DX Andromedae

DX Andromedae
Observation data; Epoch J2000 Equinox J2000
Constellation	Andromeda
Right ascension	23h 29m 46.6839s[1]
Declination	+43° 45′ 04.03439″[1]
Apparent magnitude (V)	11.0 – 15.5 variable [2]
Characteristics
Spectral type	pec(UG)[2] (K1 V[3])
Apparent magnitude (B)	11.00[4]
Apparent magnitude (G)	14.7821[1]
Apparent magnitude (J)	13.106[5]
Apparent magnitude (H)	12.512[5]
Apparent magnitude (K)	12.390[5]
Variable type	Dwarf nova
Astrometry
Radial velocity (Rv)	-2[4] km/s
Proper motion (μ)	RA: −8.343±0.035[1] mas/yr ; Dec.: −9.835±0.030[1] mas/yr
Parallax (π)	1.6685 ± 0.0249[1] mas
Distance	1,950 ± 30 ly ; (599 ± 9 pc)
Orbit
Period (P)	10.6 hours[6]
Inclination (i)	45[7]°
Details[7]
White Dwarf
Mass	0.8 (assumed) M☉
Temperature	25,000 K
Donor star
Surface gravity (log g)	4.0 cgs
Temperature	5,000 K
Metallicity [Fe/H]	0 dex
Rotational velocity (v sin i)	79±5 km/s
Other designations
	2MASS J23294667+4345040
Database references
SIMBAD	data

DX Andromedae (often abbreviated to DX And) is a cataclysmic variable star in the constellation Andromeda. It has a typical apparent visual magnitude of 15.5 during the quiescent phase, but becomes brighter (up to a magnitude of 11.0) during outbursts recurring with a mean cycle length of 330 days[6], thus is classified as a dwarf nova of the SS Cygni type.[2]

System

The system of DX Andromedae consists of a white dwarf accreting matter from a donor star through an accretion disk. The system shows a spectral type at quiescence of K1 V (plus emission lines),[3] but the donor is considered to be a hydrogen-deficient star that has evolved off the main sequence and is overfilling its roche lobe. The donor star dominates the visible spectrum during the quiescent phase.[6][7]

The spectral classification of DX Andromedae as a whole is classified as peculiar of the U Geminorum type.[2] The spectrum of the donor star is itself peculiar; enhanced absorption lines of Ca_I and Cr_I have been observed.[3]

Variability

The outburst of dwarf novae are thought to arise from a thermal instability of the disk, that increases mass flow and temperature and hence the luminosity increases. In DX Andromedae different outbursts don't reach the same peak luminosity and don't occur at a regular rate, but they retain the same shape in the decaying part. It seems that the peak luminosity is correlated to the length of the preceding cycle, and the more luminous is the outburst, the faster the luminosity peak is reached. These trends can be explained by matter accumulating in the disk; more matter is accumulated in the disk during a longer cycle, and it can power a stronger outburst.[6]

gollark: *should stare at the times for four*

gollark: I need to stop procrastinating and measure the ToDs of the things I want to ND tomorrow.

gollark: Er, pretty sure he said 2 CBs.

gollark: Maybe someone offered a hatchling.

gollark: Strange.

References

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.
DX 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 2018-10-17.
Bruch, A.; Vrielmann, S.; Hessman, F. V.; Kochsiek, A.; Schimpke, T. (November 1997). "A spectroscopic study of the long-period dwarf nova DX Andromedae". Astronomy and Astrophysics. 327: 1107–1113. Bibcode:1997A&A...327.1107B.
"DX And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 1, 2018.
Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; et al. (June 2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues (2246): II/246. Bibcode:2003yCat.2246....0C.
Šimon, V. (2000). "Activity of DX Andromedae - the dwarf nova with a very long recurrence time of outbursts". Astronomy and Astrophysics. 364: 694–700. Bibcode:2000A&A...364..694S.
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.

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[Gaia-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. Gaia DR2 record for this source at VizieR.

[GCVS-2] DX 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 2018-10-17.

[Bruch1997-3] Bruch, A.; Vrielmann, S.; Hessman, F. V.; Kochsiek, A.; Schimpke, T. (November 1997). "A spectroscopic study of the long-period dwarf nova DX Andromedae". Astronomy and Astrophysics. 327: 1107–1113. Bibcode:1997A&A...327.1107B.

[Simbad-4] "DX And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 1, 2018.

[2MASS_Cat-5] Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; et al. (June 2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues (2246): II/246. Bibcode:2003yCat.2246....0C.

[Šimon2000-6] Šimon, V. (2000). "Activity of DX Andromedae - the dwarf nova with a very long recurrence time of outbursts". Astronomy and Astrophysics. 364: 694–700. Bibcode:2000A&A...364..694S.

[Harrison2018-7] 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.