U Hydrae

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U Hydrae
UHyaLightCurve.png
A visual band light curve for U Hydrae, plotted from ASAS data [1]
Observation data
Epoch J2000       Equinox J2000
Constellation Hydra
Right ascension 10h 37m 33.27295s [2]
Declination −13° 23′ 04.3529″ [2]
Apparent magnitude  (V)4.89 [3]
Characteristics
Evolutionary stage AGB [4]
Spectral type C-N5 C2 5- [5]
B−V color index 2.80±0.51 [3]
Variable type SRb [6]
Astrometry
Radial velocity (Rv)−25.8±1.7 [7]  km/s
Proper motion (μ)RA: +42.59 [2]   mas/yr
Dec.: −37.72 [2]   mas/yr
Parallax (π)4.80 ± 0.23  mas [2]
Distance 680 ± 30  ly
(208 ± 10  pc)
Absolute magnitude  (MV)−1.70 [3]
Details
Mass 0.75 [4]   M☉
Radius 96.0+9.1
−16.5 [8]   R☉
Luminosity 3,476 [4]   L☉
Surface gravity (log g)−0.28 [4]   cgs
Temperature 3,200 [4]   K
Metallicity [Fe/H]−0.1 [9]   dex
Other designations
U Hya, BD−12°3218, HD  92055, HIP  52009, HR  4163, SAO  156110 [10]
Database references
SIMBAD data

U Hydrae is a single [11] star in the equatorial constellation of Hydra, near the northern constellation border with Sextans. It is a semiregular variable star of sub-type SRb, [6] with its brightness ranging from visual magnitude (V) 4.7 to 5.2 over a 450-day period, with some irregularity. [12] This object is located at a distance of approximately 680  light years from the Sun based on parallax. [2] It is drifting closer with a radial velocity of −26 km/s. [7]

This is a carbon-rich red giant star on the asymptotic giant branch [4] – a carbon star – with s-process elements appearing in the spectrum. It has a stellar classification of C-N5 with a carbon star class of C2 5-. [5] The star is losing mass at the rate of 1.2×10−7  M☉ ·yr−1, with an outflow velocity of 6.9 km/s. Technetium has been detected in the spectrum, suggesting the star has experienced a third dredge-up episode due to thermal pulses of the helium-burning shell some time within the last 100,000 years. [13]

An ultraviolet (UV) excess has been detected coming from an extended elliptical ring that surrounds this star. It has a mean angular radius of 110″ and lines up with a detached shell of dusty material that was previously detected in the infrared band. The material was most likely ejected from the star due to mass loss episodes. The probable cause of the UV emission is from the movement of the star through space and possibly shock-excited molecules of H2. The emission does not show a bow-shock-like structure. [14]

Related Research Articles

<span class="mw-page-title-main">R Hydrae</span> Variable star in the constellation Hydra

R Hydrae, abbreviated R Hya, is a single star in the equatorial constellation of Hydra, about 2.7° to the east of Gamma Hydrae. It is a Mira-type variable that ranges in apparent visual magnitude from 3.5 down to 10.9 over a period of 389 days. At maximum brightness the star can be seen with the naked eye, while at minimum a telescope of at least 5 cm is needed. This star is located at a distance of approximately 410 light-years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −10 km/s.

3 Centauri is a triple star system in the southern constellation of Centaurus, located approximately 300 light years from the Sun. It is visible to the naked eye as a faint, blue-white hued star with a combined apparent visual magnitude of 4.32. As of 2017, the two visible components had an angular separation of 7.851″ along a position angle of 106°. The system has the Bayer designation k Centauri; 3 Centauri is the Flamsteed designation. It is a suspected eclipsing binary with a variable star designation V983 Centauri.

Delta Hydrae, Latinized from δ Hydrae, is a double star in the equatorial constellation of Hydra. It is visible to the naked eye with an apparent visual magnitude of 4.146. Based upon an annual parallax shift of 20.34 mas, it is located about 160 light years from the Sun.

<span class="mw-page-title-main">Xi Hydrae</span> Star in the constellation Hydra

Xi Hydrae, Latinised from ξ Hydrae, is a solitary star in the equatorial constellation of Hydra. It was also given the Flamsteed designation 19 Crateris. This magnitude 3.54 star is situated 130 light-years from Earth and has a radius about 10 times that of the Sun. It is radiating 58 times as much luminosity as the Sun.

