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Observations of Quasi-Periodic Pulsations in Stellar Flares with XMM-Newton

Study of quasi-periodic pulsations in stellar flares using XMM-Newton observations. Analysis includes Fourier and wavelet techniques to identify oscillations and their parameters. Significant features in light curves of various stars are examined.

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Observations of Quasi-Periodic Pulsations in Stellar Flares with XMM-Newton

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  1. Quasi-periodic pulsations in stellar flares observed with XMM-Newton Alexey Kuznetsov, Robert Sych Institute of Solar-Terrestrial Physics (Irkutsk, Russia)

  2. Example of observations (AD Leo, started on 14 May 2001, 21:04:21 UT): XMM-Newton: imaging spectroscopic observations in the soft X-ray range (0.1–12 keV), FOV 30′×30′. Image Spectrum XMM-Newton Serendipitous Source Catalogue (Rosen, Webb, Watson, et al., 2016): http://xmmssc.irap.omp.eu/ 3XMM-DR7 Interface – Observatory of Strasbourg: http://xcatdb.unistra.fr/3xmmdr7/ Light curve

  3. Pye, Rosen, Fyfe, & Schroder (2015): • correlation of the XMM-Newton Serendipitous Source Catalogue with the Hipparcos-Tycho catalogue; • 2000-2007 years; • search for flares; • F-M stars selected. • ~130 flares on ~70 stars were found. Our subset: single (or wide binaries) main-frequency stars only (no RS CVn, T Tau, etc.)  45 light curves with flares on 40 stars were selected. Time resolution: ≥10 s. ...

  4. Analysis: • Fourier analysis (to obtain integral power spectra of oscillations); • wavelet analysis (to study the dynamics of oscillations). Aim: search for oscillations and analyze their parameters. Significance level: 90%.

  5. Features found in the XMM light curves • “Slow flare” without pulsations GSC 09414-00787 (G5) 70 Oph (K0+K5)

  6. Features found in the XMM light curves • “Fast flare” without pulsations NU UMa (G5) HD 59581 (F6)

  7. Features found in the XMM light curves • “Slow flare” with QPPs chi01 Ori (G0?) EQ Peg (M3.5+M4.5) Periods: 0.9, 5.6, 15 min. Periods: 10, 33, 61 min.

  8. Features found in the XMM light curves • Drifting QPPs before/after flare HK Aqr(M0) 47 Cas B(G0) Periods: 61, 107, 307 min. Periods: 15, 34, 92 min.

  9. Features found in the XMM light curves Features found in the XMM light curves • QPPs with frequency jump CD-53 544 (K6) Periods: 45, 64, 103 min.

  10. Features found in the XMM light curves • QPPs with increasing/decreasing intensity HD 166191 (F4) HD 285845 (G6) Periods: 16, 45, 205 min. Periods: 116 min.

  11. Features found in the XMM light curves • Quasi-periodic bursts (flares) DG CVn(M4) AD Leo(M3.5) Periods: 35, 50, 102 min. Periods: 60, 118, 199 min.

  12. Summary • Among 45 light curves: • “slow flares” without QPPs: 6 (14.3%); • “fast flares” without QPPs: 11 (26.2%); • “slow flares” with QPPs: 6 (14.3%); • flares with QPPs with drifting frequency: 6 (14.3%); • damping QPPs at the decay phase of the flare: 2 (4.5%); • growing QPPs at the pre-flare phase: 1 (2.2%); • quasi-periodic flares: 10 (23.8%). In some “slow flares”, high-frequency pulsations (with periods of ~5 min) were detected. Such pulsations may be caused by the processes similar to the solar P-mode oscillations. Impulsive flares make the high-frequency pulsations unobservable, and only the relatively slow pulsations were detected.

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