  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda |
| Right ascension | 00h 24m 01.94575s1 |
| Declination | +38° 34′ 37.3701″1 |
| Apparent magnitude (V) | 5.8 - 15.22 |
| Characteristics | |
| Evolutionary stage | AGB3 |
| Spectral type | S3,5e-S8,8e(M7e)2 |
| B−V color index | 1.974 |
| Variable type | Mira2 |
| Astrometry | |
| Radial velocity (Rv) | −6.40 5 km/s |
| Proper motion (μ) | RA: −16.021±0.1481 mas/yr Dec.: −32.794±0.1411 mas/yr |
| Parallax (π) | 2.6444±0.1600 mas1 |
| Distance | 1,230 ± 70 ly (380 ± 20 pc) |
| Absolute magnitude (MV) | −5.196 |
| Details | |
| Mass | 3.77 M☉ |
| Radius | 7308a or 476±120 – 493±1299 R☉ |
| Luminosity | 6,3008 L☉ |
| Surface gravity (log g) | −1.0210 cgs |
| Temperature | 1,900 – 2,50010 K |
| Metallicity [Fe/H] | −1.0111 dex |
| Other designations | |
| HR 90, BD +37°58, HD 1967, SAO 53860, HIP 1901. | |
| Database references | |
| SIMBAD | data |
R Andromedae (R And) is a Mira-type variable star in the constellation Andromeda. Its spectral class is type S because it shows absorption bands of zirconium monoxide (ZrO) in its spectrum. It was among the stars found by Paul Merrill to show absorption lines of the unstable element technetium,12 establishing that nucleosynthesis must be occurring in stars. The SH molecule was found for the first time outside earth in the atmosphere of this star.13 The star is losing mass due to stellar winds at a rate of 1.09×10−6 M☉/yr.6
Variability
R Andromedae shows periodic variations in its brightness approximately every 409 days. The maximum brightness is not the same every cycle and can reach a peak magnitude of mv = 5.8, with the lowest known minima nearly 10 magnitudes fainter. The rise to maximum brightness is approximately twice as fast as the fall to minimum brightness. It is classified as a Mira variable. Those stars contract and expand regularly, changing size and temperature, and this causes the brightness variations.2
Properties
R Andromedae has a spectral type that varies as its brightness changes. At a typical maximum it is assigned a spectral type of S5/4.5e. This makes it an S-type star, a red giant similar to class M stars but with unusually strong molecular bands of ZrO in its spectrum compared to the titanium oxide (TiO) bands seen in other cool giants. S stars are intermediate between carbon stars and the more typical oxygen-rich giants. The S5 indicates its relative temperature, while the number after the slash is a measure of the relative C:O ratio, 4.5 meaning carbon is about 97% as abundant as oxygen. ZrO bands in R Andromedae are about twenty times stronger than those of TiO.14 When it is fainter, the spectral type has been classified as late as S8,8e. On this older classification system for S stars, the number after the comma is an indication of the relative strength of ZrO and TiO bands which used to be considered to show the C:O ratio.15
R Andromedae, like all Mira variables, is an asymptotic giant branch star, one that has exhausted its core helium and is burning it in a shell outside the core and hydrogen in a shell closer to the surface. These stars undergo dredge-up events which cause convection of fusion products to the surface and anomalies such as enhanced carbon and zirconium. Asymptotic giant branch stars are very cool and luminous red giants; R Andromedae varies in temperature and luminosity but is typically about 2,500 K and 6,300 L☉. The angular diameter of R Andromedae has been measured at 8.63±1.42 mas and 8.32±1.27 mas on different dates, corresponding to radii of 493±129 R☉ and 476±120 R☉ respectively, assuming a distance of 532 pc.9 Other measurements based on the spectral energy distribution of the star give a luminosity of 6,000 L☉ and a very cool temperature of 1,900 K,8 which imply a very large radius of 730 R☉.a R Andromedae is one of the largest known stars.
Notes
Notes
- Applying the Stefan–Boltzmann law with a nominal solar effective temperature of 5,772 K:
- .
References
References
- 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.
- Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
- Son, Seong-Min; Cho, Se-Hyung; Kim, Jaeheon; Baek, Hyeon; Yoon, Dong-Hwan; Suh, Kyung-Won (2025). "Survey of S-type AGB Stars Using the KVN Four-band Receiving System: SMASTES II". The Astronomical Journal. 170 (5): 266. Bibcode:2025AJ....170..266S. doi:10.3847/1538-3881/ae0586.
- "R And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 7, 2018.
- de Bruijne, J. H. J.; Eilers, A.-C. (October 2012). "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project". Astronomy & Astrophysics. 546: 14. arXiv:1208.3048. Bibcode:2012A&A...546A..61D. doi:10.1051/0004-6361/201219219. S2CID 59451347. A61.
- Guandalini, R. (April 2010). "Infrared photometry and evolution of mass-losing AGB stars. III. Mass loss rates of MS and S stars". Astronomy and Astrophysics. 513: A4. arXiv:1002.2458. Bibcode:2010A&A...513A...4G. doi:10.1051/0004-6361/200911764. S2CID 119193286.
- Khalatyan, A.; Anders, F.; Chiappini, C.; Queiroz, A. B. A.; Nepal, S.; Dal Ponte, M.; Jordi, C.; Guiglion, G.; Valentini, M.; Torralba Elipe, G.; Steinmetz, M.; Pantaleoni-González, M.; Malhotra, S.; Jiménez-Arranz, Ó.; Enke, H.; Casamiquela, L.; Ardèvol, J. (2024). "Transferring spectroscopic stellar labels to 217 million Gaia DR3 XP stars with SHBoost". Astronomy and Astrophysics. 691: A98. arXiv:2407.06963. Bibcode:2024A&A...691A..98K. doi:10.1051/0004-6361/202451427.
- Ramstedt, S.; Olofsson, H. (2014). "The12CO/13CO ratio in AGB stars of different chemical type". Astronomy & Astrophysics. 566: A145. arXiv:1405.6404. Bibcode:2014A&A...566A.145R. doi:10.1051/0004-6361/201423721. S2CID 59125036.
- van Belle, G. T.; et al. (1997). "Angular Size Measurements of Carbon Miras and S-Type Stars". The Astronomical Journal. 114 (5): 2150–2156. Bibcode:1997AJ....114.2150V. doi:10.1086/118635.
- Ortiz, Roberto; Guerrero, Martín A. (2016). "Ultraviolet emission from main-sequence companions of AGB stars". Monthly Notices of the Royal Astronomical Society. 461 (3): 3036. arXiv:1606.09086. Bibcode:2016MNRAS.461.3036O. doi:10.1093/mnras/stw1547. S2CID 118619933.
- Gáspár, András; Rieke, George H.; Ballering, Nicholas (2016). "The Correlation between Metallicity and Debris Disk Mass". The Astrophysical Journal. 826 (2): 171. arXiv:1604.07403. Bibcode:2016ApJ...826..171G. doi:10.3847/0004-637X/826/2/171. S2CID 119241004.
- Merrill, P. W. (1952). "Technetium in the stars". Science. 115 (2992): 479–489 [484]. Bibcode:1952Sci...115..479.. doi:10.1126/science.115.2992.479. PMID 17792758.
- Yamamura, Issei; et al. (January 2000). "Identification of SH ∆v=1 Ro-vibrational Lines in R Andromedae". The Astrophysical Journal. 528 (1): L33–L36. arXiv:astro-ph/9911080. Bibcode:2000ApJ...528L..33Y. doi:10.1086/312420. PMID 10587489.
- Keenan, P. C.; Boeshaar, P. C. (1980). "Spectral types of S and SC stars on the revised MK system". The Astrophysical Journal Supplement Series. 43: 379. Bibcode:1980ApJS...43..379K. doi:10.1086/190673.
- Keenan, Philip C.; Garrison, Robert F.; Deutsch, Armin J. (1974). "Revised Catalog of Spectra of Mira Variables of Types ME and Se". The Astrophysical Journal Supplement Series. 28: 271. Bibcode:1974ApJS...28..271K. doi:10.1086/190318.