AAVSO: American Association of Variable Star Observers

CT Lacertae: Another Long-period Carbon Star with Long-Timescale Variations?

Volume 42 number 2 (2014)

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Matthew R Templeton
AAVSO, 49 Bay State Road, Cambridge, MA 02138; address email correspondence to matthewt@aavso.org
Peter Maurer
AAVSO, 49 Bay State Road, Cambridge, MA 02138; address email correspondence to matthewt@aavso.org
Wolfgang Kriebel
AAVSO, 49 Bay State Road, Cambridge, MA 02138; address email correspondence to matthewt@aavso.org
Wayne M. Lowder
AAVSO, 49 Bay State Road, Cambridge, MA 02138; address email correspondence to matthewt@aavso.org
Etienne Morelle
AAVSO, 49 Bay State Road, Cambridge, MA 02138; address email correspondence to matthewt@aavso.org
Steve O'Connor
AAVSO, 49 Bay State Road, Cambridge, MA 02138; address email correspondence to matthewt@aavso.org
Andrzej Arminski
AAVSO, 49 Bay State Road, Cambridge, MA 02138; address email correspondence to matthewt@aavso.org
Laurent Bichon
AAVSO, 49 Bay State Road, Cambridge, MA 02138; address email correspondence to matthewt@aavso.org
John E. Bortle
AAVSO, 49 Bay State Road, Cambridge, MA 02138; address email correspondence to matthewt@aavso.org

Abstract

The poorly-studied semiregular-type variable CT Lacertae is a long-period variable of the carbon spectral type, and is also a member of the LPV subclass that exhibits double maxima. More importantly, CT Lac is also undergoing a long-timescale dimming episode spanning the last few thousand days. Analysis of the AAVSO’s 45-year visual light curve shows no clear changes in period during the course of its observational history, but current and past changes in mean light and amplitude suggest long-term, observable changes occur in the star itself or in its circumstellar environment. Long-term data are currently too short and sparse to say whether dimming episodes are cyclical as they are in some other long-period carbon Miras and semiregulars, but the ongoing dimming episode could be related to similar events which do recur in other long-period carbon stars like RU Vir and V Hya. CT Lac is an interesting variable and is recommended as a long-term target for both visual and instrumental observation. Increased visual observation is strongly encouraged, as are multicolor photometry and high resolution spectroscopy.