Observation of the Gamma-Ray Binary HESS J0632+057 with the HESS, MAGIC, and VERITAS Telescopes

The results of gamma-ray observations of the binary system HESS J0632 + 057 collected during 450 hr over 15 yr, between 2004 and 2019, are presented. Data taken with the atmospheric Cherenkov telescopes H.E.S.S., MAGIC, and VERITAS at energies above 350 GeV were used together with observations at X-ray energies obtained with Swift-XRT, Chandra, XMM-Newton, NuSTAR, and Suzaku. Some of these observations were accompanied by measurements of the H alpha emission line. A significant detection of the modulation of the very high-energy gamma-ray fluxes with a period of 316.7 +/- 4.4 days is reported, consistent with the period of 317.3 +/- 0.7 days obtained with a refined analysis of X-ray data. The analysis of data from four orbital cycles with dense observational coverage reveals short-timescale variability, with flux-decay timescales of less than 20 days at very high energies. Flux variations observed over a timescale of several years indicate orbit-to-orbit variability. The analysis confirms the previously reported correlation of X-ray and gamma-ray emission from the system at very high significance, but cannot find any correlation of optical H alpha parameters with fluxes at X-ray or gamma-ray energies in simultaneous observations. The key finding is that the emission of HESS J0632 + 057 in the X-ray and gamma-ray energy bands is highly variable on different timescales. The ratio of gamma-ray to X-ray flux shows the equality or even dominance of the gamma-ray energy range. This wealth of new data is interpreted taking into account the insufficient knowledge of the ephemeris of the system, and discussed in the context of results reported on other gamma-ray binary systems

3D3C velocimetry measurements of an electrothermal microvortex using wavefront deformation PTV and a single camera

We study the three-dimensional fluid transport in an electrothermal microvortex (EMV), by using wavefront deformation particle-tracking velocimetry (PTV) developed at Universitat der Bundeswehr Munchen. By using a cylindrical lens in conjunction with a microscope objective lens, systematic wavefront deformations in the particle images are created. The particles are observed by a single camera and appear as ellipses. The elliptical nature of the particle images encodes out-of-plane information regarding the particle\u27s position. This new technique is ideally suited for measuring transport in the EMV and provides full three-dimensional, time-resolved particle trajectories with Lagrangian velocity and acceleration. Measurements reveal the toroidal nature of the EMV and the experimentally obtained velocities are used to validate a simplistic model, which describes the interaction between the applied laser illumination and the microfluidic device. The model allows one to conduct numerical simulations of the complex fluid transport in the EMV