HD 170873

HD 170873, also known as HR 6954 or rarely 19 G. Telescopii, is a solitary orange-hued star located in the southern constellation Telescopium. It has an apparent magnitude of 6.20,^[2] placing it near the limit for naked eye visibility. Gaia DR3 parallax measurements imply a distance of 551 light years^[1] and it is currently receding with a heliocentric radial velocity of 23.8 km/s.^[5] At its current distance, HD 170873's brightness is diminished by 0.39 magnitudes due to interstellar dust,^[13] and it has an absolute magnitude of −0.31.^[6]

HD 170873

Location of HD 170873 (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Telescopium
Right ascension	18h 34m 31.11856s[1]
Declination	−52° 53′ 29.4756″[1]
Apparent magnitude (V)	6.20±0.01[2]
Characteristics
Spectral type	K2 III[3]
B−V color index	+1.27[4]
Astrometry
Radial velocity (Rv)	23.8±0.4[5] km/s
Proper motion (μ)	RA: −16.944 mas/yr[1] Dec.: −42.325 mas/yr[1]
Parallax (π)	5.9179 ± 0.0283 mas[1]
Distance	551 ± 3 ly (169.0 ± 0.8 pc)
Absolute magnitude (MV)	−0.31[6]
Details
Mass	3.20±0.04[1] M☉
Radius	22.6±1.2[7] R☉
Luminosity	170±2[1] L☉
Surface gravity (log g)	1.86[8] cgs
Temperature	4,473±122[9] K
Metallicity [Fe/H]	−0.01[8] dex
Rotational velocity (v sin i)	<1[10] km/s
Age	318+30 −31[1] Myr
Other designations
19 G. Telescopii[11], CD−52°8714, CPD−52°11158, GC 25324, HD 170873, HIP 91062, HR 6954, SAO 245559[12]
Database references
SIMBAD	data

HD 170873 is an evolved red giant with a stellar classification of K2 III.^[3] It has 3.2 times the mass of the Sun but at the age of 318 million years,^[1] it has expanded to 22.6 times the Sun's radius.^[7] It radiates 170 times the luminosity of the Sun^[1] from its enlarged photosphere at an effective temperature of 4,473 K.^[9] It has a near-solar metallicity at [Fe/H] = −0.01^[8] and spins too slowly for its projected rotational velocity to be measured accurately.^[10]

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. Houk, Nancy (1978). Michigan catalogue of two-dimensional spectral types for the HD stars: Declinations −53° to −40°. Vol. 2. Bibcode:1978mcts.book.....H.
4. Corben, P. M. (April 1971). "Photoelectric Magnitudes and Colours for Bright Southern Stars". Monthly Notes of the Astronomical Society of South Africa. 30 (4): 37. Bibcode:1971MNSSA..30...37C. ISSN 0024-8266.
5. Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35,495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. eISSN 1562-6873. ISSN 1063-7737. S2CID 119231169.
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. Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (October 2004). "The angular sizes of dwarf stars and subgiants. Surface brightness relations calibrated by interferometry". Astronomy & Astrophysics. 426 (1): 297–307. arXiv:astro-ph/0404180. Bibcode:2004A&A...426..297K. doi:10.1051/0004-6361:20035930. eISSN 1432-0746. ISSN 0004-6361. S2CID 6077801.
8. 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.
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. De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (January 2014). "A catalog of rotational and radial velocities for evolved stars V: Southern stars". Astronomy & Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. eISSN 1432-0746. ISSN 0004-6361. S2CID 54046583.
11. Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino. 1. Bibcode:1879RNAO....1.....G.
12. "HD 170873". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved March 2, 2023.
13. 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.