TT Cygni

TT Cygni
	; A light curve for TT Cygni, plotted from Hipparcos data
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Cygnus
Right ascension	19h 40m 57.01599s
Declination	+32° 37′ 05.7555″
Apparent magnitude (V)	7.26 - 8.0
Characteristics
Evolutionary stage	AGB
Spectral type	C5,4e(N3e)
B−V color index	+2.917±0.073
Variable type	SRb
Astrometry
Radial velocity (Rv)	−49.0±3.1 km/s
Proper motion (μ)	RA: −5.178 mas/yr ; Dec.: −1.832 mas/yr
Parallax (π)	1.4908 ± 0.0368 mas
Distance	2,190 ± 50 ly ; (670 ± 20 pc)
Absolute magnitude (MV)	−1.297 (var.)
Details
Radius	166 R☉
Luminosity	2,735 L☉
Surface gravity (log g)	−0.4 cgs
Temperature	3,200 K
Other designations
	TT Cyg, BD+32°3522, HD 186047, HIP 96836, SAO 68688
Database references
SIMBAD	data

TT Cygni is a carbon star located 561 parsecs (1,830 ly) away in the northern constellation of Cygnus. It is classified as a semiregular variable of subtype SRb that ranges in brightness from magnitude 7.26 down to 8.0 with a period of 118 days.^[3] This object is called a carbon star because it has a high ratio of carbon to oxygen in its surface layers. The carbon was produced by helium fusion, dredged up from inside the star by deep convection triggered by a flash from the helium shell.

A thin spherical shell around the star, about half a light year across, was emitted 7,000 years ago.^[10] It was first detected from its carbon monoxide emission and has a mass around four thousandths M_☉, of which about a tenth is dust. The dust is thought to be mostly amorphous carbon.^[8]

References

^ "Hipparcos Tools Interactive Data Access". Hipparcos. ESA. Retrieved 8 December 2021.
^ ^a ^b ^c ^d ^e Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
^ ^a ^b ^c "TT Cygni", International Variable Star Index, AAVSO, retrieved 2021-02-04.
^ ^a ^b Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
^ Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
^ Gontcharov, G. A. (2011), "The red giant branch in the Tycho-2 catalogue", Astronomy Letters, 37 (10): 707–717, arXiv:1607.00557, Bibcode:2011AstL...37..707G, doi:10.1134/S1063773711090040, S2CID 119272127.
^ McDonald, I.; Zijlstra, A. A.; Watson, R. A. (2017), "Fundamental parameters and infrared excesses of Tycho–Gaia stars", Monthly Notices of the Royal Astronomical Society, 471 (1): 770–791, arXiv:1706.02208, Bibcode:2017MNRAS.471..770M, doi:10.1093/mnras/stx1433.
^ ^a ^b ^c ^d Groenewegen, M. A. T. (2012), "An extension of the DUSTY radiative transfer code and an application to OH 26.5 and TT Cygni", Astronomy and Astrophysics, 543: A36, Bibcode:2012A&A...543A..36G, doi:10.1051/0004-6361/201218965.
^ "TT Cyg". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2021-02-03.{{cite web}}: CS1 maint: postscript (link)
^ Olofsson, H.; et al. (January 2000), "A high-resolution study of episodic mass loss from the carbon star TT Cygni", Astronomy and Astrophysics, 353: 583–597, Bibcode:2000A&A...353..583O.