Early Swift-XRT detection of heavily-absorbed shock-powered X-rays from nova V1935 Cen = PNV J14372177-5847400
ATel #17418; Kirill Sokolovsky (UIUC), Kim Page (U. Leicester), Elias Aydi (TTU), Laura Chomiuk, Peter Craig, Isabella Molina (MSU), Jennifer Sokoloski (Columbia), Justin Linford (NRAO), Koji Mukai (NASA/GSFC)
on 24 Sep 2025; 21:42 UT
Credential Certification: Kirill Sokolovsky (kirx@scan.sai.msu.ru)
Nova Centauri 2025, also known as V1935 Cen and
PNV J14372177-5847400 was discovered by John Seach at magnitude 6.2
using DSLR camera images obtained on 2025-09-22.396 UT with
a 40-mm-f.l. f/1.4 lens. Nothing brighter than magnitude 11.0 was
visible at the nova position in images obtained the previous night
on 2025-09-21.366 with the same setup. A low-resolution optical
spectrum obtained by Rob Kaufman on 2025-09-23.383 was interpreted
as that of a classical nova (CBET #5611). The nova was detected as
a bright GeV source by Fermi-LAT with the first detection in
a 6-hr bin starting on 2025-09-21.50, prior to the optical discovery
(ATel #17414).
V1935 Cen was observed with Swift for 3.4ks split in two visits
centered on 2025-09-23.64 (1.2 days after the optical discovery,
2.3 days after the latest optical non-detection). Swift-XRT was
operating in Windowed Timing mode to minimize optical loading.
A bright and hard X-ray source was detected at the position
of the nova having the grade 0-2 count rate of 0.20 +/-0.01 cts/s
with all the source counts being above 1.5 keV. The spectrum is
consistent with that of a thermal plasma with kT= 15 keV absorbed
by an equivalent hydrogen column of N_H= 1.1x10^23 cm^-2, an order
of magnitude above the Galactic value in this direction
(8.6x10^21 cm^-2; Kalberla et al. 2005 A&A, 440, 775).
The unabsorbed flux extrapolated to the full Swift-XRT band
of 0.3-10 keV is 4.7x10^-11 ergs/cm^2/s.
Most classical novae remain undetected by Swift-XRT at the time
when they emit gamma-rays (Gordon et al. 2021, ApJ, 910, 134),
while novae embedded in red giant wind tend to show early
detections (e.g., RS Oph; Cheung et al. 2022, ApJ, 935, 44).
The early Swift-XRT detection of V1935 Cen may indicate a symbiotic
nature of the host binary system. Alternatively, this nova may be
unusually fast in clearing up its ejecta sufficiently to enable
Swift-XRT detection two days after the eruption.
We thank the Neil Gehrels Swift Observatory team and PI, Brad Cenko,
for rapid execution this ToO observation.
