Michael Bremer
A5065037986- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Particle Accelerators and Free-Electron Lasers
- Galaxies: Formation, Evolution, Phenomena
- Astronomical Observations and Instrumentation
- Superconducting and THz Device Technology
- Antenna Design and Optimization
- Estrogen and related hormone effects
- Astrophysics and Star Formation Studies
- Calibration and Measurement Techniques
- Gene expression and cancer classification
- Spacecraft Design and Technology
- Ionosphere and magnetosphere dynamics
- Geophysics and Gravity Measurements
- Laser and Thermal Forming Techniques
- Neutrino Physics Research
- Adaptive optics and wavefront sensing
- Computational Drug Discovery Methods
- Mechanics and Biomechanics Studies
Ausonius Institut de Recherche sur l'Antiquité et le Moyen age
2002-2025
Institut de Radioastronomie Millimétrique
2015-2024
TH Köln - University of Applied Sciences
2024
Max Planck Institute for Radio Astronomy
2009-2016
Boston University
2016
Center for Astrophysics Harvard & Smithsonian
2016
W.M. Keck Observatory
2016
Max Planck Society
2015
Max Planck Innovation
2015
Université Grenoble Alpes
1996-2010
When surrounded by a transparent emission region, black holes are expected to reveal dark shadow caused gravitational light bending and photon capture at the event horizon. To image study this phenomenon, we have assembled Event Horizon Telescope, global very long baseline interferometry array observing wavelength of 1.3 mm. This allows us reconstruct event-horizon-scale images supermassive hole candidate in center giant elliptical galaxy M87. We resolved central compact radio source as an...
We present measurements of the properties central radio source in M87 using Event Horizon Telescope data obtained during 2017 campaign. develop and fit geometric crescent models (asymmetric rings with interior brightness depressions) two independent sampling algorithms that consider distinct representations visibility data. show family is statistically preferred over other comparably complex we explore. calibrate model parameters general relativistic magnetohydrodynamic (GRMHD) emission...
We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at 1.3 mm wavelength. These show a prominent ring with diameter ~40 micro-as, consistent size and shape lensed photon orbit encircling "shadow" supermassive black hole. The is persistent across four observing nights shows enhanced brightness in south. To assess reliability these results, we implemented two-stage imaging procedure. In stage, teams, each blind to others' work, produced M87 both...
The Event Horizon Telescope (EHT) has mapped the central compact radio source of elliptical galaxy M87 at 1.3 mm with unprecedented angular resolution. Here we consider physical implications asymmetric ring seen in 2017 EHT data. To this end, construct a large library models based on general relativistic magnetohydrodynamic (GRMHD) simulations and synthetic images produced by ray tracing. We compare observed visibilities confirm that is consistent earlier predictions strong gravitational...
We present the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A$^*$), Galactic center source associated with a supermassive black hole. These were conducted in 2017 using global interferometric array eight telescopes operating at wavelength $\lambda=1.3\,{\rm mm}$. The EHT data resolve compact emission region intrahour variability. A variety imaging and modeling analyses all support an image that is dominated by bright, thick ring diameter $51.8 \pm 2.3$\,\uas (68\%...
The Event Horizon Telescope (EHT) is a very long baseline interferometry (VLBI) array that comprises millimeter- and submillimeter-wavelength telescopes separated by distances comparable to the diameter of Earth. At nominal operating wavelength ~1.3 mm, EHT angular resolution (lambda/D) ~25 micro-as, which sufficient resolve nearby supermassive black hole candidates on spatial temporal scales correspond their event horizons. With this capability, scientific goals are probe general...
We present the calibration and reduction of Event Horizon Telescope (EHT) 1.3mm radio wavelength observations supermassive black hole candidate at center galaxy M87 quasar 3C 279, taken during 2017 April 5-11 observing campaign. These global very long baseline interferometric include for first time highly sensitive Atacama Large Millimeter/submillimeter Array (ALMA); reaching an angular resolution 25 micro-as, with characteristic sensitivity limits ~1 mJy on baselines to ALMA ~10 other...
Previous studies have suggested that breast cancer risk factors are associated with estrogen receptor (ER) and progesterone (PR) expression status of the tumors.
Event Horizon Telescope (EHT) observations at 230 GHz have now imaged polarized emission around the supermassive black hole in M87 on event-horizon scales. This synchrotron radiation probes structure of magnetic fields and plasma properties near hole. Here we compare resolved polarization observed by EHT, along with simultaneous unresolved Atacama Large Millimeter/submillimeter Array, to expectations from theoretical models. The low fractional linear image suggests that is scrambled scales...
Astrophysical black holes are expected to be described by the Kerr metric. This is only stationary, vacuum, axisymmetric metric, without electromagnetic charge, that satisfies Einstein's equations and does not have pathologies outside of event horizon. We present new constraints on potential deviations from prediction based 2017 EHT observations Sagittarius A* (Sgr A*). calibrate relationship between geometrically defined hole shadow observed size ring-like images using a library includes...
Abstract In this paper we provide a first physical interpretation for the Event Horizon Telescope's (EHT) 2017 observations of Sgr A*. Our main approach is to compare resolved EHT data at 230 GHz and unresolved non-EHT from radio X-ray wavelengths predictions library models based on time-dependent general relativistic magnetohydrodynamics simulations, including aligned, tilted, stellar-wind-fed simulations; radiative transfer performed assuming both thermal nonthermal electron distribution...
