V Hydrae

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V Hydrae
Hydra constellation map.svg
Red circle.svg
Location of V Hydrae (circled)
Observation data
Epoch J2000       Equinox J2000
Constellation Hydra
Right ascension 10h 51m 37.25661s [1]
Declination −21° 15′ 00.3245″ [1]
Apparent magnitude  (V)6.0 - 12.3 [2]
Characteristics
Spectral type C6,3e-C7,5e(N6e) [3]
B−V color index +5.43 [4]
Variable type SRa [3]
Astrometry
Radial velocity (Rv)−14.80 [5]  km/s
Proper motion (μ)RA: −11.02 ± 1.14 [1]   mas/yr
Dec.: 2.29 ± 1.16 [1]   mas/yr
Parallax (π)1.44 ± 1.41  mas [1]
Distance approx. 2,000  ly
(approx. 700  pc)
Absolute magnitude  (MV)−3.5 to +1.8 [6]
Orbit [7]
Period (P)17.45+0.34
−0.29 yr
Semi-major axis (a)11.2+1.2
−1.5  AU
Eccentricity (e)0.024+0.027
−0.017
Inclination (i)37.7+2.2
−2.0°
Longitude of the node (Ω)159.7+43.0
−3.3°
Periastron epoch (T) JD = 2,458,684+2,128
−2,582
Argument of periastron (ω)
(secondary)		343+147
−122°
Details
A
Mass 1.9±1.0 [7]   M☉
Radius 420 [8] –430 [9]   R☉
Luminosity 7,850 [10]   L☉
Surface gravity (log g)−0.5 [10]   cgs
Temperature 2,650 [10]   K
Rotational velocity (v sin i)11 - 14 [10]  km/s
B
Mass 2.63+0.63
−0.69 [7]   M☉
Radius 1.5 [7]   R☉
Temperature 9,950 [7]   K
Other designations
V  Hya, BD −20°3283, HIP  53085, 2MASS  J10513724-2115002, IRAS  10491-2059, WDS  J10516-2115
Database references
SIMBAD data

V Hydrae (V Hya) is a carbon star in the constellation Hydra. To date perhaps uniquely in our galaxy it has plasma ejections/eruptions on a grand scale that could be caused by its near, unseen companion.

Contents

Variability

A visual band light curve for V Hydrae, plotted from AAVSO data VHyaLightCurve.png
A visual band light curve for V Hydrae, plotted from AAVSO data

In the 1870s, Benjamin Apthorp Gould suspected that the star is variable, based on observations with opera glasses. In May 1888, Seth Carlo Chandler confirmed that the star is variable, citing observations from 1797 through 1879, and he derived a period of 535 days, which is very close to the currently accepted value. [12] Later that year, Chandler included the star with its variable star designation, V Hydrae, in his Catalogue of Variable Stars. [13]

V Hydrae is a semiregular variable star of type SRa, sometimes considered to be a Mira variable. It pulsates with a period of 530 days and a brightness range of 1-2 magnitudes, but also shows deep fades at intervals of about 17.5 years when it may drop below magnitude 12. [2] [14]

Evolutionary stage

V Hydrae is a late carbon star, an asymptotic giant branch (AGB) star that has dredged up sufficient material from its interior to have more carbon in its atmosphere than oxygen. The rate of mass loss from V Hydrae indicates that it is almost at the end of the AGB stage and about to lose its atmosphere completely and form a planetary nebula. It is sometimes considered to be a post-AGB object. [15]

Companions

V Hydrae has a visible binary companion 46" distant. It is a magnitude 11.5 K0 giant. [6]

V Hydrae also has an unseen companion inferred by its ultraviolet excess and radial-velocity monitoring. [7] [16] [9] It has been suggested that the steep drops in brightness every 17 years or so are caused by obscuration by a cloud associated with the companion passing in front of the giant star. [16] A study in 2024 used astrometry and radial velocity measurements and constrained the orbital parameters of the companion, as well as its mass, being 36% larger than the mass of the primary and equivalent to 2.6 times the mass of the Sun. [7]

Bullets

Artist's illustration of plasma ejections from V Hydrae. Artist's illustration of scenario for plasma ejections from V Hydrae.jpg
Artist's illustration of plasma ejections from V Hydrae.

