OU Andromedae

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OU Andromedae
OUAndLightCurve.png
The light curve of an X-ray flare observed in 2001 by the Chandra X-ray Observatory is shown. This flare is believed to have been produced by a coronal mass ejection. (Adapted from Argiroffi et al., 2019 [1] )
Observation data
Epoch J2000       Equinox J2000
Constellation Andromeda
Right ascension 23h 49m 40.9598s [2]
Declination +36° 25′ 31.0082″ [2]
Apparent magnitude  (V)5.87 - 5.94 [3]
Characteristics
Spectral type G1 IIIe [4]
Apparent magnitude  (G)5.6187 [2]
Apparent magnitude  (J)4.723 [5]
Apparent magnitude  (H)4.208 [5]
Apparent magnitude  (K)4.097 [5]
B−V color index 0.79 [4]
Variable type FK Com [3]
Astrometry
Radial velocity (Rv)−1.89±0.25 [2]  km/s
Proper motion (μ)RA: −0.858±0.094 [2]   mas/yr
Dec.: −47.402±0.078 [2]   mas/yr
Parallax (π)7.1692 ± 0.0677  mas [2]
Distance 455 ± 4  ly
(139 ± 1  pc)
Details [6]
Mass 2.85  M☉
Radius 9.46  R☉
Luminosity 71.2  L☉
Surface gravity (log g)2.8  cgs
Temperature 5,360  K
Metallicity [Fe/H]−0.07  dex
Rotation 24.3 days
Rotational velocity (v sin i)21.5 km/s
Age 645 –891 [7]   Myr
Other designations
2MASS J23494097+3625309, FK5 3914, HIP 117503, SAO 73535, BD+35°5110, HR 9024, HD 223460
Database references
SIMBAD data

OU Andromedae (also HR 9024) is a rotationally variable star in the constellation Andromeda. Varying between magnitudes 5.87 and 5.94, it has been classified as an FK Comae Berenices variable, but the classification is still uncertain. It has a spectral classification of G1IIIe, meaning that it is a giant star that shows emission lines in its spectrum. [3] It is also likely in its horizontal branch phase of evolution. [7]

Contents

In 1985, Jeffrey Hopkins et al. discovered that HR 9024 is a variable star, with a period of ~23.3 days. [8] It was given the variable star designation OU Andromedae in 1986. [9] Paola Testa et al. reported that the star showed X-ray flare activity, in 2007. [10]

Fast rotation

The spin rate of OU Andromedae is unusually high for an evolved star of this type, showing a projected rotational velocity of 21.5 km/s. One possible explanation is that it may have engulfed a nearby giant planet, such as a hot Jupiter, since an infrared excess has been observed. [4] Another explanation relies on its strong magnetic field; if OU Andromedae was an Ap star during its main sequence stage of evolution, it could have retained both the strong magnetic field and the fast rotation of Ap stars. [6]

X-ray source

OU Andromedae is a bright X-ray source, due to the activity of its corona; it's estimated that solar-like active regions cover 30% of the surface. This is another effect of the strong magnetic field, which produces an uninterrupted flaring activity that generates a large volume of hot plasma at coronal temperatures (~7.5×106 K). [11]

Related Research Articles

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<span class="mw-page-title-main">28 Andromedae</span> Star in the constellation Andromeda

28 Andromedae is a Delta Scuti variable star in the constellation Andromeda. 28 Andromedae is the Flamsteed designation. It also bears the variable star name GN Andromedae. Its apparent magnitude is 5.214, varying by less than 0.1 magnitudes.

<span class="mw-page-title-main">13 Andromedae</span> Star in the constellation Andromeda

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Z Andromedae is a binary star system consisting of a red giant and a white dwarf. It is the prototype of a type of cataclysmic variable star known as symbiotic variable stars or simply Z Andromedae variables. The brightness of those stars vary over time, showing a quiescent, more stable phase and then an active one with a more pronounced variability and stronger brightening and/or dimming.

