HD 77361
  | |
| Observation data Epoch J2000.0[1] Equinox J2000.0[1] | |
|---|---|
| Constellation | Pyxis |
| Right ascension | 09h 01m 11.41956s[1] |
| Declination | −26° 39′ 49.3773″[1] |
| Apparent magnitude (V) | 6.187[2] |
| Characteristics | |
| Evolutionary stage | RGB[3] |
| Spectral type | K1IIICNII[4] |
| U−B color index | 1.18±0.05[5] |
| B−V color index | 1.165[2] |
| J−H color index | 0.690[6] |
| J−K color index | 0.749[6] |
| Astrometry | |
| Radial velocity (Rv) | −23.17±0.12[7] km/s |
| Proper motion (μ) | RA: 25.441[1] mas/yr Dec.: −53.283[1] mas/yr |
| Parallax (π) | 7.5091 ± 0.0242 mas[1] |
| Distance | 434 ± 1 ly (133.2 ± 0.4 pc) |
| Details[8] | |
| Mass | 1.78 M☉ |
| Luminosity | 74.1+3.5 −3.3 L☉ |
| Surface gravity (log g) | 2.35[9] cgs |
| Temperature | 4,600±90 K |
| Metallicity [Fe/H] | −0.02[9] dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 77361 is an orange-hued star in the southern constellation of Pyxis. With an apparent magnitude of 6.187, it can be faintly seen by the naked eye from Earth. As such, it is listed in the Bright Star Catalogue as HR 3597. It is located at a distance of 434 light-years (133 parsecs) according to Gaia DR3 parallax measurements. The star is notable for its unusually high lithium content.
Physical properties
[edit]This is an aging red-giant branch star (RGB) at the RGB bump,[3] with the spectral type K1III. This means that it has evolved past the main-sequence stage after exhausting its core hydrogen, causing it to bloat into a red giant. It has now reached a point where a discontinuity in hydrogen abundance produced by deep stellar convection results in a short-term decline in energy production, hampering its ascent of the RGB.[11] The "CNII" in its spectral type indicates a strong cyanogen signature in the star's outer atmosphere, as strong as that of a normal K1 bright giant (luminosity class II).[12]
According to a 2020 study,[8] the star has a mass of 1.78 M☉, an effective temperature of roughly 4,600 K (4,330 °C; 7,820 °F), and radiates 74.1 times the luminosity of the Sun from its photosphere. Some earlier publications, however, present smaller values for the mass (1.3±0.2 M☉[5] or 1.5±0.2 M☉[3]), luminosity (45.7 L☉[9]), and temperature (4,370±100 K[5]). The star is slightly poorer in iron than the Sun, with a metallicity of [Fe/H]=−0.02 dex (10−0.02 ≈ 95% solar abundance).
Anomalous abundances
[edit]The star is considered a super Li-rich star, a star so enhanced in lithium that its existence cannot be explained by the standard stellar evolution theory.[5] It is thought that the lithium is actively being generated within the star, as unstable beryllium-7 atoms produced in the inner layers well up to the upper atmosphere via an unknown mechanism and then decay into stable lithium-7.[13]
The star also has a very small 12C/13C ratio of 4.3±0.5,[3] compared to 89.4±0.2 of the Sun. It was the first population I super Li-rich low-luminosity low-mass K giant discovered to have such a small 12C/13C ratio.[13]
Similar stars
[edit]The K-type giant star TYC 3251-581-1 is similar to HD 77361 in several aspects; namely, both stars have an extremely high lithium abundance and a low 12C/13C ratio, are currently at the RGB bump phase, and belong to the thin disk stellar population.[14]
References
[edit]- ^ a b c d e f 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 Høg, E.; et al. (February 2000). "The Tycho-2 Catalogue of the 2.5 Million Brightest Stars". Astronomy and Astrophysics. 355 (1): L27–L30. Bibcode:2000A&A...355L..27H.
- ^ a b c d Kumar, Y. Bharat; Reddy, Bacham E. (20 September 2009). "HD 77361: A New Case of Super Li-Rich K Giant with Anomalous Low 12 C/ 13 C Ratio". The Astrophysical Journal. 703 (1): L46–L50. Bibcode:2009ApJ...703L..46K. doi:10.1088/0004-637X/703/1/L46. ISSN 0004-637X.
- ^ Houk, N. (1982). "Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Volume_3. Declinations -40_ƒ0 to -26_ƒ0". Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Ann Arbor, Michigan: University of Michigan. Bibcode:1982mcts.book.....H.
- ^ a b c d Lyubimkov, L. S.; Kaminsky, B. M.; Metlov, V. G.; Pavlenko, Ya. V.; Poklad, D. B.; Rachkovskaya, T. M. (2015). "The cool giant HD 77361—a super Li-rich star". Astronomy Letters. 41 (12): 809–823. arXiv:1602.02000. Bibcode:2015AstL...41..809L. doi:10.1134/S1063773715120075. ISSN 1063-7737.
- ^ a b Cutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". CDS/ADC Collection of Electronic Catalogues. 2246: II/246. Bibcode:2003yCat.2246....0C.
- ^ 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 Charbonnel, C.; Lagarde, N.; Jasniewicz, G.; North, P. L.; Shetrone, M.; Krugler Hollek, J.; Smith, V. V.; Smiljanic, R.; Palacios, A.; Ottoni, G. (2020). "Lithium in red giant stars: Constraining non-standard mixing with large surveys in the Gaia era". Astronomy & Astrophysics. 633: A34. arXiv:1910.12732. Bibcode:2020A&A...633A..34C. doi:10.1051/0004-6361/201936360. ISSN 0004-6361.
- ^ a b c Kumar, Yerra Bharat; Reddy, Bacham E.; Lambert, David L. (20 March 2011). "Origin of Lithium Enrichment in K Giants". The Astrophysical Journal. 730 (1): L12. arXiv:1102.2299. Bibcode:2011ApJ...730L..12K. doi:10.1088/2041-8205/730/1/L12. ISSN 2041-8205.
- ^ "HD 77361". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 23 November 2024.
- ^ Cassisi, S.; Marín-Franch, A.; Salaris, M.; Aparicio, A.; Monelli, M.; Pietrinferni, A. (2011). "The magnitude difference between the main sequence turn off and the red giant branch bump in Galactic globular clusters". Astronomy & Astrophysics. 527: A59. arXiv:1012.0419. Bibcode:2011A&A...527A..59C. doi:10.1051/0004-6361/201016066. S2CID 56067351.
- ^ Keenan, Philip C. (1987). "Spectral types and their uses". Publications of the Astronomical Society of the Pacific. 99: 713. Bibcode:1987PASP...99..713K. doi:10.1086/132036.
- ^ a b Asplund, Martin; Grevesse, Nicolas; Sauval, A. Jacques; Scott, Pat (1 September 2009). "The Chemical Composition of the Sun". Annual Review of Astronomy and Astrophysics. 47 (1): 481–522. arXiv:0909.0948. Bibcode:2009ARA&A..47..481A. doi:10.1146/annurev.astro.46.060407.145222. ISSN 0066-4146.
- ^ Zhou, Y. T.; Shi, J. R.; Yan, H. L.; Gao, Q.; Zhang, J. B.; Zhao, G.; Pan, K.; Kumar, Y. B. (2018). "Super lithium-rich K giant with low 12 C to 13 C ratio". Astronomy & Astrophysics. 615: A74. Bibcode:2018A&A...615A..74Z. doi:10.1051/0004-6361/201730389. ISSN 0004-6361.
