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 |
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]
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 |
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]