Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Taurus |
A | |
Right ascension | 03h 36m 47.291s [1] |
Declination | 00° 35′ 15.94″ [1] |
Apparent magnitude (V) | 5.91 [2] |
B | |
Right ascension | 03h 36m 46.844s [3] |
Declination | 00° 35′ 15.93″ [3] |
Apparent magnitude (V) | 8.79 [2] |
Characteristics | |
Spectral type | K2:Vnk [4] (K1 IV + G5 V + K3 V) [5] |
Variable type | RS CVn [6] |
Astrometry | |
A | |
Radial velocity (Rv) | −21.24±6.62 [1] km/s |
Proper motion (μ) |
RA: −32.894
mas/
yr
[1] Dec.: −161.772 mas/ yr [1] |
Parallax (π) | 33.7528 ± 0.0866 mas [1] |
Distance | 96.6 ± 0.2
ly (29.63 ± 0.08 pc) |
Absolute magnitude (MV) | 3.6 [2] |
B | |
Radial velocity (Rv) | −15.34±0.18 [3] km/s |
Proper motion (μ) |
RA: −34.359
mas/
yr
[3] Dec.: −138.137 mas/ yr [3] |
Parallax (π) | 33.8664 ± 0.0226 mas [3] |
Distance | 96.31 ± 0.06
ly (29.53 ± 0.02 pc) |
Absolute magnitude (MV) | 6.5 [2] |
Orbit [7] | |
Period (P) | 2.83774 d |
Semi-major axis (a) | 10.3 R☉ [8] |
Eccentricity (e) | 0.00 (assumed) |
Inclination (i) | 38 [9]° |
Periastron epoch (T) | 2,442,767.4 HJD |
Argument of periastron (ω) (secondary) | 0.00 (assumed)° |
Semi-amplitude (K1) (primary) | 52.6 km/s |
Semi-amplitude (K2) (secondary) | 64.1 km/s |
Details | |
Component Aa | |
Mass | 1.0 [8] M☉ |
Radius | 3.7 [8] R☉ |
Surface gravity (log g) | 3.30 [5] cgs |
Temperature | 4,750 [5] K |
Metallicity [Fe/H] | −0.16 [10] dex |
Rotational velocity (v sin i) | 39 [9] km/s |
Component Ab | |
Mass | 0.8 [8] M☉ |
Radius | 1.1 [8] R☉ |
Surface gravity (log g) | 4.26 [5] cgs |
Temperature | 5,500 [5] K |
Component B | |
Mass | 0.78 [11] M☉ |
Radius | 0.78 [11] R☉ |
Luminosity | 0.30 [11] L☉ |
Surface gravity (log g) | 4.55 [11] cgs |
Temperature | 4,829 [11] K |
Metallicity [Fe/H] | +0.10 [10] dex |
Rotational velocity (v sin i) | 4.1 [12] km/s |
Age | 2.2 [3] Gyr |
Other designations | |
Database references | |
SIMBAD | data |
HR 1099 is a triple star system in the equatorial constellation of Taurus, positioned 11 ′ to the north of the star 10 Tauri. [15] This system has the variable star designation V711 Tauri, while HR 1099 is the star's identifier from the Bright Star Catalogue. It ranges in brightness from a combined apparent visual magnitude of 5.71 down to 5.94, [6] which is bright enough to be dimly visible to the naked eye. The distance to this system is 96.6 light years based on parallax measurements, [1] but it is drifting closer with a radial velocity of about −15 km/s.
