 A visual band light curve for IW Andromedae, plotted from AAVSO data | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 01 01 08.907 |
| Declination | 43° 23′ 25.79″ |
| Apparent magnitude (V) | 13.7 to 17.3 |
| Characteristics | |
| Spectral type | sdOB |
| Variable type | Z Cam(?) |
| Astrometry | |
| Proper motion (μ) | RA: +2.471 mas/yr Dec.: −5.904 mas/yr |
| Parallax (π) | 1.1413 ± 0.0326 mas |
| Distance | 2,860 ± 80 ly (880 ± 30 pc) |
| Details | |
| White dwarf | |
| Mass | 0.75 M☉ |
| Radius | 0.015 R☉ |
| Temperature | 25,000 K |
| Donor star | |
| Mass | 0.27 M☉ |
| Other designations | |
| IW And, 2MASS J01010890+4323257, AAVSO 0055+42 | |
| Database references | |
| SIMBAD | data |
IW Andromedae is a binary star system in the northern constellation of Andromeda, abbreviated IW And. It is the prototype of a class of variable stars known as IW And variables, which is an anomalous sub-class of the Z Camelopardalis (Z Cam) variables. The brightness of this system ranges from an apparent visual magnitude of 13.7 down to 17.3, which requires a telescope to view. The system is located at a distance of approximately 2,860 light years from the Sun based on parallax measurements.
The irregular variability of this star was discovered by L. Meinunger in 1975. The spectra was found to resemble a blue–hued OB star with some peculiarities. It is a confirmed cataclysmic variable (CV) but its properties differ markedly from other sub-classes of that type. The photometric behavior of the star is dissimilar to that of a dwarf or polar nova as it shows rapid brightening of up to three magnitudes in periods of around a day, but stays in a low excitement state about 72% of the time. Evidence for weak emission of the hydrogen–alpha line was discovered by W. Liu and associates in 1999.
This is a close binary system with an orbital period of 223 minutes (3.7 hours). The primary component is a white dwarf star with 75% of the mass of the Sun. The secondary component has 27% of the Sun's mass and is overflowing its Roche lobe, resulting in mass transfer to an accretion disk orbiting the primary. The accretion rate for the primary is 3×10 M☉·yr.
T. Kato and associates in 2003 found the light curve matched a Z Cam variable, with the previously observed inactive states being caused by a characteristic standstill. The duty cycle of its standstill is unusually long for a variable of this class. Outbursts during these standstills may be explained by flares on the secondary, which result in brief surges in mass transfer.
Other variables displaying IW And–type behavior have since been discovered, including HO Puppis, BC Cassiopeiae, IM Eridani, V507 Cygni, and FY Vulpecula.
References
- "Download Data", aavso.org, AAVSO, retrieved 9 April 2023.
- ^ Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
- ^ Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
- Meinunger, L. (May 1980), "Spectra of Four Blue Irregular Variables in Andromeda", Information Bulletin on Variable Stars, 1795: 1, Bibcode:1980IBVS.1795....1M.
- ^ Szkody, Paula; et al. (December 2013), "A Study of the Unusual Z Cam Systems IW Andromedae and V513 Cassiopeia", Publications of the Astronomical Society of the Pacific, 125 (934): 1421–1428, arXiv:1311.1557, Bibcode:2013PASP..125.1421S, doi:10.1086/674170, S2CID 118631716.
- "IW ANd". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2023-04-07.
- ^ Kato, Taichi (January 2019), "Three Z Camelopardalis-type dwarf novae exhibiting IW Andromedae-type phenomenon", Publications of the Astronomical Society of Japan, 71 (1): 20, arXiv:1811.05038, Bibcode:2019PASJ...71...20K, doi:10.1093/pasj/psy138, 20.
- Meinunger, L. (1975), "Veränderliche in einem Feld um ν Andromedae", Mitteilungen über Veränderliche Sterne, 7: 1–21, Bibcode:1975MitVS...7....1M.
- ^ Liu, Wu; et al. (May 1999), "Spectroscopic Confirmation of 55 Northern and Equatorial Cataclysmic Variables. I. 27 Confirmed Cataclysmic Variables", The Astrophysical Journal Supplement Series, 122 (1): 243–255, Bibcode:1999ApJS..122..243L, doi:10.1086/313210, S2CID 122899189.
- ^ Kato, Taichi; et al. (February 2003), "IW And is a Z Cam-Type Dwarf Nova", Information Bulletin on Variable Stars, 5376: 1, arXiv:astro-ph/0204353, Bibcode:2003IBVS.5376....1K.
- Meinunger, L.; Andronov, I. L. (September 1987), "Photometric Study of the Blue Variables IW, IZ and IO Andromedae", Information Bulletin on Variable Stars, 3081: 1, Bibcode:1987IBVS.3081....1M.
- Hameury, J. -M.; Lasota, J. -P. (September 2014), "Anomalous Z Cam stars: a response to mass-transfer outbursts", Astronomy & Astrophysics, 569: A48, arXiv:1407.3156, Bibcode:2014A&A...569A..48H, doi:10.1051/0004-6361/201424535, S2CID 119238557, A48.
- Lee, Chien-De; et al. (April 2021), "HO Puppis: Not a Be Star, but a Newly Confirmed IW And-type Star", The Astrophysical Journal, 911 (1): 51, arXiv:2102.09748, Bibcode:2021ApJ...911...51L, doi:10.3847/1538-4357/abe871, S2CID 231979353, 51.
- Kato, Taichi; Kojiguchi, Naoto (December 2020), "BC Cassiopeiae: First detection of IW Andromedae-type phenomenon among post-eruption novae", Publications of the Astronomical Society of Japan, 72 (6): 98, arXiv:2009.12993, Bibcode:2020PASJ...72...98K, doi:10.1093/pasj/psaa096, 98.
| Constellation of Andromeda | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Stars |
| ||||||||||||
| |||||||||||||
| Star clusters |
| ||||||||||||
| Nebulae |
| ||||||||||||
| Galaxies |
| ||||||||||||
| |||||||||||||
| |||||||||||||
 Category | |||||||||||||