AO Serpentis

A visual band light curve for AO Serpentis, plotted from ASAS-SN data[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Serpens
Right ascension 15h 58m 18.410s[2]
Declination +17° 16′ 10.00″[2]
Apparent magnitude (V) 11.04±0.09[3]
Characteristics
Spectral type A2[4]
B−V color index 0.22[3]
Variable type β Per + δ Sct[5]
Astrometry
Primary
Proper motion (μ) RA: −8.236 mas/yr[2]
Dec.: −10.444 mas/yr[2]
Parallax (π)2.2539 ± 0.0229 mas[2]
Distance1,450 ± 10 ly
(444 ± 5 pc)
Absolute magnitude (MV)+1.88±0.03
Secondary
Absolute magnitude (MV)+5.17±0.05
Orbit[5]
Period (P)0.8793496±0.0000047 d
Semi-major axis (a)5.59±0.05 R☉
Inclination (i)90.0±1.5°
Longitude of the node (Ω)3.645±0.002°
Periastron epoch (T)2,457,127.5076±0.0041 HJD
Semi-amplitude (K1)
(primary)		51.6±1.1 km/s
Semi-amplitude (K2)
(secondary)		270.3±3.6 km/s
Details[5]
Primary
Mass2.55±0.09 M☉
Radius1.64±0.02 R☉
Luminosity14.45+0.69
−0.65 L☉
Surface gravity (log g)4.42±0.01 cgs
Temperature8,820±62 K
Rotational velocity (v sin i)90±18 km/s
Secondary
Mass0.49±0.02 M☉
Radius1.38±0.02 R☉
Luminosity0.93+0.05
−0.04 L☉
Surface gravity (log g)3.85±0.01 cgs
Temperature4,786±11[4] K
Other designations
AO Ser, BD+17°2942, TYC 1496-3-1, GSC 01496-00003, 2MASS J15581840+1716101[6]
Database references
SIMBADdata

AO Serpentis is an eclipsing binary star system in the Serpens Caput segment of the Serpens constellation. It is invisible to the naked eye with a typical apparent visual magnitude of 11.04.[3] Variable star observers record a peak magnitude of 10.7, dropping to 12.0 during the primary eclipse and 10.8 from the secondary eclipse.[7] The distance to this system is approximately 1,450 light years based on parallax measurements.[2]

This system was discovered by C. Hoffmeister to be an Algol-type eclipsing binary in 1935.[8] The following year, P. Guthnick and R. Prager reported a brightness variation between 10.5 and 12.0.[9] In 2004, S. -L. Kim and associates determined that one of the components of this system is pulsating with a short period.[10]

This is a semi-detached binary star system with the secondary component completely filling its Roche lobe while the primary is 61% full. It has an orbital period of 21.1 hours and a semimajor axis of just 5.6 times the radius of the Sun. The orbital plane is inclined by an angle of 90° to the line of sight, causing the secondary component to be completely eclipsed once per orbit.[5] The orbital period shows long-term cyclic variations, changing by up to 0.0051 days every 17.32 years. This may be due to magnetic activity cycles or the influence of a third body. The orbital period as a whole is steadily decreasing at the rate of (−5.39±0.03)×10−7 days yr−1 due to loss of mass and angular momentum by the system.[4]

The physical properties of the stellar components can be explained by a mass transfer. At some point in the past, mass flowed from the (at the time) more massive and evolved secondary component. This has left the primary as an A-type main-sequence star while the secondary is less massive but overly large. The hotter primary component is a Delta Scuti variable that is undergoing radial pulsation with a dominant frequency of 21.852 days−1 and a secondary frequency of 23.484 days−1.[5]

References

  1. ↑ "ASAS-SN Variable Stars Database". ASAS-SN Variable Stars Database. ASAS-SN. Retrieved 6 January 2022.
  2. 1 2 3 4 5 6 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.
  3. 1 2 3 Høg, E.; et al. (2000), "The Tycho-2 catalogue of the 2.5 million brightest stars", Astronomy and Astrophysics, 355: L27, Bibcode:2000A&A...355L..27H, doi:10.1888/0333750888/2862, ISBN 978-0333750889.
  4. 1 2 3 Yang, Y. -G.; et al. (April 2010), "Photometric Properties for Selected Algol-type Binaries. II. AO Serpentis and V338 Herculis", The Astronomical Journal, 139 (4): 1360–1368, Bibcode:2010AJ....139.1360Y, doi:10.1088/0004-6256/139/4/1360, S2CID 122306646.
  5. 1 2 3 4 5 Park, Jang-Ho; et al. (December 2020), "Physical Nature of the Eclipsing δ Scuti Star AO Serpentis", The Astronomical Journal, 160 (6): 9, arXiv:2010.02441, Bibcode:2020AJ....160..247P, doi:10.3847/1538-3881/abbef4, S2CID 222141749, 247.
  6. ↑ "AO Ser". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-02-19.
  7. ↑ Samus', N. N; et al. (2017), "General catalogue of variable stars", Astronomy Reports, GCVS 5.1, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  8. ↑ Hoffmeister, Cuno (June 1935), "162 neue Veräderliche", Astronomische Nachrichten, 255 (22): 401, Bibcode:1935AN....255..401H, doi:10.1002/asna.19352552202.
  9. ↑ Guthnick, P.; Prager, R. (October 1936), "Benennung von veränderlichen Sternen", Astronomische Nachrichten, 260 (22): 393, Bibcode:1936AN....260..393G, doi:10.1002/asna.19362602202.
  10. ↑ Kim, S. -L.; et al. (June 2004), "Discovery of a short-periodic pulsating component in the Algol-type eclipsing binary system AO Ser", Information Bulletin on Variable Stars, 5538: 1, Bibcode:2004IBVS.5538....1K.
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