TW Horologii

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TW Horologii
TWHorLightCurve.png
A visual band light curve for TW Horologii, plotted from data published by Tabur et al. (2009) [1]
Observation data
Epoch J2000       Equinox J2000
Constellation Horologium
Right ascension 03h 12m 33.16062s [2]
Declination −57° 19′ 17.5710″ [2]
Apparent magnitude  (V)5.71 [3] (5.52 to 5.95) [4]
Characteristics
Spectral type C-N4IIIb: (C23.5) [5]
U−B color index +2.93 [6]
B−V color index +2.419±0.014 [3]
Variable type SRb [4]
Astrometry
Radial velocity (Rv)+14.3±2.9 [3]  km/s
Proper motion (μ)RA: +18.492 [2]   mas/yr
Dec.: +13.298 [2]   mas/yr
Parallax (π)2.3755 ± 0.1295  mas [2]
Distance 1,370 ± 70  ly
(420 ± 20  pc)
Absolute magnitude  (MV)−1.79 [3]
Absolute bolometric
magnitude  (Mbol)		−4.62 [7]
Details
Mass 3.29±0.65 [8]   M☉
Radius 303 [9] [lower-alpha 1]   R☉
Luminosity 6,700 [9]   L☉
Surface gravity (log g)0.049 [10]   cgs
Temperature 3,000 [9]   K
Other designations
TW Hor, CD−57°626, FK5  118, HD  20234, HIP  14930, HR  977, SAO  233037 [11]
Database references
SIMBAD data

TW Horologii is a carbon star and semiregular variable in the southern constellation of Horologium, [12] 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, [4] is visible to the naked eye and one of the brightest carbon stars. [12] Based on parallax measurements, it is located at a distance of approximately 1,370  light years from the Sun. [2] It is drifting further away with a radial velocity of +14 km/s. [3] In the past this star has been considered a member of the open cluster NGC 1252, but this now seems unlikely. [13]

This is an aging red giant star on the asymptotic giant branch [7] with a stellar classification of C-N4IIIb: and a C2 index of C23.5. It has been listed as a standard star for that MK spectral class. [5] The star is classified as a semiregular variable of type SRb and has a periodicity of 158 days. [4] It has expanded to 303 times the radius of the Sun and, on average, is radiating 6,700 times the Sun's luminosity from its swollen photosphere at an effective temperature of 3,000 K. [9] The short-lived element technetium has been observed in the spectrum, an indicator of thermal pulses during helium shell burning. [14]

Based on the detection of excess ultraviolet excess, it is most likely a binary star system. [15] An analysis of the motion of TW Horologii suggests a low-mass companion, although the UV excess suggests it is hot. [8]

In 2013 the luminosity of Mira variables, based on Hipparcos parallaxes, was used to calibrate a Period-luminosity relationship for carbon stars. The absolute magnitude of TW Horologii was calculated to be −1.79. [3]

Notes

  1. ↑ Applying the Stefan–Boltzmann law with a nominal solar effective temperature of 5,772  K:
    .

Related Research Articles

<span class="mw-page-title-main">Horologium (constellation)</span> Constellation in the southern celestial hemisphere

Horologium is a constellation of six stars faintly visible in the southern celestial hemisphere. It was first described by the French astronomer Nicolas-Louis de Lacaille in 1756 and visualized by him as a clock with a pendulum and a second hand. In 1922 the constellation was redefined by the International Astronomical Union (IAU) as a region of the celestial sphere containing Lacaille's stars, and has since been an IAU designated constellation. Horologium's associated region is wholly visible to observers south of 23°N.

<span class="mw-page-title-main">RV Tauri variable</span> Class of luminous variable star

RV Tauri variables are luminous variable stars that have distinctive light variations with alternating deep and shallow minima.

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

Omega Virginis is a solitary star in the zodiac constellation Virgo. It has an apparent visual magnitude of +5.2, which is bright enough to be faintly visible to the naked eye. Based upon an annual stellar parallax shift of 6.56 milliarcseconds, it is located about 500 light years from the Sun.

<span class="mw-page-title-main">Theta Apodis</span> Star in the constellation Apus

Theta Apodis is a variable star in the southern circumpolar constellation of Apus. It is a variable star with an apparent visual magnitude range of 4.65 to 6.20, which, according to the Bortle Dark-Sky Scale, means it is a faint star but visible to the naked eye from dark suburban skies. The distance to Theta Apodis is approximately 350 light-years, based upon parallax measurements made from the Gaia telescope. It is unusual in that it is a red star with a high proper motion.

27 Cancri is a single star in the zodiac constellation of Cancer, located around 990 light-years away from the Sun. It is visible to the naked eye as a faint, red-hued star with a typical apparent visual magnitude of around +5.56. The star is moving closer to the Earth with a heliocentric radial velocity of −8.3 km/s. It is a member of the Arcturus stream, a group of stars with high proper motion and metal-poor properties thought to be the remnants of a small galaxy consumed by the Milky Way.

<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 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">NO Aurigae</span> Star in the constellation Auriga

NO Aurigae is a pulsating variable star in the constellation Auriga. It is an unusually-luminous asymptotic giant branch star about 3,500 light years away.

<span class="mw-page-title-main">PZ Cassiopeiae</span> Star in the constellation Cassiopeia

PZ Cassiopeiae is a red supergiant star located in the constellation of Cassiopeia, and a semi-regular variable star.

