HD 178911 is a triple star system with an exoplanetary companion in the northern constellation of Lyra. With a combined apparent visual magnitude of 6.70,[2] it is a challenge to view with the naked eye. The system is located at a distance of approximately 161 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −38 km/s.[1]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Lyra |
| Right ascension | 19h 09m 04.35193s[1] |
| Declination | +34° 36′ 01.2420″[1] |
| Apparent magnitude (V) | 6.70[2] (6.89 + 8.96 + 7.88)[3] |
| Characteristics | |
| HD 178911 Aa/Ab | |
| Evolutionary stage | Main sequence |
| Spectral type | G1V + K1V[4] |
| B−V color index | 0.643±0.007[2] |
| HD 178911 B | |
| Spectral type | G5V[5] |
| B−V color index | 0.750±0.015[2]
... |
| Astrometry | |
| HD 178911 Aa/Ab | |
| Radial velocity (Rv) | −38.09±1.01[1] km/s |
| Proper motion (μ) | RA: 76.618[1] mas/yr Dec.: 207.126[1] mas/yr |
| Parallax (π) | 20.2306 ± 0.3846 mas[1] |
| Distance | 161 ± 3 ly (49.4 ± 0.9 pc) |
| Absolute magnitude (MV) | 3.28[2] |
| HD 178911 B | |
| Radial velocity (Rv) | −40.324±0.0012[6] km/s |
| Proper motion (μ) | RA: 57.177[7] mas/yr Dec.: 195.900[7] mas/yr |
| Parallax (π) | 24.3775 ± 0.0274 mas[7] |
| Distance | 133.8 ± 0.2 ly (41.02 ± 0.05 pc) |
| Absolute magnitude (MV) | 4.90[2] |
| Orbit[4] | |
| Primary | HD 178911 Aa |
| Companion | HD 178911 Ab |
| Period (P) | 1,296.984±0.355 d yr |
| Semi-major axis (a) | 0.074±0.002″ |
| Eccentricity (e) | 0.597±0.003 |
| Inclination (i) | 147.29±0.99° |
| Longitude of the node (Ω) | 276.91±1.45° |
| Argument of periastron (ω) (secondary) | 83.88±0.87° |
| Semi-amplitude (K1) (primary) | 6.47±0.09 km/s |
| Semi-amplitude (K2) (secondary) | 8.33±0.18 km/s |
| Details | |
| HD 178911 Aa | |
| Mass | 0.802±0.055 M☉[4] 1.234±0.027[8] M☉ |
| HD 178911 Ab | |
| Mass | 0.622±0.053 M☉[4] 0.942±0.021[8] M☉ |
| HD 178911 B | |
| Mass | 1.03±0.02 M☉[9] |
| Radius | 1.05±0.02 R☉[9] |
| Luminosity | 1.00±0.02 L☉[9] |
| Surface gravity (log g) | 4.40±0.02 cgs[9] |
| Temperature | 5,642±29 K[9] |
| Metallicity [Fe/H] | 0.23[10] |
| Rotational velocity (v sin i) | 4.6[10] |
| Age | 4.8±1.3 Gyr[9] |
| Other designations | |
| HD 178911 A: BD+34 3439, HIP 94076, SAO 67879, PPM 82386, LTT 15608, NLTT 47474[11] | |
| HD 178911 B: BD+34 3438, HIP 94075, SAO 67875, PPM 82385, LTT 15608, NLTT 47473[12] | |
| Database references | |
| SIMBAD | data |
Stellar system
editA companion star, designated component B, was first reported by F. G. W. Struve in 1823. As of 2019, the two have an angular separation of 16.0″ along a position angle of 263°.[3] Component B shares a common motion through space with the primary, and thus they form a wide binary.[13] This secondary is a magnitude 7.88[3] G-type main-sequence star with a stellar classification of G5V.[5] The physical properties of this star are similar to the Sun, although it has a higher metallicity.[9][10]
In 1985, the primary was determined to be a spectroscopic binary pair using the CHARA speckle interferometry program.[14] Designated components Aa and Ab, these have an orbital period of 3.55 yr and an eccentricity (ovalness) of 0.6.[4] They are magnitude 6.89 and 8.96.[3] Based on based on a combined class of G5V for the pair,[8] they have derived main sequence stellar classifications of G1V and K1V, respectively.[4] C. D. Farrington and associates (2014) found dynamic masses for the components of 0.80 and 0.62, respectively.[4] However, based on the classes, the expected masses should be around 1.0 and 0.8. Manuel Andrade (2019) derived higher dynamic masses of 1.20 and 0.94.[8]
An additional companion HD 178911 C is a chance optical alignment and is not part of the system.[4]
Planetary system
editIn 2001 an extrasolar planet was discovered in orbit around HD 178911 B.[15][13]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | >7.35 ± 0.60 MJ | 0.345 ± 0.20 | 71.511 ± 0.011 | 0.139 ± 0.014 | — | — |
See also
editReferences
edit- ^ a b c d e f g Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b c d e f 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.
