GRAVITATIONALLY REDSHIFTED 6.4 KEV LINE IN T CORONAE BOREALIS
We propose to measure the gravitational redshift at the surface of a massive accreting white dwarf (WD) in T CrB. It is a hard X-ray luminous symbiotic recurrent nova, with an estimated WD mass of >1.15 Msun, above the likely upper limit of WD birth mass. If confirmed, it implies that the WD in T CrB is growing in mass, establishing a subset of symbiotic stars as a viable progenitor channel of Type Ia supernovae. The primary X-ray source is located just above the WD surface, and it is the latter that produces the reflection continuum and the Fe Kalpha and Kbeta fluorescent lines. Measuring the centroids of both will enable us to determine the ionization state of the WD photosphere and the WD mass.
TELESCOP= 'XRISM ' / Mission name INSTRUME= 'XTEND ' / Instrument name OBS_ID = '300008010' / Observation identification string OBJECT = 'T_CORONA_BOREALIS' / Object name OBSERVER= 'XRISM Collaboration' / PI name OBS_MODE= 'POINTING' / POINTING or SLEW or ALL RA_OBJ = 239.87567 / [deg] Object Right ascension DEC_OBJ = 25.92017 / [deg] Object Declination RA_PNT = 239.888979125484 / Pointing RA DEC_PNT = 25.9147518185799 / Pointing DEC RA_NOM = 239.874560284555 / [deg] Nominal aspect point R.A. DEC_NOM = 25.9215057930303 / [deg] Nominal aspect point Dec. PA_NOM = 321.170657454231 / [deg] Nominal aspect point roll. TELAPSE = 555370.963135988 / Elapsed time DATE-OBS= '2024-06-27T00:57:37.036864' / Start date DATE-END= '2024-07-03T11:13:48' / Stop date ONTIME = 230377.31614 / On-source time EXPOSURE= 230377.31614 / Exposure time PROCVER = '03.00.013.009' / Processing script version MKFFF = 'ISAS/JAXA' / Origin of First FITS file ORIGIN = 'GSFC/NASA' / Origin of Processed FITS file SOFTVER = 'Hea_21Aug2024_V6.34_XRISM_21Aug2024_V001' / Version of HEADAS used CALDBVER= 'gen20240315_xtd20240815_rsl20240815' / Version of CALDB used DATE = '2024-09-22T05:44:55' / Date and time this file was created or updated SIB2_VER= / SIB2 version JAXA