We perform milliarcsecond X-ray astrometry of the quadruply lensed radio-quiet quasar GraL J065904.1+162909 (J0659). This zs = 3.083 quasar is lensed into four images and was discovered with the second Data Release of the Gaia Space Observatory (Gaia DR2). Our J0659 study exploits strong gravitational lenses as high-resolution telescopes. This technique shows promise to elucidate the origin of optical and X-ray emission in distant lensed quasars at spatial scales beyond the reach of current instruments. In our study, we use Gaia DR3 and Hubble Space Telescope observations of J0659 to infer a mass model for the deflector. Our model reproduces the Gaia DR3 quasar lensed image positions to one milliarcsecond and determines the position of the optical source in J0659 to within this precision. Next, we analyze Chandra observations of J0659 and conduct a Bayesian test evaluating whether the X-ray emission region coincides with the optical source. We then constrain the origin of the X-ray emission to within a 0.'' 020 & times; 0.'' 010 ellipse centered 0.'' 014 away from the optical source at the 1 sigma level. We demonstrate that our approach can be extended to pinpoint the distinct locations of the soft and hard X-ray emission regions in lensed quasars. We discuss the potential of upcoming broadband and spectrally resolved X-ray astrometric studies to probe complex quasar morphology and multiplicity of active galactic nuclei at subkiloparsec scales otherwise inaccessible at high redshifts.

Active galactic nuclei (AGN) are some of the most powerful objects in the Universe. For this reason, they can be observed up to high redshifts (z), giving valuable insights into the evolution of our Universe. However, high-z AGN are too distant to be spatially resolved with current or upcoming X-ray facilities. In this paper, we show how we can exploit gravitationally lensed AGN to significantly increase spatial resolution even at high z. We combine astrometric data from Gaia DR3 with imaging from the Chandra X-ray Observatory of the quadruply lensed quasar HE 0435-1223 to measure for the first time possible offsets between the optical and the X-ray emissions. We measure the X-ray source position for HE 0435-1223 within a 1 sigma quasi-elliptical region of 0.5 x 1.3 milliarcsecond (mas), about 150 pc2 at the redshift of the source (z = 1.689). We find evidence for the X-ray emission being offset by a projected 3 mas from the Gaia (optical) emission. The positional offset is most likely associated with a portion of the X-ray emission arising from an X-ray jet or outflow. We also discuss how this method can be used to indicate the presence of a binary/offset AGN system.

Active galactic nuclei (AGN) are some of the most powerful objects in the Universe. For this reason, they can be observed up to high redshifts (z), giving valuable insights into the evolution of our Universe. However, high-z AGN are too distant to be spatially resolved with current or upcoming X-ray facilities. In this paper we show how we can exploit gravitationally lensed AGN to significantly increase spatial resolution even at high-z. We combine astrometric data from Gaia DR3 with imaging from the Chandra X-ray Observatory of the quadruply-lensed quasar HE 0435–1223 to measure for the first time possible offsets between the optical and the X-ray emissions. We measure the X-ray source position for HE 0435-1223 within a 1σ quasi-elliptical region of 0.5 x 1.3 milli-arcsecond (mas), about 150 pc^2 at the redshift of the source (z=1.689). We find evidence for the X-ray emission being offset by a projected 3 mas from the Gaia (optical) emission. The positional offset is most likely associated to a portion of the X-ray emission arising from an X-ray jet or outflow. We also discuss how this method can be used to indicate the presence of a binary/offset AGN system.

Infrasonic Hemodynography (IH) captures low-frequency vibrations detected by in-ear microphones, offering a new approach to blood pressure monitoring. We report a strong correlation (r = 0.95) between IH waveforms and aortic blood pressure measurements obtained through cardiac catheterization (CC). Temporal analysis confirms the aortic origin of IH signals, with minimal differences in aortic valve opening timings between IH and CC (1.6 ± 12.1 ms), rejecting the hypothesis of peripheral origins. We test an approach to predict systolic (SBP) and diastolic (DBP) blood pressure from waveform morphology. The standard deviations of the differences between predicted and reference BP values averaged across 12 subjects is 4.1 mmHg (SBP) and 2.4 mmHg (DBP) for CC, and 5.8 mmHg (SBP) and 3.7 mmHg (DBP) for IH. These results demonstrate that BP information is encoded in the waveform shape dynamic. By capturing precise cardiovascular signals non-invasively, IH could enable earlier interventions and more personalized treatments.

