Rho Herculis
Rho Herculis (ρ Her, ρ Herculis) is a double star in the constellation of Hercules. The apparent magnitudes of the components are 4.510 and 5.398, respectively. Parallax measurements published in Gaia Data Release 2 put the system at some 360-390 light-years (111-121 parsecs) away.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hercules |
| ρ Her A | |
| Right ascension | 17h 23m 40.972s[1] |
| Declination | +37° 08′ 45.33″[1] |
| Apparent magnitude (V) | 4.510[1] |
| ρ Her B | |
| Right ascension | 17h 23m 40.718s |
| Declination | +37° 08′ 48.44″[1] |
| Apparent magnitude (V) | 5.398[1] |
| Characteristics | |
| ρ Her A | |
| Spectral type | A0IIIpHgMn[2] |
| U−B color index | −0.06[3] |
| B−V color index | +0.00[3] |
| ρ Her B | |
| Spectral type | B9.5IVn[2] |
| Astrometry | |
| ρ Her A | |
| Radial velocity (Rv) | −21.0 ± 2[4] km/s |
| Proper motion (μ) | RA: −38.6[5] mas/yr Dec.: 9.2[5] mas/yr |
| Parallax (π) | 8.3380 ± 0.3358 mas[6] |
| Distance | 390 ± 20 ly (120 ± 5 pc) |
| ρ Her B | |
| Radial velocity (Rv) | −19.3 ± 2[4] km/s |
| Proper motion (μ) | RA: −38.6[1] mas/yr Dec.: 9.2[1] mas/yr |
| Parallax (π) | 9.0354 ± 0.1135 mas[7] |
| Distance | 361 ± 5 ly (111 ± 1 pc) |
| Details | |
| A | |
| Mass | 4.00/2.93[8] M☉ |
| Temperature | 9,118[6] K |
| Metallicity [Fe/H] | 0.0[9] dex |
| Rotational velocity (v sin i) | 75[10] km/s |
| B | |
| Mass | 3.27[8] M☉ |
| Surface gravity (log g) | 3.6[9] cgs |
| Temperature | 8,755[7] K |
| Rotational velocity (v sin i) | 291[10] km/s |
| Other designations | |
| ρ Her A: HD 157779, HR 6485, SAO 66001 | |
| ρ Her B: HD 157778, HR 6484, SAO 66000 | |
| Database references | |
| SIMBAD | ρ Her |
| ρ Her A | |
| ρ Her B | |
The two stars of Rho Herculis are separated by four arcseconds, and are known as Rho Herculis A and B, respectively. A is an A-type giant star, while B is a B-type subgiant star.[2] They are also referred to, rarely, as Rho1 Herculis and Rho2 Herculis. Rho Herculis A is itself a close binary which has been resolved using speckle interferometry, with the two components separated by 0.252″.[11]
The two visual components have very similar spectral types, between A0 and B9. Rho Herculis A is generally assigned a giant luminosity class, with Rho Herculis B most often considered to be a main sequence star.[12] Rho Herculis A has been considered to be an Ap star, with unusually strong silicon or mercury and manganese absorption lines in its spectrum,[2][13] but this is now considered to be dubious.[14]
References
- ^ a b c d e f g Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H.
- ^ a b c d Abt, Helmut A.; Morrell, Nidia I. (1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". The Astrophysical Journal Supplement Series. 99: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182.
- ^ a b Johnson, H. L. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99. Bibcode:1966CoLPL...4...99J.
- ^ a b Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Carnegie Institute Washington D.C. Publication: 0. Bibcode:1953GCRV..C......0W.
- ^ a b Zacharias, N. (2012). "The fourth US Naval Observatory CCD Astrograph Catalog (UCAC4)". VizieR On-line Data Catalog. Bibcode:2012yCat.1322....0Z.
- ^ a b Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b "Multiple Star Catalog". Cerro Tololo Inter-American Observatory. Retrieved 2018-11-30.
- ^ a b Gebran, M.; Farah, W.; Paletou, F.; Monier, R.; Watson, V. (2016). "A new method for the inversion of atmospheric parameters of A/Am stars". Astronomy and Astrophysics. 589: A83. arXiv:1603.01146. Bibcode:2016A&A...589A..83G. doi:10.1051/0004-6361/201528052. S2CID 118549566.
- ^ a b Royer, F.; Grenier, S.; Baylac, M. -O.; Gómez, A. E.; Zorec, J. (2002). "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin I". Astronomy and Astrophysics. 393 (3): 897–911. arXiv:astro-ph/0205255. Bibcode:2002A&A...393..897R. doi:10.1051/0004-6361:20020943.
- ^ Mason, Brian D.; Hartkopf, William I.; Gies, Douglas R.; Henry, Todd J.; Helsel, John W. (2009). "The High Angular Resolution Multiplicity of Massive Stars". The Astronomical Journal. 137 (2): 3358. arXiv:0811.0492. Bibcode:2009AJ....137.3358M. doi:10.1088/0004-6256/137/2/3358. S2CID 119268845.
- ^ Skiff, B. A. (2014). "VizieR Online Data Catalog: Catalogue of Stellar Spectral Classifications (Skiff, 2009-2016)". VizieR On-line Data Catalog. Bibcode:2014yCat....1.2023S.
- ^ Abt, H. A.; Cardona, O. (1984). "The nature of the visual companions of AP and AM stars". The Astrophysical Journal. 276: 266. Bibcode:1984ApJ...276..266A. doi:10.1086/161610.
- ^ Renson, P.; Manfroid, J. (2009). "Catalogue of Ap, HgMn and Am stars". Astronomy and Astrophysics. 498 (3): 961. Bibcode:2009A&A...498..961R. doi:10.1051/0004-6361/200810788.