NICER observations of Nova Her 2021
ATel #14798; Songpeng Pei (Padova University), Gerardo Juan Manuel Luna (CONICET - University of Buenos Aires), Marina Orio (University of Wisconsin and INAF-Padova), Ehud Behar (Technion), Morgan Giese (University of Wisconsin), Joanna Mikolajewska (Nicolaus Copernicus Astronomical Center of the PAC), Jan-Uwe Ness (ESA - ESAC)
on 19 Jul 2021; 08:02 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Marina Orio (orio@astro.wisc.edu)
Nova Her 2021 (V1674 Her, TCP J18573095+1653396, see ATels #14704, #14705, #14707, #14710, #14713, #14718, #14720, #14723, #14728, #14731, #14736, #14737, #14740, #14741, #14746, #14747, #14758, #14765, #14776) was observed with the Neutron Star Interior Composition Explorer (NICER) during a total time of about 22 ks, in 14 distinct exposures between 2021 Jul 10 and 2021 July 12. The average count rate in the 0.2-12 keV range was 458.4 ± 0.7 cts/s, but the count rate varied by up a factor of ~20 even during single exposures of about 20 minutes. The spectrum was very soft, peaking at 0.5 keV and with almost no counts above 0.9 keV. It does not appear to be due to a single component; it is instead consistent with a dominant white dwarf atmospheric component at temperature between 700,000 K and a million K, depending on the assumed abundances, and one or more components at higher energy and lower flux. The power spectrum of the X-ray light curve is very complex. It presents a a dominant peak at a period of 501.8 ± 0.7 s, consistent with the measurement of Maccarone et al., ATel #14776. This period has also been measured in the optical data before the outburst and attributed to the rotation of an intermediate polar white dwarf (Mroz et al. ATel #14720). A more sophisticated analysis is necessary to confirm or rule out other periodic modulations. A preliminary inspection of the X-ray light curve obtained with the Chandra HRC (ATel #14776) also suggests significant complexity.