<span class="mw-page-title-main">FK Comae Berenices</span> Star in the constellation of Coma Berenices

FK Comae Berenices is a variable star that varies in apparent magnitude between 8.14 and 8.33 over a period of 2.4 days. It is the prototype for the FK Comae Berenices class of variable stars. The variability of FK Com stars may be caused by large, cool spots on the rotating surfaces of the stars. This star is thought to be the result of a recent binary merger, resulting in a high rate of both spin and magnetic activity.

<span class="mw-page-title-main">HD 4778</span> Star in the constellation Andromeda

HD 4778, also known as HR 234 and GO Andromedae, is a variable star in the constellation Andromeda. Its magnitude varies by 0.04 magnitudes from the median of 6.12 with a period of approximately 2.55 days. The star is located 350 light years away, as determined from its annual parallax shift of 9.32 mas.

HD 224801, also known as CG Andromedae, is an Alpha² Canum Venaticorum variable star in the constellation Andromeda. Located approximately 188 parsecs (610 ly) away, the star varies between apparent magnitudes 6.32 and 6.42 over a period of approximately 3.74 days.

<span class="mw-page-title-main">LN Andromedae</span> Star in the constellation Andromeda

LN Andromedae, also known as HD 217811, HR 8768, is a formerly suspected variable star in the constellation Andromeda. Located approximately 458 parsecs (1,490 ly) away from Earth, it shines with an apparent visual magnitude 6.41, thus it can be seen by the naked eye under very favourable conditions. Its spectral classification is B2V, meaning that it's a hot main sequence star, emitting light approximately with a blackbody spectrum at an effective temperature of 18,090 K.

<span class="mw-page-title-main">V385 Andromedae</span> Star in the constellation Andromeda

V385 Andromedae is a variable star in the constellation Andromeda, about 360 parsecs (1,200 ly) away. It is a red giant over a hundred times larger than the sun. It has an apparent magnitude around 6.4, just about visible to the naked eye in ideal conditions.

<span class="mw-page-title-main">ET Andromedae</span> Star in the constellation Andromeda

ET Andromedae is a binary star system star in the northern constellation of Andromeda. It has an apparent visual magnitude of 6.48, placing it at the nominal limit for visibility with the naked eye. The distance to this system can be estimated from its annual parallax shift of 5.42 mas, which yields a value of 602 light years.

<span class="mw-page-title-main">RT Andromedae</span> Star in the constellation Andromeda

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<span class="mw-page-title-main">SU Andromedae</span> Star in the constellation Andromeda

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Gamma Comae Berenices, Latinized from γ Comae Berenices, is a single, orange-hued star in the northern constellation of Coma Berenices. It is faintly visible to the naked eye, having an apparent visual magnitude of 4.36. Based upon an annual parallax shift of 19.50 mas as seen from Earth, its distance can be estimated as around 167 light years from the Sun. The star is moving away from the Sun with a radial velocity of +3 km/s.

<span class="mw-page-title-main">37 Comae Berenices</span> Triple-star system in the constellation Coma Berenices

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31 Comae Berenices is a yellow giant star in the constellation Coma Berenices. Its apparent magnitude is about 4.9 and slightly variable. It is a rare FK Comae Berenices variable, a variable star that spins rapidly and has large starspots on its surface. It is currently in the Hertzsprung gap and its outer envelope has just begun convection. In 1989 it was given as a spectral standard for the class G0IIIp.

QV Andromedae is an Alpha2 Canum Venaticorum variable in the constellation Andromeda. Its maximum apparent visual magnitude is 6.6, so it can be seen by the naked eye under very favourable conditions. The brightness varies slightly following a periodic cycle of approximately 5.23 days.

<span class="mw-page-title-main">EG Andromedae</span> Binary star system in the constellation Andromeda

EG Andromedae is a symbiotic binary in the constellation Andromeda. Its apparent visual magnitude varies between 6.97 and 7.80.

<span class="mw-page-title-main">FF Andromedae</span> Star in the constellation Andromeda

FF Andromedae is a spectroscopic binary in the constellation Andromeda. It has a typical apparent visual magnitude of 10.4, but undergoes flare events that can increase its brightness by about a magnitude.

