R Aquilae

R Aquilae is a variable star in the equatorial constellation of Aquila. It is located approximately 780 light years distant from the Sun based on parallax,[1] 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 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.

R Aquilae

Observation data Epoch J2000      Equinox J2000
Constellation	Aquila
Right ascension	19^h 06^m 22.25105^s[1]
Declination	+08° 13′ 48.0004″[1]
Apparent magnitude (V)	5.3 to 12.0[2]
Characteristics
Evolutionary stage	asymptotic giant branch[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[1] mas/yr Dec.: −68.042[1] mas/yr
Parallax (π)	4.2030 ± 0.4306[1] mas
Distance	approx. 780 ly (approx. 240 pc)
Details
Mass	1.0[3] M☉
Radius	259±67[6] R☉
Luminosity	3,470±50[3] L☉
Temperature	3,000±300[3] K
Other designations
R Aql, BD+08°3970, HD 177940, HIP 93820, HR 7243, SAO 124266[4]
Database references
SIMBAD	data

R Aquilae light curve

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.[9] The star may have recently undergone a helium flash.[6] It is oxygen-rich in abundance with the same mass as the Sun but has expanded to 259[6] times the Sun's radius. On average, the star is radiating 3,470 K[3] times the luminosity of the Sun from its swollen photosphere at an effective temperature of 3000 K or so. It is losing mass at the rate of (6 – 35) × 10⁻⁷ M_☉ yr⁻¹, forming a dusty silicate shell.[3]

References

1. 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.
2. 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.
3. 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.
4. "R Aql". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-08-17.
5. 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.
6. 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. arXiv:astro-ph/0210167. Bibcode:2002AJ....124.1706V. doi:10.1086/342282.
7. VSX; Otero, Sebastian (January 4, 2011). "R Aquilae". AAVSO Website. American Association of Variable Star Observers. Retrieved 2013-12-21.
8. 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.
9. 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.