DQ Herculis

DQ Herculis, or Nova Herculis 1934, was a slow, bright nova occurring in the northern constellation of Hercules in December 1934. This cataclysmic variable star was discovered on 13 December 1934 by J. P. M. Prentice from Stowmarket, Suffolk.[12] It reached peak brightness on 22 December 1934 with an apparent magnitude of 1.5.[3] The nova remained visible to the naked eye for several months.[13]

This article is about the star DQ Herculis. For the type of cataclysmic variable known as DQ Herculis variables, see intermediate polar.
DQ Herculis

RGB composite color image of the shell surrounding the nova DQ Her, made from three narrow band images: Blue = 4800Å, green = Hα at 6563 Å and red = [NII] at 6583 Å. From Santamaria et al. 2020[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Hercules
Right ascension 18h 07m 30.25108s[2]
Declination +45° 51′ 32.5646″[2]
Apparent magnitude (V) 1.5[3] - 15.16[4]
Characteristics
Spectral type DBe + M2V
Variable type DQ Her[5]
Astrometry
Proper motion (μ) RA: −0.948[2] mas/yr
Dec.: +12.423[2] mas/yr
Parallax (π)1.9975 ± 0.0237 mas[2]
Distance1,630 ± 20 ly
(501 ± 6 pc)
Absolute magnitude (MV)−6.94[6]
Orbit
Period (P)0.1936208977 ± 0.0000000017 d[7]
Semi-major axis (a)0.003 AU
Inclination (i)86.5±1.6[8]°
Details
A
Mass0.6[9] M☉
Radius0.0121[8] R☉
B
Mass0.4[9] M☉
Other designations
Nova Her 1934, DQ Her, 2MASS J18073024+4551325, CDS 959, PLX 4164, AN 452.1934, GCRV 10587, CSI+45-18061, SBC7 665, AAVSO 1804+45[10]
Database references
SIMBADdata
The light curve of DQ Herculis, from AAVSO data. The pronounced "dust dip" roughly four months after peak brightness was caused by dust forming as the ejected shell expanded and cooled.[11]

This is a binary star system consisting of a white dwarf primary with an estimated 60% of the mass of the Sun and a red dwarf secondary with 40% of the Sun's mass.[8] They orbit each other tightly with a period of 4.65 hours.[7] The system shows orbital period variation, possibly due to the presence of a third body.[5] The orbital plane of the pair is inclined by an angle of 86.5° to the line of sight from the Earth, causing the white dwarf to undergo a deep eclipse every orbit.[8]

DQ Herculis is the prototype for a category of cataclysmic variable stars called intermediate polars.[5] The red dwarf has filled its Roche lobe and matter is being drawn off at the rate of 2.7 × 10−9 M☉ yr−1, forming an accretion disk orbiting the primary. This disk has inferred temperatures ranging from 5,000 to 13,500 K. A bright spot in the inner disk appears to pulsate with a 71-second period. In this class of variables, the white dwarf is magnetized, directing infalling matter onto the magnetic poles.[8]

Two images of the shell surrounding DQ Hercules taken 21 years apart, showing the nebula's expansion. Both were taken with Hα filters, left at the William Herschel Telescope, and right with the Nordic Optical Telescope.[1]

The shell of ejected material from the nova outburst is visible as an emission nebula, similar in appearance to a planetary nebula. This roughly elliptical nebula had a size of 32.0 × 24.2 arc seconds as of 2018, and it is expanding at a rate of about 0.16 arc seconds per year.[1]

The location of nova DQ Herculis (circled in red)

The nova was one of the brightest objects observable in the night sky. In addition to scientific articles, and received significant coverage in popular news publications.[14][15] Brad Ricca, an English professor at Case Western Reserve University, has suggested that Nova Herculis may have influenced the development of the origin story of the comic book superhero Superman.[16]

References
  1. Santamaria, E.; Guerrero, M.A.; Ramos-Larios, G.; Toala, J.A.; Sabin, L.; Rubio, G.; Quino-Mendoza, J.A. (March 2020). "Angular Expansion of Nova Shells". The Astrophysical Journal. 892 (1): 60. arXiv:2002.06749. Bibcode:2020ApJ...892...60S. doi:10.3847/1538-4357/ab76c5. S2CID 211132830.
  2. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  3. Wright, W. H. (1935). "Comments on Nova Herculis 1934". Publications of the Astronomical Society of the Pacific. 47 (275): 47–49. Bibcode:1935PASP...47...47.. doi:10.1086/124534. JSTOR 40670634.
  4. Norton, A. J.; et al. (2007). "New periodic variable stars coincident with ROSAT sources discovered using SuperWASP". Astronomy and Astrophysics. 467 (2): 785–905. arXiv:astro-ph/0702631. Bibcode:2007A&A...467..785N. doi:10.1051/0004-6361:20077084. S2CID 16358048.
  5. Dai, Z. B.; Qian, S. B. (2009). "Plausible explanations for the variations of orbital period in the old nova DQ Herculis". Astronomy and Astrophysics. 503 (3): 883–888. Bibcode:2009A&A...503..883D. doi:10.1051/0004-6361/200810909.
  6. Harrison, Thomas E.; et al. (2013). "Hubble Space Telescope Fine Guidance Sensor Parallaxes for Four Classical Novae". The Astrophysical Journal. 767 (1). 7. arXiv:1302.3245. Bibcode:2013ApJ...767....7H. doi:10.1088/0004-637X/767/1/7. S2CID 118376206.
  7. Schaefer, Bradley E. (March 2020). "Sudden and steady orbital period changes across the classical nova eruptions of DQ Her and BT Mon". Monthly Notices of the Royal Astronomical Society. 492 (3): 3323–3342. arXiv:1912.06169. Bibcode:2020MNRAS.492.3323S. doi:10.1093/mnras/stz3325. S2CID 209370404.
  8. Saito, R. K.; et al. (June 2010). "Spectral Mapping of the Intermediate Polar DQ Herculis". The Astronomical Journal. 139 (6): 2542–2556. arXiv:1005.1612. Bibcode:2010AJ....139.2542S. doi:10.1088/0004-6256/139/6/2542. S2CID 118447217.
  9. Zhang, E.; et al. (November 1995). "The 71 Second Oscillation in the Light Curve of the Old Nova DQ Herculis". Astrophysical Journal. 454: 447. Bibcode:1995ApJ...454..447Z. doi:10.1086/176496.
  10. "DQ Her". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-11-14.{{cite web}}: CS1 maint: postscript (link)
  11. Rosenbush, A.E. (January 1999). "On the possibility of systematizing classical novae by light curve type. I. Type criteria". Astrophysics. 42 (1): 43–53. Bibcode:1999Ap.....42...43R. doi:10.1007/BF02700913. S2CID 120593343. Retrieved 6 December 2020.
  12. "DQ Her". www.britastro.org. Retrieved 2017-08-09.
  13. "Nova Herculis, Discovered in December 1934, Varies From First to Thirteenth Magnitudes--Now Fading, About Sixth". 1935-12-07. Retrieved 2013-08-08.
  14. Kaempffert, Waldemar (1934-12-23). "The Week In Science: STAR OF BETHLEHEM A NOVA?; Recent Brilliant Outburst Recalls the Orb the Magi Followed". The New York Times. Retrieved 2013-08-08.
  15. "Science: Nova Herculis; Swaseya". Time. 1934-12-31. Archived from the original on November 25, 2010. Retrieved 2013-08-08.
  16. "Superman's Origins Possibly Born from Star Explosion". Space.com. 2013-07-12. Retrieved 2013-08-07.
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