V Hydrae has high-speed outflows of material collimated into jets, and also a disk of material around the star. Since the star itself is considered to be at the end of the Asymptotic Giant Branch (AGB) phase of evolution and starting to generate a planetary nebula, the mechanism for the ejection of this material can give key insights to the formation of planetary nebulae. Microwave spectra of rotational transitions of carbon monoxide show that portions of the envelope, probably the jets, are moving away from the star at 200 km/sec. This is far faster than the ~15 km/sec stellar wind that is typically seen around AGB stars. [17]

Related Research Articles

<span class="mw-page-title-main">Red supergiant</span> Stars with a supergiant luminosity class with a spectral type of K or M

Red supergiants (RSGs) are stars with a supergiant luminosity class and a stellar classification K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Antares A are the brightest and best known red supergiants (RSGs), indeed the only first magnitude red supergiant stars.

<span class="mw-page-title-main">Mira variable</span> Type of variable star

Mira variables are a class of pulsating stars characterized by very red colours, pulsation periods longer than 100 days, and amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wavelengths. They are red giants in the very late stages of stellar evolution, on the asymptotic giant branch (AGB), that will expel their outer envelopes as planetary nebulae and become white dwarfs within a few million years.

<span class="mw-page-title-main">Asymptotic giant branch</span> Stars powered by fusion of hydrogen and helium in shell with an inactive core of carbon and oxygen

The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) late in their lives.

<span class="mw-page-title-main">Chi Cygni</span> Star in the constellation Cygnus

Chi Cygni is a Mira variable star in the constellation Cygnus, and also an S-type star. It is around 500 light years away.

<span class="mw-page-title-main">RV Tauri</span> Star in the constellation Taurus

RV Tauri is a star in the constellation Taurus. It is a yellow supergiant and is the prototype of a class of pulsating variables known as RV Tauri variables. It is a post-AGB star and a spectroscopic binary about 4,700 light years away.

<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 but is drifting closer with a radial velocity of −10 km/s.

Mu<sup>1</sup> Cancri Red giant star in the constellation Cancer

Mu1 Cancri, Latinised from μ1 Cancri, is a variable star in the zodiac constellation of Cancer. The name Mu1 comes from the Bayer naming system: the "1" in the name is because (from Earth) it appears to be close to 10 Cancri, or Mu2 Cancri. It is also known by the variable star designation BL Cancri. The star is dimly visible to the naked eye with an apparent visual magnitude that ranges from 5.87 down to 6.07. Parallax measurements put it about 630 light-years (192 parsecs) from the Sun. At that distance, the visual magnitude is diminished by an extinction factor of 0.28. The position of the star near the ecliptic means it is subject to lunar occultations.

<span class="mw-page-title-main">La Superba</span> Variable star in the constellation Canes Venatici

La Superba is a strikingly red giant star in the constellation Canes Venatici. It is faintly visible to the naked eye, and the red colour is very obvious in binoculars. It is a carbon star and semiregular variable.

<span class="mw-page-title-main">R Andromedae</span> Star in the constellation Andromeda

R Andromedae is a Mira-type variable star in the constellation Andromeda. Its spectral class is type S because it shows absorption bands of zirconium monoxide (ZrO) in its spectrum. It was among the stars found by Paul Merrill to show absorption lines of the unstable element technetium, establishing that nucleosynthesis must be occurring in stars. The SH molecule was found for the first time outside earth in the atmosphere of this star. The star is losing mass due to stellar winds at a rate of 1.09×10−6M☉/yr.

<span class="mw-page-title-main">Red giant</span> Type of large cool star

A red giant is a luminous giant star of low or intermediate mass in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around 5,000 K [K] or lower. The appearance of the red giant is from yellow-white to reddish-orange, including the spectral types K and M, sometimes G, but also class S stars and most carbon stars.

