HD 70573

HD 70573 is a variable star in the equatorial constellation of Hydra. At a mean apparent visual magnitude of +8.71,[2] this yellow-hued star is too dim to be visible to the naked eye. Based upon parallax measurements, it is located at a distance of 193 light years from the Sun, and is drifting further away with a radial velocity of 20.5 km/s.[1] It is a candidate member of the proposed Hercules-Lyra Association of co-moving stars,[4] although this membership is disputed.[9]

HD 70573
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hydra
Right ascension 08h 22m 49.95284s[1]
Declination +01° 51′ 33.5542″[1]
Apparent magnitude (V) +8.711[2]
Characteristics
Evolutionary stage main sequence
Spectral type G1/2V[3]
B−V color index 0.59[4]
Variable type BY Dra[5]
Astrometry
Radial velocity (Rv)20.46±0.28[1] km/s
Proper motion (μ) RA: -51.434[1] mas/yr
Dec.: -49.185[1] mas/yr
Parallax (π)16.8683 ± 0.0443[1] mas
Distance193.4 ± 0.5 ly
(59.3 ± 0.2 pc)
Absolute magnitude (MV)+0.4[6]
Details
Mass1.0±0.1[6] M☉
Radius0.98+0.01
−0.03[1] R☉
Luminosity0.998±0.004[1] L☉
Surface gravity (log g)4.59±0.10[6] cgs
Temperature5,837+80
−51[1] K
Metallicity [Fe/H]−0.18±0.20[6] dex
Rotation3.296 days[6]
Rotational velocity (v sin i)14.7±1.0[6] km/s
Age60+65
−30[7] Myr
Other designations
V478 Hya, NSV 17868, BD+02°1951, SAO 116694[8]
Database references
SIMBADdata

This is a G-type main-sequence star with a stellar classification of G1/2V.[3] It is a BY Draconis variable that ranges in brightness from magnitude 8.66 down to 8.77 with a rotationally-modulated period of 3.296 days.[5] This is a young star with an age of around 60[7] million years and a projected rotational velocity of 15 km/s.[6] It has about the same mass, size, and luminosity as the Sun.

Planetary system

On March 19, 2007, an extrasolar planet was announced, having been discovered by the radial velocity method. This is thus far (as of 2007) the youngest host star discovered to have an orbiting planet.[6] The system displays an infrared excess, which matches the black body signature of a debris disk orbiting 21.8 AU from the host star with a mean temperature of 60 K.[10]

The HD 70573 planetary system[6]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b ≥6.1±0.4 MJ 1.76±0.05 851.8±11.6 0.4±0.1 — —

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. Kiraga, M. (March 2012). "ASAS Photometry of ROSAT Sources. I. Periodic Variable Stars Coincident with Bright Sources from the ROSAT All Sky Survey". Acta Astronomica. 62 (1): 67–95. arXiv:1204.3825. Bibcode:2012AcA....62...67K.
  3. Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars". Michigan Spectral Survey. 5. Bibcode:1999MSS...C05....0H.
  4. López-Santiago, J.; et al. (2006). "The Nearest Young Moving Groups". The Astrophysical Journal. 643 (2): 1160–1165. arXiv:astro-ph/0601573. Bibcode:2006ApJ...643.1160L. doi:10.1086/503183. S2CID 119520529.
  5. 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.
  6. Setiawan; et al. (2007). "Evidence for a Planetary Companion around a Nearby Young Star". The Astrophysical Journal Letters. 660 (2): L145–L148. arXiv:0704.0441. Bibcode:2007ApJ...660L.145S. doi:10.1086/518213. S2CID 18721503.
  7. Meshkat, Tiffany; et al. (December 2017). "A Direct Imaging Survey of Spitzer-detected Debris Disks: Occurrence of Giant Planets in Dusty Systems". The Astronomical Journal. 154 (6): 21. arXiv:1710.04185. Bibcode:2017AJ....154..245M. doi:10.3847/1538-3881/aa8e9a. S2CID 42042014. 245.
  8. "HD 70573". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-01-08.
  9. Eisenbeiss, T.; et al. (August 2013). "The Hercules-Lyra association revisited. New age estimation and multiplicity study". Astronomy & Astrophysics. 556: 19. arXiv:1312.4045. Bibcode:2013A&A...556A..53E. doi:10.1051/0004-6361/201118362. S2CID 119275785. A53.
  10. Cotten, Tara H.; Song, Inseok (July 2016). "A Comprehensive Census of Nearby Infrared Excess Stars". The Astrophysical Journal Supplement Series. 225 (1): 24. arXiv:1606.01134. Bibcode:2016ApJS..225...15C. doi:10.3847/0067-0049/225/1/15. S2CID 118438871. 15.

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