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  mas [7]
Distance approx. 4,000  ly
(approx. 1,200  pc)
Absolute magnitude  (MV)~ −2 – −3 [8]
Details
Mass 0.55–0.68 [9]   M☉
Radius 160 [10] [lower-alpha 1]   R☉
Luminosity 9,400 [10]   L☉
Surface gravity (log g)0.0 [10]   cgs
Temperature 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

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">Supergiant</span> Type of star that is massive and luminous

Supergiants are among the most massive and most luminous stars. Supergiant stars occupy the top region of the Hertzsprung–Russell diagram with absolute visual magnitudes between about −3 and −8. The temperature range of supergiant stars spans from about 3,400 K to over 20,000 K.

<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">Delta Scuti</span> 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.

<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">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">119 Tauri</span> 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. It is a similar star to Betelgeuse although redder and more distant.

<span class="mw-page-title-main">FF Aquilae</span> Star and possible star system in the constellation Aquila

FF Aquilae is a classical Cepheid variable star located in the constellation Aquila, close to the border with Hercules. It ranges from apparent magnitude 5.18 to 5.51 over a period of 4.47 days, meaning it is faintly visible to the unaided eye in rural or suburban settings.

<span class="mw-page-title-main">Yellow supergiant</span> Star that has a supergiant luminosity class, with a spectral type of F or G

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.

<span class="mw-page-title-main">S Persei</span> Red supergiant or hypergiant variable star in the constellation Perseus

S Persei is a red supergiant or hypergiant located near the Double Cluster in Perseus, north of the cluster NGC 869. It is a member of the Perseus OB1 association and one of the largest known stars. If placed in the Solar System, its photosphere would engulf the orbit of Jupiter. It is also a semiregular variable, a star whose variations are less regular than those of Mira variables.

<span class="mw-page-title-main">Type II Cepheid</span>

Type II Cepheids are variable stars which pulsate with periods typically between 1 and 50 days. They are population II stars: old, typically metal-poor, low mass objects.

<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">UY Scuti</span> Star in the constellation Scutum

UY Scuti (BD-12°5055) is a red supergiant star, located 5,900 light-years away in the constellation Scutum. It is also a pulsating variable star, with a maximum brightness of magnitude 8.29 and a minimum of magnitude 10.56, which is too dim for naked-eye visibility. It is considered to be one of the largest known stars, with a radius estimated at 909 solar radii, thus a volume of 750 million times that of the Sun. This estimate implies if it were placed at the center of the Solar System, its photosphere would extend past the orbit of Mars or even the asteroid belt.

AH Scorpii is a red supergiant variable star located in the constellation Scorpius. It is one of the largest stars known by radius and is also one of the most luminous red supergiant stars in the Milky Way.

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

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.

<span class="mw-page-title-main">AC Herculis</span> Spectroscopic binary 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.

<span class="mw-page-title-main">HP Lyrae</span> Variable star in the constellation Lyra

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.

<span class="mw-page-title-main">U Monocerotis</span> Variable star system in the constellation Monoceros

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.

<span class="mw-page-title-main">IRAS 08544−4431</span> 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.

<span class="mw-page-title-main">SX Centauri</span> Supergiant variable star in the constellation Centaurus

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.

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

SZ Tauri is a variable star in the equatorial constellation of Taurus. The brightness of this star varies from an apparent visual magnitude of 6.39 down to 6.69 with a period of 3.149 days, which is near the lower limit of visibility to the naked eye. The distance to this star is approximately 2,070 light years based on parallax measurements. There is some indication this may be a binary system, but the evidence is inconclusive.

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. ↑ 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 5 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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