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δ Hydri

Location of δ Hydri (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Hydrus
Right ascension	02 21 44.94286
Declination	−68° 39′ 33.9038″
Apparent magnitude (V)	4.09
Characteristics
Spectral type	A2 V
U−B color index	+0.05
B−V color index	+0.03
Astrometry
Radial velocity (Rv)	+6.00 km/s
Proper motion (μ)	RA: -49.95 mas/yr Dec.: +2.48 mas/yr
Parallax (π)	23.35 ± 0.34 mas
Distance	140 ± 2 ly (42.8 ± 0.6 pc)
Absolute magnitude (MV)	0.92
Details
Mass	2.25 M☉
Radius	2.3 R☉
Luminosity	39.52 L☉
Surface gravity (log g)	3.98 cgs
Temperature	9,880±336 K
Metallicity	+0.12 dex
Rotational velocity (v sin i)	162 km/s
Age	209 Myr
Other designations
δ Hyi, CPD−69° 113, FK5 1065, GC 2872, HD 15008, HIP 11001, HR 705, SAO 248545
Database references
SIMBAD	data

Delta Hydri, Latinized from δ Hydri, is a single, white-hued star in the southern constellation of Hydrus. It is bright enough to be faintly visible to the naked eye with an apparent visual magnitude of 4.09. The distance to this star, based upon an annual parallax shift of 23.35 mas, is about 140 light years. It is moving away from the Sun with a radial velocity of +6 km/s.

This is an ordinary A-type main-sequence star with a stellar classification of A2 V It is about 209 million years old and has a high rate of spin, showing a projected rotational velocity of 162 km/s. This is giving the star an oblate shape with an equatorial bulge that is 7% larger than the polar radius. The star has 2.25 times the mass of the Sun and 2.3 times the Sun's radius. It is radiating 39.5 times the Sun's luminosity from its photosphere at an effective temperature of around 9.880. Delta Hydri has been checked for an infrared excess, but none was found.

References

1. ^ Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Vizier catalog entry
2. ^ 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.
3. ^ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644. Vizier catalog entry
4. ^ Kharchenko, N.V.; Scholz, R.-D.; Piskunov, A.E.; Röser, S.; Schilbach, E. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. S2CID 119323941.
5. ^ Allende Prieto, C.; Lambert, D. L. (1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: Masses, radii and effective temperatures". Astronomy and Astrophysics. 352: 555–562. arXiv:astro-ph/9911002. Bibcode:1999A&A...352..555A. Vizier catalog entry
6. ^ David, Trevor J.; Hillenbrand, Lynne A. (2015). "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets". The Astrophysical Journal. 804 (2): 146. arXiv:1501.03154. Bibcode:2015ApJ...804..146D. doi:10.1088/0004-637X/804/2/146. S2CID 33401607. Vizier catalog entry
7. ^ Rodriguez, David R.; et al. (May 2015), "Stellar multiplicity and debris discs: an unbiased sample", Monthly Notices of the Royal Astronomical Society, 449 (3): 3160–3170, arXiv:1503.01320, Bibcode:2015MNRAS.449.3160R, doi:10.1093/mnras/stv483, S2CID 119237891.
8. van Belle, Gerard T. (March 2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2, S2CID 119273474.

v t e Constellation of Hydrus
List of stars in Hydrus Hydrus in Chinese astronomy
Stars	Bayer α β γ δ ε ζ η η θ ι κ λ μ ν π π σ τ τ Variable VW HD 1237 10180 20003 Other AB8 SMSS J0313−6708 WISEPC J014807.25−720258.7
Exoplanets η Hydri b GJ 3021 b HD 10180 c
Star clusters NGC 602 NGC 643 NGC 1466
Galaxies	NGC 646 802 813 Other KKs 3 PGC 6240 Small Magellanic Cloud (mostly in Tucana) Large Magellanic Cloud (mostly in Dorado, partly in Mensa)
Category

• A-type main-sequence stars
• Hydrus
• Bayer objects
• Durchmusterung objects
• Henry Draper Catalogue objects
• Hipparcos objects
• Bright Star Catalogue objects