To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
In order to measure precisely the polarization of Crab Nebula and Cygnus X-1, we have been developing a hard X-ray polarimeter for balloon-borne experiments called PHENEX (Polarimetry of High ENErgy X-rays). It consists of several detectors called unit counters. The unit counter has a detection efficiency of 20% and a modulation factor of 53% at 80 keV. Up to now, we have finished the installation of eight unit counters to the polarimeter, that will be launched in Spring 2009 to observe the Crab Nebula. If the polarization of this source is more than 30%, the PHENEX polarimeter will be able to measure the degree and the direction of the polarization with errors less than 10% and 10°, respectively.
X-ray astronomy has been much advanced by three observations: spectroscopy, timing, and imaging. Also in the hard X-ray region, these three observations will be realized by ASTRO-H and XEUS. However, the observation of the polarization is at the moment left out in spite of its potential usefulness. This is because of the difficulty of developing polarimeters with high sensitivity. Since the origin of the polarization is often due to nonthermal radiation processes such as synchrotron radiation, observations in the hard X-ray region are possibly more important than those in the soft X-ray region: it is expected that the degree of polarization in the hard X-ray region would be higher than that at lower energies.