1 Delphini

1 Delphini

Location of 1 Delphini (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Delphinus
A
Right ascension	20^h 30^m 17.9623^s[1]
Declination	+10° 53′ 45.335″[1]
Apparent magnitude (V)	6.20±0.01[2]
B
Right ascension	20^h 30^m 17.9505^s[3]
Declination	+10° 53′ 46.244″[3]
Apparent magnitude (V)	8.00±0.01[2]
Characteristics
Spectral type	A1:III shell[4]
U−B color index	−0.11[5]
B−V color index	−0.03[5]
Astrometry
Radial velocity (Rv)	−15.5 ± 2[6] km/s
Absolute magnitude (MV)	−0.69[7]
A
Proper motion (μ)	RA: +19.320 mas/yr[1] Dec.: +4.645 mas/yr[1]
Parallax (π)	4.6400 ± 0.0616 mas[1]
Distance	703 ± 9 ly (216 ± 3 pc)
B
Proper motion (μ)	RA: +19.545[3] mas/yr Dec.: +4.710[3] mas/yr
Parallax (π)	4.1851 ± 0.1421 mas[3]
Distance	780 ± 30 ly (239 ± 8 pc)
Details
A
Mass	3.1±0.3[8] M☉
Surface gravity (log g)	3.66±0.77[8] cgs
Temperature	10,651^+932 −1156[8] K
Metallicity [Fe/H]	0.00[9] dex
Rotational velocity (v sin i)	217[10] km/s
Age	246[9] Myr
B
Surface gravity (log g)	4.14^+0.19 −0.47[8] cgs
Rotational velocity (v sin i)	370[10] km/s
Other designations
1 Delphini, BD+10°4303, HD 195325, HIP 101160, HR 7836, SAO 106172, WDS J20303+1054AB
Database references
SIMBAD	data

1 Delphini (1 Del) is the Flamsteed designation for a close binary star in the equatorial constellation Delphinus. With a combined apparent magnitude of 6.08, it is barely visible to the naked eye, even under ideal conditions. Parallax measurements put the components at a distance 703 and 780 light years respectively. However, its approaching the Solar System with a radial velocity of 15 km/s.

1 Del consists of three components. The brightest of them has a magnitude of 6.1; a companion located around 0.9 arcseconds from the primary has an apparent magnitude of 8.1; and a third star, located much farther away at around 17 arcseconds from component A, is the faintest with a magnitude of around 14 and is an unrelated background object.^[11]

The entire system has a stellar classification of A1: III sh, indicating that it is a white giant + a shell star. However, there is some uncertainty about the temperature class. When resolved, the secondary has a class of B9. 1 Del A has 3 times the mass of the Sun and an effective temperature of 10,651 K,^[8] giving it a bluish white glow. It is estimated to be almost 250 million years old and has a solar metallicity.^[9] Both components spin rapidly, with projected rotational velocities of 217 and 370 km/s respectively.^[10] As for the peculiarities, the shell star is a primary component; the spectrum of the secondary shows broad absorption lines.^[10]

Due to the stability of the emission lines data from 1 Delphini has been used for developing models of shell stars and Be stars.^[10]

References

1. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
2. Fabricius, C.; Høg, E.; Makarov, V. V.; Mason, B. D.; Wycoff, G. L.; Urban, S. E. (March 2002). "The Tycho double star catalogue". Astronomy & Astrophysics. 384 (1): 180–189. Bibcode:2002A&A...384..180F. doi:10.1051/0004-6361:20011822. ISSN 0004-6361.
3. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
4. Abt, Helmut A.; Morrell, Nidia I. (July 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. ISSN 0067-0049.
5. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
6. Ralph Elmer Wilson (1953). "General Catalogue of Stellar Radial Velocities". Carnegie Institute Washington D.C. Publication. Carnegie Institution of Washington. Bibcode:1953GCRV..C......0W. LCCN 54001336.
7. Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. ISSN 1063-7737. S2CID 255204555.
8. Anders, F.; et al. (February 2022). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia EDR3 stars brighter than G = 18.5". Astronomy & Astrophysics. 658: A91. arXiv:2111.01860. Bibcode:2022A&A...658A..91A. doi:10.1051/0004-6361/202142369. ISSN 0004-6361.
9. Gontcharov, G. A. (December 2012). "Dependence of kinematics on the age of stars in the solar neighborhood". Astronomy Letters. 38 (12): 771–782. arXiv:1606.08814. Bibcode:2012AstL...38..771G. doi:10.1134/S1063773712120031. ISSN 0320-0108. S2CID 255201789.
10. Kubát, Jiří; Kubátová, Brankica; Doležalová, Barbora; Iliev, Lubomir; Šlechta, Miroslav (2016). "Spectroscopy of close visual binary components of the stable shell star 1 Delphini". Astronomy and Astrophysics. 587: A22. arXiv:1601.05236. Bibcode:2016A&A...587A..22K. doi:10.1051/0004-6361/201526414. S2CID 118706088.
11. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.

Further reading

• Merrill, Paul W.; Burwell, Cora G. (November 1949). "Second Supplement to the Mount Wilson Catalogue and Bibliography of Stars of Classes B and a whose Spectra have Bright Hydrogen Lines". The Astrophysical Journal. 110: 387. Bibcode:1949ApJ...110..387M. doi:10.1086/145215. eISSN 1538-4357. ISSN 0004-637X.

• Merrill, Paul W. (January 1952). "Spectra of Two Stars with Stable Shells". The Astrophysical Journal. 115: 42. Bibcode:1952ApJ...115...42M. doi:10.1086/145507. eISSN 1538-4357. ISSN 0004-637X.

• van den Bos, W. H. (February 1958). "Micrometer measures of double stars". The Astronomical Journal. 63: 63. Bibcode:1958AJ.....63...63V. doi:10.1086/107694. ISSN 0004-6256.

• Ringuelet-Kaswalder, Adela E. (August 1963). "Shell Stars and Rotationally Unstable Be Stars". Publications of the Astronomical Society of the Pacific. 75 (445): 323. Bibcode:1963PASP...75..323R. doi:10.1086/127960. eISSN 1538-3873. ISSN 0004-6280.

• Gray, David F.; Marlborough, J. M. (March 1974). "Photoelectric Profile Measurements of Halpha and Hbeta in be Stars". The Astrophysical Journal Supplement Series. 27: 121. Bibcode:1974ApJS...27..121G. doi:10.1086/190291. eISSN 1538-4365. ISSN 0067-0049.