Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Sagittarius |
Right ascension | 17h 47m 33.62410s [1] |
Declination | −27° 49′ 50.8490″ [1] |
Apparent magnitude (V) | 4.54 [2] |
Characteristics | |
Spectral type | F7II [3] |
U−B color index | +0.50 [2] |
B−V color index | +0.80 [2] |
Variable type | Cepheid [4] |
Astrometry | |
Radial velocity (Rv) | −10.10 [5] km/s |
Proper motion (μ) |
RA: −5.097
[1]
mas/
yr Dec.: −9.722 [1] mas/ yr |
Parallax (π) | 3.4314 ± 0.2020 mas [1] |
Distance | 950 ± 60
ly (290 ± 20 pc) |
Absolute magnitude (MV) | −2.85 [6] |
Details | |
Mass | 6.31 [7] M☉ |
Radius | 53±3 [8] R☉ |
Luminosity | 2,647 [7] L☉ |
Surface gravity (log g) | 1.77 [9] cgs |
Temperature | 6,305 [7] K |
Metallicity [Fe/H] | −0.01 [6] dex |
Rotational velocity (v sin i) | 27.1 [10] km/s |
Other designations | |
Database references | |
SIMBAD | data |
X Sagittarii is a variable star and candidate binary star system in the southern constellation of Sagittarius, near the western constellation boundary with Ophiuchus. It has a yellow-white hue and is visible to the naked eye with an apparent visual magnitude that fluctuates around 4.54. [2] The star is located at a distance of approximately 950 light years from the Sun based on parallax, [1] and is drifting closer with a radial velocity of −10 km/s. [5] The star has an absolute magnitude of around −2.85. [6]
This is an F-type bright giant with a stellar classification of F7II. [3] It is a Classical Cepheid variable that ranges in apparent magnitude from 4.20 down to 4.90 with a period of 7.01283 days. [13] Its variation in brightness is accompanied by a change in spectral classification, from G2 to F5. [4] The amplitude of each pulsation causes the stellar radius to vary by ~9%. [14] Analysis of the spectra suggest there are two shock waves per pulsation period, with complicated patterns appearing in the metallic lines. [15] The star is surrounded by an optically-thin circumstellar envelope at 15–20 stellar radii, which appears as an infrared excess of 13.3%. [16] This may be composed of amorphous carbon. [14]
László Szabados suggested in 1990 that this might be a binary system with a period of 507 days. A detection of this projected companion was reported in 2013 using the VLTI/AMBER instrument. However, the object was at the detection limit of the instrument, showing an angular separation of 10.7 mas from the primary and a magnitude difference of 5.6 in the K-band. [8] A subsequent optical search reported a failure to detect the companion in 2014, excluding companions brighter than a A-type main-sequence star class of A9V. [17] The estimated mass of this object is 0.2–0.3 M☉. [15]
Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Sagittarius |
Right ascension | 17h 47m 33.62410s [1] |
Declination | −27° 49′ 50.8490″ [1] |
Apparent magnitude (V) | 4.54 [2] |
Characteristics | |
Spectral type | F7II [3] |
U−B color index | +0.50 [2] |
B−V color index | +0.80 [2] |
Variable type | Cepheid [4] |
Astrometry | |
Radial velocity (Rv) | −10.10 [5] km/s |
Proper motion (μ) |
RA: −5.097
[1]
mas/
yr Dec.: −9.722 [1] mas/ yr |
Parallax (π) | 3.4314 ± 0.2020 mas [1] |
Distance | 950 ± 60
ly (290 ± 20 pc) |
Absolute magnitude (MV) | −2.85 [6] |
Details | |
Mass | 6.31 [7] M☉ |
Radius | 53±3 [8] R☉ |
Luminosity | 2,647 [7] L☉ |
Surface gravity (log g) | 1.77 [9] cgs |
Temperature | 6,305 [7] K |
Metallicity [Fe/H] | −0.01 [6] dex |
Rotational velocity (v sin i) | 27.1 [10] km/s |
Other designations | |
Database references | |
SIMBAD | data |
X Sagittarii is a variable star and candidate binary star system in the southern constellation of Sagittarius, near the western constellation boundary with Ophiuchus. It has a yellow-white hue and is visible to the naked eye with an apparent visual magnitude that fluctuates around 4.54. [2] The star is located at a distance of approximately 950 light years from the Sun based on parallax, [1] and is drifting closer with a radial velocity of −10 km/s. [5] The star has an absolute magnitude of around −2.85. [6]
This is an F-type bright giant with a stellar classification of F7II. [3] It is a Classical Cepheid variable that ranges in apparent magnitude from 4.20 down to 4.90 with a period of 7.01283 days. [13] Its variation in brightness is accompanied by a change in spectral classification, from G2 to F5. [4] The amplitude of each pulsation causes the stellar radius to vary by ~9%. [14] Analysis of the spectra suggest there are two shock waves per pulsation period, with complicated patterns appearing in the metallic lines. [15] The star is surrounded by an optically-thin circumstellar envelope at 15–20 stellar radii, which appears as an infrared excess of 13.3%. [16] This may be composed of amorphous carbon. [14]
László Szabados suggested in 1990 that this might be a binary system with a period of 507 days. A detection of this projected companion was reported in 2013 using the VLTI/AMBER instrument. However, the object was at the detection limit of the instrument, showing an angular separation of 10.7 mas from the primary and a magnitude difference of 5.6 in the K-band. [8] A subsequent optical search reported a failure to detect the companion in 2014, excluding companions brighter than a A-type main-sequence star class of A9V. [17] The estimated mass of this object is 0.2–0.3 M☉. [15]