A Cepheid is No More: Hubble's Variable 19 in M33
Abstract
We report on the remarkable evolution in the light curve of a variable star discovered by Hubble (1926) in M33 and classified by him as a Cepheid. Early in the 20th century, the variable, designated as V19, exhibited a 54.7 day period, an intensity-weighted mean B magnitude of 19.59+/-0.23 mag, and a B amplitude of 1.1 mag. Its position in the P-L plane was consistent with the relation derived by Hubble from a total of 35 variables. Modern observations by the DIRECT project show a dramatic change in the properties of V19: its mean B magnitude has risen to 19.08 +/- 0.05 mag and its B amplitude has decreased to less than 0.1 mag. V19 does not appear to be a classical (Population I) Cepheid variable at present, and its nature remains a mystery. It is not clear how frequent such objects are nor how often they could be mistaken for classical Cepheids.
Cite
@article{arxiv.astro-ph/0102453,
title = {A Cepheid is No More: Hubble's Variable 19 in M33},
author = {L. M. Macri and D. D. Sasselov and K. Z. Stanek},
journal= {arXiv preprint arXiv:astro-ph/0102453},
year = {2009}
}
Comments
Accepted for publication in the Astrophysical Journal Letters. Finding charts and photometry data can be downloaded from http://cfa-www.harvard.edu/~kstanek/DIRECT/