TT Aquilae

TT Aquilae (TT Aql) is a Classical Cepheid (δ Cep) variable star in the constellation Aquila.

TT Aquilae
Observation data
Epoch J2000      Equinox J2000
Constellation Aquila
Right ascension  19h 08m 13.75081s[1]
Declination +01° 17′ 55.1600″[1]
Apparent magnitude (V) 6.52 - 7.65[2]
Characteristics
Spectral type G0/2Ib[3] (F6-G5[2])
U−B color index +0.638 - +1.601[4]
B−V color index +0.932 - +1.637[4]
Variable type δ Cep[2]
Astrometry
Radial velocity (Rv)3.00[5] km/s
Proper motion (μ) RA: +1.17[1] mas/yr
Dec.: −3.33[1] mas/yr
Parallax (π)0.18 ± 1.26[1] mas
Absolute magnitude (MV)−4.26[6]
Details
Mass6.2 - 8.6[7] M☉
Radius83.8 - 100.5[8] R☉
Luminosity5,284[7] L☉
Surface gravity (log g)1.10 - 1.70[6] cgs
Temperature5,007 - 5,630[6] (- 6,200[9]) K
Metallicity+0.10[6]
Other designations
TT Aql, HD 178359, HIP 93390, BD+01°3899, SAO 124305
Database references
SIMBADdata
Data sources:
Hipparcos Catalogue,
CCDM (2002),
Bright Star Catalogue (5th rev. ed.)

The visual apparent magnitude of TT Aql ranges from 6.52 to 7.65 over 13.7546 days.[2] 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.[10]

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,[9] 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.[8]

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.[7]

References
  1. Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  3. Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars, Vol. 5". Michigan Spectral Survey. 05: 0. Bibcode:1999MSS...C05....0H.
  4. Berdnikov, L. N. (2008). "VizieR Online Data Catalog: Photoelectric observations of Cepheids in UBV(RI)c (Berdnikov, 2008)". VizieR On-line Data Catalog: II/285. Originally Published in: 2008yCat.2285....0B. 2285. Bibcode:2008yCat.2285....0B.
  5. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065.
  6. Kovtyukh, V. V.; Andrievsky, S. M.; Belik, S. I.; Luck, R. E. (2005). "Phase-dependent Variation of the Fundamental Parameters of Cepheids. II. Periods Longer than 10 Days". The Astronomical Journal. 129 (1): 433–453. Bibcode:2005AJ....129..433K. doi:10.1086/426339.
  7. Gieren, W. P. (1989). "Towards a reconciliation of Cepheid masses". Astronomy and Astrophysics. 225: 381. Bibcode:1989A&A...225..381G.
  8. Imbert, M. (1999). "Détermination des rayons de Céphéides. V. Vitesses radiales et dimensions de 22 Céphéides galactiques. Determination of the radii of Cepheids V. Radial velocities and dimensions of 22 galactic Cepheids". Astronomy and Astrophysics Supplement. 140: 79–87. Bibcode:1999A&AS..140...79I. doi:10.1051/aas:1999515.
  9. Luck, R. E.; Andrievsky, S. M.; Fokin, A.; Kovtyukh, V. V. (2008). "Phase-Dependent Variation of the Fundamental Parameters of Cepheids. Iv. S-CEPHEIDS". The Astronomical Journal. 136 (1): 98. Bibcode:2008AJ....136...98L. doi:10.1088/0004-6256/136/1/98.
  10. Schaltenbrand, R.; Tammann, G. A. (1971). "The light curve parameters of photoelectrically observed galactic Cepheids". Astronomy and Astrophysics Supplement. 4: 265. Bibcode:1971A&AS....4..265S.
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