HIP 79098
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 08m 43.7s[1] |
| Declination | −23° 41′ 07.5″[1] |
| Apparent magnitude (V) | +5.88[1] (5.87 to 5.90)[2] |
| Characteristics | |
| Spectral type | B9V[1] B9 Mn P Ga[3] B9 IVn + Ap(Si)s[4] |
| U−B color index | +0.02[1] |
| B−V color index | −0.31[1] |
| Variable type | α2 CVn[2] |
| Absolute magnitude (MV) | −0.33±0.07[6] |
| Details | |
Myr | |
| Database references | |
| SIMBAD | data |
HIP 79098 is a
parsecs) from Earth.[5]
This system consists of a
spectroscopic companion of unknown type. Two additional distant red dwarfs may be part of the system, at separations of 9,500 and 12,900 AU. In 2019, a brown dwarf was discovered orbiting the central binary at a distance of about 350 AU.[6]
Star system
This is a young stellar system, belonging to the Upper Scorpius subgroup of the
OB association to the Sun. This is an association of stars with common origin and movement. The Upper Scorpius subgroup is the youngest of the association and has an estimated age of around 10 million years, which is therefore the age of HIP 79098.[6]
HIP 79098 has a
B-type main sequence star. The system's spectrum is complex and has also been classified as B9 Mn P Ga,[3] and B9IVn+Ap(Si)s.[4] The primary is a chemically peculiar star of the type HgMn (mercury-manganese star),[7] and has strong manganese and gallium lines, and weak helium lines.[3] It is also a variable star, oscillating between magnitudes 5.87 and 5.90 with a period of 2.69 days, being classified as a α2 Canum Venaticorum variable.[2] A secondary period of 0.28 days has also been detected. These variability cycles can be caused by the rotation of the star or by pulsations.[7] The mass of the primary star is estimated at 2.5 times the solar mass.[6]
The system's spectrum has the lines of a second star, which means HIP 79098 is a double-lined
spectroscopic binary.[10] While its exact nature is unknown, the secondary star is probably quite massive, possibly almost as massive as the primary. The primary's radial velocity seems to have large variations caused by the orbit of the stars, but different studies give contradictory results regarding the size of these variations, so it is not possible to determine the basic parameters of the system like masses and orbit.[6] The presence of the second star is also seen in the astrometic data by the Hipparcos and Gaia spacecraft, which show a large anomaly from the constant proper motion hypothesis.[11]
There are two other stars close to HIP 79098 in the sky which have proper motion and distances similar to those of HIP 79098, and therefore can be physical companions. They are both low-mass
arcseconds, or 9,500 AU. The second star is brighter and has a spectral type of M3.25, and is separated by 88 arcseconds, or 12,900 AU.[12][6]
Brown dwarf
The discovery of a
SPHERE instrument at the Very Large Telescope. Previous studies had seen the object, but considered it too red to be part of the HIP 79098 system, so it was rejected as a likely background star. The 2019 study combined all the observations of the object and showed that it has a common proper motion with HIP 79098, confirming that it is physically linked to the system.[6]
Named HIP 79098 (AB)b, the brown dwarf is
The mass ratio between HIP 79098 (AB)b and the central binary is estimated at 0.3–1%. This is a low value similar to some systems with massive planets, which can suggest that HIP 79098 (AB)b represents the upper end of the planet population, as opposed to having been formed as a star.[6]
References
- ^ a b c d e f g h i j "HIP 79098", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2022-04-01
- ^ a b c "VSX : Detail for NSV 7470", The International Variable Star Index, American Association of Variable Star Observers (AAVSO), retrieved 2022-04-01
- ^ Bibcode:2009yCat....102025S
- ^ doi:10.1086/192182
- ^ .
- ^ S2CID 174801322
- ^
- ^ S2CID 73582386
- S2CID 118621218
- S2CID 119273467
- S2CID 119491061
- S2CID 119190361