Abstract In 2017 April, the Event Horizon Telescope (EHT) observed near-horizon region around supermassive black hole at core of M87 galaxy. These 1.3 mm wavelength observations revealed a compact asymmetric ring-like source morphology. This structure originates from synchrotron emission produced by relativistic plasma located in immediate vicinity hole. Here we present corresponding linear-polarimetric EHT images center M87. We find that only part ring is significantly polarized. The...
Abstract We present the first event-horizon-scale images and spatiotemporal analysis of Sgr A* taken with Event Horizon Telescope in 2017 April at a wavelength 1.3 mm. Imaging has been conducted through surveys over wide range imaging assumptions using classical CLEAN algorithm, regularized maximum likelihood methods, Bayesian posterior sampling method. Different prescriptions have used to account for scattering effects by interstellar medium toward Galactic center. Mitigation rapid intraday...
The 2017 Event Horizon Telescope (EHT) observations of the central source in M87 have led to first measurement size a black-hole shadow. This observation offers new and clean gravitational test metric strong-field regime. We show analytically that spacetimes deviate from Kerr but satisfy weak-field tests can lead large deviations predicted shadows are inconsistent with even current EHT measurements. use numerical calculations regular, parametric, non-Kerr metrics identify common...
We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at position supermassive black hole Sagittarius A* (Sgr A*), collected during 2017 April 5--11 campaign. The observations were carried out with eight facilities six locations across globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. majority emission arises from horizon scales, where intrinsic structural variability is detected on timescales minutes hours. effects...
In this paper we quantify the temporal variability and image morphology of horizon-scale emission from Sgr A*, as observed by EHT in 2017 April at a wavelength 1.3 mm. We find that A* data exhibit exceeds what can be explained uncertainties or effects interstellar scattering. The magnitude substantial fraction correlated flux density, reaching $\sim$100\% on some baselines. Through an exploration simple geometric source models, demonstrate ring-like morphologies provide better fits to than...
Our understanding of strong gravity near supermassive compact objects has recently improved thanks to the measurements made by Event Horizon Telescope (EHT). We use here M87* shadow size infer constraints on physical charges a large variety nonrotating or rotating black holes. For example, we show that quality is already sufficient rule out highly charged dilaton hole. Similarly, when considering holes with two and independent charges, are able exclude considerable regions space parameters...
We present multiwavelength observations of the afterglow GRB 130427A, brightest (in total fluence) gamma-ray burst (GRB) past 29 yr. Optical spectroscopy from Gemini-North reveals redshift to be z = 0.340, indicating that its unprecedented brightness is primarily result relatively close proximity Earth; intrinsic luminosities both and are not extreme in comparison other bright GRBs. a large suite spanning 300 s 130 days after demonstrate shows simple, smooth evolution at all frequencies,...
M87 is one of the nearest radio galaxies with a prominent jet extending from sub-pc to kpc-scales. Because its proximity and large mass central black hole, it best sources study formation. We aim at studying physical conditions near base projected separations BH $\sim7-100$ Schwarzschild radii ($R_{\rm sch}$). Global mm-VLBI Array (GMVA) observations 86 GHz ($\lambda=3.5\,$mm) provide an angular resolution $\sim50\mu$as, which corresponds spatial only $7~R_{\rm sch}$ reach small scale. use...
The nearby radio galaxy M87 is a prime target for studying black hole accretion and jet formation1,2. Event Horizon Telescope observations of in 2017, at wavelength 1.3 mm, revealed ring-like structure, which was interpreted as gravitationally lensed emission around central hole3. Here we report images obtained 2018, 3.5 showing that the compact core spatially resolved. High-resolution imaging shows structure [Formula: see text] Schwarzschild radii diameter, approximately 50% larger than...
The Event Horizon Telescope (EHT) observed the compact radio source, Sagittarius A* (Sgr A*), in Galactic Center on 2017 April 5-11 1.3 millimeter wavelength band. At same time, interferometric array data from Atacama Large Millimeter/submillimeter Array and Submillimeter were collected, providing Sgr light curves simultaneous with EHT observations. These sets, complementing very-long-baseline interferometry, are characterized by a cadence signal-to-noise ratio previously unattainable for at...
Abstract Event Horizon Telescope (EHT) observations have revealed a bright ring of emission around the supermassive black hole at center M87 galaxy. EHT images in linear polarization further identified coherent spiral pattern hole, produced from ordered magnetic fields threading emitting plasma. Here we present first analysis circular using data, acquired 2017, which can potentially provide additional insights into and plasma composition near hole. Interferometric closure quantities...
Abstract The Event Horizon Telescope observed the horizon-scale synchrotron emission region around Galactic center supermassive black hole, Sagittarius A* (Sgr A*), in 2017. These observations revealed a bright, thick ring morphology with diameter of 51.8 ± 2.3 μ as and modest azimuthal brightness asymmetry, consistent expected appearance hole mass M ≈ 4 × 10 6 ⊙ . From these observations, we present first resolved linear circular polarimetric images Sgr A*. polarization demonstrate that is...
Abstract In a companion paper, we present the first spatially resolved polarized image of Sagittarius A* on event horizon scales, captured using Event Horizon Telescope, global very long baseline interferometric array operating at wavelength 1.3 mm. Here interpret this both simple analytic models and numerical general relativistic magnetohydrodynamic (GRMHD) simulations. The large linear polarization fraction (24%–28%, peaking ∼40%) is most stringent constraint parameter space, disfavoring...