<span class="mw-page-title-main">TX Camelopardalis</span> Star in the constellation Camelopardalis

TX Camelopardalis is a Mira-type variable star in the constellation Camelopardalis. It is a classical long period variable star with pulsational period of 558.7 days. Water masers have been observed around the star.

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

W Hydrae is a Mira-type variable star in the constellation Hydra. The star is nearly located within the Solar neighborhood, between 75 and 120 parsecs, likely at 320 light years from the Sun. It has a visual apparent magnitude range of 5.6 to 10. In the near-infrared J band it has a magnitude of -1.7, is the 7th brightest star in the night sky, and is even brighter than Sirius.

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

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

<span class="mw-page-title-main">Y Lyncis</span> Variable star in the constellation Lynx

Y Lyncis is a semiregular variable star in the constellation Lynx. It is an asymptotic giant branch star of spectral type M6S, with a luminosity class of Ib, indicating a supergiant luminosity. It is around 1,160 light years away. Y Lyncis ranges in brightness from magnitude 6.2 to 8.9. When it is at its brightest, it very faintly visible to the naked eye under excellent observing conditions.

<span class="mw-page-title-main">TW Horologii</span> Star in the constellation Horologium

TW Horologii is a carbon star and semiregular variable in the southern constellation of Horologium, near the eastern constellation border with Reticulum. It has a ruddy hue and, with an apparent visual magnitude that ranges from 5.52 down to 5.95, is visible to the naked eye and one of the brightest carbon stars. Based on parallax measurements, it is located at a distance of approximately 1,370 light years from the Sun. It is drifting further away with a radial velocity of +14 km/s. In the past this star has been considered a member of the open cluster NGC 1252, but this now seems unlikely.

<span class="mw-page-title-main">IK Tauri</span> Mira variable star in the constellation Taurus

IK Tauri or NML Tauri is a Mira variable star located about 280 parsecs (910 ly) from the Sun in the zodiac constellation of Taurus.

<span class="mw-page-title-main">Y Tauri</span> Variable star in the constellation Taurus

Y Tauri is a carbon star located in the constellation Taurus. Parallax measurements by Gaia put it at a distance of approximately 2,170 light-years.

<span class="mw-page-title-main">EP Aquarii</span> Variable star in the constellation Aquarius

EP Aquarii is a semiregular variable star in the equatorial constellation of Aquarius. At its peak brightness, visual magnitude 6.37, it might be faintly visible to the unaided eye under ideal observing conditions. A cool red giant on the asymptotic giant branch (AGB), its visible light brightness varies by about 1/2 magnitude over a period of 55 days. EP Aquarii has a complex circumstellar envelope (CSE), which has been the subject of numerous studies.

<span class="mw-page-title-main">R Volantis</span> Carbon star in the constellation Volans

R Volantis is a single variable star in the southern circumpolar constellation Volans. It has an average apparent magnitude of 8.7, making it readily visible in amateur telescopes but not to the naked eye. The object is relatively far at a distance of about 2,300 light years but is drifting closer with a radial velocity of −5 km/s.

<span class="mw-page-title-main">SW Virginis</span> Star in the constellation Virgo

SW Virginis is a star in the equatorial constellation of Virgo, abbreviated SW Vir. It is a variable star that ranges in brightness from an apparent visual magnitude of 6.65 down to 7.95, with a pulsation period of 153.8 days. The star is located at a distance of approximately 590 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −16 km/s. SW Vir is located near the ecliptic and is subject to lunar occultation, which has allowed its angular diameter to be directly measured.

