstrate that a significant amount of plasma is ejected in the lateral direction; a phenomenon that is under-estimated in typical magnetohydrodynamic simulations and often neglected in astrophysical models. This changes the properties of the post-shock region considerably and has important implications for many astrophysical studies.

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Accretion disk coronae of intermediate polar cataclysmic variables

Cited by 8 publications

References 58 publications

Discovery of four super-soft X-ray sources in XMM-Newton observations of the Large Magellanic Cloud

Discovery of four super-soft X-ray sources in XMM-Newton observations of the Large Magellanic Cloud

Discovery of four super-soft X-ray sources in XMM-Newton observations of the Large Magellanic Cloud

Laboratory study of stationary accretion shock relevant to astrophysical systems

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