This system was discovered to be a double star by F. G. W. Struve in 1822, with the components A and B having an angular separation of 5.4 ″. (The separation was measured at 6.7″ in 2016.) [16] R. E. Wilson in 1953 determined that the brighter member of this pair, component A, has a variable radial velocity. In 1963, O. C. Wilson noted that the same component shows very high emission cores in the calcium H and K absorption lines. [17] Follow-up observations by O. C. Wilson in 1964 showed that the hydrogen–α line of component A is fully in emission and it displays moderate broadening due to rotation. He found a stellar classification of K3 V for component B, matching an ordinary K-type main-sequence star. [18]
Observations during 1974–1975 demonstrated that component A is a spectroscopic binary star system of the RS Canum Venaticorum variable class. Given its average magnitude of around 5.9, it is one of the brighter known variables of this type. [20] No eclipses were observed, but an orbital period of 2.838 days was determined. Most of the emission was found to be coming from the more massive member of this pair. [21] Radio emission from the binary was detected by F. N. Owen in 1976. [22] It was shown to be a soft X-ray source in 1978 using the HEAO 1 satellite. [23]
This double-lined spectroscopic binary system consists of an evolving K-type subgiant and an ordinary G-type main sequence star. The two stars are orbiting so close to each other that their tidal effects are giving them an elliptical shape. The subgiant is filling about 80% of its Roche lobe. [5] The chromosphere of the subgiant is one of the most active known, with a deep convective zone powering the magnetic dynamo. [24] [4] The G-type companion has a shallow convection zone and is less active. [5]
In 1980, significant variations were found in some spectral features related to surface temperature, suggesting the presence of starspots. [25] Doppler imaging confirmed these starspots are associated with the K subgiant. (It was the first cool star to have its surface Doppler imaged. [26]) The evidence suggests that the spots first appear at low latitude then migrated toward the poles. [20] These spots are much larger than they are on the Sun. [5] About 70% of all spots have been observed at latitudes higher than 50°, particularly around the polar region. [9] [24] A polar spot has persisted for at least twenty years. [5]
The baseline apparent magnitudes of the two stars, after subtracting the effects of starspots, is 5.80 and 7.20. [5] Long term monitoring indicates the subgiant has two activity cycles, similar to the 11-year solar cycle. A 5.3±0.1 year cycle is associated with symmetrical flip-flopping of the spotted area between hemispheres. The longer 15–16 year cycle is a periodic variation in the total spot area. The global magnetic field of the star may be precessing with respect to the axis of rotation. [26]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Taurus |
A | |
Right ascension | 03h 36m 47.291s [1] |
Declination | 00° 35′ 15.94″ [1] |
Apparent magnitude (V) | 5.91 [2] |
B | |
Right ascension | 03h 36m 46.844s [3] |
Declination | 00° 35′ 15.93″ [3] |
Apparent magnitude (V) | 8.79 [2] |
Characteristics | |
Spectral type | K2:Vnk [4] (K1 IV + G5 V + K3 V) [5] |
Variable type | RS CVn [6] |
Astrometry | |
A | |
Radial velocity (Rv) | −21.24±6.62 [1] km/s |
Proper motion (μ) |
RA: −32.894
mas/
yr
[1] Dec.: −161.772 mas/ yr [1] |
Parallax (π) | 33.7528 ± 0.0866 mas [1] |
Distance | 96.6 ± 0.2
ly (29.63 ± 0.08 pc) |
Absolute magnitude (MV) | 3.6 [2] |
B | |
Radial velocity (Rv) | −15.34±0.18 [3] km/s |
Proper motion (μ) |
RA: −34.359
mas/
yr
[3] Dec.: −138.137 mas/ yr [3] |
Parallax (π) | 33.8664 ± 0.0226 mas [3] |
Distance | 96.31 ± 0.06
ly (29.53 ± 0.02 pc) |
Absolute magnitude (MV) | 6.5 [2] |
Orbit [7] | |
Period (P) | 2.83774 d |
Semi-major axis (a) | 10.3 R☉ [8] |
Eccentricity (e) | 0.00 (assumed) |
Inclination (i) | 38 [9]° |
Periastron epoch (T) | 2,442,767.4 HJD |
Argument of periastron (ω) (secondary) | 0.00 (assumed)° |
Semi-amplitude (K1) (primary) | 52.6 km/s |
Semi-amplitude (K2) (secondary) | 64.1 km/s |
