Abstract:
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.