<span class="mw-page-title-main">GR Andromedae</span> Variable star in the constellation Andromeda

GR Andromedae is a variable star in the constellation Andromeda. Its apparent visual magnitude varies between 6.87 and 6.95 in a cycle of 518.2 days. It is classified as an α2 Canum Venaticorum variable.

<span class="mw-page-title-main">QX Andromedae</span> Eclipsing binary star system in the constellation Andromeda

QX Andromedae is an eclipsing binary in the constellation Andromeda. It varies from a maximum apparent visual magnitude of 11.28 to a minimum of 11.50. Since it is impossible to specify the onset time of the eclipses, it is classified as a W Ursae Majoris variable star. It is also observed as an X-ray source and is a member of the open cluster NGC 752.

References

  1. ↑ Argiroffi, C.; Reale, F.; Drake, J. J.; Ciaravella, A.; Testa, P.; Bonito, R.; Miceli, M.; Orlando, S.; Peres, G. (August 2019). "A stellar flare-coronal mass ejection event revealed by X-ray plasma motions". Nature Astronomy. 3: 742–748. arXiv: 1905.11325 . doi:10.1038/s41550-019-0781-4. S2CID   256704200.
  2. 1 2 3 4 5 6 7 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. 1 2 3 N. N. Samus; O. V. Durlevich; et al. "OU And database entry". Combined General Catalog of Variable Stars (2017 ed.). CDS . Retrieved 2018-11-12.
  4. 1 2 3 Rodrigues da Silva, R.; et al. (March 2015). "On the Nature of Rapidly Rotating Single Evolved Stars". The Astrophysical Journal. 801 (1): 6. arXiv: 1503.03447 . Bibcode:2015ApJ...801...54R. doi:10.1088/0004-637X/801/1/54. S2CID   119271718. 54.
  5. 1 2 3 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. 1 2 Borisova, A.; Aurière, M.; Petit, P.; Konstantinova-Antova, R.; Charbonnel, C.; Drake, N. A. (June 2016). "The different origins of magnetic fields and activity in the Hertzsprung gap stars, OU Andromedae and 31 Comae". Astronomy & Astrophysics. 591: 15. arXiv: 1604.07647 . Bibcode:2016A&A...591A..57B. doi:10.1051/0004-6361/201526726. S2CID   55676875. A57.
  7. 1 2 Stock, S.; Reffert, S.; Quirrenbach, A. (August 2018). "Precise radial velocities of giant stars. X. Bayesian stellar parameters and evolutionary stages for 372 giant stars from the Lick planet search". Astronomy & Astrophysics. 616: 15. arXiv: 1805.04094 . Bibcode:2018A&A...616A..33S. doi:10.1051/0004-6361/201833111. S2CID   119361866. A33.
  8. ↑ Hopkins, J. L.; Boyd, L. J.; Genet, R. M.; Hall, D. S. (March 1985). "Discovery of Variability in HR 9024" (PDF). Information Bulletin on Variable Stars. 2684: 1. Bibcode:1985IBVS.2684....1H . Retrieved 7 February 2023.
  9. ↑ Kholopov, P. N.; Samus, N. N.; Kazarovets, E. V.; Kireeva, N. N. (August 1987). "The 68th Name-List of Variable Stars" (PDF). Information Bulletin on Variable Stars. 3058: 1. Bibcode:1987IBVS.3058....1K . Retrieved 7 February 2023.
  10. ↑ Testa, Paola; Reale, Fabio; Garcia-Alvarez, David; Huenemoerder, David P. (July 2007). "Detailed Diagnostics of an X-Ray Flare in the Single Giant HR 9024". The Astrophysical Journal. 663 (2): 1232–1243. arXiv: astro-ph/0703422 . Bibcode:2007ApJ...663.1232T. doi:10.1086/518241. S2CID   17916110 . Retrieved 7 February 2023.
  11. ↑ Gondoin, P. (October 2003), "The corona of HD 223460 (HR 9024)", Astronomy and Astrophysics, 409: 263–274, Bibcode:2003A&A...409..263G, doi: 10.1051/0004-6361:20030978
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