X-ray emission of the progenitor of the Type Ia supernova SN2025rbs

ATel #17287; A. K.H. Kong (NTHU), Ruolan Jin (NTTU), C.-Y. Hui (CNU), K.-Y. Au, K.-L. Li, L. C.-C. Lin (NCKU)
on 17 Jul 2025; 14:48 UT
Credential Certification: Albert Kong (akong@phys.nthu.edu.tw)

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Following the discovery of the Type Ia supernova SN2025rbs in the nearby galaxy NGC 7331 (https://www.wis-tns.org/object/2025rbs), we have searched for X-ray emission of its progenitor with the Chandra Source Catalog (Evans et al. 2024). Based on the 13 Chandra observations of NGC 7331 taken between 2001 and 2020 (242 ks total observing time), an X-ray source in the Chandra Source Catalog, 2CXO J223703.6+342507, is located at about 0.7 arcsec from the supernova’s position. The 95% positional uncertainty of the X-ray source is 0.47 arcsec. Given the separation between the X-ray source and the supernova, we tentatively conclude that the X-ray progenitor was not detected.

The X-ray source 2CXO J223703.5+342507 is also in the NGC 7331 X-ray source catalog (Jin and Kong 2019) which is based on a 126 ks stacked Chandra image. It was classified as a low-mass X-ray binary according to the X-ray colours. The X-ray spectrum can be fitted with an absorbed power-law with a photon index of 1.85 and a 0.3-8 keV X-ray luminosity of 4.5e38 erg/s (D=14.7 Mpc). No optical counterpart was found from the Hubble Space Telescope observations.

The X-ray luminosity limit of the progenitor of SN2025rbs can be constrained to approximately 3.6e37 erg/s (0.3-8 keV), based on the X-ray detection threshold reported by Jin & Kong (2019). Further analysis incorporating more recent Chandra observations is currently underway to better constrain the X-ray emission from the progenitor of SN2025rbs.