English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Two XMM observations of the fast classical nova V2491Cyg were carried out ondays 39.93 and 49.62 after discovery, during the supersoft source (SSS) phase,yielding simultaneous X-ray and UV light curves and high-resolution X-rayspectra. The first X-ray light curve is highly variable with periodicoscillations (37.2 min) after an extended dip of factor of three lasting ~3hours. The cause of the dip is currently unexplained and could have the sameorigin as similar events in V4743Sgr and RSOph, as it occurred on the same timescale. The 37-min period is not present during the dip and also not in thesecond observation. The UV light curves are variable but contain no dips and noperiod. High-resolution X-ray spectra are presented for 4 intervals ofdifferent intensity. All spectra are atmospheric continua with absorption linesand absorption edges. Interstellar lines of OI and NI are seen at their restwavelengths, and a large number of high-ionization absorption lines are foundat blue shifts indicating an expansion velocity of 3000-3400 km/s, which doesnot change significantly during the epochs of observation. Comparisons with theslower nova V4743Sgr and the symbiotic recurrent nova RSOph are presented. TheSSS spectrum of V4743Sgr is much softer with broader and more complexphotospheric absorption lines. Meanwhile, the absorption lines in RSOph are asnarrow as in V2491Cyg, but they are less blue shifted. A remarkable similarityin the continua of V2491Cyg and RSOph is found. The only differences aresmaller line shifts and additional emission lines in RSOph that are related toa dense stellar wind from the evolved companion. Three unidentified absorptionlines are present in the X-ray spectra of all three novae, with restwavelengths 26.05AA, 29.45AA, and 30.0AA. No satisfactory spectral model iscurrently available for the soft X-ray spectra of novae in outburst.

XMM-Newton X-ray and UV observations of the fast nova V2491 Cyg during the supersoft source phase