Bibliographic Details
| Title: |
Multimission observations of the old nova GK Per during the 2015 outburst. |
| Authors: |
Zemko, P.1 polina.zemko@studenti.unipd.it, Orio, M.2,3, Luna, G. J. M.4,5, Mukai, K.6,7, Evans, P. A.8, Bianchini, A.1,2 |
| Source: |
Monthly Notices of the Royal Astronomical Society. Jul2017, Vol. 469 Issue 1, p476-491. 16p. |
| Subject Terms: |
*METEOR showers, *ACCRETION in galactic x-ray sources, *WHITE dwarf stars, *DWARF novae, *ASTRONOMICAL observations |
| Abstract: |
GK Per, a classical nova of 1901, is thought to undergo variable mass accretion on to a magnetized white dwarf (WD) in an intermediate polar system. We organized a multimission observational campaign in the X-ray and ultraviolet energy ranges during its dwarf nova outburst in 2015 March-April. Comparing data from quiescence and near outburst, we have found that the maximum plasma temperature decreased from about 26 to 16.2-0.4+0.5 keV. This is consistent with the previously proposed scenario of increase in mass accretion rate while the inner radius of the magnetically disrupted accretion disc shrinks, thereby lowering the shock temperature. A NuSTAR observation also revealed a high-amplitude WD spin modulation of the very hard X-rays with a single-peaked profile, suggesting an obscuration of the lower accretion pole and an extended shock region on the WD surface. The X-ray spectrum of GK Per measured with the Swift X-Ray Telescope varied on time-scales of days and also showed a gradual increase of the soft X-ray flux below 2 keV, accompanied by a decrease of the hard flux above 2 keV. In the Chandra observation with the High Energy Transmission Gratings, we detected prominent emission lines, especially of Ne, Mg and Si, where the ratios of H-like to He-like transition for each element indicate a much lower temperature than the underlying continuum. We suggest that the X-ray emission in the 0.8-2 keV range originates from the magnetospheric boundary. [ABSTRACT FROM AUTHOR] |
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