Observation data Epoch J2000.0 [1] Equinox J2000.0 [1] | |
---|---|
Constellation | Cetus |
Right ascension | 01h 31m 16.47427s |
Declination | −11° 07′ 07.9356″ |
Apparent magnitude (V) | 9.38 [2] (combined) |
Characteristics | |
Evolutionary stage | Main-sequence star |
Spectral type | A3V, [3] A3 SrEuCr [4] |
Apparent magnitude (K) | 9.08 ± 0.03 (A), 10.77 ± 0.05 (B) [5] |
B−V color index | 0.25 [2] |
J−H color index | 0.086 [6] |
J−K color index | 0.095 [6] |
Variable type | Rapidly oscillating Ap star |
Astrometry | |
Radial velocity (Rv) | 11.352±0.0017 [7] km/s |
Proper motion (μ) | RA: -8.756 [1] mas/yr Dec.: −24.435 [1] mas/yr |
Parallax (π) | 3.2569 ± 0.1379 mas [1] |
Distance | 1,000 ± 40 ly (310 ± 10 pc) |
Orbit [5] | |
Primary | HD 9289 A |
Companion | HD 9289 B |
Semi-major axis (a) | 0.441±0.003″ |
Details | |
Luminosity | 8.7+1.5 −1.3 [3] L☉ |
Surface gravity (log g) | 4.50±0.20 [3] cgs |
Temperature | 8710+410 −392, [3] 7750 [8] K |
Rotation | 8.660±0.006 d [8] |
Rotational velocity (v sin i) | 10.50 [9] km/s |
Other designations | |
Database references | |
SIMBAD | data |
HD 9289 is a white-hued variable star in the constellation of Cetus. It has the variable-star designation BW Ceti (abbreviated to BW Cet). With an apparent magnitude of 9.38, it is too faint to be observed by the naked eye from Earth. It is located at a distance of approximately 1,000 light-years (310 parsecs) according to Gaia EDR3 parallax measurements, and is moving away from the Solar System at a heliocentric radial velocity of 11.352 km/s.
HD 9289 is an A-type main-sequence star with the spectral type A3 SrEuCr. The suffix indicates that the star shows strong spectral lines of strontium, europium, and chromium, characteristic of an Ap star. The star radiates roughly 8.7 times the luminosity of the Sun from its photosphere. It possesses a magnetic field with a strength of 2.0 kG, [10] which is 3,000–9,000 times stronger than Earth's magnetic field (0.22–0.67 G [11] ).
The star was first classified as a rapidly oscillating Ap star (roAp) in 1993 by Kurtz et al. when it was found to pulsate at multiple periods, all clustered around 10.5 minutes (1585.06 μHz). [14] Additional observations confirmed the presence of rotational amplitude modulation, similar to that of the well-studied roAp star HR 1217. [15] In 2011, a new set of pulsation frequencies were discovered, the strongest of them being at 1585.936 μHz with an amplitude of 0.63 mmag. Few of them were consistent with the initial reports, however, which was explained by the fact that the measurements by Kurtz et al. were affected by aliasing that caused misidentifications, though an innate shift in the star's pulsation behavior could not be ruled out. [12]
In 2012, the rotational period of HD 9289 was constrained to 8.55±0.08 d through differential photometry observations. [16] This was revised slightly upward in 2021 to 8.660±0.006 d. [8]
In 2012, a previously undetected visual companion was discovered at a separation of 0.441 arcseconds to the east-northeast of HD 9289. The probability that the two stars are unrelated and aligned by chance is very low (2.16×10−4 %), therefore the pair are most certainly part of a wide binary system. The secondary star is about 1.70 magnitudes fainter than the primary when observed in the K band. [5]
10 Aquilae is a star in the equatorial constellation of Aquila. 10 Aquilae is the Flamsteed designation. It has an apparent visual magnitude of 5.9 and thus is a faint star that is just visible to the naked eye in dark skies. The brightness of this star is diminished by 0.17 in visual magnitude from extinction caused by interstellar gas and dust. Based on an annual parallax shift of 13.45 mas, the distance to this star is around 240 light-years.
Przybylski's Star, or HD 101065, is a rapidly oscillating Ap star at roughly 356 light-years from the Sun in the southern constellation of Centaurus. It has a unique spectrum showing over-abundances of most rare-earth elements, including some short-lived radioactive isotopes, but under-abundances of more common elements such as iron.
Ap and Bp stars are chemically peculiar stars of spectral types A and B which show overabundances of some metals, such as strontium, chromium, or europium. In addition, larger overabundances are often seen in praseodymium and neodymium. These stars have a much slower rotation than normal for A- and B-type stars, although some exhibit rotation velocities up to about 100 kilometers per second.
IQ Aurigae is a single, variable star in the northern constellation of Auriga. It is visible to the naked eye as a dim, white-hued star with an apparent visual magnitude that fluctuates around 5.38. The star is located at a distance of about 460 light-years from the Sun based on parallax and is drifting further away with a radial velocity of +28.6 km/s.
Rapidly oscillating Ap stars (roAp stars) are a subtype of the Ap star class that exhibit short-timescale rapid photometric or radial velocity variations. The known periods range between 5 and 23 minutes. They lie in the δ Scuti instability strip on the main sequence.