Details | |
Component Aa | |
Mass | 1.0 [8] M☉ |
Radius | 3.7 [8] R☉ |
Surface gravity (log g) | 3.30 [5] cgs |
Temperature | 4,750 [5] K |
Metallicity [Fe/H] | −0.16 [10] dex |
Rotational velocity (v sin i) | 39 [9] km/s |
Component Ab | |
Mass | 0.8 [8] M☉ |
Radius | 1.1 [8] R☉ |
Surface gravity (log g) | 4.26 [5] cgs |
Temperature | 5,500 [5] K |
Component B | |
Mass | 0.78 [11] M☉ |
Radius | 0.78 [11] R☉ |
Luminosity | 0.30 [11] L☉ |
Surface gravity (log g) | 4.55 [11] cgs |
Temperature | 4,829 [11] K |
Metallicity [Fe/H] | +0.10 [10] dex |
Rotational velocity (v sin i) | 4.1 [12] km/s |
Age | 2.2 [3] Gyr |
Other designations | |
Database references | |
SIMBAD | data |
HR 1099 is a triple star system in the equatorial constellation of Taurus, positioned 11 ′ to the north of the star 10 Tauri. [15] This system has the variable star designation V711 Tauri, while HR 1099 is the star's identifier from the Bright Star Catalogue. It ranges in brightness from a combined apparent visual magnitude of 5.71 down to 5.94, [6] which is bright enough to be dimly visible to the naked eye. The distance to this system is 96.6 light years based on parallax measurements, [1] but it is drifting closer with a radial velocity of about −15 km/s.
This system was discovered to be a double star by F. G. W. Struve in 1822, with the components A and B having an angular separation of 5.4 ″. (The separation was measured at 6.7″ in 2016.) [16] R. E. Wilson in 1953 determined that the brighter member of this pair, component A, has a variable radial velocity. In 1963, O. C. Wilson noted that the same component shows very high emission cores in the calcium H and K absorption lines. [17] Follow-up observations by O. C. Wilson in 1964 showed that the hydrogen–α line of component A is fully in emission and it displays moderate broadening due to rotation. He found a stellar classification of K3 V for component B, matching an ordinary K-type main-sequence star. [18]
Observations during 1974–1975 demonstrated that component A is a spectroscopic binary star system of the RS Canum Venaticorum variable class. Given its average magnitude of around 5.9, it is one of the brighter known variables of this type. [20] No eclipses were observed, but an orbital period of 2.838 days was determined. Most of the emission was found to be coming from the more massive member of this pair. [21] Radio emission from the binary was detected by F. N. Owen in 1976. [22] It was shown to be a soft X-ray source in 1978 using the HEAO 1 satellite. [23]
This double-lined spectroscopic binary system consists of an evolving K-type subgiant and an ordinary G-type main sequence star. The two stars are orbiting so close to each other that their tidal effects are giving them an elliptical shape. The subgiant is filling about 80% of its Roche lobe. [5] The chromosphere of the subgiant is one of the most active known, with a deep convective zone powering the magnetic dynamo. [24] [4] The G-type companion has a shallow convection zone and is less active. [5]
In 1980, significant variations were found in some spectral features related to surface temperature, suggesting the presence of starspots. [25] Doppler imaging confirmed these starspots are associated with the K subgiant. (It was the first cool star to have its surface Doppler imaged. [26]) The evidence suggests that the spots first appear at low latitude then migrated toward the poles. [20] These spots are much larger than they are on the Sun. [5] About 70% of all spots have been observed at latitudes higher than 50°, particularly around the polar region. [9] [24] A polar spot has persisted for at least twenty years. [5]
The baseline apparent magnitudes of the two stars, after subtracting the effects of starspots, is 5.80 and 7.20. [5] Long term monitoring indicates the subgiant has two activity cycles, similar to the 11-year solar cycle. A 5.3±0.1 year cycle is associated with symmetrical flip-flopping of the spotted area between hemispheres. The longer 15–16 year cycle is a periodic variation in the total spot area. The global magnetic field of the star may be precessing with respect to the axis of rotation. [26]