HD 202628

HD 202628 is a single[8] star in the southern constellation of Microscopium. It has an apparent visual magnitude of +6.7,[2] which makes it too faint to be readily visible to the naked eye. The star is located at a distance of 77.7 light years from the Sun based on parallax,[1] and it is drifting further away with a radial velocity of +12.1 km/s.[2] The absolute magnitude of this star is 4.86.[2]

HD 202628
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Microscopium
Right ascension 21h 18m 27.26933s[1]
Declination −43° 20′ 04.7461″[1]
Apparent magnitude (V) +6.742±0.004[2]
Characteristics
Spectral type G1.5V[2]
B−V color index +0.637±0.001[3]
Astrometry
Radial velocity (Rv)+12.071±0.0027[2] km/s
Proper motion (μ) RA: +242.190[1] mas/yr
Dec.: +21.633[1] mas/yr
Parallax (π)41.9622 ± 0.0455[1] mas
Distance77.73 ± 0.08 ly
(23.83 ± 0.03 pc)
Absolute magnitude (MV)4.856±0.005[2]
Details[4]
Mass1.068±0.038 M☉
Radius0.951±0.013 R☉
Luminosity0.951±0.026 L☉
Surface gravity (log g)4.510±0.011 cgs
Temperature5,843±6 K
Metallicity [Fe/H]0.003±0.004 dex
Rotational velocity (v sin i)2.64±0.11[5] km/s
Age1.1±0.4 Gyr
2.3±1[6] Gyr
Other designations
CD−43°14464, GJ 825.2 & 9730, HD 202628, HIP 105184, SAO 230622, LTT 8444[7]
Database references
SIMBADdata
Exoplanet Archivedata
Extrasolar Planets
Encyclopaedia		data

The stellar classification of HD 202628 is G1.5V,[2] matching a yellow-hued G-type main-sequence star similar to the Sun. The chromospheric activity level and amount of X-ray emission is consistent with a star that is younger that the Sun.[6] It is spinning with a projected rotational velocity of 2.6 km/s.[5] The star has 107% of the mass of the Sun and 95% of the Sun's radius. The metalicity, or abundance of heavier elements, appears to be about the same as in the Sun. It is radiating 95% of the luminosity of the Sun from its photosphere at an effective temperature of 5,843 K.[4]

In 2010, an infrared excess from a circumstellar disk of dust was detected around this star by the Spitzer Space Telescope. The net emission at 70 microns (70 μm) is almost 20 times as high as the star's flux at this wavelength.[2] The disk has been directly imaged by the Hubble Space Telescope.[6] It is oval-shaped with an orbital eccentricity of 0.18, and is inclined at 64° to the line of sight from the Earth. The inner edge of the ring, which lies at around 158 AU from the star, is sharply defined.[6] This suggests that there is an exoplanet responsible for this defined edge, and it has been calculated as orbiting between 86 and 158 AU from HD 202628.[9]

The HD 202628 planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(years)		 Eccentricity Inclination Radius
b (unconfirmed) > 1 M⊕ 86-158[9] — ~ 0.2 — —
Disk 150–220 AU 64°° —

References
  1. 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.
  2. Faramaz, Virginie; et al. (October 2019), "From Scattered-light to Millimeter Emission: A Comprehensive View of the Gigayear-old System of HD 202628 and its Eccentric Debris Ring", The Astronomical Journal, 158 (4): 21, arXiv:1909.04162, Bibcode:2019AJ....158..162F, doi:10.3847/1538-3881/ab3ec1, 162.
  3. 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.
  4. Gáspár, András; et al. (2016), "The Correlation between Metallicity and Debris Disk Mass", The Astrophysical Journal, 826 (2): 171, arXiv:1604.07403, Bibcode:2016ApJ...826..171G, doi:10.3847/0004-637X/826/2/171.
  5. dos Santos, Leonardo A.; et al. (August 2016), "The Solar Twin Planet Search. IV. The Sun as a typical rotator and evidence for a new rotational braking law for Sun-like stars", Astronomy & Astrophysics, 592 (156): 8, arXiv:1606.06214, Bibcode:2016A&A...592A.156D, doi:10.1051/0004-6361/201628558, A156.
  6. Krist, John E.; et al. (2012), "Hubble Space Telescope Observations of the HD 202628 Debris Disk", The Astronomical Journal, 144 (2): 9, arXiv:1206.2078, Bibcode:2012AJ....144...45K, doi:10.1088/0004-6256/144/2/45, 45.
  7. "9 Cet". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-12-23.
  8. Fuhrmann, K.; et al. (February 2017), "Multiplicity among Solar-type Stars", The Astrophysical Journal, 836 (1): 23, Bibcode:2017ApJ...836..139F, doi:10.3847/1538-4357/836/1/139, 139.
  9. Nesvold, Erika R.; Kuchner, Marc J. (2015), "Gap Clearing by Planets in a Collisional Debris Disk", The Astrophysical Journal, 798 (2): 10, arXiv:1410.7784, Bibcode:2015ApJ...798...83N, doi:10.1088/0004-637X/798/2/83, 83.
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