Searching for Jet Emission in LMXBs: A Polarimetric View

We present results taken from a study aiming at detecting the emission from relativistic particles jets in neutron star-low mass X-ray binaries using optical polarimetric observations. First, we focus on a polarimetric study performed on the persistent LMXB 4U 0614+091. Once corrected for interstellar effects, we measured an intrinsic linear polarization in the r-band of ~3% at a 3σ confidence level. This is in-line with the observation of an infrared excess in the spectral energy distribution (SED) of the source, reported in a previous work, which the authors linked to the optically thin synchrotron emission of a jet. We then present a study performed on the transitional millisecond pulsar PSR J1023+0038 during quiescence. We measured a linear polarization of 1.09 ± 0.27% and 0.90 ± 0.17% in the V and R bands, respectively. The phase-resolved polarimetric curve of the source in the R-band reveals a hint of a sinusoidal modulation at the source orbital period. The NIR -optical SED of the system did not suggest the presence of a jet. We conclude that the optical linear polarization observed for PSR J1023+0038 is possibly due to Thomson scattering with electrons in the disc, as also suggested by the hint of the modulation of the R-band linear polarization at the system orbital period

Chasing the break: tracing the full evolution of a black hole X-ray binary jet with multiwavelength spectral modeling

Black hole (BH) X-ray binaries (XRBs) are ideal targets to study the connection between accretion inflow and jet outflow. Here we present quasi-simultaneous, multiwavelength observations of the Galactic BH system MAXI J1820+070, throughout its 2018–2019 outburst. Our data set includes coverage from the radio through X-ray bands from 17 different instruments/telescopes, and encompasses 19 epochs over a 7 month period, resulting in one of the most well-sampled multiwavelength data sets of a BH XRB outburst to date. With our data, we compile and model the broadband spectra of this source using a phenomenological model that includes emission from the jet, a companion star, and an accretion flow. This modeling allows us to track the evolution of the spectral break in the jet spectrum, a key observable that samples the jet launching region. We find that the spectral break location changes over at least ≈3 orders of magnitude in electromagnetic frequency over this period. Using these spectral break measurements, we link the full cycle of jet behavior, including the rising, quenching, and reignition, to the changing accretion flow properties as the source evolves through its different accretion states. Our analysis shows consistent jet behavior with other sources in similar phases of their outbursts, reinforcing the idea that jet quenching and recovery may be a global feature of BH XRB systems in outburst. Our results also provide valuable evidence supporting a close connection between the geometry of the inner accretion flow and the base of the jet

Measurements of production cross sections of polarized same-sign W boson pairs in association with two jets in proton-proton collisions at s=13 TeV

The first measurements of production cross sections of polarized same-sign W±W±boson pairs in proton-proton collisions are reported. The measurements are based on a data sample collected with the CMS detector at the LHC at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 137fb−1. Events are selected by requiring exactly two same-sign leptons, electrons or muons, moderate missing transverse momentum, and two jets with a large rapidity separation and a large dijet mass to enhance the contribution of same-sign W±W±scattering events. An observed (expected) 95% confidence level upper limit of 1.17 (0.88)fbis set on the production cross section for longitudinally polarized same-sign W±W±boson pairs. The electroweak production of same-sign W±W±boson pairs with at least one of the Wbosons longitudinally polarized is measured with an observed (expected) significance of 2.3 (3.1) standard deviations.SCOAP

Novel SOI inertial sensors with optical readout based on transparent metals

A novel optical microsensor has been fabricated using a SOI-based technology. The basic device is a symmetric flexure in which the central plate is used both as seismic mass and as optical target for displacement measurements. The device includes a multilayer, metal-dielectric Photonic Band Gap (PBG) structure, deposited on a flat substrate and bonded topside at a fixed distance from the movable plate. The reflection intensity of a light beam, pointed to the overall optical structure (top PBG, air gap, the moving plate), will depend on the air gap thickness whose value is determined by the displacement of the proof mass induced by the measurand, the external force. In particular, the realization of highly sensitive accelerometers is addressed here, the structure presented allows for detecting accelerations of the order of a few mG that produce displacements of the plate of few nanometers. Experimental prototypes have been realized and some results are shown

Tunable absorption resonance in electromechanical one-dimensional metallodielectric photonic band gap structures

