title: TT Aquilae
text: # TT Aquilae
  
  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.
  
  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.
  
  