R Scuti

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R Scuti
Scutum constellation map.svg
Red circle.svg
Location of R Scuti (circled)
Observation data
Epoch J2000       Equinox J2000
Constellation Scutum
Right ascension 18h 47m 28.95s [1]
Declination −05° 42′ 18.5″ [1]
Apparent magnitude  (V)4.2–8.6 [2]
Characteristics
Evolutionary stage Asymptotic giant branch [3]
Spectral type G0Iae-K2p(M3)Ibe [4]
U−B color index 1.53 [5]
B−V color index 1.47 [5]
Variable type RV Tau [2]
Astrometry
Radial velocity (Rv)43.80 [6]  km/s
Proper motion (μ)RA: −45.399 [7]   mas/yr
Dec.: −32.410 [7]   mas/yr
Parallax (π)0.8572 ± 0.2549 [7]   mas
Distance approx. 4,000  ly
(approx. 1,200  pc)
Absolute magnitude  (MV)~ −2 – −3 [8]
Details
Mass 0.55–0.68 [9]   M☉
Radius 84 [3]   R☉
Luminosity 5,000 [3] - 9,400 [10]   L☉
Surface gravity (log g)0.0 [10]   cgs
Temperature 4,000 [3] - 4,500 [10]   K
Metallicity [Fe/H]–0.4 [10]   dex
Other designations
HD  173819, HIP  92202, 2MASS  J18472894-0542185, SAO  142620, BD−05°4760, AAVSO  1842-05
Database references
SIMBAD data

R Scuti (R Sct) is a star in the constellation of Scutum. It is a yellow supergiant and is a pulsating variable known as an RV Tauri variable. It was discovered in 1795 by Edward Pigott at a time when only a few variable stars were known to exist. [11]

Contents

Observation

R Sct is the brightest of the RV Tau-type stars [12] and the American Association of Variable Star Observers (AAVSO) contains over 110,000 observations of this star. [13] At its brightest it is visible to the naked eye, and at its dimmest can be located with good binoculars. [13] In the sky it is about 1 degree northwest of the Wild Duck Cluster (Messier 11). [13]

RV Tauri variables often have somewhat irregular light curves, both in amplitude and period, but R Scuti is extreme. It has one of the longest periods known for an RV Tau variable, and the light curve has a number of unusual features: occasional extreme minima; intermittent standstills with only small erratic variation that may last for years; and periods of chaotic brightness changes. [14] [15]

AAVSO light curve of R Sct from 1 Jan 2009 to 24 Nov 2010. Up is brighter and down is fainter. Day numbers are Julian day. R-Sct-Lightcurve-AAVSO.gif
AAVSO light curve of R Sct from 1 Jan 2009 to 24 Nov 2010. Up is brighter and down is fainter. Day numbers are Julian day.

Properties

The spectrum of R Scuti is peculiar, especially at cooler temperatures near the minima. In deep minima, much of the spectrum corresponds to an early K supergiant, but the spectrum also develops TiO bands more typical of an M-class star. [16]

The recognised spectral type of G0Iae-K2p(M3)Ibe gives an idea of the complexities of this star. Both the radius and temperature change, with maximum brightness corresponding to maximum temperature. The radius changes lag and the smallest size occurs about a quarter of the period after the minimum brightness. [4]

The spectral luminosity type classes R Sct as a supergiant, a bright supergiant (class Ia) near maximum, but it is actually thought to be a highly evolved and expanded low-mass star probably no more than 10,000 times the luminosity of the sun even at its brightest. The period-luminosity relation for type II Cepheids suggests a luminosity of 9300 L☉, similar to the spectrophotometric derivation at 9400 L☉. [8] Other derivations have produced much lower values, but often making unrealistic assumptions about the distance based on an obsolete Hipparcos parallax value. [8]

An extreme post-AGB star would be expected to show measurable secular changes in its temperature and period over the time that R Scuti has been closely observed. Instead a relatively low mass loss rate with an extended cool atmosphere and fairly constant temperature and period of variation is seen. One suggestion is that R Scuti is still a thermally pulsing AGB star, consistent with calculated levels of mass loss. [9]

The evolutionary status of R Scuti is uncertain and estimates of the mass vary wildly. RV Tau variables as post-AGB stars are expected to have masses near or below that of the sun and this is confirmed for a number of RV Tau stars in binary systems. [17] Old estimates based simply on the supergiant luminosity class gave much higher masses. [18]

See also

Related Research Articles

Supergiant Type of star that is massive and luminous

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Red supergiant Stars with a supergiant luminosity class

Red supergiants (RSGs) are stars with a supergiant luminosity class of spectral type 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 are the brightest and best known red supergiants (RSGs), indeed the only first magnitude red supergiant stars.

