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    EW Aquarii

    Topic: Astronomy

     From Handwiki - Reading time: 4 min
    Short description: Variable star in the constellation Aquarius
    EW Aquarii
    EWAqrLightCurve.png
    Six visual band light curves of for EW Aquarii, adapted from Hobart et al. (1989)[1]
    Observation data
    Equinox J2000.0]] (ICRS)
    Constellation Aquarius
    Right ascension  21h 11m 41.33844s[2]
    Declination −14° 28′ 20.5590″[2]
    Apparent magnitude (V) 6.47[3] (6.41 - 6.48)[4]
    Characteristics
    Spectral type A8 III[4] or Fm δ Del[5]
    U−B color index 0.15[6]
    B−V color index 0.316±0.007[3]
    Variable type δ Sct[4]
    Astrometry
    Radial velocity (Rv)−39.2±2.9[3] km/s
    Proper motion (μ) RA: +39.263[2] mas/yr
    Dec.: +0.614[2] mas/yr
    Parallax (π)7.4366 ± 0.0435[2] mas
    Distance439 ± 3 ly
    (134.5 ± 0.8 pc)
    Absolute magnitude (MV)0.825[7]
    Details
    Mass2.203[7] M☉
    Radius3.99±0.20[2] R☉
    Luminosity37.026±0.314[2] L☉
    Surface gravity (log g)3.91[8] cgs
    Temperature7,640[8] K
    Rotational velocity (v sin i)134[6] km/s
    Other designations
    BD−15°5908, FK5 5868, HD 201707, HIP 104634, HR 8102, SAO 164204[9]
    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,[3] 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.[3] The star is positioned near the ecliptic and thus is subject to lunar occultations.[10] It may be a member of the Hyades Group.[11]

    In 1969, HR 8102 was flagged as a suspected metal-lined Delta Delphini star[12] and was catalogued as such.[13] During a search for ultra-short period Cepheid variables in 1974, this star was found to vary in brightness[11] and was determined to be a low amplitude Delta Scuti variable.[14][8] In 1977, it was catalogued in the 62nd name-list of variable stars with the designation EW Aqr.[15] The star varies between magnitudes 6.41 and 6.48 with a primary period of 2.16 hours.[4] 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.[13]

    The stellar classification of EW Aqr is Fm δ Del, indicating an F-type Am star of the Delta Delphini type.[5] It has 2.2[7] times the mass of the Sun and four[2] times the Sun's radius. The star has a high rate of spin, showing a projected rotational velocity of 134 km/s.[6] On average, it is radiating 37[2] times the luminosity of the Sun from its photosphere at an effective temperature of 7,640 K.[8]

    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. https://ui.adsabs.harvard.edu/abs/1989RMxAA..17..103H/abstract. Retrieved 16 October 2021. 
    2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
    3. ↑ 3.0 3.1 3.2 3.3 3.4 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A. 
    4. ↑ 4.0 4.1 4.2 4.3 Watson, Christopher (4 January 2010). "EW Aquarii". The International Variable Star Index. American Association of Variable Star Observers. http://www.aavso.org/vsx/index.php?view=detail.top&oid=1011. 
    5. ↑ 5.0 5.1 Houk, Nancy; Smith-Moore, M. (1978). Michigan catalogue of two-dimensional spectral types for the HD stars. 4. Ann Arbor: Dept. of Astronomy, University of Michigan. Bibcode: 1988mcts.book.....H. 
    6. ↑ 6.0 6.1 6.2 Rodríguez, E. et al. (June 2000). "A revised catalogue of δ Sct stars". Astronomy and Astrophysics Supplement 144 (3): 469–474. doi:10.1051/aas:2000221. Bibcode: 2000A&AS..144..469R. 
    7. ↑ 7.0 7.1 7.2 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. doi:10.1046/j.1365-8711.1999.02125.x. Bibcode: 1999MNRAS.302..349B. 
    8. ↑ 8.0 8.1 8.2 8.3 Kilambi, G. C. et al. (April 1978). "uvby analysis of HR 8102". Publications of the Astronomical Society of the Pacific 90: 194–200. doi:10.1086/130307. Bibcode: 1978PASP...90..194K. 
    9. ↑ "HD 199603". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+199603. 
    10. ↑ Edwards, D. A. et al. (April 1980). "Photoelectric observations of lunar occultations. XI.". Astronomical Journal 85: 478–489. doi:10.1086/112700. Bibcode: 1980AJ.....85..478E.  See run #5217, for example.
    11. ↑ 11.0 11.1 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. doi:10.1086/128719. Bibcode: 1968PASP...80..746C. 
    13. ↑ 13.0 13.1 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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