Delta Scuti

Delta Scuti (δ Sct, δ Scuti) is a giant star in the southern constellation Scutum. With an apparent visual magnitude of 4.72,[4] it is the fifth-brightest star in this small and otherwise undistinguished constellation. Analysis of the parallax measurements made during the Hipparcos mission place this star at a distance of about 202 light-years (62 parsecs) from Earth.[1] Delta Scuti is the prototype of the Delta Scuti type variable stars. It is a high-amplitude δ Scuti type pulsator with light variations of about 0.15 minutes. The peculiar chemical abundances of this star are similar to those of Am stars.[8]

δ Scuti

Location of Delta Scuti (center).
Observation data
Epoch J2000      Equinox J2000
Constellation Scutum
Right ascension 18h 42m 16.422137s[1]
Declination −09° 03′ 09.19206″[1]
Apparent magnitude (V) 4.60 - 4.79[2]
Characteristics
Spectral type F2 IIIp[3]
U−B color index +0.16[4][2]
B−V color index +0.35[4]
Variable type δ Sct
Astrometry
Radial velocity (Rv)−44.8[5] km/s
Proper motion (μ) RA: 9.21[1] mas/yr
Dec.: 0.82[1] mas/yr
Parallax (π)16.11 ± 0.31[1] mas
Distance202 ± 4 ly
(62 ± 1 pc)
Absolute magnitude (MV)0.72±0.04[6]
Details
Mass2.23+0.06
−0.05[7] M☉
Surface gravity (log g)3.5[8] cgs
Temperature7000[8] K
Metallicity [Fe/H]0.41[6] dex
Rotational velocity (v sin i)25.5[8] km/s
Age0.7±0.1[6] Gyr
Other designations
2 Sct, BD−09° 4796, FK5 1486, HD 172748, HIP 91726, HR 7020, SAO 142515.[9]
Database references
SIMBADdata

In 1900, William W. Campbell and William H. Wright used the Mills spectrograph at the Lick Observatory to determine that this star has a variable radial velocity.[10] The 0.19377-day period of this variability as well as 0.2 magnitude changes in luminosity demonstrated in 1935 that the variability was intrinsic, rather than being the result of a spectroscopic binary.[11] In 1938, a secondary period was discovered and a pulsation theory was proposed to model the variation.[12] Since then, observation of Delta Scuti has shown that it pulsates in multiple discrete radial and non-radial modes. The strongest mode has a frequency of 59.731 μHz, the next strongest has a frequency of 61.936 μHz, and so forth, with a total of eight different frequency modes now modeled.[13]

The space velocity components of this star in the galactic coordinate system are [U, V, W] = [–42, –17, –1] km·s−1. It is following an orbit through the Milky Way galaxy that has an eccentricity of 0.11, carrying it as close as 22.31 kly (6.84 kpc) to, and as far as 27.59 kly (8.46 kpc) from the galactic center.[6] If Delta Scuti maintains its current movement and brightness, it will pass within 10 light-years of the solar system,[14] becoming the brightest star in the sky between 1150000 and 1330000 CE. It will reach an apparent magnitude of -1.84, brighter than the current -1.46 of Sirius.[15]

This star has two optical companions. The first is a +12.2 magnitude star that is 15.2 arcseconds from Delta Scuti. The second is a +9.2 magnitude star that is 53 arcseconds away.[16]

Flamsteed did not recognise the constellation Scutum and included several of its stars in Aquila. δ Scuti was catalogued as 2 Aquilae. The Bayer designation δ was assigned by Gould rather than Bayer.[17]

References
  1. van Leeuwen, F. (November 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
  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.
  3. Cowley, Anne; Fraquelli, Dorothy (February 1974), "MK Spectral Types for Some Bright F Stars", Publications of the Astronomical Society of the Pacific, 86 (509): 7, Bibcode:1974PASP...86...70C, doi:10.1086/129562
  4. Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
  5. Evans, D. S. (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten, Alan Henry; Heard, John Frederick (eds.). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. Bibcode:1967IAUS...30...57E.
  6. Holmberg, J.; Nordström, B.; Andersen, J. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191
  7. Nordström, B.; et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs", Astronomy and Astrophysics, 418: 989–1019, arXiv:astro-ph/0405198, Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959
  8. Yushchenko, A.; et al. (May 2005). "The chemical composition of δ Scuti". Monthly Notices of the Royal Astronomical Society. 359 (55): 865–873. Bibcode:2005MNRAS.359..865Y. doi:10.1111/j.1365-2966.2005.08921.x.
  9. "del Sct – Variable star of delta Sct type". SIMBAD Astronomical Object Database. Centre de Données astronomiques de Strasbourg. Retrieved 2009-10-23.
  10. Campbell, W. W.; Wright, W. H. (1900). "A list of nine stars whose velocities in the line of sight are variable". Astrophysical Journal. 12: 254–257. Bibcode:1900ApJ....12..254C. doi:10.1086/140765. Listed as 2 Scuti on p. 256.
  11. Colacevich, A. (August 1935). "On the variable radial velocity of δ Scuti". Publications of the Astronomical Society of the Pacific. 47 (278): 231–232. Bibcode:1935PASP...47..231C. doi:10.1086/124599.
  12. Sterne, T. E. (March 1938). "The Secondary Variation of δ Scuti". Astrophysical Journal. 87: 133–150. Bibcode:1938ApJ....87..133S. doi:10.1086/143913.
  13. Templeton, Matthew R.; et al. (October 1997). "A New Pulsation Spectrum and Asteroseismology of delta Scuti". The Astronomical Journal. 114: 1592–1601. Bibcode:1997AJ....114.1592T. doi:10.1086/118590.
  14. García-Sánchez, J.; et al. (2001), "Stellar encounters with the solar system", Astronomy and Astrophysics, 379 (2): 634–659, Bibcode:2001A&A...379..634G, doi:10.1051/0004-6361:20011330
  15. Sky and Telescope, April 1998 (p60), based on computations from Hipparcos mission data.
  16. Burnham, Robert (1978). Burnham's celestial handbook: an observer's guide to the universe beyond the solar system. 3. Courier Dover Publications. p. 1746. ISBN 0-486-23673-0.
  17. Wagman, M. (August 1987). "Flamsteed's Missing Stars". Journal for the History of Astronomy. 18 (3): 212. Bibcode:1987JHA....18..209W. doi:10.1177/002182868701800305.
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