TT Aquilae
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquila |
| Right ascension | 19h 08m 13.75081s |
| Declination | +01° 17′ 55.1600″ |
| Apparent magnitude (V) | 6.52 - 7.65 |
| Characteristics | |
| Spectral type | G0/2Ib (F6-G5) |
| U−B color index | +0.638 - +1.601 |
| B−V color index | +0.932 - +1.637 |
| Variable type | δ Cep |
| Astrometry | |
| Radial velocity (Rv) | 3.00 km/s |
| Proper motion (μ) | RA: +1.17 mas/yr Dec.: −3.33 mas/yr |
| Parallax (π) | 0.18±1.26 mas |
| Absolute magnitude (MV) | −4.26 |
| Details | |
| Mass | 6.2 - 8.6 M☉ |
| Radius | 83.8 - 100.5 R☉ |
| Luminosity | 5,284 L☉ |
| Surface gravity (log g) | 1.10 - 1.70 cgs |
| Temperature | 5,007 - 5,630 (- 6,200) K |
| Metallicity | +0.10 |
| Other designations | |
| TT Aql, HD 178359, HIP 93390, BD+01°3899, SAO 124305 | |
| Database references | |
| SIMBAD | data |
| Data sources: | |
| Hipparcos Catalogue, CCDM (2002), Bright Star Catalogue (5th rev. ed.) | |
TT Aquilae (TT Aql) is a Classical Cepheid (δ Cep) variable star in the constellation Aquila.
The visual apparent magnitude of TT Aql ranges from 6.52 to 7.65 over 13.7546 days. The light curve is asymmetric, with the rise from minimum to maximum brightness only taking half the time of the fall from maximum to minimum.
The announcement that the star's brightness varies was made in 1907 by Annie Jump Cannon. It had been observed on 506 photographs taken from May 22, 1888 through November 9, 1906, from which a period of 13.75 days had been derived.
TT Aql is a yellow-white supergiant around five thousand times brighter than the sun. It pulsates and varies in temperature between about 5,000 K and 6,000 K, and the spectral type varies between F6 and G5. The radius is 91.4 R☉ at maximum brightness, varying between 84 R☉ and 100 R☉ as the star pulsates.
Cepheid masses can be estimated using Baade-Wesselink relations and this gives 8.6 M☉. The mass estimated by matching to evolutionary tracks is 7.7 M☉. The mass calculated by modelling the pulsations is 6.2 M☉. The discrepancies between the masses obtained by the different methods occurs for most Cepheid variables.