Soft X-ray and FUV observations of Nova Her 2021 (V1674~Her) with AstroSat

• Main Authors: Bhargava, Yash, Dewangan, Gulab Chand, Anupama, G. C, Kamath, U. S, Sonith, L. S, Singh, Kulinder Pal, Drake, J. J, Beardmore, A, Luna, G. J. M, Orio, M, Page, K. L
• Format: Journal Article
• Language: English
• Published: 15-12-2023
• Subjects: Physics - High Energy Astrophysical Phenomena
• DOI: 10.48550/arxiv.2312.10291

Nova Her 2021 or V1674 Her was one of the fastest novae to be observed so
far. We report here the results from our timing and spectral studies of the
source observed at multiple epochs with AstroSat. We report the detection of a
periodicity in the source in soft X-rays at a period of 501.4--501.5 s which
was detected with high significance after the peak of the super-soft phase, but
was not detected in the far ultraviolet (FUV) band of AstroSat. The shape of
the phase-folded X-ray light curves has varied significantly as the nova
evolved. The phase-resolved spectral studies reveal the likely presence of
various absorption features in the soft X-ray band of 0.5--2 keV, and suggest
that the optical depth of these absorption features may be marginally dependent
on the pulse phase. Strong emission lines from Si, N and O are detected in the
FUV, and their strength declined continuously as the nova evolved and went
through a bright X-ray state.