Publications of the Astronomical Society of Australia Publications of the Astronomical Society of Australia Society
Publications of the Astronomical Society of Australia

Rotational and Candidate-Eclipsing-Binary Light Curves for Pre-Main-Sequence Stars in the Chamaeleon I Star-Forming Cloud

Warrick A. Lawson A C and Lisa A. Crause B
+ Author Affiliations
- Author Affiliations

A School of Physical, Enviromental & Mathematical Sciences, University of New South Wales, Australian Defence Force Academy, Canberra, ACT 2600, Australia

B South African Astronomical Observatory, P.O. Box 9, Observatory 7935, South Africa

C Corresponding author. Email:

Publications of the Astronomical Society of Australia 26(1) 31-36
Submitted: 7 July 2008  Accepted: 11 November 2008   Published: 2 April 2009


We present the results of a photometric survey for variability in ten X-ray-emitting low-mass stars in the Chamaeleon region. Eight of the stars we observed are bona fide pre-main-sequence members of the ~2 Myr-old Chamaeleon I star-forming cloud. The other two stars are young with high levels of relative X-ray emission, but with discordant proper motions they are probable non-members of the cloud. In six of the stars we monitored, periodic variations on timescales of 2.5–11.5 d were detected, that we ascribe to stellar rotation and the presence of cool starspots. Two other stars, CHXR 20 and CHXR 85, show large amplitude variations at visual and near-infrared wavelengths and are candidate eclipsing binaries. Compared to the rotational properties of low-mass stars in the ≈8 Myr-old η Chamaeleontis cluster, we find that the older η Chamaeleontis stars have several times higher surface specific angular momentum than the younger Chamaeleon I stars. The apparent increase in angular momentum between ~2 and 8 Myr might be due to changes in stellar internal structure as the stars evolve, or evidence for a different rotational history between members of the two star-forming regions.

Keywords: open clusters and associations: individual (Chamaeleon I) — stars: individual (CHXR 3, CHXR 20, CHXR 33, CHXR 37, CHXR 40, CHXR 47, CHXR 53, CHXR 59, CHXR 71, CHXR 85) — stars: pre-main sequence — stars: rotation — stars: spots — binaries: eclipsing


The observations reported in this paper were obtained using facilities at the South African Astronomical Observatory. We thank SAAO for the allocation of telescope time for this project. We thank the referee whose comments considerably improved this paper, and Dr Eric Mamajek (University of Rochester) for alerting us to the availability of 2MASS light curves and of proper motions for these stars.


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