Supermassive black hole binary systems (SMBHBs) should be the most powerful sources of gravitational waves (GWs) in the universe. Once pulsar timing arrays (PTAs) detect the stochastic GW background from their cosmic merger history, searching for individually resolvable binaries will take on new importance. Since these individual SMBHBs are expected to be rare, here we explore how strong gravitational lensing can act as a tool for increasing their detection prospects by magnifying fainter sources and bringing them into view. Unlike for electromagnetic waves, when the geometric optics limit is nearly always valid, for GWs the wave-diffraction-interference effects can become important when the wavelength of the GWs is larger than the Schwarzchild radius of the lens, i.e., Mlens∼108fmHz−1M⊙ . For the GW frequency range explored in this work, the geometric optics limit holds. We investigate GW signals from SMBHBs that might be detectable with current and future PTAs under the assumption that quasars serve as bright beacons that signal a recent merger. Using the black hole mass function derived from quasars and a physically motivated magnification distribution, we expect to detect a few strongly lensed binary systems out to z ≈ 2. Additionally, for a range of fixed magnifications 2 ≤ μ ≤ 100, strong lensing adds up to ∼30 more detectable binaries for PTAs. Finally, we investigate the possibility of observing both time-delayed electromagnetic signals and GW signals from these strongly lensed binary systems—that will provide us with unprecedented multi-messenger insights into their orbital evolution.

LMC P3 is a gamma-ray binary comprising of an unconfirmed compact object and an O-star and is located in the Large Magellanic Cloud. Initially discovered in Fermi-LAT data, it shows an orbital period of 10.3 days. H.E.S.S. has reported the detected VHE gamma-ray emission during only 20% of the orbit, between orbital phases 0.2 and 0.4, which roughly corresponds to the inferior conjunction of the compact object. H.E.S.S. has continued the observations of this object since then. Here we will present new results obtained with a much deeper data set. The new data allow a more precise measurement of the location of the VHE gamma-ray peak along the orbit of the system to be made. We will interpret these results with respect to emission and absorption mechanisms in gamma-ray binary systems.

Noninvasive infrasonic hemodynography using the MindMics earbuds captures low-frequency acoustic vibrations throughout the cardiac cycle. In an n-of-1 analysis, we propose a new method of assessing severe aortic stenosis by using infrasonic hemodynography to detect its characteristic systolic ejection murmur before and after transcatheter aortic valve replacement.

The Galactic Centre (GC) region is a highly interesting region for very high energy gamma-ray studies due to its proximity and diverse sources. It is also a unique place for Dark Matter (DM) searches, since we expect a large amount of DM in this region and it is nearby. Currently a new detector is under development to observe the GC region, called the Southern Wide field-of-view Gamma-ray Observatory (SWGO). This instrument will be the first water Cherenkov detector located in the Southern Hemisphere sensitive to >100 GeV gamma rays. In our work, we are going to present a simulation of the GC gamma-ray mission as seen by a SWGO-like observatory. To do so we are using the models published by the Cherenkov Telescope Array (CTA) Collaboration together with simulated Instrument Response Functions (IRFs) for testing purposes. This also allows us to predict the expected sensitivity of SWGO to WIMP DM annihilations using a template based method. A sensitivity study during the design phase of the observatory is important in order to choose the best detector design to get outstanding physics results.

Fast Radio Bursts (FRBs) are highly energetic, extremely short-lived bursts of radio flashes. Despite extensive research, the exact cause of these outbursts remains a mystery. One of the most accredited models suggests that they originate from highly magnetized and rapidly spinning neutron stars known as magnetars. The high luminosity, short duration, and high dispersion measure of these events suggest they result from extreme, high-energy astrophysical processes of extragalactic origin. The number of detected FRBs, including repeating ones, has grown rapidly in recent years. Except for FRB20200428, that is associated to the galactic magnetar SGR1925+2154, no multi-wavelength counterparts to any FRB has been detected yet. The High Energy Stereoscopic System (H.E.S.S.) telescope has developed a program to uncover the nature of these mysterious events by searching for their gamma-ray counterparts. This contribution provides an overview of the searches for FRB sources conducted by H.E.S.S., including follow-up observations and simultaneous multi-wavelength campaigns with radio and X-ray observatories