<span class="mw-page-title-main">RS Telescopii</span> Star in the constellation Telescopium

RS Telescopii, abbreviated RS Tel, is a variable star in the southern constellation of Telescopium. It is a dim star with an apparent visual magnitude of 10.67, which is much too faint to be visible without a telescope. The variability of this star was discovered by Evelyn F. Leland and announced by Edward C. Pickering in 1910. It was first studied by Cecilia H. Payne in 1928 at the Harvard College Observatory.

<span class="mw-page-title-main">S Apodis</span> Variable star in the constellation Apus

S Apodis, also known as HD 133444 is a variable star located in the southern circumpolar constellation Apus. It has an apparent magnitude ranging from 9.6 to 17, which is below the limit for naked eye visibility. The object is located relatively far at a distance of approximately 15,000 light years based on Gaia DR3 parallax measurements, but it is drifting closer with a heliocentric radial velocity of −75 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.

<span class="mw-page-title-main">V915 Scorpii</span> Variable star in the constellation Scorpius

V915 Scorpii is a hypergiant and semiregular variable star, located 1,718 parsecs (5,600 ly) away in the constellation Scorpius. Its apparent magnitude varies between 6.22 and 6.64, being heavily diminshed by 2.93 magnitudes due to interstellar extinction.

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

BC Cygni is a red supergiant and pulsating variable star of spectral type M3.5Ia in the constellation Cygnus.

<span class="mw-page-title-main">II Lupi</span> Star in the constellation Lupus

II Lupi is a Mira variable and carbon star located in the constellation Lupus. It is the brightest carbon star in the southern hemisphere at 12 μm.

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

V Crucis is a carbon star in the constellation Crux. A Mira variable, its apparent magnitude ranges from 8.7 to 11.1 over 376.5 days. The fact that this star's period is nearly equal to one year makes it hard to get good observational coverage over the entire cycle. Its near-infrared light curve shows a contribution from the first harmonic of the fundamental period.

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

R Fornacis is a Mira variable and carbon star located in the constellation Fornax. It is around 1,800 light years away based on parallax measurements.

<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">56 Leonis</span> Variable star in the constellation Leo

56 Leonis is a red giant variable star located approximately 390 light years away in the constellation Leo.

References

  1. ↑ Tabur, V.; Bedding, T. R.; Kiss, L. L.; Moon, T. T.; Szeidl, B.; Kjeldsen, H. (December 2009). "Long-term photometry and periods for 261 nearby pulsating M giants". Monthly Notices of the Royal Astronomical Society. 400 (4): 1945–1961. arXiv: 0908.3228 . Bibcode:2009MNRAS.400.1945T. doi: 10.1111/j.1365-2966.2009.15588.x .
  2. 1 2 3 4 5 6 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.
  3. 1 2 3 4 5 6 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 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.
  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. ↑ Nicolet, B. (1978). "Catalogue of homogeneous data in the UBV photoelectric photometric system". Astronomy and Astrophysics Supplement Series. 34: 1–49. Bibcode:1978A&AS...34....1N.
  7. 1 2 Guandalini, R.; Cristallo, S. (2013). "Luminosities of carbon-rich asymptotic giant branch stars in the Milky Way". Astronomy & Astrophysics. 555: 7. arXiv: 1305.4203 . Bibcode:2013A&A...555A.120G. doi:10.1051/0004-6361/201321225. S2CID   54918450. A120.
  8. 1 2 Kervella, Pierre; Arenou, Frédéric; Mignard, François; Thévenin, Frédéric (2019). "Stellar and substellar companions of nearby stars from Gaia DR2. Binarity from proper motion anomaly". Astronomy and Astrophysics. 623: A72. arXiv: 1811.08902 . Bibcode:2019A&A...623A..72K. doi:10.1051/0004-6361/201834371. S2CID   119491061.
  9. 1 2 3 4 Siderud, Emelie (2020). Dust emission modelling of AGB stars.
  10. ↑ McDonald, I.; Zijlstra, A. A.; Watson, R. A. (2017). "Fundamental parameters and infrared excesses of Tycho-Gaia stars". Monthly Notices of the Royal Astronomical Society. 471 (1): 770. arXiv: 1706.02208 . Bibcode:2017MNRAS.471..770M. doi:10.1093/mnras/stx1433.
  11. ↑ "V* TW Hor". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 19 March 2016.
  12. 1 2 Streicher, Magda (October 2009). "The Pendulum Clock". Monthly Notes of the Astronomical Society of South Africa. 68 (9–10): 202–206. Bibcode:2009MNSSA..68..202S.
  13. ↑ de la Fuente Marcos, R.; et al. (September 2013). "NGC 1252: a high altitude, metal poor open cluster remnant". Monthly Notices of the Royal Astronomical Society. 434 (1): 194–208. arXiv: 1306.1643 . Bibcode:2013MNRAS.434..194D. doi:10.1093/mnras/stt996.
  14. ↑ Lebzelter, T.; Hron, J. (December 2003). "Technetium and the third dredge up in AGB stars. I. Field stars". Astronomy and Astrophysics. 411 (3): 533–542. arXiv: astro-ph/0310018 . Bibcode:2003A&A...411..533L. doi:10.1051/0004-6361:20031458. S2CID   18879265.
  15. ↑ Ortiz, Roberto; Guerrero, Martín A. (September 2016). "Ultraviolet emission from main-sequence companions of AGB stars". Monthly Notices of the Royal Astronomical Society. 461 (3): 3036–3046. arXiv: 1606.09086 . Bibcode:2016MNRAS.461.3036O. doi:10.1093/mnras/stw1547.
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