Abstract:
Aims. Our aim is to investigate the variability in the temperature as a function of time among a
sample of coronal X-ray bright points (XBPs).
Methods. We analysed a 7-hour (17:00 UT - 24:00 UT) long time sequence of soft X-ray images
observed almost simultaneously in two filters (Ti poly and Al mesh) on April 14, 2007 with XRay
Telescope (XRT) on-board the Hinode mission. We identified and selected a sample of 14
XBPs and 2 background coronal regions for a detailed analysis. The light curves of XBPs have
been derived using SolarSoft library in IDL. The temperature of XBPs was determined using the
calibrated temperature response curves of the two filters by intensity ratio method.
Results. We find that the XBPs show a high variability in their temperature and
the average temperature ranges from 1.1 MK to 3.4 MK. The variations in the
temperature are related to the different X-ray emission fluxes. These results suggest
that XBPs of different temperatures may be present at the same height in the corona. It is evident
from the results of time series that the heating rate of XBPs is highly variable on short time
scales, and these variations provide a support for magnetic reconnection as the origin of XBPs.
