R Aquilae is a variable star in the equatorial constellation of Aquila. It is located approximately 760 light years distant from the Sun[6] and is drifting further away with a radial velocity of 35 km/s.[5] This is a thermally-pulsating Mira variable that ranges in brightness from magnitude 5.3 down to 12.0 with a period of 269.84 days.[2][7] The period was over 300 days when first observed, and has declined steadily since – decreasing from 320 in 1915 down to 264 in 2010, at an average rate of 0.4 days per year. The amplitude of the variation has also decreased by about a magnitude since discovery.[8] The peak magnitude is bright enough for the star to be visible to the naked eye as a dim, red-hued star.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquila |
| Right ascension | 19h 06m 22.25105s[1] |
| Declination | 08° 13′ 48.0004″[1] |
| Apparent magnitude (V) | 5.3 to 12.0[2] |
| Characteristics | |
| Evolutionary stage | AGB[3] |
| Spectral type | M5-9IIIe[2] |
| U−B color index | 0.37[4] |
| B−V color index | 1.60[4] |
| Variable type | Mira[2] |
| Astrometry | |
| Radial velocity (Rv) | 34.6±0.6[5] km/s |
| Proper motion (μ) | RA: 4.404 mas/yr[1] Dec.: −68.042 mas/yr[1] |
| Parallax (π) | 4.2030 ± 0.4306 mas[1] |
| Distance | 763±29 ly (234±9 pc)[6] |
| Details | |
| Mass | 1.0[3] M☉ |
| Radius | 275[6][a] R☉ |
| Luminosity | 3,470±50[3] L☉ |
| Temperature | 2,800[6] K |
| Other designations | |
| Database references | |
| SIMBAD | data |
The discovery of R Aquilae was announced by Friedrich Wilhelm Argelander on May 20, 1856. It had been under observation by Argelander and his colleagues at Bonn Observatory since 1854. No name was given to the star in Argelander's announcement, but by October of 1856 it was being called R Aquilae, its variable star designation, in the astronomical literature.[9][10][7]
R Aquilae is an aging red giant on the asymptotic giant branch[3] with a stellar classification that varies over time, between M5e and M9e,[2] where the 'e' suffix indicates emission features in the spectrum. The cooler spectral types occur near the minimum visual magnitude, and the hottest near maximum.[11] The star may have recently undergone a helium flash.[12] It is oxygen-rich in abundance with the same mass as the Sun but has expanded to 275[6] times the Sun's radius. On average, the star is radiating 3,470[3] times the luminosity of the Sun from its swollen photosphere at an effective temperature of 2,800 K or so.[6] It is losing mass at the rate of (6 – 35) × 10−7 M☉ yr−1, forming a dusty silicate shell.[3]
Notes
edit- ^ Calculated using angular diameter and distance in Table 1
References
edit- ^ a b c d 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 Samus, N. N.; et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
- ^ a b c d e f Zhao-Geisler, R.; et al. (2012). "Dust and molecular shells in asymptotic giant branch stars". Astronomy & Astrophysics. 545: A56. arXiv:1207.3767. Bibcode:2012A&A...545A..56Z. doi:10.1051/0004-6361/201118150. S2CID 53992211.
- ^ a b c "R Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-08-17.
- ^ a b Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
- ^ a b c d e f Montargès, M.; Cannon, E.; Koter, A. de; Khouri, T.; Lagadec, E.; Kervella, P.; Decin, L.; McDonald, I.; Homan, W.; Waters, L. B. F. M.; Sahai, R.; Gottlieb, C. A.; Malfait, J.; Maes, S.; Pimpanuwat, B. (2023-03-01). "The VLT/SPHERE view of the ATOMIUM cool evolved star sample - I. Overview: Sample characterization through polarization analysis". Astronomy & Astrophysics. 671: A96. arXiv:2301.02081. doi:10.1051/0004-6361/202245398. ISSN 0004-6361.
- ^ a b VSX; Otero, Sebastian (January 4, 2011). "R Aquilae". AAVSO Website. American Association of Variable Star Observers. Retrieved 2013-12-21.
- ^ Greaves, J; Howarth, J. J. (June 2000). "Further investigations of R Aquilae". Journal of the British Astronomical Association. 110 (3): 131–142. Bibcode:2000JBAA..110..131G.
- ^ Argelander, Friedrich Wilhelm August (June 1856). "Planeten-Oppositionen, beobachtet am Bonner Meridian kreise von Herrn Prof. Argelander, Dir. der Sternw. zu Bonn". Astronomische Nachrichten. 43: 331. Bibcode:1856AN.....43Q.331A. Retrieved 21 November 2024.
- ^ Gould, B. A. (October 1856). "Observations of the variable stars". Astronomical Journal. 4 (96): 190–191. Bibcode:1856AJ......4..190G. doi:10.1086/100548. Retrieved 21 November 2024.
- ^ Keenan, Philip C.; et al. (1974). "Revised Catalog of Spectra of Mira Variables of Types ME and Se". Astrophysical Journal Supplement. 28: 271. Bibcode:1974ApJS...28..271K. doi:10.1086/190318.
- ^ Van Belle, G. T.; et al. (2002). "Angular Size Measurements of Mira Variable Stars at 2.2 Microns. II". The Astronomical Journal. 124 (3): 1706–1715. arXiv:astro-ph/0210167. Bibcode:2002AJ....124.1706V. doi:10.1086/342282. S2CID 33832649.