References

  1. 1 2 3 4 5 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 Watson, Christopher (4 January 2010). "V Hydrae". The International Variable Star Index. American Association of Variable Star Observers . Retrieved 2016-10-12.
  3. 1 2 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. Bibcode:2009yCat....102025S.
  4. ↑ 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.
  5. ↑ Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 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.
  6. 1 2 Gordon, Courtney P. (1968). "The Absolute Magnitudes of Carbon Stars". Publications of the Astronomical Society of the Pacific. 80 (476): 597. Bibcode:1968PASP...80..597G. doi: 10.1086/128694 .
  7. 1 2 3 4 5 6 7 Planquart, L.; Jorissen, A.; et al. (2024). "A dynamic view of V Hydrae. Monitoring of a spectroscopic-binary AGB star with an alkaline jet". Astronomy & Astrophysics. 682: A143. arXiv: 2405.07820 . Bibcode:2024A&A...682A.143P. doi:10.1051/0004-6361/202347947.
  8. ↑ Luttermoser, Donald G.; Brown, Alexander (1992). "A VLA 3.6 centimeter survey of N-type carbon stars". Astrophysical Journal. 384: 634. Bibcode:1992ApJ...384..634L. doi:10.1086/170905.
  9. 1 2 Sahai, R.; Scibelli, S.; Morris, M. R. (2016). "High-speed Bullet Ejections during the AGB-to-Planetary Nebula Transition: HST Observations of the Carbon Star, V Hydrae". The Astrophysical Journal. 827 (2): 92. arXiv: 1605.06728 . Bibcode:2016ApJ...827...92S. doi: 10.3847/0004-637X/827/2/92 . S2CID   119209118.
  10. 1 2 3 4 Zhao-Geisler, R.; Quirrenbach, A.; Köhler, R.; Lopez, B. (2012). "Dust and molecular shells in asymptotic giant branch stars". Astronomy & Astrophysics. 545: A56. arXiv: 1207.3767 . Bibcode:2012A&A...545A..56Z. doi:10.1051/0004-6361/201118150. S2CID   53992211.
  11. ↑ "Download Data". aavso.org. AAVSO. Retrieved 1 October 2021.
  12. ↑ Chandler, S. C. (May 1888). "On a new variable of long period". Astronomical Journal. 8 (171): 24. Bibcode:1888AJ......8...24C. doi:10.1086/101016 . Retrieved 22 December 2024.
  13. ↑ Chandler, S. C. (September 1888). "Catalogue of Variable Stars". Astronomical Journal. 8: 81–94. Bibcode:1888AJ......8...81C. doi:10.1086/101060 . Retrieved 22 December 2024.
  14. ↑ Olivier, Enrico A.; Whitelock, Patricia; Marang, Fred (2001). "Dust-enshrouded asymptotic giant branch stars in the solar neighbourhood". Monthly Notices of the Royal Astronomical Society. 326 (2): 490. arXiv: astro-ph/0103294 . Bibcode:2001MNRAS.326..490O. doi: 10.1046/j.1365-8711.2001.04511.x . S2CID   15509666.
  15. ↑ Knapp, G. R.; Crosas, M.; Young, K.; Ivezić, Željko (2000). "Atomic Carbon in the Envelopes of Carbon-rich Post–Asymptotic Giant Branch Stars". The Astrophysical Journal. 534 (1): 324–334. arXiv: astro-ph/9912496 . Bibcode:2000ApJ...534..324K. doi:10.1086/308731. S2CID   2963393.
  16. 1 2 Sahai, R.; Findeisen, K.; Gil De Paz, A.; Sánchez Contreras, C. (2008). "Binarity in Cool Asymptotic Giant Branch Stars: A GALEX Search for Ultraviolet Excesses" (PDF). The Astrophysical Journal. 689 (2): 1274–1278. arXiv: 0807.1944 . Bibcode:2008ApJ...689.1274S. doi:10.1086/592559. S2CID   12437723.
  17. ↑ Knapp, G.R.; Jorissen, A.; Young, K. (October 1997). "A 200 km/sec Molecular Wind in the Peculiar Carbon Star V Hya". Astronomy and Astrophysics. 326: 318–328. Bibcode:1997A&A...326..318K . Retrieved 16 November 2020.
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