U Hydrae

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

U Hydrae is a single [10] star in the equatorial constellation of Hydra, near the northern constellation border with Sextans. It is a semiregular variable star of sub-type SRb, [5] with its brightness ranging from visual magnitude (V) 4.7 to 5.2 over a 450-day period, with some irregularity. [11] This object is located at a distance of approximately 680  light years from the Sun based on parallax. [1] It is drifting closer with a radial velocity of −26 km/s. [6]

This is a carbon-rich red giant star on the asymptotic giant branch [3] – 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-. [4] 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. [12]

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. [13]

Related Research Articles

R Hydrae variable star in the constellation Hydra

R Hydrae, also known as R Hya, is a Mira-type variable star in the constellation Hydra.

U Antliae star

U Antliae is a variable star in the constellation Antlia. It is a carbon star surrounded by two thin shells of dust.

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.

Xi Hydrae star in the constellation Hydra

Xi Hydrae, Latinized 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.

28 Cygni is a single star in the northern constellation of Cygnus. It is a faint blue-white hued star but visible to the naked eye with an apparent visual magnitude of 4.93. The distance to 28 Cyg, as estimated from its annual parallax shift of 5.3 mas, is around 620 light years. It has an absolute magnitude of −2.56, which means that if the star were just 10 parsecs away it would be brighter than Sirius, the brightest star in the night sky.

37 Comae Berenices is a variable star system located around 690 light years away from the Sun in the northern constellation of Coma Berenices. It has the variable star designation LU Comae Berenices. 37 Comae Berenices was a later Flamsteed designation of 13 Canum Venaticorum. This object is visible to the naked eye as a faint, yellow-hued star with a baseline apparent visual magnitude of 4.88. It is drifting closer to the Earth with a heliocentric radial velocity of −14 km/s.

64 Eridani is a single, yellow-white hued star in the constellation Eridanus having variable star designation S Eridani. It is faintly visible to the naked eye with an apparent visual magnitude of 4.77. The annual parallax shift is measured at 12.01 mas, which equates to a distance of about 272 light years. In addition to its proper motion, it is moving closer to the Sun with a radial velocity of around −9 km/s.

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.

Eta Hydrae is the Bayer designation for 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.

Rho Hydrae star in the constellation Hydra

Rho Hydrae, equally written ρ Hydrae, is a binary star in the equatorial constellation of Hydra. It is visible to the naked eye with an apparent visual magnitude of 4.34. The distance to this system, based upon an annual parallax shift of 9.21 mas, is about 354 light years. At that distance, the visual magnitude is diminished by an interstellar extinction of 0.06 magnitudes, due to intervening dust.

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.

Chi1 Hydrae is a binary star in the equatorial constellation of Hydra. It originally received the Flamsteed designation of 9 Crateris before being placed in the Hydra constellation. Based upon an annual parallax shift of 22.8 mas as seen from Earth, it is located about 143 light years from the Sun. It is visible to the naked with a combined apparent visual magnitude of 4.94.

Psi Hydrae is a star in the equatorial constellation of Hydra. Based upon an annual parallax shift of 14.09 mas as seen from Earth, it is located around 231 light years away from the Sun. It is faintly visible to the naked eye with an apparent magnitude of 4.97.

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, Latinized 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.

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.

X Cancri variable star in the constellation Cancer

X Cancri is a variable star in the northern constellation of Cancer. It has a red hue and is visible to the naked eye at peak magnitude, fluctuating around an apparent visual magnitude of 6.28. The distance to this object is approximately 2,900 light years based on parallax measurements, but is drifting closer with a radial velocity of −5 km/s. It lies very close to the equinox and so is subject to lunar occultations.

References

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. "U Hya". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 19 March 2016.
  10. 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.
  11. Monks, Neale (2010). Go-To Telescopes Under Suburban Skies. Springer. p. 65. ISBN   978-1-4419-6851-7.
  12. 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.
  13. 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.