QR Andromedae

QR Andromedae (often abbreviated to QR And) is an eclipsing binary star in the constellation Andromeda. Its maximum apparent visual magnitude is 12.16, but its light curve shows clearly eclipsing events where its brightness can drop to a magnitude of 13.07.[6] This leads to its classification as an Algol variable star.[3]

QR Andromedae

The visual band light curve of QR Andromedae (adapted from Matsumoto (1996)), The phase is with respect to the 15.85 hour orbital period.[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Andromeda
Right ascension 00h 19m 49.9253s[2]
Declination +21° 56′ 52.1666″[2]
Apparent magnitude (V) 12.16 – 13.07 variable[3]
Characteristics
Spectral type pec(e)[3]
Apparent magnitude (B) 12.38[4]
Apparent magnitude (R) 11.86[4]
Apparent magnitude (G) 12.2395[2]
Apparent magnitude (J) 12.432[5]
Apparent magnitude (H) 12.295[5]
Apparent magnitude (K) 12.092[5]
Variable type Algol[3]
Astrometry
Proper motion (μ) RA: 18.469±0.071 [2] mas/yr
Dec.: −5.529±0.079[2] mas/yr
Parallax (π)0.4993 ± 0.0452 mas[2]
Distance6,500 ± 600 ly
(2,000 ± 200 pc)
Orbit
Period (P)0.6604 days[4]
Semi-amplitude (K1)
(primary)		61.8±4.4[6] km/s
Other designations
2MASS J00194992+2156521, AAVSO 0014+21
Database references
SIMBADdata

Spectrum

The optical spectrum of QR Andromedae is not of a typical stellar blackbody, but is peculiar with many emission lines,[3] the strongest being the HeII line. Balmer series and OVI lines are also present. It was also one of the super soft X-ray sources discovered by ROSAT satellite, one of the few source of this kind observed so far in the Milky Way.[6]

System

It is now commonly accepted that super soft X-ray sources are white dwarfs that are burning matter with nuclear fusion on their surfaces, sustained by a high accretion rate of matter coming from a companion star. QR Andromedae is the nearest and brightest of those sources, and it has an orbital period of 15.85 hours. The companion star has a mass between 0.3 – 0.5 M☉ and should be a remnant of a more massive evolved star that is filling its Roche lobe.[6]

Variability

Photographic plates from the Harvard College and Sonneberg observatories have recorded QR Andromedae's brightness history since the late 19th century. Jochen Greiner and Wolfgang Wenzel constructed a 100 year light curve for the star. They found that the light curve exhibited brightness changes of up to one magnitude, on a variety of timescales. They proposed that this was the result of unstable mass transfers onto the white dwarf, triggering sporadic hydrogen burning.[7]

Eclipses in the light curve of QR Andromedae are not symmetrical: the ingress is more gradual than the egress. The secondary minimum is variable in occurring phase and depth, meaning that the occultation of the secondary star happens behind a variable part of the disk. Out of the eclipses, light flickering can be clearly seen, and in some observations a periodicity arises.[6]

References
  1. Matsumoto, Katsura (1 December 1996). "BVRI Photometric Light Curves of the Galactic Supersoft X-Ray Source RX J0019.8+2156". Publications of the Astronomical Society of Japan. 48 (6): 827–831. doi:10.1093/pasj/48.6.827. Retrieved 5 October 2021.
  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. N. N. Samus; O. V. Durlevich; et al. "QR And database entry". Combined General Catalog of Variable Stars (2017 ed.). CDS. Retrieved 2018-11-12.
  4. Norton, A. J.; Wheatley, P. J.; West, R. G.; Haswell, C. A.; Street, R. A.; Collier Cameron, A.; Christian, D. J.; Clarkson, W. I.; Enoch, B.; Gallaway, M.; Hellier, C.; Horne, K.; Irwin, J.; Kane, S. R.; Lister, T. A.; Nicholas, J. P.; Parley, N.; Pollacco, D.; Ryans, R.; Skillen, I.; Wilson, D. M. (2007). "New periodic variable stars coincident with ROSAT sources discovered using SuperWASP". Astronomy and Astrophysics. 467 (2): 785. arXiv:astro-ph/0702631. Bibcode:2007A&A...467..785N. doi:10.1051/0004-6361:20077084. S2CID 16358048.
  5. Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (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.
  6. McGrath, T. K.; Schmidtke, P. C.; Cowley, A. P.; Ponder, A. L.; Wagner, R. M. (2001). "Simultaneous Photometry and Spectroscopy of the Supersoft X-Ray Source RX J0019.8+2156 (QR Andromedae)". The Astronomical Journal. 122 (3): 1578–1585. Bibcode:2001AJ....122.1578M. doi:10.1086/322109.
  7. Greiner, J.; Wenzel, W. (February 1995). "Optical variability of the supersoft source RXJ0019.8+2156". Astronomy and Astrophysics. 294: L5–L8. arXiv:astro-ph/9411113. Bibcode:1995A&A...294L...5G. Retrieved 9 February 2023.
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