X-ray upper limit on the progenitor of the Type Ia supernova 2026ahvu in NGC 1433

ATel #18148; A. K.H. Kong (NTHU)
on 10 Nov 2026; 08:56 UT
Credential Certification: Albert Kong (akong@phys.nthu.edu.tw)

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Following the discovery of the Type Ia supernova (SN) 2026ahvu in the nearby galaxy NGC 1433 (https://www.wis-tns.org/astronotes/astronote/2026-310), we searched for the progenitor X-ray counterpart with the archival Chandra X-ray Observatory data. Chandra observed the host galaxy NGC 1433 twice in 2015 March 4 and 2024 December 3 for 49 ks and 47 ks, respectively. We combined the two observations with a total effective exposure time of ~95 ks. Within a 2 arcsec radius circular region centered at the position of the SN, no X-ray emission is visible in the 0.3-7 keV energy range. Assuming an absorbed power-law spectral model with a photon index of 2 and N_H of 1e20 cm^-2 (Galactic value based on the HI 4 Pi Survey), we derive a 3-sigma 0.3-10 keV luminosity limit of 2.3e37 erg/s (d=9.1 Mpc; Sabbi et al. 2018) or 1.0e38 erg/s (d=18.9 Mpc; Scheuermann et al. 2022). It is worth noting that the distance to NGC 1433 is uncertain (see Sarbadhicary et al. 2026 for discussion). Since some progenitors of Type Ia SNe are expected to be supersoft X-ray sources (see Nielsen et al. 2013, MNRAS, 435, 187 for a review), we also assumed an absorbed blackbody model with N_H=1e20 cm^-2 and kT=100 eV. The resulting 3-sigma 0.3-10 keV luminosity upper limit is 1.2e39 erg/s (d=9.1 Mpc) or 5.1e39 erg/s (d=18.9 Mpc).