Search

We present newly obtained X-ray and radio observations of Tycho's supernova remnant using Chandra and the Karl G. Jansky Very Large Array in 2015 and 2013/14, respectively. When combined with earlier epoch observations by these instruments, we now have time baselines for expansion measurements of the remnant of 12-15 year in the X-rays and 30 year in the radio. The remnant's large angular size allows for proper motion measurements at many locations around the periphery of the blast wave. We find, consistent with earlier measurements, a clear gradient in the expansion velocity of the remnant, despite its round shape. The proper motions on the western and southwestern sides of the remnant are about a factor of two higher than those in the east and northeast. We showed in an earlier work that this is related to an offset of the explosion site from the geometric center of the remnant due to a density gradient in the ISM, and using our refined measurements reported here, we find that this offset is ∼ 23'' towards the northeast. An explosion center offset in such a circular remnant has implications for searches for progenitor companions in other remnants.

Background: Interactive Voice Response Systems (IVRS) and other electronic data collection methods have begun to replace conventional paper diaries as a way to capture daily patient reports. However, these methods have not been compared in head and neck (H&N) cancer patients receiving radiation therapy., Methods: 15 subjects with H&N cancer were asked to complete daily IVRS calls and daily paper diaries during radiation therapy. We compared response consistency and comparative adherence across the two methods., Results: 86.1% (1920/2231) of participants' responses were consistent between IVRS and paper diaries. 79.5% of the expected number of paper diaries were completed, compared to 66.2% of IVRS phone calls., Conclusions: In this pilot study of H&N cancer patients undergoing radiation therapy, concordance was high between responses recorded by paper diaries and IVRS. Although adherence appeared to be higher for the paper diaries, it is possible that they may not have been completed at the proper time.

Rotation-powered radio pulsars are born with inferred initial rotation periods of order 300 ms (some as short as 20 ms) in core-collapse supernovae. In the traditional picture, this fast rotation is the result of conservation of angular momentum during the collapse of a rotating stellar core. This leads to the inevitable conclusion that pulsar spin is directly correlated with the rotation of the progenitor star. So far, however, stellar theory has not been able to explain the distribution of pulsar spins, suggesting that the birth rotation is either too slow or too fast. Here we report a robust instability of the stalled accretion shock in core-collapse supernovae that is able to generate a strong rotational flow in the vicinity of the accreting proto-neutron star. Sufficient angular momentum is deposited on the proto-neutron star to generate a final spin period consistent with observations, even beginning with spherically symmetrical initial conditions. This provides a new mechanism for the generation of neutron star spin and weakens, if not breaks, the assumed correlation between the rotational periods of supernova progenitor cores and pulsar spin.