Astronomy:Delta Coronae Borealis
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| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Corona Borealis |
| Right ascension | 15h 49m 35.64700s[1] |
| Declination | +26° 04′ 06.2143″[1] |
| Apparent magnitude (V) | 4.57 to 4.69[2] |
| Characteristics | |
| Evolutionary stage | red giant branch[1] |
| Spectral type | G5III-IV Fe-1[3] |
| U−B color index | +0.32[4] |
| B−V color index | +0.78[4] |
| Variable type | RS CVn?[2] |
| Astrometry | |
| Radial velocity (Rv) | −20.356±0.035[5] km/s |
| Proper motion (μ) | RA: −78.907[1][1] mas/yr Dec.: −64.894[1] mas/yr |
| Parallax (π) | 19.4965 ± 0.0850[1] mas |
| Distance | 167.3 ± 0.7 ly (51.3 ± 0.2 pc) |
| Absolute magnitude (MV) | +1.18[5] |
| Details | |
| Mass | 2.4[6] M☉ |
| Radius | 7.4[6] R☉ |
| Luminosity | 34.3[6] L☉ |
| Surface gravity (log g) | 3.29[5] cgs |
| Temperature | 5,180[6] K |
| Metallicity [Fe/H] | −0.12[5] dex |
| Rotation | 59[6] days |
| Rotational velocity (v sin i) | 4.56[5] km/s |
| Age | 851[5] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Delta Coronae Borealis is a variable star in the constellation of Corona Borealis. It has the proper name Matrichakra;[8] Delta Coronae Borealis is its Bayer designation, which is Latinized from δ Coronae Borealis and abbreviated Delta CrB or δ CrB. This star is visible to the naked eye with an apparent visual magnitude that varies regularly between apparent magnitude 4.57 and 4.69. Based on parallax measurements it is around 167 light-years (51 pc) 167 light-years distant from the Earth. The star is drifting closer with a line of sight velocity component of −20 km/s.[5]
In Indian astronomy, Corona Borealis is known as Mātṛcakra (मातृचक्र), the circle. The IAU Working Group on Star Names adopted the English phonetic spelling Matrichakra as a name for Delta Coronae Borealis on 14 May 2026.[8]
Observations
δ Coronae Borealis is a yellow giant star of spectral type G3.5III that is around 2.4 times as massive as the Sun and has swollen to 7.4 times its radius. It has a surface temperature of 5180 K.[10]
For most of its existence, Delta Coronae Borealis was a blue-white main sequence star of spectral type B before it ran out of hydrogen fuel in its core. Its luminosity and spectrum suggest it has just crossed the Hertzsprung gap, having finished burning core hydrogen and now begun burning hydrogen in its shell.[11][1] However, one recent paper gives a 64% chance that it has begun fusing core helium and is on the horizontal branch.[12] It is a strong source of X-rays due to its hot corona.[6]
In 1989, it was noticed that the brightness of δ Coronae Borealis is not constant. Approximately every 45 days, its brightness changes sinusoidally between 4.57 and 4.69, too small to be noticed without close monitoring. The evolutionary state of the star and its probable rotation period mean that the variations may be due to its rotation with different parts of the surface having spots or different temperatures. This would make it an RS Canum Venaticorum variable.[13] The period has since been refined to 59 days and this is now accepted as the star's rotation period.[6]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 2.0 2.1 Samus, N. N. et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S 1: B/GCVS. Bibcode: 2009yCat....102025S.
- ↑ Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins Catalog of Revised MK Types for the Cooler Stars". The Astrophysical Journal Supplement Series 71: 245. doi:10.1086/191373. Bibcode: 1989ApJS...71..245K.
- ↑ 4.0 4.1 Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data., 0 (1986): 0. Bibcode: 1986EgUBV........0M. http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?1986EgUBV........0M&db_key=AST&nosetcookie=1.
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Niedzielski, A. et al. (2016). "The Penn State - Toruń Centre for Astronomy Planet Search stars". Astronomy and Astrophysics 585: A73. doi:10.1051/0004-6361/201527362. Bibcode: 2016A&A...585A..73N.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 Gondoin, P. (2005). "The X-ray activity of the slowly rotating G giant δ CrB". Astronomy and Astrophysics 431 (3): 1027–1035. doi:10.1051/0004-6361:20041991. Bibcode: 2005A&A...431.1027G.
- ↑ "del CrB". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=del+CrB.
- ↑ 8.0 8.1 "IAU Catalog of Star Names". https://exopla.net/star-names/modern-iau-star-names/.
- ↑ Fernie, J. D. (October 1991). "R Coronae Borealis and Delta Coronae Borealis in 1990". Publications of the Astronomical Society of the Pacific 103: 1091–1093. doi:10.1086/132930. Bibcode: 1991PASP..103.1091F.
- ↑ Gondoin, P. (2005). "The X-ray activity of the slowly rotating G giant δ CrB". Astronomy & Astrophysics 431 (3): 1027–35. doi:10.1051/0004-6361:20041991. Bibcode: 2005A&A...431.1027G.
- ↑ Berdyugina, S. V. (1994). "Li and CNO abundances in the atmospheres of stars evolving to the red-giant branch". Astronomy Letters 20 (5): 631. Bibcode: 1994AstL...20..631B.
- ↑ Stock, Stephan et al. (2018). "Precise radial velocities of giant stars. X. Bayesian stellar parameters and evolutionary stages for 372 giant stars from the Lick planet search". Astronomy and Astrophysics 616: A33. doi:10.1051/0004-6361/201833111. Bibcode: 2018A&A...616A..33S.
- ↑ Fernie, J. D. (1987). "Delta Coronae Borealis : A chromospherically active giant ?". Publications of the Astronomical Society of the Pacific 99: 183. doi:10.1086/131975. Bibcode: 1987PASP...99..183F.
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