HD 202908, also known as HIP 105200, is a triple star located in the equatorial constellation Equuleus. It has an apparent magnitude of 7.01,[17] making it readily visible in binoculars but not to the naked eye. When resolved, the components have apparent magnitudes of 7.25 and 8.87 respectively.[2] The system is located relatively close at a distance of 169 light years based on Gaia DR3 parallax measurements[9] but it is receding with a heliocentric radial velocity of 6.24 km/s.[8]
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Equuleus |
| A | |
| Right ascension | 21h 18m 34.85s[1] |
| Declination | +11° 34′ 08.2″[1] |
| Apparent magnitude (V) | 7.25±0.03[2] |
| B | |
| Right ascension | 21h 18m 34.80s[1] |
| Declination | +11° 34′ 08.0″[1] |
| Apparent magnitude (V) | 8.87±0.14[2] |
| Characteristics | |
| Spectral type | G0 V (combined)[3] |
| U−B color index | +0.07[4] |
| B−V color index | +0.56[4] |
| Aa | |
| Spectral type | F9 V[5] or G1 V[6] |
| Ab | |
| Spectral type | G0 V[5] or G2 V[6] |
| B | |
| Spectral type | G1.5 V[5] or G6 V[7] |
| Astrometry | |
| Radial velocity (Rv) | 6.24±0.04[8] km/s |
| Proper motion (μ) | RA: +29.213 mas/yr[9] Dec.: −49.564 mas/yr[9] |
| Parallax (π) | 19.3447 ± 0.0543 mas[9] |
| Distance | 168.6 ± 0.5 ly (51.7 ± 0.1 pc) |
| A | |
| Absolute magnitude (MV) | +3.73±0.13[2] |
| B | |
| Absolute magnitude (MV) | +5.35±0.19[2] |
| Orbit[10] | |
| Primary | A |
| Companion | B |
| Period (P) | 28,685±173 d |
| Semi-major axis (a) | 0.5177±0.0046″ |
| Eccentricity (e) | 0.8651±0.0008 |
| Inclination (i) | 100.36±0.16° |
| Longitude of the node (Ω) | 255.03±0.17° |
| Periastron epoch (T) | 24,468,123±3 JD |
| Argument of periastron (ω) (secondary) | 171.9±0.3° |
| Semi-amplitude (K1) (primary) | 6.13±0.07 km/s |
| Semi-amplitude (K2) (secondary) | 13.95±0.09 km/s |
| Orbit[10] | |
| Primary | Aa |
| Companion | Ab |
| Period (P) | 3.9660465±0.0000015 d |
| Eccentricity (e) | 0.0033±0.0008 |
| Argument of periastron (ω) (secondary) | 271±13° |
| Semi-amplitude (K1) (primary) | 66.03±0.06 km/s |
| Semi-amplitude (K2) (secondary) | 69.69±0.06 km/s |
| Details | |
| The System | |
| Metallicity [Fe/H] | −0.04[11] dex |
| Age | 6.4±0.7[12] Gyr |
| The A Subystem | |
| Temperature | 6,100±150[13] K |
| Rotational velocity (v sin i) | 10[14] km/s |
| Aa | |
| Mass | 1.14[15] M☉ |
| Radius | 1.06±0.08[13] R☉ |
| Luminosity | 1.41+0.15 −0.14[13] L☉ |
| Ab | |
| Mass | 1.08[15] M☉ |
| Radius | 0.97±0.08[13] R☉ |
| Luminosity | 1.16+0.13 −0.11[13] L☉ |
| B | |
| Mass | 0.97[15] M☉ |
| Radius | 0.91±0.08[13] R☉ |
| Luminosity | 0.84+0.09 −0.08[13] L☉ |
| Temperature | 5,703±1,090[2] K |
| Rotational velocity (v sin i) | 9[14] km/s |
| Other designations | |
| Database references | |
| SIMBAD | The system |
| A | |
| B | |
Stellar system
edit| Aa | |||||||||||||||
| Period = 3.966 d | |||||||||||||||
| Ab | |||||||||||||||
| Separation = 0.5″ Period = 78 y | |||||||||||||||
| B | |||||||||||||||
Hierarchy of orbits in the HD 202908 system[5]
The system was first observed by astronomer S.W. Burnham.[18]
The "A" component is a double-lined spectroscopic binary that contains two solar-type stars with spectral classifications of F9 V and G0 V respectively.[5] The pair take roughly 4 days to orbit each other.[10]
The tertiary companion designated "B" has a class of G1.5 V, indicating that it is an ordinary G-type main-sequence star like our Sun. HD 202908 A and B both complete an eccentric orbit every 78 years.[10]
Physical characteristics
editHD 202908 Aa and Ab have masses 1.08 and 1.14 times that of the Sun[15] and radii 97% and 106% of the Sun respectively.[13] The former radiates 1.41 times the luminosity of the Sun from its photosphere and the latter radiates 1.16 times the Sun's luminosity.[13] The A subsystem has an effective temperature of 6,100 K,[13] giving it a whitish-yellow hue.
The B component has 97% the mass of the Sun[15] and 91% of its radius. It radiates 84% of the Sun's luminosity[13] from its photosphere at an effective temperature of 5,703 K.[2] The system is estimated to be 6.4 billion years old.[12]
References
edit- ^ a b c d Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (December 2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466–3471. Bibcode:2001AJ....122.3466M. doi:10.1086/323920. ISSN 0004-6256. S2CID 119533755.