We present the results of an experimental study of an electromechanical, one-dimensional, metallodielectric photonic band gap structure. We monitor the reflectance as a function of the thickness of an air gap located inside the stack. The results suggest that, by changing the thickness of the air gap by approximately 20 nm, a large contrast can be achieved between high- and low-reflectance states, as reflectance switches from a fraction of a percent to about 70%. Using this approach, we are able to selectively remove a relatively narrow but tunable wavelength range from the reflected spectrum, thus making possible applications to accelerometers, linear optical switches, modulators, and other specialized filters in the visible range. The characteristic absorption spectrum can be controlled by varying air gap and dielectric layer thicknesses

Optical switching application of ZnSe/MgF2 photonic band gap structures based on thermal nonlinear nonlinearities

We studied a ZnSe/MgF2 multilayer in order to modulate its optical reflectance. An electrically induced temperature increase is responsible for changes in the refractive index of the layers. The reflected signal is therefore decreased

Optical limiting effects in hybrid electromechanical-metallo-dielectric Ag/ZnO photonic band gap structures

We study a combination of nonlinear interactions and electromechanical switching in one-dimensional metallo-dielectric photonic band gap (PBG) structures. The structure, which is composed of two similar stacks consisting of ZnO and Ag alternating layers separated by an air layer of tunable thickness, is arranged to take advantage of both active and passive transmission control mechanisms. Active transmission control is provided by the activation of electromechanical switches, and acts on a time scale of microseconds. Passive transmission control is based on the onset on nonlinear two-photon absorption in the ZnO layers for high incident intensities, and occurs on a time scale of picoseconds. Preliminary samples were prepared to show that the two degrees of freedom can be implemented in a metallo-dielectric structure. The reduction of transmittance with increasing incident intensity was demonstrated in Ag/ZnO samples realized by means of dual ion beam sputtering technique. Electromechanical transmission control was instead demonstrated in a metallo-dielectric structure composed of thermally evaporated Ag/MgF2 multilayer stack which contained an air gap. We therefore show that the combination of the nonlinear behavior exhibited by ZnO and modulation of an air gap results in a more responsive, faster device, with stronger attenuation and higher contrasts in the transmission of light between "on" and "off states. We conclude that this kind of structure has great potential for broadband optical limiting and switching applications

Optical switching applications of ZnSe/MgF2 photonic band gap structures based on thermal nonlinearities

We investigate a thermo-optical device based on a ZnSe/MgF2 multilayer and demonstrate the modulation of its optical reflectance around the band edge. An electrically induced temperature increase is responsible for the change of the refractive indices of the layers. As a result, the reflection spectrum shifts and the reflected signal decreases. The structure was grown using a thermal evaporation technique, and was designed in such a way that a band edge appears at 632.8 nm, i.e. accessible to a low-power He-Ne laser. The reflection characteristics were investigated as a function of the applied voltage and we found that the photonic band edge shifts by a maximum of 7 nm for an applied voltage of 90 V. Furthermore, different sets of measurements have shown that the spectral shift depends on the voltage squared, thus allowing experimental data analysis in terms of the thermally driven optical nonlinearity. © Springer-Verlag 2005

Chasing the break: Tracing the full evolution of a black hole X-ray binary jet with multi-wavelength spectral modeling

International audienceBlack hole X-ray binaries (BH XRBs) are ideal targets to study the connection between accretion inflow and jet outflow. Here we present quasi-simultaneous, multi-wavelength observations of the Galactic black hole system MAXI J1820+070, throughout its 2018-2019 outburst. Our data set includes coverage from the radio through X-ray bands from 17 different instruments/telescopes, and encompasses 19 epochs over a 7 month time period, resulting in one of the most well-sampled multi-wavelength data sets of a BH XRB outburst to date. With our data, we compile and model the broad-band spectra of this source using a phenomenological model that includes emission from the jet, companion star, and accretion flow. This modeling allows us to track the evolution of the spectral break in the jet spectrum, a key observable that samples the jet launching region. We find that the spectral break location changes over at least $\approx3$ orders of magnitude in electromagnetic frequency over this period. Using these spectral break measurements, we link the full cycle of jet behavior, including the rising, quenching, and re-ignition, to the changing accretion flow properties as the source evolves through its different accretion states. Our analyses show a consistent jet behavior with other sources in similar phases of their outbursts, reinforcing that the jet quenching and recovery may be a global feature of BH XRB systems in outburst. Our results also provide valuable evidence supporting a close connection between the geometry of the inner accretion flow and the base of the jet