Phi2 Hydrae

Phi² Hydrae
	; A light curve for Phi2 Hydrae, plotted from Hipparcos data
Observation data; Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation	Hydra
Right ascension	10h 36m 16.65890s
Declination	−16° 20′ 39.5764″
Apparent magnitude (V)	6.1
Characteristics
Evolutionary stage	AGB
Spectral type	M1 III
U−B color index	+1.95
B−V color index	+1.64
Variable type	SR
Astrometry
Radial velocity (Rv)	+15.7±2.9 km/s
Proper motion (μ)	RA: −30.651 mas/yr ; Dec.: +4.212 mas/yr
Parallax (π)	2.929±0.1349 mas
Distance	1,110 ± 50 ly ; (340 ± 20 pc)
Absolute magnitude (MV)	−0.80
Details
Mass	6.4 M☉
Radius	85 R☉
Luminosity	1,470 L☉
Surface gravity (log g)	1.25 cgs
Temperature	3,873 K
Other designations
	φ2 Hya, BD−15°3087, HD 91880, HIP 51905, HR 4156, SAO 156093
Database references
SIMBAD	data

Phi² Hydrae, Latinized from φ² Hydrae, is a star in the constellation Hydra. It originally received the Flamsteed designation of 1 Crateris before being placed in the Hydra constellation.^[11] Based upon an annual parallax shift of 2.9 mas as seen from Earth, it is located roughly 1,110 light years from the Sun. The star is faintly visible to the naked eye with an apparent visual magnitude of about 6.1.^[4] It forms a triangle with the fainter φ¹ Hydrae and the brighter φ³ Hydrae, between μ Hydrae and ν Hydrae.

Pulsations^[8]
Period (days)	Amplitude (magnitude)
11.0	0.008
110.3	0.012
153.6	0.015

This is an evolved red giant star with a stellar classification of M1 III.^[5] It is currently on the asymptotic giant branch,^[5] and is a semiregular variable that undergoes changes in luminosity according to three pulsation periods,^[8] although it is formally still only a suspected variable.^[12] The star is radiating an estimated 1,470 times the Sun's luminosity from its photosphere at an effective temperature of 3,873 K.

Phi² Hydrae has a faint visual companion: a magnitude 12.20 star at an angular separation of 3.50 arc seconds along a position angle of 280°, as of 1959.^[13] The companion has a similar Gaia Data Release 3 parallax to Phi² Hydrae^[14] and is at a distance of 329+5
−4 pc.^[15]

References

^ EAS (1997), "The HIPPARCOS and TYCHO catalogues", Astrometric and Photometric Star Catalogues Derived from the ESA Hipparcos Space Astrometry Mission, ESA SP Series, 1200, Noordwijk, Netherlands: ESA Publications Division, Bibcode:1997HIP...C......0E, ISBN 9290923997, retrieved 14 December 2024.
^ ^a ^b 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.
^ ^a ^b ^c ^d ^e ^f ^g Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
^ ^a ^b ^c de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.
^ ^a ^b ^c Eggen, Olin J. (July 1992), "Asymptotic giant branch stars near the sun", Astronomical Journal, 104 (1): 275–313, Bibcode:1992AJ....104..275E, doi:10.1086/116239.
^ Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
^ ^a ^b Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.
^ ^a ^b ^c Tabur, V.; et al. (2009), "Long-term photometry and periods for 261 nearby pulsating M giants", Monthly Notices of the Royal Astronomical Society, 400 (4): 1945–61, arXiv:0908.3228, Bibcode:2009MNRAS.400.1945T, doi:10.1111/j.1365-2966.2009.15588.x, S2CID 15358380.
^ ^a ^b ^c Fetherolf, Tara; Pepper, Joshua; Simpson, Emilie; Kane, Stephen R.; Močnik, Teo; English, John Edward; Antoci, Victoria; Huber, Daniel; Jenkins, Jon M.; Stassun, Keivan; Twicken, Joseph D.; Vanderspek, Roland; Winn, Joshua N. (2023), "Variability Catalog of Stars Observed during the TESS Prime Mission", The Astrophysical Journal Supplement Series, 268 (1): 4, arXiv:2208.11721, Bibcode:2023ApJS..268....4F, doi:10.3847/1538-4365/acdee5.
^ "* phi02 Hya", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2017-03-17.
^ Wagman, M. (August 1987), "Flamsteed's Missing Stars", Journal for the History of Astronomy, 18 (3): 216, Bibcode:1987JHA....18..209W, doi:10.1177/002182868701800305, S2CID 118445625.
^ Samus, N. N.; Durlevich, O. V.; 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.
^ Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
^ Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
^ Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Demleitner, M.; Andrae, R. (2021), "Estimating Distances from Parallaxes. V. Geometric and Photogeometric Distances to 1.47 Billion Stars in Gaia Early Data Release 3", The Astronomical Journal, 161 (3): 147, arXiv:2012.05220, Bibcode:2021AJ....161..147B, doi:10.3847/1538-3881/abd806.

