FF Aquilae

FF Aquilae

Location of FF Aquilae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Aquila
Right ascension	18^h 58^m 14.74830^s[1]
Declination	+17° 21′ 39.2976″[1]
Apparent magnitude (V)	5.18 - 5.51[2]
Characteristics
Spectral type	F6Ib[3]
U−B color index	0.43[4]
B−V color index	0.8[4]
Variable type	δ Cep[2]
Astrometry
Radial velocity (Rv)	−15.47±1.61[1] km/s
Proper motion (μ)	RA: −1.151[1] mas/yr Dec.: −9.823[1] mas/yr
Parallax (π)	1.9057 ± 0.0712 mas[1]
Distance	1,710 ± 60 ly (520 ± 20 pc)
Absolute magnitude (MV)	−3.4[5]
Details
Mass	3.2[6] M☉
Radius	39[5] R☉
Luminosity	2,238[7] L☉
Surface gravity (log g)	1.28[8] cgs
Temperature	6,195[5] K
Metallicity [Fe/H]	+0.04[9] dex
Rotational velocity (v sin i)	10.0[10] km/s
Age	60[9] Myr
Other designations
FF Aql, HD 176155, HIP 93124, BD+17°3799, HR 7165, SAO 104296.
Database references
SIMBAD	data

FF Aquilae is a classical Cepheid variable star located in the constellation Aquila, close to the border with Hercules. It ranges from apparent magnitude 5.18 to 5.51 over a period of 4.47 days,[2] meaning it is faintly visible to the unaided eye in rural or suburban settings.[11]

The visual band light curve of FF Aquilae, adapted from Kiss (1998)[12]

Originally known as HR 7165, it was noted to be variable by Charles Morse Huffer in August 1927, who observed its Cepheid pattern. It then received the variable star designation FF Aquilae.[13] Analysis of its brightness over 122 years shows that its period is increasing by 0.072±0.011 seconds per year.[14] It is a small amplitude classical Cepheid, and as such is expected to be a supergiant near the red edge of the instability strip.[2]

A yellow supergiant, FF Aqlilae pulsates with varying temperature, diameter, and luminosity.[5] It has been estimated to be 1,710 ± 60 light-years (520 ± 20 parsecs) distant from Earth by extrapolating from its angular diameter and estimated radius.[5]

FF Aquilae is a possible quadruple star system. Analysis of its spectrum shows that it is a spectroscopic binary system with the fainter companion calculated to be a main sequence star of spectral type A9V to F3V, orbiting every 3.92 years. A third star, revealed by speckle interferometry, is likely to be a cooler star that has evolved off the main sequence.[15] A fourth star, that is of magnitude 11.4 and located 6 arcseconds away, is a somewhat evolved star slightly hotter, larger, and more luminous than the Sun.[16] Several studies found it unlikely to be a member of the system,[6][17] although Gaia Data Release 3 finds it to be at a similar distance and with a similar proper motion.[16]

References

1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
2. Watson, Christopher (4 January 2010). "FF Aquilae". AAVSO Website. American Association of Variable Star Observers. Retrieved 18 July 2014.
3. Abt, Helmut A. (2009). "MK Classifications of Spectroscopic Binaries". The Astrophysical Journal Supplement. 180 (1): 117–118. Bibcode:2009ApJS..180..117A. doi:10.1088/0067-0049/180/1/117. S2CID 122811461.
4. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
5. Turner, D. G.; Kovtyukh, V. V.; Luck, R. E.; Berdnikov, L. N. (2013). "The Pulsation Mode and Distance of the Cepheid FF Aquilae". The Astrophysical Journal. 772 (1): L10. arXiv:1306.1228. Bibcode:2013ApJ...772L..10T. doi:10.1088/2041-8205/772/1/L10. S2CID 54710833.
6. Gallenne, A.; Kervella, P.; Mérand, A.; Evans, N. R.; Girard, J. H. V.; Gieren, W.; Pietrzyński, G. (2014). "Searching for visual companions of close Cepheids". Astronomy & Astrophysics. 567: A60. arXiv:1406.0493. Bibcode:2014A&A...567A..60G. doi:10.1051/0004-6361/201423872. S2CID 55702630.
7. Groenewegen, M. A. T. (2020). "The flux-weighted gravity-luminosity relation of Galactic classical Cepheids". Astronomy and Astrophysics. 640: A113. arXiv:2007.02148. Bibcode:2020A&A...640A.113G. doi:10.1051/0004-6361/202038292. S2CID 220364506.
8. Stassun, Keivan G.; Oelkers, Ryan J.; Pepper, Joshua; et al. (20 August 2018). "The TESS Input Catalog and Candidate Target List". The Astronomical Journal. 156 (3): 102. arXiv:1706.00495. Bibcode:2018AJ....156..102S. doi:10.3847/1538-3881/aad050. eISSN 1538-3881.
9. Acharova, I. A.; et al. (2012). "Galactic restrictions on iron production by various types of supernovae". Monthly Notices of the Royal Astronomical Society. 420 (2): 1590. arXiv:1111.2152. Bibcode:2012MNRAS.420.1590A. doi:10.1111/j.1365-2966.2011.20161.x. S2CID 118404944.
10. De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (January 2014). "A catalog of rotational and radial velocities for evolved stars: V. Southern stars⋆⋆⋆". Astronomy & Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. ISSN 0004-6361.
11. Bortle, John E. (2001). "Introducing the Bortle Dark-Sky Scale". Sky and Telescope. 101 (2): 126. Bibcode:2001S&T...101b.126B.
12. Kiss, La ́szlo ́ L. (July 1998). "A photometric and spectroscopic study of the brightest northern Cepheids – I. Observations". Monthly Notices of the Royal Astronomical Society. 297 (3): 825–838. Bibcode:1998MNRAS.297..825K. doi:10.1046/j.1365-8711.1998.01559.x.
13. Sanford, Roscoe F. (1935). "On the Radial-Velocity Variation of the Cepheid Variable FF Aquilae". Astrophysical Journal. 81: 132–39. Bibcode:1935ApJ....81..132S. doi:10.1086/143621.
14. Berdnikov, L. N.; Turner, D. G.; Henden, A. A. (2014). "A search for evolutionary period variations of Cepheids using the Harvard plate stacks: FF Aql". Astronomy Reports. 58 (4): 240–48. Bibcode:2014ARep...58..240B. doi:10.1134/S1063772914040015. S2CID 121684735.
15. Evans, Nancy Remage; Welch, Douglas L.; Scarfe, Colin D.; Teays, Terry J. (1990). "The orbit and companions of the classical Cepheid FF AQL". Astronomical Journal. 99: 1598–1611. arXiv:astro-ph/9706292. Bibcode:1990AJ.....99.1598E. doi:10.1086/115442. ISSN 0004-6256.
16. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
17. Udalski, A.; Evans, Nancy R. (1993). "The visual companion of the classical Cepheid FF AQL". Astronomical Journal. 106 (1): 348–51. Bibcode:1993AJ....106..348U. doi:10.1086/116643. ISSN 0004-6256.