| 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−Bcolor index | 0.37[4] |
| B−Vcolor index | 1.60[4] |
| Variable type | Mira[2] |
| Astrometry | |
| Radial velocity (Rv) | 34.6±0.6[5] km/s |
| Proper motion (μ) | RA: +4.404mas/yr[1] Dec.: −68.042mas/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 | |
| R Aql,AAVSO 1901+08,BD+08°3970,HD 177940,HIP 93820,HR 7243,SAO 124266[4] | |
| Database references | |
| SIMBAD | data |
R Aquilae is avariable star in theequatorialconstellation ofAquila. It is located approximately 760 light years distant from the Sun[6] and is drifting further away with aradial velocity of 35 km/s.[5] This is a thermally-pulsatingMira variable that ranges in brightness frommagnitude 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 thenaked eye as a dim, red-hued star.
The discovery of R Aquilae was announced byFriedrich 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, itsvariable star designation, in the astronomical literature.[9][10][7]
R Aquilae is an agingred giant on theasymptotic giant branch[3] with astellar classification that varies over time, between M5e and M9e,[2] where the 'e' suffix indicatesemission features in thespectrum. The cooler spectral types occur near the minimum visual magnitude, and the hottest near maximum.[11] The star may have recently undergone ahelium flash.[12] It is oxygen-rich in abundance with the same mass as the Sun but has expanded to 275[6] times theSun's radius. On average, the star is radiating 3,470[3] times theluminosity of the Sun from its swollenphotosphere at aneffective temperature of 2,800 K or so.[6] It is losing mass at the rate of(6 – 35) × 10−7M☉ yr−1, forming a dusty silicate shell.[3]
