  | |
| Observation data Epoch J2000.0[1] Equinox J2000.0[1] | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 19h 07m 09.77940s |
| Declination | −26° 19′ 54.5064″ |
| Apparent magnitude (V) | 9.15[2] |
| Characteristics | |
| Evolutionary stage | A5 SrEuCr[3] |
| B−Vcolor index | 0.45[2] |
| J−Hcolor index | 0.071[4] |
| J−Kcolor index | 0.055[4] |
| Astrometry | |
| Proper motion (μ) | RA: -2.063[1]mas/yr Dec.: −4.425[1]mas/yr |
| Parallax (π) | 2.5411±0.0186 mas[1] |
| Distance | 1,284 ± 9 ly (394 ± 3 pc) |
| Absolute magnitude (MV) | 1.55,[5] 1.166[6] |
| Details[5] | |
| Mass | 1.81, 2.2[7] M☉ |
| Radius | 2.57 R☉ |
| Luminosity | 18.9, 26.9,[6] ~32[7] L☉ |
| Surface gravity (log g) | 3.79 cgs |
| Temperature | 7420, 7002,[6] 8000[7] K |
| Rotational velocity (v sin i) | 2.50[8] km/s |
| Age | 955 Myr |
| Other designations | |
| CD−26° 13816,CPD−26° 6650,Gaia DR2 6763969142066777344,HD 177765,SAO 187692,PPM 269324,EPIC 214503319,TIC 465996299,TYC 6882-1808-1,GSC 06882-01808,2MASS J19070978-2619543, Renson 49550[4] | |
| Database references | |
| SIMBAD | data |
HD 177765 is a white-hued star in the southernconstellation ofSagittarius. With anapparent magnitude of 9.15, it is too faint to be seen by the naked eye fromEarth, but is dimly visible usingbinoculars.[9] It is located at a distance of 1,284 light-years (394 parsecs) according toGaia EDR3parallax measurements.
The star is classified as arapidly oscillating Ap star (roAp star). It shows super-solar abundances ofchromium andstrontium as well as manyrare-earth elements such aseuropium andcerium, but is depleted ofcarbon andnickel.[8] In 2012, the star was found topulsate with a lowradial velocityamplitude of 7–150 m/s and a period of 23.6 minutes, the latter being the longest out of any known roAp star at the time.[7] Two additional pulsation frequencies were detected in 2016.[10]
The precise stellar parameters vary from publication to publication, but the star is considered to be part of a group ofevolved roAp stars with long pulsation periods, alongsideβ CrB A andHD 116114. The existence of this group implies a systematic shift of rare-earthemission line anomalies as roAp stars age.[7]