[CDS-1] EAS (1997), "The HIPPARCOS and TYCHO catalogues", Astrometric and Photometric Star Catalogues Derived from the ESA Hipparcos Space Astrometry Mission, ESA SP Series, 1200, Noordwijk, Netherlands: ESA Publications Division, Bibcode:1997HIP...C......0E, ISBN 9290923997, retrieved 14 December 2024.

[Anderson2012-2] 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.

[dr3-3] ^ ^a ^b ^c ^d ^e ^f ^g Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.

[deBruijne2012-4] Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, S2CID 59451347, A61.

[Eggen1992-5] Eggen, Olin J. (July 1992), "Asymptotic giant branch stars near the sun", Astronomical Journal, 104 (1): 275–313, Bibcode:1992AJ....104..275E, doi:10.1086/116239.

[houk1978-6] Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.

[Mermilliod1986-7] Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data, SIMBAD, Bibcode:1986EgUBV........0M.

[tabur2009-8] Tabur, V.; et al. (2009), "Long-term photometry and periods for 261 nearby pulsating M giants", Monthly Notices of the Royal Astronomical Society, 400 (4): 1945–61, arXiv:0908.3228, Bibcode:2009MNRAS.400.1945T, doi:10.1111/j.1365-2966.2009.15588.x, S2CID 15358380.

[fetherolf2023-9] Fetherolf, Tara; Pepper, Joshua; Simpson, Emilie; Kane, Stephen R.; Močnik, Teo; English, John Edward; Antoci, Victoria; Huber, Daniel; Jenkins, Jon M.; Stassun, Keivan; Twicken, Joseph D.; Vanderspek, Roland; Winn, Joshua N. (2023), "Variability Catalog of Stars Observed during the TESS Prime Mission", The Astrophysical Journal Supplement Series, 268 (1): 4, arXiv:2208.11721, Bibcode:2023ApJS..268....4F, doi:10.3847/1538-4365/acdee5.

[SIMBAD-10] "* phi02 Hya", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2017-03-17.

[Wagman1987-11] Wagman, M. (August 1987), "Flamsteed's Missing Stars", Journal for the History of Astronomy, 18 (3): 216, Bibcode:1987JHA....18..209W, doi:10.1177/002182868701800305, S2CID 118445625.

[gcvs-12] Samus, N. N.; Durlevich, O. V.; 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.

[WDSC2014-13] Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.

[dr3b-14] Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.

[bj2021-15] Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Demleitner, M.; Andrae, R. (2021), "Estimating Distances from Parallaxes. V. Geometric and Photogeometric Distances to 1.47 Billion Stars in Gaia Early Data Release 3", The Astronomical Journal, 161 (3): 147, arXiv:2012.05220, Bibcode:2021AJ....161..147B, doi:10.3847/1538-3881/abd806.

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Phi2 Hydrae

References

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