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EW Aquarii

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Variable star in the constellation Aquarius
EW Aquarii

Six visual band light curves of for EW Aquarii, adapted from Hobart et al. (1989)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 21 11 41.33844
Declination −14° 28′ 20.5590″
Apparent magnitude (V) 6.47 (6.41 - 6.48)
Characteristics
Spectral type A8 III or Fm δ Del
U−B color index 0.15
B−V color index 0.316±0.007
Variable type δ Sct
Astrometry
Radial velocity (Rv)−39.2±2.9 km/s
Proper motion (μ) RA: +39.263 mas/yr
Dec.: +0.614 mas/yr
Parallax (π)7.4366 ± 0.0435 mas
Distance439 ± 3 ly
(134.5 ± 0.8 pc)
Absolute magnitude (MV)0.825
Details
Mass2.203 M☉
Radius3.99±0.20 R☉
Luminosity37.026±0.314 L☉
Surface gravity (log g)3.91 cgs
Temperature7,640 K
Rotational velocity (v sin i)134 km/s
Other designations
BD−15°5908, FK5 5868, HD 201707, HIP 104634, HR 8102, SAO 164204
Database references
SIMBADdata

EW Aquarii, or HR 8102, is a variable star in the equatorial constellation of Aquarius. With an apparent visual magnitude that fluctuates around 6.47, it is a dim star near the lower limit of visibility to the naked eye. The star is located at a distance of approximately 439 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −39 km/s. The star is positioned near the ecliptic and thus is subject to lunar occultations. It may be a member of the Hyades Group.

In 1969, HR 8102 was flagged as a suspected metal-lined Delta Delphini star and was catalogued as such. During a search for ultra-short period Cepheid variables in 1974, this star was found to vary in brightness and was determined to be a low amplitude Delta Scuti variable. In 1977, it was catalogued in the 62nd name-list of variable stars with the designation EW Aqr. The star varies between magnitudes 6.41 and 6.48 with a primary period of 2.16 hours. There are three known variation periods of 0.09664, 0.1087, and 0.2121 days with amplitudes of 0.013, 0.010, and 0.007 magnitudes, respectively. The pattern of variations indicate it is a non-radial pulsator.

The stellar classification of EW Aqr is Fm δ Del, indicating an F-type Am star of the Delta Delphini type. It has 2.2 times the mass of the Sun and four times the Sun's radius. The star has a high rate of spin, showing a projected rotational velocity of 134 km/s. On average, it is radiating 37 times the luminosity of the Sun from its photosphere at an effective temperature of 7,640 K.

References

  1. Hobart, M. A.; Pena, J. H.; Peniche, R. (December 1989). "EW Aqr, a non radial Delta Scuti pulsator". Revista Mexicana de Astronomía y Astrofísica. 17: 103–108. Bibcode:1989RMxAA..17..103H. Retrieved 16 October 2021.
  2. ^ 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. ^ 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. ^ Watson, Christopher (4 January 2010). "EW Aquarii". The International Variable Star Index. American Association of Variable Star Observers. Retrieved 4 June 2015.
  5. ^ Houk, Nancy; Smith-Moore, M. (1978). Michigan catalogue of two-dimensional spectral types for the HD stars. Vol. 4. Ann Arbor: Dept. of Astronomy, University of Michigan. Bibcode:1988mcts.book.....H.
  6. ^ Rodríguez, E.; et al. (June 2000). "A revised catalogue of δ Sct stars". Astronomy and Astrophysics Supplement. 144 (3): 469–474. Bibcode:2000A&AS..144..469R. doi:10.1051/aas:2000221. hdl:10261/226673.
  7. ^ Balona, L. A.; Evers, E. A. (January 1999). "Mode identification and asteroseismology of delta Scuti stars". Monthly Notices of the Royal Astronomical Society. 302 (2): 349–361. Bibcode:1999MNRAS.302..349B. doi:10.1046/j.1365-8711.1999.02125.x.
  8. ^ Kilambi, G. C.; et al. (April 1978). "uvby analysis of HR 8102". Publications of the Astronomical Society of the Pacific. 90: 194–200. Bibcode:1978PASP...90..194K. doi:10.1086/130307. S2CID 119675836.
  9. "HD 199603". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 August 2018.
  10. Edwards, D. A.; et al. (April 1980). "Photoelectric observations of lunar occultations. XI". Astronomical Journal. 85: 478–489. Bibcode:1980AJ.....85..478E. doi:10.1086/112700. See run #5217, for example.
  11. ^ Eggen, O. J. (October 1974). "Photometry of Possible Ultrashort Period Cepheids in the Disk Populations". Information Bulletin on Variable Stars. 935: 1. Bibcode:1974IBVS..935....1E.
  12. Cowley, A. P.; et al. (December 1968). "Further Bright Peculiar A Stars". Publications of the Astronomical Society of the Pacific. 80 (477): 746. Bibcode:1968PASP...80..746C. doi:10.1086/128719. S2CID 122523455.
  13. ^ Hobart, M. A.; et al. (December 1989). "EW Aqr, a non radial Delta Scuti pulsator". Revista Mexicana de Astronomía y Astrofísica. 17: 103–108. Bibcode:1989RMxAA..17..103H.
  14. Kilambi, G. C. (July 1975). "H beta-photometry of HR 8024 and HR 8102". Information Bulletin on Variable Stars. 1024: 1. Bibcode:1975IBVS.1024....1K.
  15. Kukarkin, B. V.; et al. (March 1977). "62nd Name-List of Variable Stars". Information Bulletin on Variable Stars. 1248: 1. Bibcode:1977IBVS.1248....1K.
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