Rho1 Arae

ρ^1 Arae

The location of ρ^1 Arae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Ara
Right ascension	16^h 56^m 08.8405^s[1]
Declination	–50° 40′ 29.244″[1]
Apparent magnitude (V)	6.275[2]
Characteristics
Spectral type	B3 Vnpe
U−B color index	–0.691[2]
B−V color index	+0.008[2]
Astrometry
Radial velocity (Rv)	+19[3] km/s
Proper motion (μ)	RA: –7.66[1] mas/yr Dec.: –9.79[1] mas/yr
Parallax (π)	5.06 ± 0.39 mas[1]
Distance	640 ± 50 ly (200 ± 20 pc)
Absolute magnitude (MV)	−0.16[4]
Orbit[5]
Period (P)	236.50 ± 0.18 d
Inclination (i)	60 ± 7°
Periastron epoch (T)	HJD 2458672.10 ± 0.72
Semi-amplitude (K1) (primary)	4.33 ± 0.05 km/s
Semi-amplitude (K2) (secondary)	52.83 ± 1.49 km/s
Details
ρ^1 Ara A
Mass	6.5 ± 1.3[5] M☉
Radius	4.21 ± 0.20[6] R☉
Luminosity	1,418[7] L☉
Surface gravity (log g)	3.75[8] cgs
Temperature	19,800[8] K
Rotational velocity (v sin i)	370 ± 10[9] km/s
Age	18.4 ± 1.5[10] Myr
ρ^1 Ara B
Mass	0.53 ± 0.11[5] M☉
Radius	0.27 ± 0.04[6] R☉
Luminosity	204[6] L☉
Temperature	42,000[6] K
Other designations
ρ^1 Ara, V846 Arae, CD–50 10905, GC 22790, HD 152478, HIP 82868, HR 6274, NSV 8047, SAO 244280[11]
Database references
SIMBAD	data

Rho^1 Arae is the Bayer designation for a star in the southern constellation of Ara. Unusually for a star with a Bayer designation, it was not catalogued by Bayer in his Uranometria. It was instead first catalogued by Nicolas Lacaille, in his Coelum Australe Stelliferum published in 1763. This star gained the Bayer designation of Rho^1 Arae in Bode's Uranographia, published in 1801. Rho^1 Arae is one of the dimmest stars with a Bayer designation, having an apparent visual magnitude of just +6.275[2] According to the Bortle Dark-Sky Scale, this means the star is just barely visible to the naked eye in dark rural skies. Based upon parallax measurements, it is about 640 light-years (200 parsecs) distant from the Sun, give or take a 50-light-year margin of error.[1]

A light curve for V846 Arae, plotted from TESS data[12]

The Hipparcos data revealed that Rho^1 Arae is a variable star. It was given its variable star designation, V846 Arae, in 1999.[13] This is a spectroscopic binary system, which means that the presence of an orbiting companion is indicated by shifts in the spectrum. The primary star is a Be star, while the secondary star is a subdwarf O star; they orbit each other with a period of about 236.50 days.[5] The combined spectrum of this system matches a stellar classification of B3 Vnpe, which may indicate the primary is a B-type main-sequence star. The 'e' suffix indicates the presence of emission lines from the primary Be star. For Rho^1 Arae, the emission lines are prominent and variable.[9] The primary star is spinning rapidly with a projected rotational velocity of 370 ± 10, which makes it difficult to obtain reliable orbital elements.[9]

Rho^1 Arae has a peculiar velocity of 27.4 ± 4.9 km/s relative to its neighbors,[10] making it a runaway star system. A scenario that it was ejected from the Scorpius–Centaurus OB association as a result of a past supernova explosion seems unlikely because of its binarity.[9]

References

1. van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. Kozok, J. R. (September 1985), "Photometric observations of emission B-stars in the southern Milky Way", Astronomy and Astrophysics Supplement Series, 61: 387–405, Bibcode:1985A&AS...61..387K.
3. Evans, D. S. (June 20–24, 1966), "The Revision of the General Catalogue of Radial Velocities", in Batten, Alan Henry; Heard, John Frederick (eds.), Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, vol. 30, University of Toronto: International Astronomical Union, p. 57, Bibcode:1967IAUS...30...57E.
4. 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.
5. Wang, Luqian; Gies, Douglas R.; Peters, Geraldine J.; Han, Zhanwen (April 2023). "The Orbital and Physical Properties of Five Southern Be+sdO Binary Systems". The Astronomical Journal. 165 (5): 203. arXiv:2303.12616. Bibcode:2023AJ....165..203W. doi:10.3847/1538-3881/acc6ca. ISSN 1538-3881.
6. Wang, Luqian; Gies, Douglas R.; Peters, Geraldine J.; Götberg, Ylva; Chojnowski, S. Drew; Lester, Kathryn V.; Howell, Steve B. (2021). "The Detection and Characterization of Be+sdO Binaries from HST/STIS FUV Spectroscopy". The Astronomical Journal. 161 (5): 248. arXiv:2103.13642. Bibcode:2021AJ....161..248W. doi:10.3847/1538-3881/abf144.
7. Hohle, M. M.; Neuhäuser, R.; Schutz, B. F. (April 2010), "Masses and luminosities of O- and B-type stars and red supergiants", Astronomische Nachrichten, 331 (4): 349, arXiv:1003.2335, Bibcode:2010AN....331..349H, doi:10.1002/asna.200911355, S2CID 111387483.
8. Soubiran, C.; Le Campion, J.-F.; Cayrel de Strobel, G.; Caillo, A. (June 2010), "The PASTEL catalogue of stellar parameters", Astronomy and Astrophysics, 515: A111, arXiv:1004.1069, Bibcode:2010A&A...515A.111S, doi:10.1051/0004-6361/201014247, S2CID 118362423.
9. Jilinski, E.; et al. (September 2010), "A Dynamical Study of Suspected Runaway Stars as Traces of Past Supernova Explosions in the Region of the Scorpius–Centaurus OB Association", The Astrophysical Journal, 721 (1): 469–477, Bibcode:2010ApJ...721..469J, doi:10.1088/0004-637X/721/1/469.
10. Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873.
11. "rho01 Ara". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-08-01.
12. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
13. Kazarovets, E. V.; Samus, N. N.; Durlevich, O. V.; Frolov, M. S.; Antipin, S. V.; Kireeva, N. N.; Pastukhova, E. N. (January 1999). "The 74th Special Name-list of Variable Stars". Information Bulletin on Variable Stars. 4659: 1. Bibcode:1999IBVS.4659....1K. Retrieved 25 November 2024.

External links

• HR 6274
• HIP 82868
• Image HD 152478