14 research outputs found
Point and Interval Estimation on the Degree and the Angle of Polarization. A Bayesian approach
Linear polarization measurements provide access to two quantities, the degree
(DOP) and the angle of polarization (AOP). The aim of this work is to give a
complete and concise overview of how to analyze polarimetric measurements. We
review interval estimations for the DOP with a frequentist and a Bayesian
approach. Point estimations for the DOP and interval estimations for the AOP
are further investigated with a Bayesian approach to match observational needs.
Point and interval estimations are calculated numerically for frequentist and
Bayesian statistics. Monte Carlo simulations are performed to clarify the
meaning of the calculations.
Under observational conditions, the true DOP and AOP are unknown, so that
classical statistical considerations - based on true values - are not directly
usable. In contrast, Bayesian statistics handles unknown true values very well
and produces point and interval estimations for DOP and AOP, directly. Using a
Bayesian approach, we show how to choose DOP point estimations based on the
measured signal-to-noise ratio. Interval estimations for the DOP show great
differences in the limit of low signal-to-noise ratios between the classical
and Bayesian approach. AOP interval estimations that are based on observational
data are presented for the first time. All results are directly usable via
plots and parametric fits.Comment: 11 pages, 14 figures, 3 table
Performance of the New FlashCam-based Camera in the 28\,m Telescope of H.E.S.S
In October 2019, the central 28 m telescope of the H.E.S.S. experiment has
been upgraded with a new camera. The camera is based on the FlashCam design
which has been developed in view of a possible future implementation in the
Medium-Sized Telescopes of the Cherenkov Telescope Array (CTA), with emphasis
on cost and performance optimization and on reliability. The fully digital
design of the trigger and readout system makes it possible to operate the
camera at high event rates and to precisely adjust and understand the trigger
system. The novel design of the front-end electronics achieves a dynamic range
of over 3,000 photoelectrons with only one electronics readout circuit per
pixel. Here we report on the performance parameters of the camera obtained
during the first year of operation in the field, including operational
stability and optimization of calibration algorithms.Comment: Proceedings of the 37th International Cosmic Ray Conference (ICRC
2021
STROBE-X: A probe-class mission for x-ray spectroscopy and timing on timescales from microseconds to years
We describe the Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X), a probeclass mission concept that will provide an unprecedented view of the X-ray sky, performing timing and spectroscopy over both a broad energy band (0.2-30 keV) and a wide range of timescales from microseconds to years. STROBE-X comprises two narrow-field instruments and a wide field monitor. The soft or low-energy band (0.2-12 keV) is covered by an array of lightweight optics (3-m focal length) that concentrate incident photons onto small solid-state detectors with CCD-level (85-175 eV) energy resolution, 100 ns time resolution, and low background rates. This technology has been fully developed for NICER and will be scaled up to take advantage of the longer focal length of STROBE-X. The higher-energy band (2-30 keV) is covered by large-area, collimated silicon drift detectors that were developed for the European LOFT mission concept. Each instrument will provide an order of magnitude improvement in effective area over its predecessor (NICER in the soft band and RXTE in the hard band). Finally, STROBE-X offers a sensitive wide-field monitor (WFM), both to act as a trigger for pointed observations of X-ray transients and also to provide high duty-cycle, high time-resolution, and high spectral-resolution monitoring of the variable X-ray sky. The WFM will boast approximately 20 times the sensitivity of the RXTE All-Sky Monitor, enabling multi-wavelength and multi-messenger investigations with a large instantaneous field of view. This mission concept will be presented to the 2020 Decadal Survey for consideration
The radiation environment in L-2 orbit: implications on the non-X-ray background of the eROSITA pn-CCD cameras
A revision of soft proton scattering at grazing incidence and its implementation in the geant4 toolkit
Calibration strategies for the LAD instrument on-board LOFT
The Scientific objectives of the LOFT mission, e.g., the study of the Neutron
Star equation of state and of the Strong Gravity, require accurate energy, time
and flux calibration for the 500k channels of the SDD detectors, as well as the
knowledge of the detector dead-time and of the detector response with respect
to the incident angle of the photons. We report here the evaluations made to
asses the calibration issues for the LAD instrument. The strategies for both
ground and on-board calibrations, including astrophysical observations, show
that the goals are achievable within the current technologies.Comment: Proceedings of SPIE, Vol. 8443, Paper No. 8443-208, 201
The Wide-Field Imager for IXO: Status and future activities
The Wide Field Imager (WFI) of the International X-ray Observatory (IXO) is an X-ray imaging spectrometer based on a large monolithic DePFET (Depleted P-channel Field Effect Transistor) Active Pixel Sensor. Filling an area of 10 x 10 cm2 with a format of 1024 x 1024 pixels it will cover a field of view of 18 arcmin. The pixel size of 100 x 100 ÎĽm2 corresponds to a fivefold oversampling of the telescope's expected 5 arcsec point spread function. The WFI's basic DePFET structure combines the functionalities of sensor and integrated amplifier with nearly Fano-limited energy resolution and high efficiency from 100 eV to 15 keV. The development of dedicated control and amplifier ASICs allows for high frame rates up to 1 kHz and flexible readout modes. Results obtained with representative prototypes with a format of 256 x 256 pixels are presented