HD 194688

HD 194688, also designated as HR 7816, is a solitary star located in the northern constellation Delphinus, the dolphin. It has an apparent magnitude of 6.22,^[2] placing it near the limit for naked eye visibility. The object is located relatively far away at a distance of 886 light-years based on Gaia DR3 parallax measurements,^[1] but it is drifting closer with a heliocentric radial velocity of −17.12 km/s.^[5] At its current distance, HD 196488's brightness is diminished due to an interstellar extinction of 0.17 magnitudes^[11] and it has an absolute visual magnitude of −1.19.^[6]

HD 194688

Location of HD 194688 on the map (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Delphinus
Right ascension	20h 26m 23.15478s[1]
Declination	+17° 18′ 56.0140″[1]
Apparent magnitude (V)	6.22±0.01[2]
Characteristics
Spectral type	K0[3]
B−V color index	+1.01[4]
Astrometry
Radial velocity (Rv)	−17.12±0.27[5] km/s
Proper motion (μ)	RA: +5.397 mas/yr[1] Dec.: −5.426 mas/yr[1]
Parallax (π)	3.6827 ± 0.0184 mas[1]
Distance	886 ± 4 ly (272 ± 1 pc)
Absolute magnitude (MV)	−1.19[6]
Details
Mass	1.57[7] M☉
Radius	21.58[8] R☉
Luminosity	258+3 −2[1] L☉
Surface gravity (log g)	1.91[7] cgs
Temperature	4,995±122[9] K
Metallicity [Fe/H]	−0.13[7] dex
Other designations
AG+17°2201, BD+16°4259, FK5 3635, GC 28435, HD 194688, HIP 100807, HR 7816, SAO 106101, TIC 305526917[10]
Database references
SIMBAD	data

HD 194688 has a simple stellar classification of K0,^[3] indicating that it is an early K-type star. It has 1.57 times the mass of the Sun^[7] and an enlarged radius 21.58 times that of the Sun.^[8] It radiates 258 times the luminosity of the Sun^[1] from its photosphere at an effective temperature of 4,995 K,^[9] giving it an orangish-yellow hue when viewed in the night sky. The large radius and high luminosity suggests that HD 194688 may be an evolved giant star. It is slightly metal-deficient with an iron abundance 74.1% that of the Sun's.^[7]

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. Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27 – L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361. S2CID 17128864.
3. Cannon, Annie Jump; Pickering, Edward Charles (1923). "The Henry Draper catalogue : 19h and 20h". Annals of Harvard College Observatory. 98: 1. Bibcode:1923AnHar..98....1C.
4. Haggkvist, L.; Oja, T. (1970). "Results of BV photometry 1969-70 (Uppsala refractor)". Private Communication. Bibcode:1970Priv.........0H. S2CID 231475662.
5. Famaey, B.; Jorissen, A.; Luri, X.; Mayor, M.; Udry, S.; Dejonghe, H.; Turon, C. (January 2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters". Astronomy and Astrophysics. 430: 165. arXiv:astro-ph/0409579. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272. S2CID 17804304.
6. Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
7. Anders, F.; et al. (August 2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy & Astrophysics. 628: A94. arXiv:1904.11302. Bibcode:2019A&A...628A..94A. doi:10.1051/0004-6361/201935765. eISSN 1432-0746. ISSN 0004-6361. S2CID 131780028.
8. McDonald, I.; Zijlstra, A. A.; Watson, R. A. (15 June 2017). "Fundamental parameters and infrared excesses of Tycho–Gaia stars". Monthly Notices of the Royal Astronomical Society. 471 (1): 770–791. arXiv:1706.02208. Bibcode:2017MNRAS.471..770M. doi:10.1093/mnras/stx1433. eISSN 1365-2966. ISSN 0035-8711. S2CID 73594365.
9. Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. eISSN 1538-3881. hdl:1721.1/124721. S2CID 166227927.
10. "HD 198404". SIMBAD. Centre de données astronomiques de Strasbourg.
11. Gontcharov, George A.; Mosenkov, Aleksandr V. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society. 472 (4): 3805–3820. arXiv:1709.01160. Bibcode:2017MNRAS.472.3805G. doi:10.1093/mnras/stx2219. eISSN 1365-2966. ISSN 0035-8711. S2CID 118879856.