- ^ a b c d e f g ten Brummelaar, Theo; Mason, Brian D.; McAlister, Harold A.; Roberts, Jr., Lewis C.; Turner, Nils H.; Hartkopf, William I.; Bagnuolo, Jr., William G. (May 2000). "Binary Star Differential Photometry Using the Adaptive Optics System at Mount Wilson Observatory". The Astronomical Journal. 119 (5): 2403–2414. Bibcode:2000AJ....119.2403T. doi:10.1086/301338. ISSN 0004-6256.
- ^ Abt, H. A. (March 1981). "Visual multiples. VII - MK classifications". The Astrophysical Journal Supplement Series. 45: 437. Bibcode:1981ApJS...45..437A. doi:10.1086/190719. eISSN 1538-4365. ISSN 0067-0049. S2CID 121286745.
- ^ a b Mermilliod, J.-C. (1986), "Compilation of Eggen's UBV data, transformed to UBV (unpublished)", Catalogue of Eggen's UBV Data. SIMBAD, Bibcode:1986EgUBV........0M
- ^ a b c d e Fekel, F. C. Jr. (September 1981). "HD 202908 - A young, solar-type triple system". The Astrophysical Journal. 248: 670. Bibcode:1981ApJ...248..670F. doi:10.1086/159191. eISSN 1538-4357. ISSN 0004-637X.
- ^ a b Docobo, Jose A.; Andrade, Manuel (20 November 2006). "A Methodology for the Description of Multiple Stellar Systems with Spectroscopic Subcomponents". The Astrophysical Journal. 652 (1): 681–695. Bibcode:2006ApJ...652..681D. doi:10.1086/508053. eISSN 1538-4357. ISSN 0004-637X.
- ^ Christy, James W.; Walker, R. L. Jr. (October 1969). "MK Classification of 142 Visual Binaries". Publications of the Astronomical Society of the Pacific. 81: 643. Bibcode:1969PASP...81..643C. doi:10.1086/128831. eISSN 1538-3873. ISSN 0004-6280. S2CID 122411453.
- ^ a b Karataş, Y.; Bilir, S.; Eker, Z.; Demircan, O. (April 2004). "Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution". Monthly Notices of the Royal Astronomical Society. 349 (3): 1069–1092. arXiv:astro-ph/0404219. Bibcode:2004MNRAS.349.1069K. doi:10.1111/j.1365-2966.2004.07588.x. eISSN 1365-2966. ISSN 0035-8711.
- ^ a b c Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b c d Fekel, Francis C.; Scarfe, C. D.; Barlow, D. J.; Duquennoy, Antoine; McAlister, Harold A. (March 1997). "New and Improved Parameters of HD 202908=ADS 14839: A Spectroscopic-Visual Triple System". The Astronomical Journal. 113: 1095. Bibcode:1997AJ....113.1095F. doi:10.1086/118327. ISSN 0004-6256.
- ^ Casagrande, L.; Schönrich, R.; Asplund, M.; Cassisi, S.; Ramírez, I.; Meléndez, J.; Bensby, T.; Feltzing, S. (26 May 2011). "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s): Improved astrophysical parameters for the Geneva-Copenhagen Survey⋆". Astronomy & Astrophysics. 530: A138. arXiv:1103.4651. Bibcode:2011A&A...530A.138C. doi:10.1051/0004-6361/201016276. eISSN 1432-0746. ISSN 0004-6361. S2CID 56118016.
- ^ a b Holmberg, J.; Nordström, B.; Andersen, J. (July 2009). "The Geneva-Copenhagen survey of the solar neighbourhood: III. Improved distances, ages, and kinematics". Astronomy & Astrophysics. 501 (3): 941–947. arXiv:0811.3982. Bibcode:2009A&A...501..941H. doi:10.1051/0004-6361/200811191. ISSN 0004-6361.
- ^ a b c d e f g h i j k Torres, G.; Andersen, J.; Giménez, A. (7 October 2009). "Accurate masses and radii of normal stars: modern results and applications". The Astronomy and Astrophysics Review. 18 (1–2): 67–126. arXiv:0908.2624. Bibcode:2010A&ARv..18...67T. doi:10.1007/s00159-009-0025-1. eISSN 1432-0754. ISSN 0935-4956.
- ^ a b Cutispoto, G.; Pastori, L.; Pasquini, L.; de Medeiros, J. R.; Tagliaferri, G.; Andersen, J. (March 2002). "Fast-rotating nearby solar-type stars". Astronomy & Astrophysics. 384 (2): 491–503. Bibcode:2002A&A...384..491C. doi:10.1051/0004-6361:20020040. eISSN 1432-0746. ISSN 0004-6361. S2CID 56201169.
- ^ a b c d e Tokovinin, Andrei (14 March 2014). "From Binaries to Multiples. I. Data on F and G Dwarfs within 67 pc of the Sun". The Astronomical Journal. 147 (4): 86. arXiv:1401.6825. Bibcode:2014AJ....147...86T. doi:10.1088/0004-6256/147/4/86. eISSN 1538-3881. ISSN 0004-6256. S2CID 53965918.
- ^ "HD 202908". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved March 21, 2023.
- ^ Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361. S2CID 17128864.
- ^ Burnham, S. W. (12 December 1873). "A Third Catalogue of 76 New Double Stars, discovered with a 6-inch Alvan Clark Refractor". Monthly Notices of the Royal Astronomical Society. 34 (2): 59–71. Bibcode:1873MNRAS..34...59B. doi:10.1093/mnras/34.2.59. eISSN 1365-2966. ISSN 0035-8711.