X-RAY ROTATIONAL MODULATION IN THE YOUNG MAIN SEQUENCE STAR VXR45

VXR45 is a dG9 star with a very short photometric period of 0.223 days (Patten & Simon 1996) and vsini> 200 Km/s (Stauffer et al. 1997). Its log Lx as measured with ROSAT is 30.12 erg/s, corresponding to log(Lx/Lbol)=-3.62, which puts the star below the saturation level, making it a supersaturated star.
The XMM/Newton observation has a total exposure time of 50 ks, 33 ks of which were retained after removal of high background episodes. (Marino et al. 2003 A&A 407, L63)

EPIC-PN light-curve of VXR45 obtained in the 0.3-7.8 keV band (top) and the one of the corresponding background (bottom). The X-ray rotational modulation, with a period very similar to the photometric one (0.223 days = 19.3 ksec) is clearly evident. The X-ray variations in the light-curve are ~30% of the average value. No significant spectral modulation is present.

X-ray data of previous panel folded with the rotational period vs. phase. Circles are points observed at t < 0.223 days (the photometric period) and triangles the ones observed at t > 0.223 days. For clarity we report two photometric periods.