The binary system Eta Carinae is a unique laboratory to study particle acceleration up to very high energies (VHE) under a wide range of conditions. Particles are thought to be accelerated at shocks forming in the wind collision region. Eta Carinae has been firmly established as a source of high energy gamma-rays in Fermi-LAT data over several orbits. With its highly eccentric orbit lasting 5.5 years, the periastron passage of the two stars is extremely close. This provides an opportunity to constrain the acceleration and absorption mechanisms of the system. Eta Carinae was detected above 200 GeV by the H.E.S.S. telescopes (H.E.S.S. Collaboration, 2020) based on data before and after the 2014 periastron. Unfortunately the 2014 periastron itself could not be observed by H.E.S.S. due to visibility constraints. Hence the 2020 periastron was the first periastron passage visible for the full 5 telescope H.E.S.S. array and was therefore monitored with an extensive observation campaign spanning the phase range from 0.97 to 1.05. We report the detection of a VHE signal from Eta Carinae during the 2020 periastron and describe its spectral properties together with simultaneous Fermi-LAT data. Together with previous and follow up observations, for the first time a VHE light curve spanning a full orbit is presented.

Since the last H.E.S.S. publication on the stellar cluster Westerlund 2 in 2011, the H.E.S.S. dataset on this region has increased more than three-fold in exposure to $\sim220\,$h of total observation time. By applying a novel approach to correct for atmospheric variations in IACT data, the commonly applied data quality selection criteria can be adapted to exploit as much of this dataset as possible. In combination with current analysis techniques, it is furthermore possible to disentangle and better characterise this complex region of the gamma-ray sky. Applying an extensive 3D fitting procedure, we find three distinct VHE gamma-ray sources in the vicinity of Westerlund 2, adding a new emission region to the previously reported sources HESS J1023$-$575 and HESS~J1026$-$582. Even though the sources partly overlap, their spectral indices differ from one another, providing new clues on the relativistic particle acceleration and propagation in the region around the massive star cluster. The new source component shows an elongated morphology that seems to emerge from the star cluster, following the multi-parsec-scale CO jet cloud initially found in NANTEN data as reported in 2009.

This work aims to study the very-high-energy (VHE; 100 GeV - 100 TeV) gamma-ray emission from M 87, especially its low state emission, and probe a potential hadronic emission component in the inner Virgo Cluster. Probing a steady and extended gamma-ray signal around M 87 allows us to investigate the AGN feedback as a heating mechanism in the Virgo Cluster. We used High Energy Stereoscopic System (H.E.S.S.) observations of M 87 from 2004 to 2021 to study the source. We utilized the Bayesian block technique to identify M 87 emission states and isolate its low state. We fitted the morphology of the 120 h low state data and found no significant gamma-ray extension. We derived an upper limit on the extension that for the first time excludes the radio lobes ( ≈ 30 kpc) as the main component of the VHE gamma-ray emission from the low state of M 87. The VHE gamma-ray emission from the distinct source states of M 87 are compatible with each other and with the radio core of M 87. Based on two different models we constrained the maximum cosmic-ray to thermal pressure ratio and the total energy in CRp in the inner 20 kpc of the Virgo Cluster [1].

Supermassive black hole binary (SMBHB) is a result of galaxies coalescing, when two supermas- sive black holes form a hard binary with distances from kpc to pc. If the system reaches milliparsec separation, the black holes eventually merge. There are a growing number of few sub-pc SMBHB candidates, one of which according to Jiang et al (2022). will merge within three years. We have performed the monitoring of the host galaxy SDSSJ143016.05+230344.4 during its visibility with H.E.S.S. in April–July 2022. Given that subsequent follow-up observations with optical and X-ray instruments have not confirmed some of the predictions initially presented, and time constraints for the merger beyond 2022 are less precise, we changed our monitoring and follow-up strategy for further observations. In this work we present our results of the monitoring and discuss the prospects of these kind of observations with imaging atmospheric Cherenkov telescopes.

We report the localization of the X-ray emission from two strongly lensed AGN, CLASS B0712+472 ( z = 1.34) and CLASS B1608+656 ( z = 1.394). We obtain milliarcsecond X-ray astrometry by developing a novel method that combines parametric lens modeling with a Bayesian analysis. We spatially locate the X-ray sources in CLASS B0712+472 and CLASS B1608+656 within 11 mas and 9 mas from the radio source, respectively. For CLASS B0712+472, we find that the X-ray emission is cospatial with the radio and optical emission. On the other hand, for CLASS B1608+656, the X-ray emission is cospatial with radio but displaced with respect to the optical emission at the 1 σ level, which positions this source as an offset AGN candidate. This high astrometric precision improves on the limitations of existing X-ray instruments by two orders of magnitude. The demonstrated method opens a path to search for offset and binary AGN at z > 1, and to directly test supermassive black hole formation models in a redshift range that has been mostly underconstrained to date.

