HD 136138

HD 136138
Observation data
Epoch J2000.0      Equinox ICRS
Constellation Serpens
Right ascension 15h 18m 24.507s
Declination +20° 34′ 21.95″
Apparent magnitude (V) 5.68 + 15.3
Characteristics
Evolutionary stage Horizontal branch + white dwarf
Spectral type G8IIIa + DA1.7
B−V color index 0.972±0.004
Variable type Constant
Astrometry
Radial velocity (Rv)−7.74±0.07 km/s
Proper motion (μ) RA: −12.993 mas/yr
Dec.: −22.380 mas/yr
Parallax (π)7.7902±0.2193 mas
Distance420 ± 10 ly
(128 ± 4 pc)
Absolute magnitude (MV)0.65±0.15
Orbit
Period (P)506.45±0.18 d
Semi-major axis (a)4.14±0.52"
(≥ 41.76±0.34 Gm)
Eccentricity (e)0.3353±0.0056
Inclination (i)42.9±6.7°
Longitude of the node (Ω)207.0±7.4°
Periastron epoch (T)2,453,240.3±1.3 MJD
Argument of periastron (ω)
(secondary)		35.0±1.4°
Semi-amplitude (K1)
(primary)		6.340±0.044 km/s
Details
A
Mass1.84±0.40 M☉
Radius10.3 R☉
Luminosity56.2 L☉
Surface gravity (log g)2.68 cgs
Temperature4,960±100 K
Metallicity [Fe/H]−0.08±0.09 dex
Age1.45 Gyr
B
Mass0.59±0.12 or 0.79±0.09 M☉
Surface gravity (log g)8.25±0.15 cgs
Temperature30,400±780 K
Other designations
BD+21°2755, FK5 1400, GC 20575, HD 136138, HIP 74896, HR 5692, SAO 83755, WD 1516+207
Database references
SIMBADdata

HD 136138, or HR 5692, is a binary star system in the Serpens Caput segment of the constellation Serpens. It has a golden hue like the Sun and is dimly visible to the naked eye with an apparent visual magnitude of 5.68; the light contribution from the companion is effectively negligible. This system is located at a distance of approximately 420 light years from the Sun based on parallax. It is drifting closer with a radial velocity of −7.7 km/s and has a proper motion of 23.5 mas·yr−1.

The radial velocity variation of this star was reported by J. R. de Medeiros and M. Mayor in 1999, and it was confirmed as a binary by A. Frankowski and colleagues in 2007 using proper motion measurements. It is an unresolved, single-lined spectroscopic binary system with an orbital period of 1.39 years and an eccentricity (ovalness) of 0.335. Proper motion measurements allow an estimate of the orbital inclination angle as ~43°. Their semimajor axis is around 2.0 AU, or double the distance from the Earth to the Sun.

The stellar classification of the primary component is G8IIIa, indicating this is a evolved G-type giant star that has exhausted the supply of hydrogen at its core. It is a red clump giant that is generating energy through core helium fusion. There is some ambiguous evidence for this being a mild barium star of class Ba0.3, with the spectra showing marginal overabundances of s-process elements. A low level of X-ray emission has been detected, which appears to be coming from the star's corona.

The high level of ultraviolet flux coming from this system strongly suggests the companion is a compact white dwarf. Mass estimates put it in the range of 0.6 to 0.8 times the mass of the Sun, and the temperature is around 30,400 K. It is possible that the earlier evolution of this component contaminated its partner with s-process elements, although the resulting interaction should have circularized the orbit to some degree. The dwarf has a visual magnitude of 15.3 and a hydrogen-dominated atmospheric class of DA1.7.

References

  1. 1 2 3 4 5 6 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
  2. 1 2 3 4 5 6 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  3. 1 2 3 4 5 Holberg, J. B.; et al. (2013). "Where are all the Sirius-like binary systems?". Monthly Notices of the Royal Astronomical Society. 435 (3): 2077. arXiv:1307.8047. Bibcode:2013MNRAS.435.2077H. doi:10.1093/mnras/stt1433.
  4. 1 2 3 4 5 6 7 Stefanik, Robert P.; et al. (May 2011). "Observations and Orbital Analysis of the Giant White Dwarf Binary System HR 5692". The Astronomical Journal. 141 (5): 9. Bibcode:2011AJ....141..144S. doi:10.1088/0004-6256/141/5/144. S2CID 56137377. 144.
  5. 1 2 Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". The Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373.
  6. 1 2 3 4 Griffin, R. F. (February 2009). "Spectroscopic binary orbits from photoelectric radial velocities. Paper 204: HR 738, HR 831, HR 5692, and HR 7252". The Observatory. 129: 6–28. Bibcode:2009Obs...129....6G.
  7. 1 2 Jorissen, A.; et al. (February 1996). "New X-ray sources detected among mild barium and S stars". Astronomy and Astrophysics. 306: 467. Bibcode:1996A&A...306..467J.
  8. 1 2 3 4 5 6 Merle, T.; et al. (February 2016). "To Ba or not to Ba: Enrichment in s-process elements in binary systems with WD companions of various masses". Astronomy & Astrophysics. 586: 16. arXiv:1510.05908. Bibcode:2016A&A...586A.151M. doi:10.1051/0004-6361/201526944. S2CID 119224869. A151.
  9. ↑ "HD 136138". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2020-12-22.{{cite web}}: CS1 maint: postscript (link)