Bibcode
Beck, S. C.; Matthews, J. M.; Terranegra, L.; Kovo, O.; Martin, E. L.; Bouvier, J.; Covino, E.
Bibliographical reference
Astronomy and Astrophysics, v.299, p.89
Advertised on:
7
1995
Journal
Citations
192
Refereed citations
174
Description
We present the results of a new multi-site campaign (COYOTES II) to
monitor the light variations of T Tauri stars (TTS) of the Taurus-Auriga
dark cloud. The UBVRI light curves of 19 TTS were obtained over a two
months period to search for rotational modulation by spots. We report
new period detections for IQ Tau (6.25d), LkCa-3 (7.2d), and LkCa-14
(3.35d) and confirm previously detected periods for DF Tau (9.8d), DR
Tau (9.0d), GM Aur (11.9d), and TAP 26 (2.58d). We also report tentative
periods for CW Tau (8.2d), CY Tau (7.9d), HP Tau (5.9d), and XZ Tau
(2.6d). No periods were found in the present data set for CI Tau, DG
Tau, DQ Tau, GH Tau, RY Tau, Hubble 4, TAP 45, and TAP 57NW. Altogether,
the results of this new campaign confirm the main conclusion of COYOTES
I that classical T Tauri stars (CTTS) on average have longer rotational
periods than weak-line TTS (WTTS). The present study also confirms that
rotational modulation in WTTS is due to spots cooler than the
photosphere and we show that the amplitude of the modulation primarily
reflects the amount of areal coverage by spots. The amplitude of the
light variations, and hence the spot size, is found to increase with
both rotation rate and advancing spectral type, as expected if WTTS cool
spots correspond to photospheric regions of strong dynamo-generated
magnetic fields. Finally, combined with previous studies, these new
results provide further evidence for temporal variations of the
photometric periods of CTTS. Such variations seem to occur
preferentially in CTTS whose rotational modulation is dominated by hot
spots and we therefore argue that the observed period changes are linked
to the magnetospheric accretion process rather than to surface
differential rotation.