Rho1 Arae

ρ1 Arae
Diagram showing star positions and boundaries of the Ara constellation and its surroundings
The location of ρ1 Arae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ara
Right ascension 16h 56m 08.8405s[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]
Distance640 ± 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
ρ1 Ara A
Mass6.5 ± 1.3[5] M☉
Radius4.21 ± 0.20[6] R☉
Luminosity1,418[7] L☉
Surface gravity (log g)3.75[8] cgs
Temperature19,800[8] K
Rotational velocity (v sin i)370 ± 10[9] km/s
Age18.4 ± 1.5[10] Myr
ρ1 Ara B
Mass0.53 ± 0.11[5] M☉
Radius0.27 ± 0.04[6] R☉
Luminosity204[6] L☉
Temperature42,000[6] K
Other designations
ρ1 Ara, V846 Arae, CD–50 10905, GC 22790, HD 152478, HIP 82868, HR 6274, NSV 8047, SAO 244280[11]
Database references
SIMBADdata

Rho1 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 Rho1 Arae in Bode's Uranographia, published in 1801. Rho1 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 Rho1 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 Rho1 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]

Rho1 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]

  1. ^ a b c d e f Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference aass61_387 was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference rgcrv was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  5. ^ a b c d 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. ^ a b c d 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. ^ Cite error: The named reference an331_4_349 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference aaa515_A11 was invoked but never defined (see the help page).
  9. ^ a b c d Cite error: The named reference apj721_1_469 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference mnras410_1_190 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference MAST was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Kazarovets was invoked but never defined (see the help page).