Observation data Epoch J2000.0 Equinox J2000.0 ( ICRS) | |
---|---|
Constellation | Hydra |
Right ascension | 09h 14m 21.866s [1] |
Declination | +02° 18′ 51.64″ [1] |
Apparent magnitude (V) | 3.888 [2] |
Characteristics | |
Spectral type | B9.5 V + DA 1.6 [3] |
U−B color index | −0.118 [2] |
B−V color index | −0.065 [2] |
Astrometry | |
Radial velocity (Rv) | −10.7±0.3 [4] km/s |
Proper motion (μ) |
RA: +128.152
[1]
mas/
yr Dec.: −327.709 [1] mas/ yr |
Parallax (π) | 28.4019 ± 0.3682 mas [1] |
Distance | 115 ± 1
ly (35.2 ± 0.5 pc) |
Absolute magnitude (MV) | +0.92 [5] |
Details | |
θ Hya A | |
Mass | 2.52 [3] M☉ |
Luminosity | 52 [5] L☉ |
Surface gravity (log g) | 3.80±0.08 [6] cgs |
Temperature | 10,099±145 [6] K |
Metallicity [Fe/H] | −0.42±0.09 [6] dex |
Rotational velocity (v sin i) | 95 [7] km/s |
θ Hya B | |
Mass | 0.68 [8] or 1.21 [3] M☉ |
Temperature | 30,700 [3] K |
Other designations | |
Database references | |
SIMBAD | data |
Theta Hydrae, Latinized from θ Hydrae, is a binary star [8] system in the constellation Hydra. It is visible to the naked eye with an apparent visual magnitude of 3.9. [2] The star system has a high proper motion [8] with an annual parallax shift of 28.4 mas, [1] indicating a distance of about 115 light years. Theta Hydrae forms a double with a magnitude 9.9 star located at an angular separation of 29 arcseconds. [10]
The primary component of this system is a B-type main sequence star with a stellar classification of B9.5 V. [3] It is a candidate Lambda Boötis star, indicating it displays an underabundance of iron peak elements. [11] However, it is also underabundant in oxygen, a characteristic not shared by other Lambda Boötis stars. Instead, it may be a peculiar B star. [12]
An orbiting white dwarf companion was discovered in 1998 from its X-ray emission. This degenerate star must have evolved from a progenitor that was once more massive than the current primary. [8] Burleigh and Barstow (1999) gave a mass estimate of 0.68 [8] times the mass of the Sun, whereas Holberg et al. (2013) put it as high as 1.21 [3] times the Sun's mass. The latter would put it beyond the theoretical upper limit for white dwarf remnants of typical single stars that did not undergo a merger or mass loss. [13]
{{
cite web}}
: CS1 maint: postscript (
link)
Observation data Epoch J2000.0 Equinox J2000.0 ( ICRS) | |
---|---|
Constellation | Hydra |
Right ascension | 09h 14m 21.866s [1] |
Declination | +02° 18′ 51.64″ [1] |
Apparent magnitude (V) | 3.888 [2] |
Characteristics | |
Spectral type | B9.5 V + DA 1.6 [3] |
U−B color index | −0.118 [2] |
B−V color index | −0.065 [2] |
Astrometry | |
Radial velocity (Rv) | −10.7±0.3 [4] km/s |
Proper motion (μ) |
RA: +128.152
[1]
mas/
yr Dec.: −327.709 [1] mas/ yr |
Parallax (π) | 28.4019 ± 0.3682 mas [1] |
Distance | 115 ± 1
ly (35.2 ± 0.5 pc) |
Absolute magnitude (MV) | +0.92 [5] |
Details | |
θ Hya A | |
Mass | 2.52 [3] M☉ |
Luminosity | 52 [5] L☉ |
Surface gravity (log g) | 3.80±0.08 [6] cgs |
Temperature | 10,099±145 [6] K |
Metallicity [Fe/H] | −0.42±0.09 [6] dex |
Rotational velocity (v sin i) | 95 [7] km/s |
θ Hya B | |
Mass | 0.68 [8] or 1.21 [3] M☉ |
Temperature | 30,700 [3] K |
Other designations | |
Database references | |
SIMBAD | data |
Theta Hydrae, Latinized from θ Hydrae, is a binary star [8] system in the constellation Hydra. It is visible to the naked eye with an apparent visual magnitude of 3.9. [2] The star system has a high proper motion [8] with an annual parallax shift of 28.4 mas, [1] indicating a distance of about 115 light years. Theta Hydrae forms a double with a magnitude 9.9 star located at an angular separation of 29 arcseconds. [10]
The primary component of this system is a B-type main sequence star with a stellar classification of B9.5 V. [3] It is a candidate Lambda Boötis star, indicating it displays an underabundance of iron peak elements. [11] However, it is also underabundant in oxygen, a characteristic not shared by other Lambda Boötis stars. Instead, it may be a peculiar B star. [12]
An orbiting white dwarf companion was discovered in 1998 from its X-ray emission. This degenerate star must have evolved from a progenitor that was once more massive than the current primary. [8] Burleigh and Barstow (1999) gave a mass estimate of 0.68 [8] times the mass of the Sun, whereas Holberg et al. (2013) put it as high as 1.21 [3] times the Sun's mass. The latter would put it beyond the theoretical upper limit for white dwarf remnants of typical single stars that did not undergo a merger or mass loss. [13]
{{
cite web}}
: CS1 maint: postscript (
link)