Summary
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]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| 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 mas[2] |
| Distance | 439 ± 3 ly (134.5 ± 0.8 pc) |
| Absolute magnitude (MV) | 0.825[7] |
| Details | |
| Mass | 2.203[7] M☉ |
| Radius | 3.99±0.20[2] R☉ |
| Luminosity | 37.026±0.314[2] L☉ |
| Surface gravity (log g) | 3.91[8] cgs |
| Temperature | 7,640[8] K |
| Rotational velocity (v sin i) | 134[6] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
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 edit
- ^ 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.
- ^ a b c d e f g h i 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.
- ^ a b c d e 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.
- ^ a b c d Watson, Christopher (4 January 2010). "EW Aquarii". The International Variable Star Index. American Association of Variable Star Observers. Retrieved 4 June 2015.
- ^ a b 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.
- ^ a b c 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.
- ^ a b c 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.
- ^ a b c d 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.
- ^ "HD 199603". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 August 2018.
- ^ 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.
- ^ a b 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.
- ^ 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.
- ^ a b 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.
- ^ 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.
- ^ Kukarkin, B. V.; et al. (March 1977). "62nd Name-List of Variable Stars". Information Bulletin on Variable Stars. 1248: 1. Bibcode:1977IBVS.1248....1K.