c Hydrae
{{Short description|Star in the constellation Hydra}}
{{Starbox begin}}
{{Starbox image
| image=
{{Location mark
|image=Hydra constellation map.svg|alt=|float=center|width=300
|label=|position=right
|mark=Red circle.svg|mark_width=10|mark_link=C Hya
|x=951|y=188
}}
|caption=Location of C Hydrae (circled)
}}
{{Starbox observe
| epoch = J2000
| constell = Hydra
| dec = {{DEC|−03|54|23.1178}}
}}
{{Starbox character
| type =
| u-b =
| variable =
}}
{{Starbox astrometry
| radial_v = {{Val|+10.00|1.78}}
| parallax = 26.66
| p_error = 0.19
}}
{{Starbox detail
| source =
}}
{{Starbox catalog
| names={{odlist | B=C Hya | F=30 Mon | BD=-03°2339 | HD=71155 | HIP=41307 | HR=3314 | SAO=135896 }}
}}
{{Starbox reference
| Simbad=30+Mon
}}
{{Starbox end}}
C Hydrae is a single star in the equatorial constellation of Hydra, located 122 light years away from the Sun. It has the Flamsteed designation 30 Monocerotis, assigned when it belonged to the constellation Monoceros. The object is visible to the naked eye as a white-hued star with an apparent visual magnitude of 3.90. It is moving away from the Earth with a heliocentric radial velocity of +10 km/s.
This is an A-type main-sequence star with a stellar classification of A0 Va. It is around 162 million years old with a high rate of spin, showing a projected rotational velocity of 129 km/s. The star has 2.3 times the mass of the Sun and about 2.5 times the Sun's radius. It is radiating 37 times the luminosity of the Sun from its photosphere at an effective temperature of 9,074 K.
A statistically significant infrared excess has been detected, indicating a debris disk is orbiting {{Val|2.0|0.1|ul=AU}} from the host star with a blackbody temperature of {{Val|499|3|u=K}}. It is comparable in size to the asteroid belt. Unexplained X-ray emission has also been detected coming from these coordinates – stars of this class are not normally expected to show X-ray emission, so it may be coming from a background source or an unseen companion.
References
{{reflist|refs=
{{cite simbad | mode=cs2 | postscript=. | title=30 Mon | access-date=May 7, 2019 }}
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| arxiv=0708.1752 | bibcode=2007A&A...474..653V
| doi=10.1051/0004-6361:20078357 | s2cid=18759600
}}
| title=XHIP: An extended hipparcos compilation
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| bibcode=2012AstL...38..331A | arxiv=1108.4971
| doi=10.1134/S1063773712050015 | s2cid=119257644 }}
| title=Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer
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| arxiv=1712.08109 | bibcode=2018AJ....155...30B
| doi=10.3847/1538-3881/aa9d8b | s2cid=119427037 | doi-access=free }}
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| title=The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets
| journal=The Astrophysical Journal
| volume=804 | issue=2 | pages=146 | year=2015
| bibcode=2015ApJ...804..146D | doi=10.1088/0004-637X/804/2/146
| arxiv=1501.03154 | s2cid=33401607 | postscript=. }}
| title=High Spatial Resolution Imaging of Thermal Emission from Debris Disks
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| journal=The Astrophysical Journal
| volume=723 | issue=2 | pages=1418–1435 | date=November 2010
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| bibcode=2010ApJ...723.1418M | arxiv=1011.1410 | s2cid=118648798 }}
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| title=Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project
| journal=Astronomy & Astrophysics
| volume=546 | id=A61 | pages=14 | date=October 2012
| doi=10.1051/0004-6361/201219219 | bibcode=2012A&A...546A..61D
| arxiv=1208.3048 | s2cid=59451347 | postscript=. }}
| last1=Eggleton | first1=P. P. | last2=Tokovinin | first2=A. A.
| title=A catalogue of multiplicity among bright stellar systems
| journal=Monthly Notices of the Royal Astronomical Society
| volume=389 | issue=2 | pages=869–879 | date=September 2008
| doi=10.1111/j.1365-2966.2008.13596.x | doi-access=free | postscript=.
| bibcode=2008MNRAS.389..869E | arxiv=0806.2878 | s2cid=14878976 }}
| title=X-ray emission from A-type stars
| last1=Schröder | first1=C. | last2=Schmitt | first2=J. H. M. M.
| journal=Astronomy and Astrophysics | postscript=.
| volume=475 | issue=2 | date=November 2007 | pages=677–684
| doi=10.1051/0004-6361:20077429 | bibcode=2007A&A...475..677S | doi-access=free }}
| last1=Gray | first1=R. O. | last2=Corbally | first2=C. J.
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| last5=Bubar | first5=E. J. | last6=McGahee | first6=C. E.
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| title=Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample
| display-authors=1 | journal=The Astronomical Journal
| volume=132 | issue=1 | pages=161–170 | date=July 2006
| doi=10.1086/504637 | bibcode=2006AJ....132..161G
| arxiv=astro-ph/0603770 | s2cid=119476992 | postscript=. }}
}}
{{Stars of Hydra}}
{{DEFAULTSORT:30 Monocerotis}}
Category:A-type main-sequence stars
Category:Hydra (constellation)