TT Aquilae
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquila |
| Right ascension | 19h 08m 13.75081s[2] |
| Declination | +01° 17′ 55.1600″[2] |
| Apparent magnitude (V) | 6.52 - 7.65[3] |
| Characteristics | |
| Spectral type | G0/2Ib[4] (F6-G5[3]) |
| U−B color index | +0.638 - +1.601[5] |
| B−V color index | +0.932 - +1.637[5] |
| Variable type | δ Cep[3] |
| Astrometry | |
| Radial velocity (Rv) | 3.00[6] km/s |
| Proper motion (μ) | RA: +1.17[2] mas/yr Dec.: −3.33[2] mas/yr |
| Parallax (π) | 0.18 ± 1.26 mas[2] |
| Absolute magnitude (MV) | −4.26[7] |
| Details | |
| Mass | 6.2 - 8.6[8] M☉ |
| Radius | 83.8 - 100.5[9] R☉ |
| Luminosity | 5,284[8] L☉ |
| Surface gravity (log g) | 1.10 - 1.70[7] cgs |
| Temperature | 5,007 - 5,630[7] (- 6,200[10]) K |
| Metallicity | +0.10[7] |
| Other designations | |
| 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.[3] 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.[11]
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.[12][13]
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,[10] 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.[9]
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.[8]
References
[edit]- ^ Kiss, Laszlo L. (July 1998). "A photometric and spectroscopic study of the brightest northern Cepheids - I. Observations". Monthly Notices of the Royal Astronomical Society. 297 (3): 825. Bibcode:1998MNRAS.297..825K. doi:10.1046/j.1365-8711.1998.01559.x. S2CID 121699816.
- ^ a b c d e 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. S2CID 18759600.
- ^ a b c d 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.
- ^ 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.
- ^ a b 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.
- ^ 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. S2CID 119231169.
- ^ a b c d 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.
- ^ a b c Gieren, W. P. (1989). "Towards a reconciliation of Cepheid masses". Astronomy and Astrophysics. 225: 381. Bibcode:1989A&A...225..381G.
- ^ a b 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.
- ^ a b 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.
- ^ 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.
- ^ Cannon, A. J.; Pickering, E. C. (1907). "15 New Variable Stars in Harvard Maps Nos. 31 and 62". Harvard College Observatory Circular. 129: 1–3. Retrieved 21 November 2024.
- ^ Jordan, F. C. (October 1919). "The color changes of certain variable stars of short period". Astrophysical Journal. 50: 174–205. Bibcode:1919ApJ....50..174J. doi:10.1086/142495. Retrieved 21 November 2024.
