HD 208527 is a star with an orbiting exoplanet located in the northern constellation of Pegasus. It has a reddish hue and is dimly visible to the naked eye with an apparent visual magnitude of +6.39.[2] The star is located at a distance of approximately 1,080 light years from the Sun based on parallax,[1] and is drifting further away with a radial velocity of +4.8 km/s.[3] It is currently the largest star known to have an exoplanet.

HD 208527
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Pegasus
Right ascension 21h 56m 23.984s[1]
Declination +21° 14′ 23.49″[1]
Apparent magnitude (V) +6.39[2]
Characteristics
Spectral type M1III[3]
B−V color index 1.698±0.002[2]
Astrometry
Radial velocity (Rv)+4.79±0.06[3] km/s
Proper motion (μ) RA: 1.433 mas/yr[1]
Dec.: 14.675 mas/yr[1]
Parallax (π)3.0302 ± 0.049 mas[1]
Distance1,080 ± 20 ly
(330 ± 5 pc)
Absolute magnitude (MV)–1.24[3]
Details[3]
Mass1.6±0.4 M
Radius57.6±6.5[4] R
Luminosity729±30[4] L
Surface gravity (log g)1.6±0.3 cgs
Temperature4,035±65 K
Metallicity [Fe/H]−0.09±0.16 dex
Rotational velocity (v sin i)3.6 km/s
Age2±1.3 Gyr
Other designations
BD+20° 5046, GJ 841.1, HD 208527, HIP 108296, HR 8372, SAO 90112[5]
Database references
SIMBADdata
Exoplanet Archivedata

This was once catalogued as a K-type main-sequence star with a stellar classification of K5V, but is now known as an aging red giant with a class of M1III, based on its dimensions and low surface gravity.[3] This indicates that the two-billion year old star has exhausted the supply of hydrogen at its core then cooled and expanded off the main sequence. It has an estimated 1.6[3] times the mass of the Sun but has swollen to 58 times the Sun's radius. The star is radiating 729[4] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,035 K.[3]

Planetary system

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From September 2008 to June 2012, the team B.-C. Lee, I. Han and M.-G. Park observed HD 208527 with "the high-resolution spectroscopy of the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at Bohyunsan Optical Astronomy Observatory (BOAO)".[3]

In 2012, a long-period, wide-orbiting exoplanet was deduced by radial velocity variations. This was published in November, gaining the designation HD 208527 b. Along with HD 220074 b this is one of the first two planets proposed around an M-type red giant.[3]

The HD 208527 planetary system[3]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
Eccentricity Inclination Radius
b ≥9.9±1.7 MJ 2.1±0.2 875.5±5.8 0.08±0.04

References

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  1. ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ a b c Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
  3. ^ a b c d e f g h i j k Lee, B.-C.; et al. (2012). "Planetary companions orbiting M giants HD 208527 and HD 220074". Astronomy & Astrophysics. 549: A2. arXiv:1211.2051. Bibcode:2013A&A...549A...2L. doi:10.1051/0004-6361/201220301. S2CID 73522393.
  4. ^ a b c Johns, Daniel; et al. (November 2018). "Revised Exoplanet Radii and Habitability Using Gaia Data Release 2". The Astrophysical Journal Supplement Series. 239 (1): 14. arXiv:1808.04533. Bibcode:2018ApJS..239...14J. doi:10.3847/1538-4365/aae5fb. 14.
  5. ^ "HD 208527". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-11-25.