HD 136138

HD 136138
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Serpens
Right ascension 15h 18m 24.507s[1]
Declination +20° 34′ 21.95″[1]
Apparent magnitude (V) 5.68[2] + 15.3[3]
Characteristics
Evolutionary stage Horizontal branch + white dwarf
Spectral type G8IIIa[4] + DA1.7[3]
B−V color index 0.972±0.004[2]
Variable type Constant[5][6]
Astrometry
Radial velocity (Rv)−7.74±0.07[2] km/s
Proper motion (μ) RA: −12.993 mas/yr[1]
Dec.: −22.380 mas/yr[1]
Parallax (π)7.7902 ± 0.2193 mas[1]
Distance420 ± 10 ly
(128 ± 4 pc)
Absolute magnitude (MV)0.65±0.15[7]
Orbit[7]
Period (P)506.45±0.18 d
Semi-major axis (a)4.14±0.52"
(≥ 41.76±0.34 Gm[5])
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[7]
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[8] 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,[9] WD 1516+207[3]
Database references
SIMBADdata

HD 136138, or HR 5692, is a binary star system in the Serpens Caput segment of the Serpens constellation. It has a golden hue like the Sun and is dimly visible to the naked eye with an apparent visual magnitude of 5.68;[2] the light contribution from the companion is effectively negligible.[8] This system is located at a distance of approximately 420 light years from the Sun based on parallax.[1] It is drifting closer with a radial velocity of −7.7 km/s[2] and has a proper motion of 23.5 mas·yr−1.[8]

The radial velocity variation of this star was reported by J. R. de Medeiros and M. Mayor in 1999,[5] and it was confirmed as a binary by A. Frankowski and colleagues in 2007 using proper motion measurements.[3] 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°.[7] Their semimajor axis is around 2.0 AU, or double the distance from the Earth to the Sun.[8]

The stellar classification of the primary component is G8IIIa,[4] 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[7] of class Ba0.3,[8] with the spectra showing marginal overabundances of s-process elements.[8] A low level of X-ray emission has been detected, which appears to be coming from the star's corona.[6]

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.[7] 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.[5] The dwarf has a visual magnitude of 15.3 and a hydrogen-dominated atmospheric class of DA1.7.[3]

References

  1. ^ a b c d e 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.
  2. ^ a b c d e 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.
  3. ^ a b c d e 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. ^ a b 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.
  5. ^ a b c d 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.
  6. ^ a b 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.
  7. ^ a b c d e f 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.
  8. ^ a b c d e f 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)