(cba:news) ATel #14720 and the new Hercules nova

[Joe Patterson]

Hi CBAers,

Okay, this object already identified itself as being right up our alley 
- and now all the more so if it has a fast period.  So let's jump on it 
right away!

I apologize for my recent quiescence.  I'm teaching an intensive 
every-day  astronomy course here, so the science work has receded. 
Except for AM CVn data, which I greedily devour as soon as it arrives. 
But tomorrow is our final exam, so in 3 days I can get back to studying 
the data full time.

joe


-------- Forwarded Message --------
Subject: ATel #14720
Date: Tue, 15 Jun 2021 15:06:39 -0400 (EDT)
From: atel at astronomerstelegram.org
To: jop at astro.columbia.edu

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The Astronomer's Telegram 
http://www.astronomerstelegram.org

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ATEL #14720							     ATEL #14720

Title:	An 8.4 min period in the archival ZTF light curve of Nova Herculis
		2021
Author:	P. Mroz, K. Burdge, J. van Roestel, T. Prince (Caltech), A.
		K.H. Kong (NTHU), K.-L. Li (NCKU), on behalf of the Zwicky Transient
		Facility collaboration
Queries:	pmroz at astro.caltech.edu
Posted:	15 Jun 2021; 19:06 UT
Subjects:Optical, Cataclysmic Variable, Nova, Transient

The Zwicky Transient Facility (ZTF; Bellm et al. 2019; Graham et al. 2019)
has been observing the field of Nova Herculis 2021 (ATel #14704, #14705,
#14707, #14710, #14713, #14718) since March 2018. In total, 475 exposures
were collected in the r-band, 191 -- in the g-band, from 2018 March 26
until 2021 June 14.
We obtained the archival ZTF light curve of the nova using the ZTF 
forced-photometry
service (Masci et al. 2018) on images processed with the ZTF reduction
and image subtraction pipelines at IPAC (Masci et al. 2019) using the 
position
of the nova from ATel #14710.
We searched for periodic signals in the archival r-band light curve in
the frequency range 0.01-400 c/day using the analysis of variance and 
Lomb-Scargle
algorithms. The most significant period is 0.00580356 d = 8.357 min. There
are not any other significant independent periodicities in the data.
Additionally, the object was independently recovered in a systematic search
of 1,213,165,975 objects across the northern hemisphere using Lomb-Scargle
(frequency range 0.004-720 c/day). Among this search, the system was among
the 700 highest significance sources with a best period under 10 minutes.

The light curve folded with the 8.4-min period shows differential minima
and some additional scatter from flickering. The most likely explanation
of this period is the spin period of a white dwarf in an intermediate polar
system. The period is unlikely the orbital period of the binary - orbital
periods of cataclysmic binaries with hydrogen-rich donors (spectra of the
nova show strong Balmer lines, ATel #14704, #14710, #14718) are typically
longer than ~78 minutes (Hellier 2001).
Based on observations obtained with the Samuel Oschin Telescope 48-inch
and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky
Transient Facility project. ZTF is supported by the National Science 
Foundation
under Grant No. AST-2034437 and a collaboration including Caltech, IPAC,
the Weizmann Institute for Science, the Oskar Klein Center at Stockholm
University, the University of Maryland, Deutsches Elektronen-Synchrotron
and Humboldt University, the TANGO Consortium of Taiwan, the University
of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore 
National
Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC,
and UW. The ZTF forced-photometry service was funded under the 
Heising-Simons
Foundation grant #12540303 (PI: Graham).
Light curve of the nova progenitor folded with the 8.4-min period: 
https://sites.astro.caltech.edu/~pmroz/Nova_Her_2021.png
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Password Certification: Przemek Mroz (pmroz at astrouw.edu.pl)
https://www.astronomerstelegram.org/?read=14720
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