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Description
HR 1099 (V711 Tau) is one of the most active RS Canum Venaticorum binaries with an orbital period of 2.8377 days and has been extensively studied at various wavelengths. It is a non-eclipsing, double-lined spectroscopic binary with a K0 - K1 subgiant primary and a G5 dwarf secondary in a nearly circular orbit (Fekel 1983). We observed this object from March 6 to 10 (UT) with XRISM as one of the calibration targets. We performed simultaneous optical observations with CAT and SCAT at CHAO (CHuo-university Astronomical Observatory) on the Korakuen campus of Chuo University on March 9 and 10 (UT) . We detected a flare during the XRISM observations. The X-ray flux increased from the 7th, peaked on the 8th, and finally decayed to the pre-flare level within 50000 s from the peak. The peak flux in the 0.4-10 keV band is 1×10^-10 erg s^-1 cm^-2, which corresponds to a luminosity of 1×10^31 erg s^-1 at 29 pc (Perryman et al. 1997). We found that the X-ray flare occurred around phase 0.0, i.e. when the K supergiant is in front of us, by extrapolating the radial velocity curve in Frasca & Lanza (2005). From the Resolve and Xtend light curves we found an X-ray enhancement after the flare, at the opposite phase (the phase ∼0.5), and also another weak enhancement before the flare, again at the opposite phase (the phase ∼0.5). In the X-ray enhancement after the flare, we detected a possible redshift of the Fe K alpha line with a velocity of about 600 km/s with Xtend, and also a redshift of the H alpha line with a velocity of about 300 km/s with SCAT. We will discuss the nature of the large redshift.