Delta Scuti Star in the constellation Scutum

Delta Scuti, Latinized from δ Scuti, is a variable star in the southern constellation Scutum. With an apparent visual magnitude that fluctuates around 4.72, it is the fifth-brightest star in this small and otherwise undistinguished constellation. Analysis of the parallax measurements place this star at a distance of about 199 light-years from Earth. It is drifting closer with a radial velocity of −45 km/s.

Rho Tauri Star in the constellation Taurus

Rho Tauri is a star in the constellation Taurus and a member of the Hyades star cluster.

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.

RV Tauri variable

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

119 Tauri Star in the constellation Taurus

119 Tauri is a red supergiant star in the constellation Taurus. It is a semiregular variable and its angular diameter has been measured at about 10 mas.

Yellow supergiant

A yellow supergiant (YSG) is a star, generally of spectral type F or G, having a supergiant luminosity class. They are stars that have evolved away from the main sequence, expanding and becoming more luminous.

HR 4049 Protoplanetary nebula in the constellation Antlia

HR 4049, also known as HD 89353 and AG Antliae, is a binary post-asymptotic-giant-branch (post-AGB) star in the constellation Antlia. A very metal-poor star, it is surrounded by a thick unique circumbinary disk enriched in several molecules. With an apparent magnitude of about 5.5, the star can readily be seen under ideal conditions. It is located approximately 1,700 parsecs (5,500 ly) distant.

NO Aurigae Star in the constellation Auriga

NO Aurigae is a pulsating variable star in the constellation Auriga.

VX Sagittarii Extreme asymptotic giant branch star in the constellation Sagittarius

VX Sagittarii is an extreme asymptotic giant branch star located more than 1.5 kiloparsec away from the Sun in the constellation of Sagittarius. It is a pulsating variable star with an unusually large magnitude range. It is also one of the largest stars discovered so far, with a radius varying between 1,350 and 1,940 solar radii (940,000,000 and 1.35×109 km; 6.3 and 9.0 au). It is the most luminous known AGB star, at bolometric magnitude –8.6, which is even brighter than the theoretical limit at –8.0.

UY Scuti Red supergiant star in the constellation Scutum

UY Scuti (BD-12°5055) is a red supergiant star in the constellation Scutum. It is considered one of the largest known stars by radius and is also a pulsating variable star, with a maximum brightness of magnitude 8.29 and a minimum of magnitude 10.56. It has an estimated radius of 1,708 solar radii (1.188×109 kilometres; 7.94 astronomical units), thus a volume nearly 5 billion times that of the Sun. It is approximately 2.9 kiloparsecs (9,500 light-years) from Earth. If placed at the center of the Solar System, its photosphere would at least engulf the orbit of Jupiter.

S Vulpeculae is a star located in the constellation Vulpecula. A supergiant star, it is around 382 times the diameter of the Sun.

R Sagittae is an RV Tauri variable star in the constellation Sagitta that varies from magnitude 8.0 to 10.5 in 70.77 days. It is a post-AGB low mass yellow supergiant that varies between spectral types G0Ib and G8Ib as it pulsates. Its variable star designation of "R" indicates that it was the first star discovered to be variable in the constellation. It was discovered in 1859 by Joseph Baxendell, though classified as a semi regular variable until RV Tauri variables were identified as a distinct class in 1905.

AC Herculis Star in the constellation Hercules

AC Herculis, is an RV Tauri variable and spectroscopic binary star in the constellation of Hercules. It varies in brightness between apparent magnitudes 6.85 and 9.0.

HP Lyrae is a variable star in the constellation Lyra, with a visual magnitude varying between 10.2 and 10.8. It is likely to be an RV Tauri variable, an unstable post-AGB star losing mass before becoming a white dwarf.

U Monocerotis is a pulsating variable star and spectroscopic binary in the constellation Monoceros. The primary star is an RV Tauri variable, a cool luminous post-AGB star evolving into a white dwarf.

IRAS 08544−4431 Variable star in the constellation Vela

IRAS 08544−4431 is a binary system surrounded by a dusty ring in the constellation of Vela. The system contains an RV Tauri variable star and a more massive but much less luminous companion.

S Scuti is a carbon star located in the constellation Scutum. Parallax measurements by Hipparcos put it at a distance of approximately 1,300 light-years. Its apparent magnitude is 6.80, making it visible to the naked eye only under excellent conditions.

