Long-term X-ray variability of the symbiotic system RT Cru based on Chandra spectroscopy
Nov 14, 2020
17 pages
Published in:
- Mon.Not.Roy.Astron.Soc. 500 (2020) 4, 4801-4817
- Published: Dec 18, 2020
e-Print:
- 2011.07390 [astro-ph.HE]
DOI:
- 10.1093/mnras/staa3554 (publication)
View in:
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Abstract: (Oxford University Press)
RT Cru belongs to the rare class of hard X-ray emitting symbiotics, whose origin is not yet fully understood. In this work, we have conducted a detailed spectroscopic analysis of X-ray emission from RT Cru based on observations taken by the Chandra Observatory using the Low Energy Transmission Grating (LETG) on the High-Resolution Camera Spectrometer (HRC-S) in 2015 and the High Energy Transmission Grating (HETG) on the Advanced CCD Imaging Spectrometer S-array (ACIS-S) in 2005. Our thermal plasma modelling of the time-averaged HRC-S/LETG spectrum suggests a mean temperature of kT ∼ 1.3 keV, whereas kT ∼ 9.6 keV according to the time-averaged ACIS-S/HETG. The soft thermal plasma emission component (∼1.3 keV) found in the HRC-S is heavily obscured by dense materials (>5 × 10^23 cm^−2). The aperiodic variability seen in its light curves could be due to changes in either absorbing material covering the hard X-ray source or intrinsic emission mechanism in the inner layers of the accretion disc. To understand the variability, we extracted the spectra in the ‘low/hard’ and ‘high/soft’ spectral states, which indicated higher plasma temperatures in the low/hard states of both the ACIS-S and HRC-S. The source also has a fluorescent iron emission line at 6.4 keV, likely emitted from reflection off an accretion disc or dense absorber, which was twice as bright in the HRC-S epoch compared to the ACIS-S. The soft thermal component identified in the HRC-S might be an indication of a jet that deserves further evaluations using high-resolution imaging observations.Note:
- 28 pages, 18 figures, 4 tables, published in MNRAS
- accretion, accretion discs
- binaries: symbiotic
- stars: individual: (RT Cru)
References(104)
Figures(22)