The nature of the Cepheid T Antliae

Abstract

Abstract. The variable star T Antliae, sometimes suspected to be a type II pulsator, is demonstrated to be a classical Cepheid in the third crossing of the instability strip. It exhibits a positive period change of +0.514 ± 0.016 s yr −1 , consistent with a star on the blue side of the instability strip and evolving through it for the third time. The Cepheid exhibits no random fluctuations in pulsation period, although superimposed upon its evolutionary O-C trend are very subtle variations that may be indicative of orbital motion about an unseen companion. Archival spectroscopic data also indicate that the star sits on the edge of a putative cluster of B-type stars that may be physically associated with the Cepheid. Additional photometric and spectroscopic data for the Cepheid and cluster are needed to strengthen the case. The field reddening of T Ant established from nearby early-type stars is E B−V = 0.30 ± 0.01 (E B−V (B0) = 0.316 ± 0.014).

A Search for Evolutionary Changes in the Periods of Cepheids Using Archival Data from the Harvard Observatory Plate Collection. II. V1496 Aquilae

“…For the photoelectric observations, the calculations were made separately for data in the V and B bands of the Johnson broadband system. In the case of the photographic measurements, the photometric system is generally close to that defined by the Johnson B filter, so we reduced the data in the same fashion as for blue photoelectric measurements (e.g., Turner & Berdnikov 2003).…”

The reliability of Cepheid reddenings based on BVIC photometry

“…Turner & Berdnikov (2003) looked for early‐type stars that might be associated with T Ant by using a reddening derived from Pel (1978). Their stated E ( B − V ) is somewhat larger than that of Pel, as determined using the transformation in DWC, and there are faint early‐type stars in this field with a considerable range of reddenings.…”

Rate of Period Change as a Diagnostic of Cepheid Properties

“…Observations of period changes in Cepheids have been matched with some confidence to evolutionary models of massive stars in various crossings of the instability strip (e.g., Turner 1998;Turner & Berdnikov 2001, 2004 in order to identify the direction of strip crossing for individual variables. When used for such purposes, the study of Cepheid period changes becomes an important tool for the characterization of individual members of the class.…”