Skip to content
DraconiticResearch
Search Sources API
203,203 studies31 sourcesUpdated 47 min ago
Peer-reviewedCC BY 4.0The Astrophysical Journal

V844 Herculis: An Exceptional Intermediate Polar Hiding in an Ordinary Dwarf Nova

  • Anousha Greiveldinger1,2
  • Peter Garnavich1
  • Colin Littlefield1,3
  • Mark R. Kennedy4,5
  • Paula Szkody6
  • Jordan Tweddale1
  • Mark Whittle7
  • Teófilo Arranz8
  • Donald Collins9
  • James DeYoung10
  • Sjoerd Dufoer11
  • Charles Galdies12
7 more authors
  • Jean-Francois Gout10
  • Franz-Josef Hambsch11,13,14
  • Emmanuel Kardasis15
  • David Messier16
  • Arto Oksanen10
  • Gary Poyner17
  • Richard Sabo18
18 affiliations
  1. 1University of Notre Dame
  2. 2University of California, Berkeley
  3. 3Bay Area Environmental Research Institute
  4. 4University College Cork
  5. 5The University of Manchester
  6. 6University of Washington
  7. 7University of Virginia
  8. 8Observatorio Astronómico “Las Pegueras,”
  9. 9Warren Williams College
  10. 10AAVSO
  11. 11Vereniging Voor Sterrenkunde (VVS)
  12. 12University of Malta
  13. 13Groupe Européen d’Observations Stellaires (GEOS)
  14. 14Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne
  15. 15Pelagia-Eleni Observatory
  16. 16CBA Norwich
  17. 17BAA Variable Star Section
  18. 18CBA-Montana
Open at sourcePDFDOICite

Abstract

We present time-series spectroscopy of the SU UMa–type dwarf nova V844 Her during quiescence. We discover high-velocity Balmer and He I emission features modulated at a period of 29.3 ± 0.1 minutes. The spectroscopic periodicity is identical to the photometric period detected only during superoutbursts. Interpreting this as the result of magnetic accretion onto the white dwarf, we identify V844 Her as an intermediate polar (IP). The spin period of the white dwarf is most likely to be 29.3 minutes. In a few IP systems, optical modulation is seen at twice the spin frequency, so we cannot rule out that the spin period is 58.6 minutes. The orbital period of V844 Her is only 1.31 hr, meaning that the system has the shortest binary period and one of the smallest orbit-to-spin ratios of the confirmed IPs. We present extensive optical, ultraviolet, and X-ray observations of V844 Her during the 2023 superoutburst. Compared with quiescence, the Neil Gehrels Swift Observatory X-Ray Telescope count rate decreases during superoutburst. While the enhanced mass transfer during the superoutburst likely increases X-ray production, we propose that the drop in the count rate comes from the loss of soft X-rays due to an additional column from the outbursting disk.

Related

  1. Orbital and spin periods of the intermediate polar 2PBC J0800.5-4306
    Yabing Zhao, Chunhua Zhu, Sufen Guo +3
    arXivPreprintarXiv licenceFull textHigh-energy astrophysicsSolar & stellar physicsarXiv
  2. A micronova burst in the intermediate polar IGR J17014-4306
    Alexandre S. Oliveira, D. C. Souza, G. J. M. Luna +1
    arXivPreprintCC BY 4.0Full textHigh-energy astrophysicsSolar & stellar physicsarXiv
  3. On the frequency-dependent time lags of the intermediate polar V709 Cas
    Zackery A. Irving, Noel Castro Segura, Diego Altamirano +9
    arXivPreprintarXiv licenceFull textSolar & stellar physicsarXiv
  4. On the frequency-dependent time lags of the intermediate polar V709 Cas
    Zackery A Irving, Noel Castro Segura, Diego Altamirano +9
    Monthly Notices of the Royal Astronomical SocietyPeer-reviewedCC BY 4.0Full textSolar & stellar physicsCrossref
  5. The X-ray and optical emission of the intermediate polar Swift J0614.0+1709
    Nikita Rawat, Domitilla De Martino, David A. H. Buckley +5
    arXivPreprintCC BY 4.0Full textHigh-energy astrophysicsarXiv

Cite

BibTeXRIS
BibTeX
@article{greiveldinger2026v844,
  title = {{V844 Herculis: An Exceptional Intermediate Polar Hiding in an Ordinary Dwarf Nova}},
  author = {Anousha Greiveldinger and Peter Garnavich and Colin Littlefield and Mark R. Kennedy and Paula Szkody and Jordan Tweddale and Mark Whittle and Teófilo Arranz and Donald Collins and James DeYoung and Sjoerd Dufoer and Charles Galdies and Jean-Francois Gout and Franz-Josef Hambsch and Emmanuel Kardasis and David Messier and Arto Oksanen and Gary Poyner and Richard Sabo},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = oct,
  doi = {10.3847/1538-4357/aea840},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea840},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - V844 Herculis: An Exceptional Intermediate Polar Hiding in an Ordinary Dwarf Nova
AU  - Anousha Greiveldinger
AU  - Peter Garnavich
AU  - Colin Littlefield
AU  - Mark R. Kennedy
AU  - Paula Szkody
AU  - Jordan Tweddale
AU  - Mark Whittle
AU  - Teófilo Arranz
AU  - Donald Collins
AU  - James DeYoung
AU  - Sjoerd Dufoer
AU  - Charles Galdies
AU  - Jean-Francois Gout
AU  - Franz-Josef Hambsch
AU  - Emmanuel Kardasis
AU  - David Messier
AU  - Arto Oksanen
AU  - Gary Poyner
AU  - Richard Sabo
PY  - 2026
DA  - 2026/10/12
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/aea840
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/aea840
AB  - We present time-series spectroscopy of the SU UMa–type dwarf nova V844 Her during quiescence. We discover high-velocity Balmer and He I emission features modulated at a period of 29.3 ± 0.1 minutes. The spectroscopic periodicity is identical to the photometric period detected only during superoutbursts. Interpreting this as the result of magnetic accretion onto the white dwarf, we identify V844 Her as an intermediate polar (IP). The spin period of the white dwarf is most likely to be 29.3 minutes. In a few IP systems, optical modulation is seen at twice the spin frequency, so we cannot rule out that the spin period is 58.6 minutes. The orbital period of V844 Her is only 1.31 hr, meaning that the system has the shortest binary period and one of the smallest orbit-to-spin ratios of the confirmed IPs. We present extensive optical, ultraviolet, and X-ray observations of V844 Her during the 2023 superoutburst. Compared with quiescence, the Neil Gehrels Swift Observatory X-Ray Telescope count rate decreases during superoutburst. While the enhanced mass transfer during the superoutburst likely increases X-ray production, we propose that the drop in the count rate comes from the loss of soft X-rays due to an additional column from the outbursting disk.
SN  - 0004-637X
SN  - 1538-4357
ER  -