Investigation of a likely orbital periodicity of Nova Hercules 2021 in X-rays and γ-rays. Issue 1 (30th September 2022)

• Record Type: Journal Article
• Authors: Lin, Lupin Chun-Che; Fan, Jhih-Ling; Hu, Chin-Ping; Takata, Jumpei; Li, Kwan-Lok
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 517:Issue 1(2022)
• Page Start: L97
• Page End: L101
• Publication Date: 2022-09-30
• Subjects: time -- novae, cataclysmic variables -- methods: data analysis -- methods: observational -- X-rays: bursts -- gamma-rays: stars; Astronomy -- Research -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnrasl/slac117
• Languages: English
• ISSNs: 1745-3933

Abstract

ABSTRACT: We report a detection of a ∼0.153 d period in the classical nova V1674 Her using the NICER observations taken within a month since the outburst (i.e. ∼MJD 59405). The X-ray period is consistent with the orbital period previously found in the optical band, strongly suggesting the NICER signal as the X-ray orbital periodicity of the system. A seemingly double-humped profile was obtained by folding the detrended X-ray light curve with the period after removing the rotational X-ray pulsations of the nova. The profile may be caused by occultation by the companion or the accretion disc, possibly indicating a high inclination of the system. The γ-ray emission of V1674 Her with a significance level ≳ 5 σ was detected by Fermi-LAT close to its optical peak and the emission faded away within 1 d, which is the shortest duration known for a γ-ray nova. Folded on 0.153 d, a marginal γ-ray variability can be also seen in the LAT light curve, but without the double-hump feature observed in X-rays. If the γ-ray modulation is real, its origin is probably different from that observed in the X-ray and optical bands.