<span class="mw-page-title-main">V Hydrae</span> Variable star in the constellation Hydra

V Hydrae is a carbon star in the constellation Hydra. To date perhaps uniquely in our galaxy it has plasma ejections/eruptions on a grand scale every 8.5 years caused by its near, unseen companion in an 8.5 year orbit, inferred by its ultraviolet excess and periastron passage likely through the outer parts of the star itself.

Theta Hydrae, Latinized from θ Hydrae, is a binary star system in the constellation Hydra. It is visible to the naked eye with an apparent visual magnitude of 3.9. The star system has a high proper motion with an annual parallax shift of 28.4 mas, indicating a distance of about 115 light years. Theta Hydrae forms a double with a magnitude 9.9 star located at an angular separation of 29 arcseconds.

<span class="mw-page-title-main">Eta Hydrae</span> Star in the constellation Hydra

Eta Hydrae is a star in the equatorial constellation of Hydra. With an apparent visual magnitude of 4.3, it is visible to the naked eye. However, it is the faintest of the five stars that form the "head" of the hydra. Based upon an annual parallax shift of 5.56 mas, it is located roughly 590 light years from the Sun.

12 Hydrae is a probable astrometric binary star system located 202 light years away from the Sun in the equatorial constellation of Hydra. It has the Bayer designation D Hydrae; 12 Hydrae is the Flamsteed designation. This system is visible to the naked eye as a faint, yellow-hued star with a combined apparent visual magnitude of 4.32. It is moving closer to the Earth with a heliocentric radial velocity of −8.5 km/s.

58 Hydrae is a single star in the equatorial constellation of Hydra, located around 290 light years away from the Sun based on parallax. It has the Bayer designation E Hydrae; 58 Hydrae is the Flamsteed designation − a later designation of 6 Librae. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.42. This object is moving closer to the Earth with a heliocentric radial velocity of −9 km/s.

Upsilon2 Hydrae, Latinised from υ2 Hydrae, is a solitary star in the equatorial constellation of Hydra. Visible to the naked eye, it is photometrically stable with an apparent visual magnitude of 4.59. Based upon an annual parallax shift of 10.40 mas as seen from Earth, it is located about 314 light-years from the Sun.

Phi3 Hydrae is a binary star in the equatorial constellation of Hydra. It originally received the Flamsteed designation of 2 Crateris before being placed in the Hydra constellation. Based upon an annual parallax shift of 15.49 mas as seen from Earth, it is located around 211 light years from the Sun. It is visible to the naked eye with an apparent visual magnitude of 4.90. It forms a triangle with the fainter φ1 Hydrae and φ2 Hydrae, between μ Hydrae and ν Hydrae.

6 Hydrae is a single star in the equatorial constellation of Hydra, located 373 light-years away from the Sun. It has the Bayer designation a Hydrae; 6 Hydrae is the Flamsteed designation. This object is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 4.98. It is moving closer to the Earth with a heliocentric radial velocity of −8 km/s. Eggen (1995) listed it as a proper motion candidate for membership in the IC 2391 supercluster.

Omega Hydrae, Latinised from ω Hydrae, is a golden-hued star in the equatorial constellation of Hydra, located to the west-southwest of the brighter star Zeta Hydrae. Based upon an annual parallax shift of just 3.64 mas as seen from Earth, it is located roughly 900 light-years from the Sun. It is faintly visible to the naked eye with an apparent visual magnitude of 5.00.

Tau1 Hydrae is a triple star system in the equatorial constellation of Hydra. Based upon the annual parallax shift of the two visible components as seen from Earth, they are located about 18 parsecs (59 ly) from the Sun. The system has a combined apparent visual magnitude of +4.59, which is bright enough to be visible to the naked eye at night.

Phi1 Hydrae, Latinized from φ1 Hydrae, is a yellow-hued star in the constellation Hydra. Its apparent magnitude is 7.61, making it too faint to be seen with the naked eye. Based upon an annual parallax shift of 12.3 mas as seen from Earth, it is located about 266 light years from the Sun. It forms a triangle with the brighter φ2 Hydrae and φ3 Hydrae, between μ Hydrae and ν Hydrae.

HD 96819 is a single star in the equatorial constellation of Hydra. It was formerly known by its designation 10 Crateris, but that name fell into disuse after constellations were redrawn and the star was no longer in Crater. It is visible to the naked eye as a dim, white-hued star with an apparent visual magnitude of 5.43. Parallax measurements put it at a distance of 182 light years away from the Sun. This is most likely a member of the TW Hydrae association.