Gamma Equulei, Latinized from γ Equulei, is a double star in the northern constellation of Equuleus. It is located at a distance of around 118 light-years from Earth and is visible to the naked eye with a slightly variable apparent visual magnitude of around 4.7. The star is drifting closer to the Sun with a radial velocity of −16.5 km/s.
CU Virginis is a single star in the equatorial constellation of Virgo. It has an apparent visual magnitude of 4.99, which is bright enough to be faintly visible to the naked eye. The distance to this star can be estimated from its annual parallax shift of 13.9 mas, yielding a separation of 234 light years.
HD 175640 is a star in the equatorial constellation of Aquila. It has an apparent visual magnitude of 6.20, which is bright enough to be visible to the naked eye under suitable seeing conditions. The star is located at a distance of approximately 516 light years as determined through parallax measurements. At that distance, the star's color is modified by an extinction of 0.36 magnitude due to interstellar dust. It is drifting closer with a heliocentric radial velocity of roughly −26 km/s.
HD 126053 is the Henry Draper Catalogue designation for a star in the equatorial constellation of Virgo. It has an apparent magnitude of 6.25, which means it is faintly visible to the naked eye. According to the Bortle scale, it requires dark suburban or rural skies to view. Parallax measurements made by the Hipparcos spacecraft provide an estimated distance of 57 light years to this star. It is drifting closer with a heliocentric radial velocity of −19.2 km/s.
Xi Phoenicis, Latinized from ξ Phoenicis, is a visual binary star system in the southern constellation of Phoenix. It is faintly visible to the naked eye, having an apparent visual magnitude of 5.70. Based upon an annual parallax shift of 14.61 mas as measured from Earth, it is located around 223 light years from the Sun. The system is moving away from the Sun with a radial velocity of about +10 km/s.
HD 74423 is a heartbeat binary star and one component pulsates on only one hemisphere. This is caused by tidal interaction with its partner. The star is located in the Volans constellation.
V1794 Cygni is a single variable star in the northern constellation Cygnus. It has the identifier HD 199178 from the Henry Draper Catalogue; V1794 Cygni is its variable star designation. With an apparent visual magnitude of 7.24, it's too dim to be visible with the naked eye but can be seen with binoculars. V1794 is located at a distance of 367 light-years (113 pc) based on parallax measurements, but is drifting closer to the Sun with a radial velocity of −31 km/s. It lies superimposed over a region of faint nebulosity to the west of the North American Nebula.
HR 3831, also known as HD 83368, is a binary star system in the southern constellation of Vela at a distance of 233 light years. This object is barely visible to the naked eye as a dim, blue star with an apparent visual magnitude of 6.232. It is approaching the Earth with a heliocentric radial velocity of 4.0±0.3 km/s.
HD 42618 is a well-studied star with an exoplanetary companion in the equatorial constellation of Orion. With an apparent visual magnitude of 6.85 it is too faint to be readily visible to the naked eye. This system is located at a distance of 79.6 light years from the Sun based on parallax measurements. It has a relatively high proper motion, traversing the celestial sphere at an angular rate of 0.321″ per year. HD 42618 is drifting closer with a radial velocity of −53.5 km/s and is predicted to come as near as 42.6 light-years in around 297,000 years.
HD 125248 is a binary star system in the equatorial constellation of Virgo. It has the variable star designation CS Virginis, while HD 125248 is the designation from the Henry Draper Catalogue. This system is dimly visible to the naked eye as a point of light with an apparent visual magnitude that ranges from 5.84 down to 5.95. It is located at a distance of approximately 280 light years from the Sun based on parallax measurements, but is drifting closer with a heliocentric radial velocity of −8 km/s.
FG Virginis is a well-studied variable star in the equatorial constellation of Virgo. It is a dim star, near the lower limit of visibility to the naked eye, with an apparent visual magnitude that ranges from 6.53 down to 6.58. The star is located at a distance of 273.5 light years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of +16 km/s. Because of its position near the ecliptic, it is subject to lunar occultations.
HR 1217 is a variable star in the constellation Eridanus. It has the variable star designation DO Eridani, but this seldom appears in the astronomical literature; it is usually called either HR 1217 or HD 24712. At its brightest, HR 1217 has an apparent magnitude of 5.97, making it very faintly visible to the naked eye for an observer with excellent dark-sky conditions.
QQ Telescopii, also known as HD 185139 or simply QQ Tel, is a solitary variable star located in the southern constellation Telescopium. It has an apparent magnitude of 6.25, placing it near the limit for naked eye visibility, even under ideal conditions. Gaia DR3 parallax measurements imply a distance of 333 light years and it is currently receding with a heliocentric radial velocity of 7.8 km/s. At its current distance, QQ Telescopii's brightness is diminished by two tenths of a magnitude due to interstellar dust and it has an absolute magnitude of +1.01.
HD 177765 is a white-hued star in the southern constellation of Sagittarius. With an apparent magnitude of 9.15, it is too faint to be seen by the naked eye from Earth, but is dimly visible using binoculars. It is located at a distance of 1,284 light-years according to Gaia EDR3 parallax measurements.
HD 166473 is a rapidly oscillating Ap star and an α2 CVn variable located about 455 light-years away in the southern constellation of Corona Australis. It has the variable star designation V694 Coronae Australis. With an apparent magnitude of 7.953, it is too faint to be seen by the naked eye from Earth, but can be observed using binoculars.