DQ Herculis

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]

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 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]

  1. ^ a b c 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. ^ a b c d e Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Wright1935 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Norton2007 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference DaiQian2009 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Harrison2013 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Schaefer2020 was invoked but never defined (see the help page).
  8. ^ a b c d e Cite error: The named reference Saito2010 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Zhang1995 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  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. ^ Cite error: The named reference britastro was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference crimson1935 was invoked but never defined (see the help page).