SX Centauri is a variable star in the constellation Centaurus. An RV Tauri variable, its light curve alternates between deep and shallow minima, varying its apparent magnitude from 9.1 to 12.4. From the period-luminosity relationship, it is estimated to be around 1.6 kpc from Earth. Gaia Data Release 2 gives a parallax of 0.2175 mas, corresponding to distance of about 4,600 pc.

References

  1. 1 2 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 "GCVS Query=R Sct". General Catalogue of Variable Stars @ Sternberg Astronomical Institute, Moscow, Russia . Retrieved 2010-11-24.
  3. 1 2 3 4 De Beck, E.; Decin, L.; De Koter, A.; Justtanont, K.; Verhoelst, T.; Kemper, F.; Menten, K. M. (2010). "Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles. II. CO line survey of evolved stars: derivation of mass-loss rate formulae". Astronomy and Astrophysics . 523: A18. arXiv: 1008.1083 . Bibcode:2010A&A...523A..18D. doi:10.1051/0004-6361/200913771. S2CID   16131273. A18.
  4. 1 2 Shenton, M.; Monier, R.; Evans, A.; Carter, B.; et al. (1994). "Multiwavelength observations of RV Tauri stars III. R Scuti". Astronomy and Astrophysics. 287: 866. Bibcode:1994A&A...287..866S.
  5. 1 2 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: 0. Bibcode:2002yCat.2237....0D.
  6. ↑ Gontcharov, G. A. (November 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.
  7. 1 2 3 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. 1 2 3 Kipper, Tõnu; Klochkova, Valentina G. (2013). "Peculiarities and Variations in the Optical Spectrum of the RV Tauri-type Star R Sct". Baltic Astronomy. 22 (2): 77. Bibcode:2013BaltA..22...77K. doi: 10.1515/astro-2017-0149 .
  9. 1 2 Matsuura, M.; Yamamura, Issei; Zijlstra, A. A.; Bedding, T. R. (2002). "The extended atmosphere and evolution of the RV Tau star, R Scuti". Astronomy and Astrophysics. 387 (3): 1022. arXiv: astro-ph/0203234 . Bibcode:2002A&A...387.1022M. doi:10.1051/0004-6361:20020391. S2CID   119342312.
  10. 1 2 3 4 Ruyter, S; Winckel; Dominik; Waters; et al. (2005). "Strong dust processing in circumstellar discs around 6 RV Tauri stars. Are dusty RV Tauri stars all binaries?". Astronomy and Astrophysics. 435 (1): 161–166. arXiv: astro-ph/0503290v1 . Bibcode:2005A&A...435..161D. doi:10.1051/0004-6361:20041989. S2CID   54547984.
  11. ↑ Pigott, Edward; Englefield, Henry C. (1797). "On the Periodical Changes of Brightness of Two Fixed Stars. By Edward Pigott, Esq. Communicated by Sir Henry C. Englefield, Bart. F. R. S". Philosophical Transactions of the Royal Society of London. 87: 133–141. Bibcode:1797RSPT...87..133P. doi: 10.1098/rstl.1797.0007 . JSTOR   106921. S2CID   186214528.
  12. ↑ "GCVS Type=RV". General Catalogue of Variable Stars @ Sternberg Astronomical Institute, Moscow, Russia . Retrieved 2010-11-24.
  13. 1 2 3 "R Scuti : A Favorite Among Its Class". AAVSO . Retrieved 2010-11-24.
  14. ↑ Lebre, A.; Gillet, D. (1991). "The bright RV Tauri star R Scuti during an exceptional irregular light phase". Astronomy and Astrophysics. 246: 490. Bibcode:1991A&A...246..490L.
  15. ↑ Gillet, D. (1992). "On the origin of the alternating deep and shallow light minima in RV Tauri stars - R Scuti and AC Herculis". Astronomy and Astrophysics. 259: 215. Bibcode:1992A&A...259..215G.
  16. ↑ Bopp, B. W.; Howell, S. B. (1982). "The Remarkable Spectrum of the RV Tauri Star R Souti at Deep Minimum". Bulletin of the American Astronomical Society. 14 (572): 762–767. Bibcode:1982BAAS...14Q.880B. JSTOR   40678238.
  17. ↑ Harris, Hugh C.; Welch, Douglas L. (1989). "The Binary Type II Cepheids IX CAS and TX Del". Astronomical Journal. 98: 981. Bibcode:1989AJ.....98..981H. doi:10.1086/115190.
  18. ↑ Robert Burnham (1978). Burnham's celestial handbook : an observer's guide to the Universe beyond the solar system . New York: Dover Publications. ISBN   0486318036.
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