HD 195019

HD 195019

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Delphinus
Right ascension	20^h 28^m 18.6367^s[1]
Declination	+18° 46′ 10.180″[1]
Apparent magnitude (V)	6.97 + 10.60[2]
Characteristics
Spectral type	G1V[3] + K3:[4]
B−V color index	0.662±0.007[5]
Astrometry
Radial velocity (Rv)	−91.290±0.0039[6] km/s
Proper motion (μ)	RA: 349.620(16) mas/yr[1] Dec.: −56.618(19) mas/yr[1]
Parallax (π)	26.6465 ± 0.0225 mas[1]
Distance	122.4 ± 0.1 ly (37.53 ± 0.03 pc)
Absolute magnitude (MV)	4.01[5]
Details[7]
HD 195019 A
Mass	1.08±0.01[8] M☉
Radius	1.47±0.04[8] R☉
Luminosity	2.23±0.02[8] L☉
Surface gravity (log g)	4.13±0.02[8] cgs
Temperature	5,825±56[8] K
Metallicity [Fe/H]	0.068±0.030[9] dex
Rotational velocity (v sin i)	2.47±0.50[9] km/s
Age	7.7±0.7[8] Gyr
HD 195019 B
Mass	0.7[10] M☉
Surface gravity (log g)	4.46[11] cgs
Temperature	4,652[11] K
Rotational velocity (v sin i)	1.71[11] km/s
Other designations
BD+18° 4505, Gaia DR2 1815418118373631360, HD 195019, HIP 100970, SAO 106138, WDS J20283+1846A, LTT 15981, NLTT 49312, GCRV 12790, 2MASS J20281860+1846103[12]
Database references
SIMBAD	data

HD 195019 is a binary star system in the northern constellation of Delphinus. The brighter star has a close orbiting exoplanet companion. This system is located at a distance of 122 light years from the Sun based on parallax measurements,[1] but it is drifting closer with a radial velocity of −91.3 km/s.[6] Although it has an absolute magnitude of 4.01,[5] at that distance the system is considered too faint to be viewed with the naked eye, having a combined apparent visual magnitude of 6.87.[5] However, it should be readily visible with a pair of binoculars or a small telescope.[13]

The spectrum of the primary member, designated component A, presents as a G-type main-sequence star with a stellar classification of G1V.[3] An older stellar classification of G3 V/IV[14] suggested it may be near the end of its main sequence lifespan and is evolving into a subgiant star.[13] This is an older star with an estimated age of nearly 8[8] billion years and a low level of magnetic activity in its chromosphere.[8] The abundance of iron is near solar.[9] The star has a mass similar to the Sun but a larger radius. It is radiating 2.23 times the luminosity of the Sun from its photosphere at an effective temperature of 5,825 K.[8]

The co-moving companion, component B, was first reported by G. W. Hough in 1881. As of 2016, it is located at an angular separation of 3.40″ along a position angle of 334° relative to the primary.[2] This corresponds to a projected separation of 131 AU. This is a K-type star with 70% of the mass of the Sun[10] and is magnitude 10.60.[2]

Planetary system

In 1998, a planet was discovered at Lick Observatory utilizing a radial velocity method, orbiting around Star HD 195019 A.[14] A search of astrometric observations from Hipparcos suggested this may be a stellar object in a near polar orbit.[15][16][13] However, interferometric observations ruled out a stellar companion in this orbit with high likelihood.[17]

The HD 195019 planetary system[9]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	>3.69 ± 0.30 MJ	0.1388 ± 0.0080	18.20132 ± 0.00039	0.0138 ± 0.0044	—	—

See also

• HD 190228
• HD 196050
• List of exoplanets discovered before 2000 - HD 195019 b

References

1. 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. Mason, Brian D.; et al. (December 2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466–3471. Bibcode:2001AJ....122.3466M. doi:10.1086/323920. ISSN 0004-6256. S2CID 119533755.
3. Gray, R. O.; et al. (April 2001). "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars". The Astronomical Journal. 121 (4): 2148–2158. Bibcode:2001AJ....121.2148G. doi:10.1086/319956. ISSN 0004-6256. S2CID 117076031.
4. Bidelman, W. P. (October 1985). "G. P. Kuiper's spectral classifications of proper-motion stars". Astrophysical Journal Supplement Series. 59: 197–227. Bibcode:1985ApJS...59..197B. doi:10.1086/191069.
5. 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.
6. Soubiran, C.; et al. (2018). "Gaia Data Release 2. The catalogue of radial velocity standard stars". Astronomy and Astrophysics. 616: A7. arXiv:1804.09370. Bibcode:2018A&A...616A...7S. doi:10.1051/0004-6361/201832795. S2CID 52952408.
7. Takeda, Yoichi (February 2005). "Precise Differential Analysis of Stellar Metallicities: Application to Solar Analogs Including 16 Cyg A and B". Publications of the Astronomical Society of Japan. 57 (1): 83–96. Bibcode:2005PASJ...57...83T. doi:10.1093/pasj/57.1.83.
8. Bonfanti, A.; et al. (2016). "Age consistency between exoplanet hosts and field stars". Astronomy & Astrophysics. 585: 14. arXiv:1511.01744. Bibcode:2016A&A...585A...5B. doi:10.1051/0004-6361/201527297. S2CID 53971692. A5.
9. Butler, R. P.; et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal. 646 (1): 505–522. arXiv:astro-ph/0607493. Bibcode:2006ApJ...646..505B. doi:10.1086/504701. S2CID 119067572.
10. Quarles, Billy; et al. (2020). "Orbital stability of circumstellar planets in binary systems". The Astronomical Journal. 159 (3): 80. arXiv:1912.11019. Bibcode:2020AJ....159...80Q. doi:10.3847/1538-3881/ab64fa. S2CID 209444271.
11. Rice, Malena; Brewer, John M. (August 2020). "Stellar Characterization of Keck HIRES Spectra with The Cannon". The Astrophysical Journal. 898 (2): 119. arXiv:2007.02942. Bibcode:2020ApJ...898..119R. doi:10.3847/1538-4357/ab9f96. 119.
12. "HD 195019". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2024-01-03.
13. Kaler, James. "HD 195019 Delphini". The Planet Project. Retrieved 2024-01-03.
14. Fischer, Debra A.; et al. (1999). "Planetary Companions around Two Solar-Type Stars: HD 195019 and HD 217107". Publications of the Astronomical Society of the Pacific. 111 (755): 50–56. arXiv:astro-ph/9810420. Bibcode:1999PASP..111...50F. doi:10.1086/316304. S2CID 17980987.
15. Han, Inwoo; et al. (February 2001). "Preliminary Astrometric Masses for Proposed Extrasolar Planetary Companions". The Astrophysical Journal. 548 (1): L57 – L60. Bibcode:2001ApJ...548L..57H. doi:10.1086/318927. S2CID 120952927.
16. Sahlmann, J.; et al. (April 2011). "HD 5388 b is a 69 MJup companion instead of a planet". Astronomy & Astrophysics. 528: L8. arXiv:1102.3372. Bibcode:2011A&A...528L...8S. doi:10.1051/0004-6361/201116533. S2CID 55566004. L8.
17. Koresko, C. D.; et al. (December 2002). "Long baseline interferometric observations of HD 195019: no K dwarf companion detected". Bulletin of the American Astronomical Society. 34: 1177. Bibcode:2002AAS...201.4613K.