Pi1 Gruis
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Grus |
| Right ascension | 22h 22m 44.20571s[2] |
| Declination | −45° 56′ 52.6115″[2] |
| Apparent magnitude (V) | 5.31 - 7.01[3] + 10.4[4] |
| Characteristics | |
| Evolutionary stage | AGB[5] |
| Spectral type | S5,7:[6] + G0V[4] |
| Variable type | SRb[7] |
| Astrometry | |
| Parallax (π) | 6.13±0.76 mas[2] |
| Distance | approx. 530 ly (approx. 160 pc) |
| Absolute magnitude (MV) | G0: +4.3[4] |
| Orbit[4] | |
| Primary | A |
| Companion | B |
| Period (P) | 6,200 years |
| Semi-major axis (a) | 2.8" (460 AU) |
| Orbit[8] | |
| Primary | A |
| Companion | C |
| Period (P) | 11.0+1.7 −1.5 years |
| Semi-major axis (a) | 7.05+0.54 −0.57 AU |
| Eccentricity (e) | 0.35+0.18 −0.17 |
| Inclination (i) | 31.75–38.04° |
| Longitude of the node (Ω) | 321.7+5.91 −5.67° |
| Periastron epoch (T) | 2015.06+1.09 −1.14 |
| Argument of periastron (ω) (primary) | 359.00+7.87 −11.26° |
| Details[8] | |
| A | |
| Mass | 1.54–2.19 M☉ |
| Radius | 319±23 R☉ |
| Luminosity | 7,440 L☉ |
| Temperature | 2,300[9] – 3,100[4] K |
| B | |
| Mass | 1.06 M☉ |
| Radius | 1.10 R☉ |
| Luminosity | 1.35 L☉ |
| Temperature | 5,930 K |
| C | |
| Mass | 0.86+0.22 −0.20 M☉ |
| Radius | If main sequence: 0.80+0.34 −0.17 R☉ If white dwarf: 0.009±0.002 R☉ |
| Luminosity | If main sequence: 0.41+1.10 −0.31 L☉ |
| Temperature | If main sequence: 5,170+820 −1,070 K |
| Other designations | |
| CD−46°14292, HR 8521, HD 212087, SAO 231105, HIP 110478 | |
| Database references | |
| SIMBAD | data |
π1 Gruis (Pi1 Gruis) is a semiregular variable star in the constellation Grus around 530 light-years from Earth. It forms a close double star with π2 Gru four arc-minutes away.
Characteristics
[edit]
π1 Gruis is an asymptotic giant branch (AGB) star of spectral type S5.[5] It is one of the brightest members of a class of stars known as S stars.[10] It is also a semi-regular variable star ranging from apparent magnitude 5.3 to 7.0 over a period of 198.8 days.[11]
An ageing star, π1 Gruis is thought to be well on its way transitioning from a red giant to a planetary nebula. A shell of material has been detected at a distance of 0.91 light-years (0.28 parsecs), which is estimated to have been ejected 21,000 years ago.[12] Closer to the star, there appears to be a cavity within 200 AU, suggesting a drop off in the ejection of material in the past 90 years. The presence of companions makes the shape of the shell irregular rather than spherical.[10][8]
The primary star has a measured diameter of 18.37 milliarcseconds,[13] corresponding to a size 350 times that of the Sun.[1]
Companions
[edit]π1 Gruis has two companion stars forming a gravitationally bound stellar system.
The inner, named π1 Gruis C, is 7.05+0.54
−0.57 AU away from the primary and has an orbital period of 11 years. Preliminary data suggest an orbital eccentricity of 0.35+0.18
−0.17, albeit the orbit may be circular. Its mass is measured at 0.86+0.20
−0.22 M☉, suggesting it is either a K-type main-sequence star or white dwarf. It is accreting matter from the red giant primary, and as of such the system may be undergoing novae every 900 years.[8]
The outer companion, named π1 Gruis B, is of apparent magnitude 10.9 and is sunlike in properties—a yellow main sequence star of spectral type G0V. Separated by 2.71″ (projected separation of 453±33 AU), the pair is thought to be gravitationally bound.[13]
History of observations
[edit]The star was catalogued by French explorer and astronomer Nicolas Louis de Lacaille in 1756 but not given a name. Instead, he gave the Bayer designation of "π Gruis" to π2. It was Thomas Brisbane who designated this star as π1.[14] Annie Jump Cannon was the first to report its unusual spectrum, sending a plate of its spectrograph made in 1895 to Paul W. Merrill and noting its similarity to R Andromedae. Merrill selected these two stars along with R Cygni to be the three prototypes of the S star class.[15] π1 Gruis was one of the first 17 stars defined as S-stars by Merrill in 1922; the only star not observed from Mount Wilson due to its southerly location in the sky.[16] Analysis of its spectrum showed bands indicating the presence of technetium,[17] as well as oxides of zirconium, lanthanum, cerium and yttrium but not titanium nor barium which have been recorded in other S stars.[18]
References
[edit]- ^ a b "Giant Bubbles on Red Giant Star's Surface". www.eso.org. Retrieved 21 December 2017.
- ^ a b c Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
- ^ Pojmanski, G. (2002). "The All Sky Automated Survey. Catalog of Variable Stars. I. 0 h - 6 h Quarter of the Southern Hemisphere". Acta Astronomica. 52: 397–427. arXiv:astro-ph/0210283. Bibcode:2002AcA....52..397P.
