HR 6819

HR 6819
HR 6819
HR 6819
Location of HR 6819 (red circle) in the SW corner of the southern constellation of Telescopium
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Telescopium
Right ascension 18h 17m 07.53243s[1]
Declination −56° 01′ 24.0576″[1]
Apparent magnitude (V) 5.36[2] (5.32 to 5.39[3])
Characteristics
Evolutionary stage giant
Spectral type B3IIIpe[4] or B3II/III[5]
B−V color index −0.050±0.018[2]
Variable type Be[6][3]
Astrometry
Radial velocity (Rv)+9.13±0.78[7] km/s
Proper motion (μ) RA: −4.021±0.111 mas/yr[1]
Dec.: −13.071±0.104 mas/yr[1]
Parallax (π)2.7122 ± 0.1187 mas[1]
Distance1,200 ± 50 ly
(370 ± 20 pc)
Absolute magnitude (MV)−1.47[2]
Orbit[7]
PrimaryStripped B giant
CompanionBe star
Period (P)40.335±0.007 d
Eccentricity (e)0 (fixed[8])
Inclination (i)32±4 (49±2[9])°
Longitude of the node (Ω)32.4±0.9[9]°
Semi-amplitude (K1)
(primary)		60.4±1.0 km/s
Semi-amplitude (K2)
(secondary)		4.0±0.8 km/s
Details[10]
Stripped B giant
Mass0.46±0.26[7] M☉
Radius4.4±0.4[7] R☉
Luminosity1,122+291
−231[7] L☉
Surface gravity (log g)2.8±0.2[7] cgs
Temperature16,000±1,000[7] K
Rotational velocity (v sin i)50±1[11] km/s
Be star
Mass7±2 (fixed)[7] M☉
Radius3.9±0.7[7] R☉
Luminosity2,239+580
−460[7] L☉
Temperature20,000±2,000[7] K
Rotational velocity (v sin i)180±10[7] km/s
Age50[12] Myr
Other designations
QV Tel, CD−56°7256, FK5 1474, GC 24906, HD 167128, HIP 89605, HR 6819, SAO 245369[13]
Database references
SIMBADdata

HR 6819, also known as HD 167128 or QV Telescopii (abbreviated QV Tel), is a double star system in the southern constellation of Telescopium. It is in the south-western corner of the constellation, near Pavo to the south and Ara to the west. The system appears as a variable star that is dimly visible to the naked eye with an apparent magnitude that ranges from 5.32 down to 5.39, which is comparable to the maximum brightness of the planet Uranus. It is about 1,120 light years from the Sun, and is drifting farther away at a rate of 9.4 km/s. Due to its location in the sky, it is visible only to observers south of 33°N latitude.

A May 2020 study hypothesized that the system contained two stars and a black hole, which would have been the closest known black hole, and the first one in a system visible to the naked eye. A study in July of the same year concluded that rather than a triple system it was much more likely to be a black hole and a star orbiting at one distance from here and another star at a different distance. Three further papers in 2020 and one in 2022 concluded that HR 6819 is simply a binary system with two main-sequence stars and no black hole at all.[9]

  1. ^ a b c d Cite error: The named reference GaiaDR3 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference vsx was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Hiltner1969 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Houk1979 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Samus2017 was invoked but never defined (see the help page).
  7. ^ a b c d e f g h i j k l Cite error: The named reference Bodensteiner2020 was invoked but never defined (see the help page).
  8. ^ An initial fit for the orbit gave an eccentricity consistent with zero given the uncertainty, so a second fit was done fixing the eccentricity at zero.
  9. ^ a b c Cite error: The named reference frost2022 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Rivinius2020 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Arcos2018 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Tetzlaff2011 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).