RX Andromedae

RX Andromedae is a variable star in the constellation of Andromeda. Although it is classified as a dwarf nova of the Z Camelopardalis (UGZ) type, it has shown low-luminosity periods typical of VY Sculptoris stars.[9] However, for most of the time it varies from an apparent visual magnitude of 15.1 at minimum brightness to a magnitude of 10.2 at maximum brightness, with a period of approximately 13 days.[2]

RX Andromedae
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension 01h 04m 35.53730s[1]
Declination +41° 17′ 57.78369″[1]
Apparent magnitude (V) 10.2 to 15.1[2]
Characteristics
Spectral type pec(UG)[2]
B−V color index -0.4556[3]
Variable type UGZ[2]
Astrometry
Radial velocity (Rv)-12[4] km/s
Proper motion (μ) RA: 1.217 ± 2.221[5] mas/yr
Dec.: -22.225 ± 0.699 [5] mas/yr
Parallax (π)5.0276 ± 0.0507[1] mas
Distance649 ± 7 ly
(199 ± 2 pc)
Orbit
Period (P)5.075[6] hours
Details
White dwarf
Mass0.8[7] M☉
Surface gravity (log g)8.2[7] cgs
Temperature40,000 - 45,000[7] K
Rotational velocity (v sin i)200[7] km/s
Donor star
Surface gravity (log g)4.5[8] cgs
Temperature3,500[8] K
Metallicity+0.07[8]
Other designations
2MASS J01043553+4117577, TYC 2807-1623-1
Database references
SIMBADdata

System

RX Andromedae is a cataclysmic variable system, where a white dwarf with a mass of 0.8 M☉ and an M2 main sequence star[8] are rotating around their center of mass. The main sequence star is overfilling its Roche lobe, so the white dwarf is stripping away matter from the companion star and accreting it through an accretion disk.[9]

Variability

Like the Z Camelopardalis variables, RX Andromedae shows some periods of roughly constant luminosity and others where its brightness oscillates between a magnitude of 10.2 at its maximum and one of 15.1 at its minimum. However, between 1996 and 1997 it was stuck at its minimum brightness like cataclysmic variables of VY Sculptoris type, before going back to the usual behaviour. This places RX Andromedae in a transitional state between those two kind of objects.[9] The white dwarf and its accretion disk seems to be entirely responsible for this variability, and it's driven by changes in the accretion rate of the white dwarf.[7]

Spectrum

RX Andromedae has been extensively studied in optical and ultraviolet. It's also one of the few dwarf nova systems that have been detected at radio wavelengths.[10]

References
  1. 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.
  2. RX And, database entry, Combined General Catalog of Variable Stars (GCVS4.2, 2004 Ed.), N. N. Samus, O. V. Durlevich, et al., CDS ID II/250 Accessed on line 2009-06-30.
  3. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (2000), "The Tycho-2 catalogue of the 2.5 million brightest stars", Astronomy & Astrophysics, 355: L27–L30, Bibcode:2000A&A...355L..27H.
  4. Kraft, R. P. (March 1962). "Binary Stars among Cataclysmic Variables. I. U Geminorum Stars (dwarf Novae)". Astrophysical Journal. 135: 408. Bibcode:1962ApJ...135..408K. doi:10.1086/147280.
  5. Gaia Collaboration; Brown, A. G. A; Vallenari, A; Prusti, T; De Bruijne, J. H. J; Mignard, F; Drimmel, R; Babusiaux, C; Bailer-Jones, C. A. L; Bastian, U; Biermann, M; Evans, D. W.; Eyer, L; Jansen, F; Jordi, C; Katz, D; Klioner, S. A.; Lammers, U; Lindegren, L; Luri, X; O'Mullane, W; Panem, C; Pourbaix, D; Randich, S; Sartoretti, P; Siddiqui, H. I.; Soubiran, C; Valette, V; Van Leeuwen, F; et al. (2016). "Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties". Astronomy & Astrophysics. 595: A2. arXiv:1609.04172. Bibcode:2016A&A...595A...2G. doi:10.1051/0004-6361/201629512. S2CID 1828208.
  6. Kaitchuck, R. H. (1989), "The Orbital Period of RX Andromedae", Publications of the Astronomical Society of the Pacific, 101: 1129, Bibcode:1989PASP..101.1129K, doi:10.1086/132587.
  7. Sepinsky, J. F.; Sion, E. M.; Szkody, P.; Gänsicke, B. T. (2002), "Hubble Space Telescope Spectroscopy of the Dwarf Nova RX Andromedae during Outburst Rise and Decline", The Astrophysical Journal, 574 (2): 937–941, Bibcode:2002ApJ...574..937S, doi:10.1086/341009.
  8. Harrison, T. E. (2018), "The Identification of Hydrogen-deficient Cataclysmic Variable Donor Stars", The Astrophysical Journal, 861 (2): 102, arXiv:1806.04612, Bibcode:2018ApJ...861..102H, doi:10.3847/1538-4357/aacbd9, S2CID 119531169.
  9. Schreiber, M. R.; Gänsicke, B. T.; Mattei, J. A. (2002), "RX And: An intermediate between Z Cam and VY Scl stars", Astronomy and Astrophysics, 384: L6–L9, Bibcode:2002A&A...384L...6S, doi:10.1051/0004-6361:20020122.
  10. Coppejans, D. L.; Körding, E. G.; Miller-Jones, J. C. A.; Rupen, M. P.; Sivakoff, G. R.; Knigge, C.; Groot, P. J.; Woudt, P. A.; Waagen, E. O.; Templeton, M. (2016). "Dwarf nova-type cataclysmic variable stars are significant radio emitters". Monthly Notices of the Royal Astronomical Society. 463 (2): 2229–2241. arXiv:1608.06295. Bibcode:2016MNRAS.463.2229C. doi:10.1093/mnras/stw2133. S2CID 31287217.


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