- ^ a b c d e f Mayer, A.; Jorissen, A.; Paladini, C.; Kerschbaum, F.; Pourbaix, D.; Siopis, C.; Ottensamer, R.; Mečina, M.; Cox, N. L. J.; Groenewegen, M. A. T.; Klotz, D.; Sadowski, G.; Spang, A.; Cruzalèbes, P.; Waelkens, C. (2014). "Large-scale environments of binary AGB stars probed by Herschel. II. Two companions interacting with the wind of π1 Gruis". Astronomy & Astrophysics. 570 (113): A113. arXiv:1408.3965. Bibcode:2014A&A...570A.113M. doi:10.1051/0004-6361/201424465. S2CID 119282752.
- ^ a b Homan, Ward; et al. (2020). "ATOMIUM: A high-resolution view on the highly asymmetric wind of the AGB star π1Gruis. I. First detection of a new companion and its effect on the inner wind". Astronomy and Astrophysics. 644: A61. arXiv:2010.05509. Bibcode:2020A&A...644A..61H. doi:10.1051/0004-6361/202039185.
- ^ Stewart, Paul N.; Tuthill, Peter G.; Nicholson, Philip D.; Sloan, G. C.; Hedman, Matthew M. (2015). "An Atlas of Bright Star Spectra in the Near-infrared from Cassini-VIMS". The Astrophysical Journal Supplement Series. 221 (2): 30. arXiv:1511.01670. Bibcode:2015ApJS..221...30S. doi:10.1088/0067-0049/221/2/30. S2CID 118435831.
- ^ 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: B/gcvs. Bibcode:2009yCat....102025S.
- ^ a b c d Montargès, M.; Malfait, J.; Esseldeurs, M.; de Koter, A.; Baron, F.; Kervella, P.; Danilovich, T.; Richards, A. M. S.; Sahai, R.; McDonald, I.; Khouri, T.; Shetye, S.; Zijlstra, A.; Van de Sande, M.; El Mellah, I.; Herpin, F.; Siess, L.; Etoka, S.; Gobrecht, D.; Marinho, L.; Wallström, S. H. J.; Wong, K. T.; Yates, aJ. (2025). "An accreting dwarf star orbiting the S-type giant star pi1 Gru". arXiv:2504.16845 [astro-ph.SR].
- ^ Wallstrom, S. H. J.; Danilovich, T.; Muller, H. S. P.; Gottlieb, C. A.; Maes, S.; Van de Sande, M.; Decin, L.; Richards, A. M. S.; Baudry, A.; Bolte, J.; Ceulemans, T.; De Ceuster, F.; de Koter, A.; Mellah, I. El; Esseldeurs, M. (December 6, 2023). "ATOMIUM: Molecular inventory of 17 oxygen-rich evolved stars observed with ALMA". Astronomy & Astrophysics. 681: A50. arXiv:2312.03467. doi:10.1051/0004-6361/202347632. ISSN 0004-6361.
- ^ a b Sacuto, S.; Jorissen, A.; Cruzalèbes, P.; Chesneau, O.; et al. (2008). "The close circumstellar environment of the semi-regular S-type star π 1 Gruis". Astronomy & Astrophysics. 482 (2): 561–74. arXiv:0803.3077. Bibcode:2008A&A...482..561S. doi:10.1051/0004-6361:20078306. S2CID 14085392.
- ^ Tabur, V.; Bedding, T. R.; Kiss, L. L.; Moon, T. T.; Szeidl, B.; Kjeldsen, H. (2009). "Long-term photometry and periods for 261 nearby pulsating M giants". Monthly Notices of the Royal Astronomical Society. 400 (4): 1945. arXiv:0908.3228. Bibcode:2009MNRAS.400.1945T. doi:10.1111/j.1365-2966.2009.15588.x. S2CID 15358380.
- ^ Young, K.; Phillips, T. G.; Knapp, G. R. (1993). "Circumstellar shells resolved in IRAS survey data. II - Analysis". Astrophysical Journal. 409: 725–38. Bibcode:1993ApJ...409..725Y. doi:10.1086/172702.
- ^ a b Paladini, C; Baron, F; Jorissen, A; Le Bouquin, J.-B; Freytag, B; Van Eck, S; Wittkowski, M; Hron, J; Chiavassa, A; Berger, J.-P; Siopis, C; Mayer, A; Sadowski, G; Kravchenko, K; Shetye, S; Kerschbaum, F; Kluska, J; Ramstedt, S (2017). "Large granulation cells on the surface of the giant star π1 Gruis". Nature. 553 (7688): 310–312. doi:10.1038/nature25001. PMID 29258298. S2CID 4466336.
- ^ Wagman, Morton (2003). Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg, VA: The McDonald & Woodward Publishing Company. pp. 360–62. ISBN 978-0-939923-78-6.
- ^ Merrill, Paul W. (1955). "Red Stars". Publ. Astron. Soc. Pac. 67 (397): 199–213. Bibcode:1955PASP...67..199M. doi:10.1086/126804. S2CID 239491440.
- ^ Merrill, Paul W. (1922). "Stellar spectra of class S". Astrophysical Journal. 56: 457–82. Bibcode:1922ApJ....56..457M. doi:10.1086/142716.
- ^ Little, Stephen J.; Little-Marenin, Irene R.; Bauer, Wendy Hagen (1987). "Additional late-type stars with technetium". Astronomical Journal. 94: 981–995. Bibcode:1987AJ.....94..981L. doi:10.1086/114532.
- ^ Murty, P.S. (1983). "Pi Gruis - Molecular identifications and spectral classification". Astrophysics and Space Science. 94 (2): 295–305. Bibcode:1983Ap&SS..94..295M. doi:10.1007/BF00653719. ISSN 0004-640X. S2CID 122165729.