κ Hydrae, Latinised as Kappa Hydrae, is a solitary star in the equatorial constellation of Hydra. Its apparent visual magnitude is 5.06, which is bright enough to be faintly visible to the naked eye. The distance to this star is around 135 pc (440 ly), based upon an annual parallax shift of 7.48 mas. It may be a variable star, meaning it undergoes repeated fluctuations in brightness by at least 0.1 magnitude.

Chi<sup>2</sup> Hydrae Binary star system in the constellation Hydra

Chi2 Hydrae, Latinised from χ2 Hydrae, is a binary star system in the equatorial constellation of Hydra. Based upon an annual parallax shift of 4.6 mas as seen from Earth, it is located roughly 685 light years from the Sun. It is visible to the naked eye with a combined apparent visual magnitude of about 5.7.

<span class="mw-page-title-main">HS Hydrae</span> Triple star in the constellation of Hydra

HS Hydrae is a triple star system in the equatorial constellation of Hydra. The inner pair were an eclipsing binary during the period 1920 until 2019, with HS Hya being the variable star designation. With a base apparent visual magnitude of 8.08, HS Hya is too dim to be viewed with the naked eye. During the primary eclipse, the magnitude dropped to 8.61; the secondary eclipse lowered the magnitude to 8.55. Based on parallax measurements, the system is located at a distance of approximately 335 light years from the Sun. It is drifting closer with a mean radial velocity of −7 km/s.

<span class="mw-page-title-main">LQ Hydrae</span> Star in the constellation Hydra

LQ Hydrae is a single variable star in the equatorial constellation of Hydra. It is sometimes identified as Gl 355 from the Gliese Catalogue; LQ Hydrae is the variable star designation, which is abbreviated LQ Hya. The brightness of the star ranges from an apparent visual magnitude of 7.79 down to 7.86, which is too faint to be readily visible to the naked eye. Based on parallax measurements, this star is located at a distance of 59.6 light years from the Sun. It is drifting further away with a radial velocity of 7.6 km/s.

References

  1. ↑ "ASAS All Star Catalogue". The All Sky Automated Survey. Retrieved 8 December 2021.
  2. 1 2 3 4 5 6 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.
  3. 1 2 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.
  4. 1 2 3 4 5 6 Rau, G.; et al. (April 2017). "The adventure of carbon stars. Observations and modeling of a set of C-rich AGB stars". Astronomy & Astrophysics. 600: 21. arXiv: 1701.04331 . Bibcode:2017A&A...600A..92R. doi:10.1051/0004-6361/201629337. S2CID   49571205. A92.
  5. 1 2 Barnbaum, Cecilia; et al. (1996). "A Moderate-Resolution Spectral Atlas of Carbon Stars: R, J, N, CH, and Barium Stars". Astrophysical Journal Supplement. 105: 419. Bibcode:1996ApJS..105..419B. doi:10.1086/192323.
  6. 1 2 Samus, N. N.; et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID   125853869.
  7. 1 2 Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv: 1606.08053 . Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID   119231169.
  8. ↑ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics . 616. A1. arXiv: 1804.09365 . Bibcode: 2018A&A...616A...1G . doi: 10.1051/0004-6361/201833051 . Gaia DR2 record for this source at VizieR.
  9. ↑ Lambert, David L.; et al. (October 1986). "The Chemical Composition of Carbon Stars. I. Carbon, Nitrogen, and Oxygen in 30 Cool Carbon Stars in the Galactic Disk". Astrophysical Journal Supplement. 62: 373. Bibcode:1986ApJS...62..373L. doi:10.1086/191145.
  10. ↑ "U Hya". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 19 March 2016.
  11. ↑ Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv: 0806.2878 . Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. S2CID   14878976.
  12. ↑ Monks, Neale (2010). Go-To Telescopes Under Suburban Skies. Springer. p. 65. ISBN   978-1-4419-6851-7.
  13. ↑ Izumiura, H.; et al. (April 2011). "Extended dust shell of the carbon star U Hydrae observed with AKARI". Astronomy & Astrophysics. 528: 14. Bibcode:2011A&A...528A..29I. doi: 10.1051/0004-6361/201015163 . A29.
  14. ↑ Sanchez, Enmanuel; et al. (January 2015). "First Detection of Ultraviolet Emission from a Detached Dust Shell: Galaxy Evolution Explorer Observations of the Carbon Asymptotic Giant Branch Star U Hya". The Astrophysical Journal Letters. 798 (2): 5. arXiv: 1412.7542 . Bibcode:2015ApJ...798L..39S. doi:10.1088/2041-8205/798/2/L39. S2CID   118434298. L39.
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