Gliese 625

GJ 625 (AC 54 1646-56) is a small red dwarf star with an exoplanetary companion in the northern constellation of Draco. The system is located at a distance of 21.1 light-years from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −13 km/s.[4] It is too faint to be visible to the naked eye, having an apparent visual magnitude of 10.13[2] and an absolute magnitude of 11.06.[2]

Gliese 625
Observation data
Epoch J2000      Equinox J2000
Constellation Draco
Right ascension 16h 25m 24.6233s[1]
Declination 54° 18′ 14.7658″[1]
Apparent magnitude (V) 10.13[2]
Characteristics
Spectral type M1.5V[3]
B−V color index 1.591±0.027[2]
Astrometry
Radial velocity (Rv)−13.01±0.6[4] km/s
Proper motion (μ) RA: 432.073±0.064 mas/yr[1]
Dec.: −171.668±0.059 mas/yr[1]
Parallax (π)154.3503 ± 0.0161 mas[5]
Distance21.131 ± 0.002 ly
(6.4788 ± 0.0007 pc)
Absolute magnitude (MV)11.06[2]
Details
Mass0.240±0.013[6] M☉
Radius0.255±0.034[6] R☉
Luminosity0.01482±0.00022[7] L☉
Surface gravity (log g)4.94±0.06[8] cgs
Temperature3,557±9[4] K
Metallicity [Fe/H]−0.401±0.005[4] dex
Rotation77.8±5.57 d[8]
Rotational velocity (v sin i)2.2±0.7[4] km/s
Other designations
GJ 625, HIP 80459, AC +54 1646, G 202-48, G 226-7, G 225-62, LSPM J1625+5418, NLTT 42804, PLX 3740.03, TYC 3878-1193-1, 2MASS J16252459+5418148[9]
Database references
SIMBADdata

This is an M-type main-sequence star with a stellar classification of M1.5V.[3] It is spinning slowly with a rotation period of roughly 78 days, and has a low magnetic activity level.[8] The star has about a quarter of the mass and size of the Sun,[6] and the metal content is 40% the abundances in the Sun's atmosphere. It is radiating just 1.5% of the luminosity of the Sun from its photosphere at an effective temperature of 3,557 K.[4]

Planetary system

On May 18, 2017, a planet was detected orbiting AC 54 1646-56 by the HARPS-N telescope.[8] The planet, AC 54 1646-56b or (GJ 625b) orbits on the inner edge of the optimistic circumstellar habitable zone of its star, and may support liquid water. Since the star is considered quiescent (having a low X-ray emission and flare rate), the radio emission from the system may be auroral in nature and coming from a short-period planet. Further observations will be needed to confirm this.[10]

The Gliese 625 planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b 2.82±0.51 M🜨 0.078 14.628±0.013 — — —

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. 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. Alonso-Floriano, F. J.; et al. (May 2015). "CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS". Astronomy & Astrophysics. 577: 19. arXiv:1502.07580. Bibcode:2015A&A...577A.128A. doi:10.1051/0004-6361/201525803. S2CID 53135130. A128.
  4. Fouqué, Pascal; et al. (April 2018). "SPIRou Input Catalogue: global properties of 440 M dwarfs observed with ESPaDOnS at CFHT". Monthly Notices of the Royal Astronomical Society. 475 (2): 1960–1986. arXiv:1712.04490. Bibcode:2018MNRAS.475.1960F. doi:10.1093/mnras/stx3246.
  5. 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.
  6. Khata, Dhrimadri; et al. (April 2020). "Understanding the physical properties of young M dwarfs: NIR spectroscopic studies". Monthly Notices of the Royal Astronomical Society. 493 (3): 4533–4550. arXiv:2002.05762. Bibcode:2020MNRAS.493.4533K. doi:10.1093/mnras/staa427.
  7. Schweitzer, A.; et al. (May 2019). "The CARMENES search for exoplanets around M dwarfs. Different roads to radii and masses of the target stars". Astronomy & Astrophysics. 625: 16. arXiv:1904.03231. Bibcode:2019A&A...625A..68S. doi:10.1051/0004-6361/201834965. S2CID 102351979. A68. VizieR entry
  8. Suárez Mascareño, A.; et al. (2017). "HADES RV Programme with HARPS-N at TNG. V. A super-Earth on the inner edge of the habitable zone of the nearby M dwarf GJ 625". Astronomy and Astrophysics. 605. A92. arXiv:1705.06537. Bibcode:2017A&A...605A..92S. doi:10.1051/0004-6361/201730957. S2CID 119003137.
  9. "G 202-48". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-11-21.
  10. Pope, Benjamin J. S.; et al. (September 2021). "The TESS View of LOFAR Radio-emitting Stars". The Astrophysical Journal Letters. 919 (1): 8. arXiv:2110.04759. Bibcode:2021ApJ...919L..10P. doi:10.3847/2041-8213/ac230c. S2CID 238583021. L10.
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