41 research outputs found
Sub-second periodicity in a fast radio burst
Fast radio bursts (FRBs) are millisecond-duration flashes of radio waves that
are visible at distances of billions of light-years. The nature of their
progenitors and their emission mechanism remain open astrophysical questions.
Here we report the detection of the multi-component FRB 20191221A and the
identification of a periodic separation of 216.8(1) ms between its components
with a significance of 6.5 sigmas. The long (~3 s) duration and nine or more
components forming the pulse profile make this source an outlier in the FRB
population. Such short periodicity provides strong evidence for a neutron-star
origin of the event. Moreover, our detection favours emission arising from the
neutron-star magnetosphere, as opposed to emission regions located further away
from the star, as predicted by some models.Comment: Updated to conform to the accepted versio
Improved Constraints on the 21 cm EoR Power Spectrum and the X-Ray Heating of the IGM with HERA Phase I Observations
We report the most sensitive upper limits to date on the 21 cm epoch of
reionization power spectrum using 94 nights of observing with Phase I of the
Hydrogen Epoch of Reionization Array (HERA). Using similar analysis techniques
as in previously reported limits (HERA Collaboration 2022a), we find at 95%
confidence that Mpc) mK at and that Mpc mK at , an improvement by a factor of 2.1 and 2.6 respectively. These limits are
mostly consistent with thermal noise over a wide range of after our data
quality cuts, despite performing a relatively conservative analysis designed to
minimize signal loss. Our results are validated with both statistical tests on
the data and end-to-end pipeline simulations. We also report updated
constraints on the astrophysics of reionization and the cosmic dawn. Using
multiple independent modeling and inference techniques previously employed by
HERA Collaboration (2022b), we find that the intergalactic medium must have
been heated above the adiabatic cooling limit at least as early as ,
ruling out a broad set of so-called "cold reionization" scenarios. If this
heating is due to high-mass X-ray binaries during the cosmic dawn, as is
generally believed, our result's 99% credible interval excludes the local
relationship between soft X-ray luminosity and star formation and thus requires
heating driven by evolved low-metallicity stars.Comment: 57 pages, 37 figures. Updated to match the accepted ApJ version.
Corresponding author: Joshua S. Dillo
Hitler's Shadow: Nazi War Criminals, U.S. Intelligence, and the Cold War
The report is based on findings from newly-declassified decades-old Army and CIA records released under the Nazi War Crimes Disclosure Act of 1998 (the Act), these records were processed and reviewed by the National Archives-led Nazi War Crimes and Japanese Imperial Government Records Interagency Working Group (IWG), and written by IWG historians Richard Breitman and Norman J.W. Goda.
The report highlights materials opened under the Act, in addition to records that were previously opened but had not been mined by historians and researchers, including records from the Office of Strategic Services (a CIA predecessor), dossiers of the Army Staff’s Intelligence Records of the Investigative Records Repository (IRR), State Department records, and files of the Navy Judge Advocate General.
Hitler’s Shadow augments the IWG’s 2005 final report to Congress, U.S. Intelligence and the Nazis, and includes wartime and postwar US intelligence documents on the search for and prosecution of Nazi war criminals; Allied protection or use of Nazi war criminals; and the postwar activities of war criminals both in the United States and abroad.Nazi War Crimes and Japanese Imperial Government Records Interagency Working Grou