T_CORONA_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.
obsid = 300008010 / Unique Observation/Sequence Number
object = T_CORONA_BOREALIS / Object name
pi_name = Collaboration XRISM / Proposal Principal Investigator Name
ra = 239.874560284555 / Right Ascension (Pointing Position) (deg)
dec = 25.9215057930303 / Declination (Pointing Position) (deg)
roll_angle = 321.170657454231 / Roll Angle (deg)
start_time = 2024-06-27T00:04:04 / Start Time of the Observation
stop_time = 2024-07-03T11:48:04 / Stop Time of the Observation
exposure = 294093.46874466 / Effective Total Observation Exposure (s)
public_date= 2025-08-31 / Public Date