- ^ a b c d Mason, B. D.; et al. (2014). "The Washington Visual Double Star Catalog". The Astronomical Journal. 122 (6): 3466–3471. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
- ^ a b c d e f g h Farrington, C. D.; et al. (2014). "Separated Fringe Packet Observations with the CHARA Array. II. omega Andromeda, HD 178911, and xi Cephei" (PDF). The Astronomical Journal. 148 (3). 48. arXiv:1407.0639. Bibcode:2014AJ....148...48F. doi:10.1088/0004-6256/148/3/48. S2CID 12909818. Archived from the original (PDF) on 2014-10-16.
- ^ a b France, Kevin; et al. (November 2018). "Far-ultraviolet Activity Levels of F, G, K, and M Dwarf Exoplanet Host Stars". The Astrophysical Journal Supplement Series. 239 (1): 24. arXiv:1809.07342. Bibcode:2018ApJS..239...16F. doi:10.3847/1538-4365/aae1a3. S2CID 119368148. 16.
- ^ Soubiran, C.; et al. (2018). "Gaia Data Release 2. The catalogue of radial velocity standard stars". Astronomy and Astrophysics. 616: 8. arXiv:1804.09370. Bibcode:2018A&A...616A...7S. doi:10.1051/0004-6361/201832795. S2CID 52952408. A7.
- ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b c d Andrade, Manuel (October 2019). "Colour-dependent accurate modelling of dynamical parallaxes and masses of visual binaries. Application to the VB+SB2 systems with definitive orbits". Astronomy & Astrophysics. 630: 11. Bibcode:2019A&A...630A..96A. doi:10.1051/0004-6361/201936199. S2CID 202933213. A96.
- ^ a b c d e f g Bonfanti, A.; Ortolani, S.; Nascimbeni, V. (2016). "Age consistency between exoplanet hosts and field stars". Astronomy & Astrophysics. 585: 14. arXiv:1511.01744. Bibcode:2016A&A...585A...5B. doi:10.1051/0004-6361/201527297. S2CID 53971692. A5.
- ^ a b c Luck, R. Earle (January 2017). "Abundances in the Local Region II: F, G, and K Dwarfs and Subgiants". The Astronomical Journal. 153 (1): 19. arXiv:1611.02897. Bibcode:2017AJ....153...21L. doi:10.3847/1538-3881/153/1/21. S2CID 119511744. 21.
- ^ a b "HD 178911". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-10-13.
- ^ "HD 178911B". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-10-13.
- ^ a b Zucker, S.; et al. (2002). "A Planet Candidate in the Stellar Triple System HD 178911". The Astrophysical Journal. 568 (1): 363–368. arXiv:astro-ph/0111550. Bibcode:2002ApJ...568..363Z. doi:10.1086/338892. S2CID 16548934.
- ^ McAlister, H. A.; et al. (1987). "ICCD speckle observations of binary stars. I - A survey for duplicity among the bright stars". The Astronomical Journal. 93: 183–194. Bibcode:1987AJ.....93..183M. doi:10.1086/114297.
- ^ "Exoplanets: The Hunt Continues!" (Press release). Garching, Germany: European Southern Observatory. April 4, 2001. Retrieved December 29, 2012.
- ^ Butler, R. P.; et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal. 646 (1): 505–522. arXiv:astro-ph/0607493. Bibcode:2006ApJ...646..505B. doi:10.1086/504701. S2CID 119067572.