Human bodily mechanisms and functions produce low-frequency vibrations. Our ability to perceive these vibrations is limited by our range of hearing. However, in-ear infrasonic hemodynography (IH) can measure low-frequency vibrations (<20 Hz) created by vital organs as an acoustic waveform. This is captured using a technology that can be embedded into wearable devices such as in-ear headphones. IH can acquire sound signals that travel within arteries, fluids, bones, and muscles in proximity to the ear canal, allowing for measurements of an individual's unique audiome. We describe the heart rate and heart rhythm results obtained in time-series analysis of the in-ear IH data taken simultaneously with ECG recordings in two dedicated clinical studies. We demonstrate a high correlation (r = 0.99) between IH and ECG acquired interbeat interval and heart rate measurements and show that IH can continuously monitor physiological changes in heart rate induced by various breathing exercises. We also show that IH can differentiate between atrial fibrillation and sinus rhythm with performance similar to ECG. The results represent a demonstration of IH capabilities to deliver accurate heart rate and heart rhythm measurements comparable to ECG, in a wearable form factor. The development of IH shows promise for monitoring acoustic imprints of the human body that will enable new real-time applications in cardiovascular health that are continuous and noninvasive.

Introduction: The cardiovascular (CV) system produces low frequency, ‘infrasonic’, auditory vibrations during the cardiac cycle. Herein, we report the first-in-person validation of a novel earbud sensor to capture CV time intervals and the feasibility of non-invasive infrasonic hemodynography (IH) using the MindMics ® wireless earbuds for long term in-ear CV monitoring. Methods: Infrasonic waveforms were captured during cardiac catheterization (CC) among 5 study subjects wearing the IH ear-buds (Figure A) who underwent CC for the evaluation of coronary artery disease. Simultaneous IH and CC waveforms were acquired and time synchronized at 1000Hz sampling rate as time-series datasets. Each subject underwent echocardiography to identify aortic valve opening/closure (AVO/AVC) and left ventricular (LV) outflow tract flow measurements with hemodynamic waveforms during CC measuring LV ejection time (LVET). Validation of the IH waveform (in-ear acoustic pressure measured in Pascals) was compared to echocardiography (AVO/AVC) and hemodynamic waveforms (LVET) with concordance and Bland-Altman analysis, and with overlaid data visualizations to CV time intervals. Results: 5 study subjects comprised 257 CV cycles with a total data set of >450,000 time-series data points. IH signals collected simultaneously with the pulsed wave Doppler demonstrated alignment with AVO/AVC (Figure B) and were synchronized to CC waveforms in the aorta (Figure C). A high correlation between LVET measured from IH and CC was observed (R=0.87, p<0.0001, Figure D), with a mean absolute error of 14.7ms and a bias of 7.2ms (Figure E) (mean±SEM of 342.3±2.1ms for CC and 349.5±2.1ms for IH). Conclusions: In a first-in-person study, we report high accuracy between IH, echocardiography, and CC hemodynamic waveforms to capture CV time intervals including CV performance measures. Further studies are underway to validate IH and the earbud sensor towards non-invasive hemodynamic monitoring.

