EW Aquarii

EW Aquarii

Six visual band light curves of for EW Aquarii, adapted from Hobart et al. (1989)[1]
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]
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]

  1. ^ Cite error: The named reference Hobart was invoked but never defined (see the help page).
  2. ^ a b c d e f g h i Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  3. ^ a b c d e Cite error: The named reference Anderson_Francis_2012 was invoked but never defined (see the help page).
  4. ^ a b c d Cite error: The named reference AAVSOEW was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Houk_Smith-Moore_1978 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference Rodríguez_et_al_2000 was invoked but never defined (see the help page).
  7. ^ a b c Cite error: The named reference Balona_Evers_1999 was invoked but never defined (see the help page).
  8. ^ a b c d Cite error: The named reference Kilambi1978 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Edwards_et_al_1980 was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference Eggen1974 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Cowley_et_al_1968 was invoked but never defined (see the help page).
  13. ^ a b Cite error: The named reference Hobart1989 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Kilambi1024 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Kukarkin_et_al_1977 was invoked but never defined (see the help page).