J/ApJ/955/150 MDM light curve of V844 Her (Greiveldinger+, 2023)
A surprising periodicity detected during a super-outburst of V844 Herculis by
TESS.
Greiveldinger A., Garnavich P., Littlefield C., Kennedy M.R.,
Halpern J.P., Thorstensen J.R., Szkody P., Oksanen A., Boyle R.S.
<Astrophys. J., 955, 150 (2023)>
=2023ApJ...955..150G 2023ApJ...955..150G
ADC_Keywords: Stars, variable; Photometry; Optical
Keywords: Cataclysmic variable stars ; Stellar oscillations ;
White dwarf stars ; X-ray stars
Abstract:
We identify a previously undetected periodicity at a frequency of
49.08±0.01days-1 (period of 29.34±0.01 minutes) during a
super-outburst of V844 Her observed by TESS. V844 Her is an SU UMa
type cataclysmic variable with an orbital period of 78.69 minutes,
near the period minimum. The frequency of this new signal is constant
in contrast to the superhump oscillations commonly seen in SU UMa
outbursts. We searched without success for oscillations during
quiescence using MDM, TESS, and XMM-Newton data. The lack of a
periodic signal in the XMM light curve and the relatively low X-ray
luminosity of V844 Her suggest that it is not a typical IP. We
consider the possibility that the 29-minute signal is the result of
super-Nyquist sampling of a dwarf nova oscillation with a period near
the 2-minute cadence of the TESS data. Our analysis of archival AAVSO
photometry from a 2006 super-outburst supports the existence of a
29-minute oscillation, although a published study of an earlier
super-outburst did not detect the signal. We compare the X-ray
properties of V844 Her with short orbital period intermediate polars
(IP), V1025 Cen and DW Cnc. We conclude that the new signal is a real
photometric oscillation coming from the V844 Her system and that it is
unlikely to be an aliased high-frequency oscillation. The steady
frequency of the new signal suggests that its origin is related to an
asynchronously rotating white dwarf in V844 Her, although the precise
mechanism producing the flux variations remains unclear.
Description:
V844 Her was observed with the MDM 1.3m McGraw-Hill telescope on four
consecutive nights starting on 2022 May 28 (UT). A GG420 long-pass
filter was used with the MDM Templeton detector. To minimize
overheads, only a 130" section of the sky was recorded for analysis.
The star was observed for 3hr each night with a 20s exposure time
resulting in an average cadence of 23s.
Objects:
----------------------------------------------------------
RA (ICRS) DE Designation(s)
----------------------------------------------------------
16 25 01.74 +39 09 26.3 V844 Her = V* V844 Her
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig10.dat 31 1791 The MDM lightcurves of V844 Her from the four
individual nights
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See also:
B/cb : Cataclysmic Binaries, LMXBs, and related objects (Ritter+, 2004)
V/123 : Catalog of Cataclysmic Variables (Downes+ 2001-2006)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
I/358 : Gaia DR3 Part 4. Variability (Gaia Collaboration, 2022)
J/ApJ/565/511 : Cataclysmic variables in the 2MASS 2IDR (Hoard+, 2002)
J/other/NewA/13.133 : 2MASS photometry of cataclysmic variables (Ak+, 2008)
J/other/JAD/15.1 : Time-series of 9 cataclysmic variables (Papadaki+, 2009)
J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)
J/MNRAS/402/436 : Dwarf novae in SDSS, GALEX and astrom. cat. (Wils+, 2010)
J/AJ/142/181 : CVs from SDSS. VIII. The final year (Szkody+, 2011)
J/PASJ/64/63 : Dwarf novae characterization using SDSS colors (Kato+, 2012)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/MNRAS/441/1186 : Cataclysmic variables from CRTS (Drake+, 2014)
J/PASJ/68/65 : Superhumps in SU UMa-type dwarf novae (Kato+, 2016)
J/MNRAS/460/2526 : Dwarf novae outbursts properties (Otulakowska-Hypka+, 2016)
J/MNRAS/492/L40 : Disentangling CVs in Gaia DR2 (Abril+, 2020)
J/MNRAS/502/5668 : Superoutburst of 206 SU UMa-type dwarf novae (Vogt+, 2021)
J/MNRAS/504/2420 : Close white dwarf binaries - Ref. samples (Inight+, 2021)
J/ApJ/910/120 : Dwarf nova outbursts detected by ASAS-SN (Kawash+, 2021)
J/ApJ/938/46 : CV orb. periods from Gaia phot. (Abrahams+, 2022)
J/AJ/165/163 : Cataclysmic variables in the Gaia era (Canbay+, 2023)
J/MNRAS/524/4867 : CVs from SDSS (Inight+, 2023)
J/A+A/675/A195 : ZTF DR11 classif. in ZTF/4MOST sky (Sanchez-Saez+, 2023)
J/A+A/687/A250 : STONKS Multi-Mission X-ray Catalog (Quintin+, 2024)
J/MNRAS/536/1057 : CVs from SDSS-V (Inight+, 2025)
Byte-by-byte Description of file: fig10.dat
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Bytes Format Units Label Explanations
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1- 14 F14.6 d BJD Barycentric Julian Day
16- 23 F8.5 mag GG420mag [17.74/18.23] Magnitude in longpass GG420 filter
25- 31 F7.5 mag e_GG420mag [0.012/0.11] Uncertainty in GG420mag
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 03-Dec-2025