The flat spectrum radio quasar (FSRQ) PKS 1510−089 is known for its complex multiwavelength behaviour and it is one of only a few FSRQs detected in very-high-energy (VHE,E > 100 GeV)γrays. The VHEγ-ray observations with H.E.S.S. and MAGIC in late May and early June 2016 resulted in the detection of an unprecedented flare, which revealed, for the first time, VHEγ-ray intranight variability for this source. While a common variability timescale of 1.5 h has been found, there is a significant deviation near the end of the flare, with a timescale of ∼20 min marking the cessation of the event. The peak flux is nearly two orders of magnitude above the low-level emission. For the first time, a curvature was detected in the VHEγ-ray spectrum of PKS 1510–089, which can be fully explained by the absorption on the part of the extragalactic background light. OpticalR-band observations with ATOM revealed a counterpart of theγ-ray flare, even though the detailed flux evolution differs from the VHEγ-ray light curve. Interestingly, a steep flux decrease was observed at the same time as the cessation of the VHEγ-ray flare. In the high-energy (HE,E > 100 MeV)γ-ray band, only a moderate flux increase was observed withFermi-LAT, while the HEγ-ray spectrum significantly hardens up to a photon index of 1.6. A search for broad-line region (BLR) absorption features in theγ-ray spectrum indicates that the emission region is located outside of the BLR. Radio very-long-baseline interferometry observations reveal a fast-moving knot interacting with a standing jet feature around the time of the flare. As the standing feature is located ∼50 pc from the black hole, the emission region of the flare may have been located at a significant distance from the black hole. If this is indeed a true correlation, the VHEγrays must have been produced far down in the jet, where turbulent plasma crosses a standing shock.

We use a Chandra X-ray observation of the gravitationally lensed system MG B2016+112 at z = 3.273 to elucidate the presence of at least two X-ray sources. We find that these sources are consistent with the very long baseline interferometry (VLBI) components measured by Spingola, which are separated by ∼200 pc. Their intrinsic 0.5–7 keV source frame luminosities are 1.5 × 1043 and 1.8 × 1044 erg s−1, respectively. Most likely this system contains a dual active galactic nucleus (AGN), but we are possibly detecting an AGN plus a parsec-scale X-ray jet, the latter lying in a region at very high magnification. The quadruply lensed X-ray source is within ±40 pc (1σ) of its VLBI counterpart. Using a gravitational lens as a telescope, and a novel statistical application, we have achieved unprecedented accuracy for measuring metric distances at such large redshifts in X-ray astronomy. This is tens of mas if the source is located close to the caustics, while it is of hundreds of mas if the source is in a region at lower amplification. The present demonstration of this approach has implications for future X-ray investigations of large numbers of lensed systems.

The presence of dark matter (DM) is suggested by a wealth of astrophysical and cosmological measurements. However, its underlying nature is yet unknown. Among the most promising candidates are weakly interacting massive particles (WIMPs): particles with mass and coupling strength at the electroweak scale and thermally produced in the early universe have a present relic density consistent with that observed today. WIMP self-annihilation would produce Standard Model particles including gamma-rays, which have been long-time recognized as a prime messenger to indirectly detect dark matter signals. The centre of the Milky Way is predicted as the brightest source of DM annihilations. The H.E.S.S. collaboration is currently performing a survey of the inner region of the Milky Way, the Inner Galaxy Survey (IGS), intended to achieve the best sensitivity to faint and diffuse emissions in a region of several degrees around the Galactic Centre. We analyzed 2014-2020 observations taken with the five-telescope array to search for a DM annihilation signal. With the current dataset of about 550 hours, we found no significant excess and therefore derived strong constraints on the velocity-weighted annihilation cross-section. TeV thermal WIMPs can be probed in different annihilation channels.

The High Altitude Water Cherenkov (HAWC) observatory and the High Energy Stereoscopic System (H.E.S.S.) are two leading instruments in the ground-based very-high-energy gamma-ray domain. HAWC employs the water Cherenkov detection (WCD) technique, while H.E.S.S. is an array of Imaging Atmospheric Cherenkov Telescopes (IACTs). The two facilities therefore differ in multiple aspects, including their observation strategy, the size of their field of view and their angular resolution, leading to different analysis approaches. Until now, it has been unclear if the results of observations by both types of instruments are consistent: several of the recently discovered HAWC sources have been followed up by IACTs, resulting in a confirmed detection only in a minority of cases. With this paper, we go further and try to resolve the tensions between previous results by performing a new analysis of the H.E.S.S. Galactic plane survey data, applying an analysis technique comparable between H.E.S.S. and HAWC. Events above 1 TeV are selected for both datasets, the point spread function of H.E.S.S. is broadened to approach that of HAWC, and a similar background estimation method is used. This is the first detailed comparison of the Galactic plane observed by both instruments. H.E.S.S. can confirm the gamma-ray emission of four HAWC sources among seven previously undetected by IACTs, while the three others have measured fluxes below the sensitivity of the H.E.S.S. dataset. Remaining differences in the overall gamma-ray flux can be explained by the systematic uncertainties. Therefore, we confirm a consistent view of the gamma-ray sky between WCD and IACT techniques.