A5027574968- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Mechanics and Biomechanics Studies
- Astrophysics and Star Formation Studies
- Radio Astronomy Observations and Technology
- High-pressure geophysics and materials
- Calibration and Measurement Techniques
- Galaxies: Formation, Evolution, Phenomena
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Particle Accelerators and Free-Electron Lasers
- Astro and Planetary Science
- Heat Transfer Mechanisms
- Relativity and Gravitational Theory
- Optical Systems and Laser Technology
- Historical Astronomy and Related Studies
- History and Developments in Astronomy
- Cosmology and Gravitation Theories
- Advanced optical system design
Max Planck Institute for Radio Astronomy
2019-2025
Max Planck Institute for Research on Collective Goods
2019-2023
University of California, Los Angeles
2012-2022
University of Cologne
2008-2013
We present new, more precise measurements of the mass and distance our Galaxy's central supermassive black hole, Sgr A*. These results stem from a new analysis that than doubles time baseline for astrometry faint stars orbiting A*, combining two decades speckle imaging adaptive optics data. Specifically, we improve images by using information about star's orbit deep data (2005 - 2013) to inform search star in years (1995 2005). When this technique is combined with first complete re-reduction...
In this Letter, we demonstrate that short-period stars orbiting around the supermassive black hole in our Galactic Center can successfully be used to probe gravitational theory a strong regime. We use 19 years of observations two best measured constrain hypothetical fifth force arises various scenarios motivated by development unification or some models dark matter and energy. No deviation from General Relativity is reported strength restricted an upper 95% confidence limit...
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...
Most, if not all, stars in the field are born binary configurations or higher multiplicity systems. In dense stellar environment such as Galactic Center (GC), many expected to be well. These binaries form hierarchical triple body systems, with massive black hole (MBH) third, distant object. The undergo large amplitude eccentricity and inclination oscillations via so-called "eccentric Kozai-Lidov" (EKL) mechanism. excitations, combined post main sequence evolution, can drive inner merge. We...
Gravitational redshift in the Galactic Center General relativity predicts that light emitted by an object a strong gravitational field—for example, close to black hole—should be shifted longer wavelengths. This does not exist Newtonian theory of gravity. Do et al. monitored position and spectrum star S0-2 as it passed Sagittarius A*, supermassive hole at center Milky Way. Around closest part S0-2's 16-year orbit, they detected effect on its spectrum. These results are more consistent with...
OJ287 is the best candidate active galactic nucleus (AGN) for hosting a supermassive binary black hole (SMBBH) at very close separation.We present 120 Very Long Baseline Array (VLBA) observations (at 15 GHz) covering time between April 1995 and 2017.We find that radio jet precessing on time-scale of ∼22 yr.In addition, our data are consistent with jet-axis rotation yearly time-scale.We model precession (24 ± 2 yr) combined motion rotation.The explains variability total flux-density via...
Sagittarius A* (Sgr A*) is the variable radio, near-infrared (NIR), and X-ray source associated with accretion onto Galactic center black hole. We present an analysis of most comprehensive NIR variability data set Sgr to date: eight 24 hr epochs continuous monitoring at 4.5 μm IRAC instrument on Spitzer Space Telescope, 93 2.18 from Naos Conica Very Large 30 2.12 NIRC2 camera Keck Observatory, in total 94,929 measurements. A new approximate Bayesian computation method for fitting first-order...
The electromagnetic counterpart to the Galactic center supermassive black hole, Sgr A*, has been observed in near-infrared for over 20 years and is known be highly variable. We report new Keck Telescope observations showing that A* reached much brighter flux levels 2019 than ever measured at wavelengths. In K$^\prime$ band, of $\sim6$ mJy, twice level previously peak from $>13,000$ measurements 130 nights with VLT Telescopes. also observe a factor 75 change 2-hour time span no obvious color...
We report new observations of the Galactic Center source G2 from W. M. Keck Observatory. is a dusty red object associated with gas that shows tidal interactions as it nears closest approach Galaxy's central black hole. Our observations, conducted passed through periapse, were designed to test proposal 3 earth mass cloud. Such cloud should be tidally disrupted during periapse passage. The data obtained using II laser guide star adaptive optics system (LGSAO) and facility near-infrared camera...
We present a comprehensive data description for Ks-band measurements of Sgr A*. characterize the statistical properties variability A* in near-infrared, which we find to be consistent with single-state process forming power-law distribution flux density. discover linear rms-flux relation flux-density range up 12 mJy on timescale 24 minutes. This and density implies phenomenological, formally non-linear model can simulate observed extrapolate its behavior higher levels longer timescales....
We present new observations and analysis of G2 - the intriguing red emission-line object which is quickly approaching Galaxy's central black hole. The were obtained with laser guide star adaptive optics systems on W. M. Keck I II telescopes include spectroscopy (R ~ 3600) centered Hydrogen Br-gamma line as well K' (2.1 micrometer) L' (3.8 imaging. Analysis these shows emission has a positional offset from continuum. This likely due to background source confusion at L'. therefore first...
We report the time-resolved spectral analysis of a bright near-infrared and moderate X-ray flare Sgr A*. obtained light curves in $M$-, $K$-, $H$-bands mid- $2-8~\mathrm{keV}$ $2-70~\mathrm{keV}$ bands X-ray. The observed slope band is $\nu L_\nu\propto \nu^{0.5\pm0.2}$; L_\nu \propto \nu^{-0.7\pm0.5}$. tested synchrotron self-Compton (SSC) scenarios. brightness faintness, together with slopes, pose challenges for all models explored. rule out scenario which emission SSC. A one-zone model...
ABSTRACT Sgr A* exhibits regular variability in its multiwavelength emission, including daily X-ray flares and roughly continuous near-infrared (NIR) flickering. The origin of this is still ambiguous since both inverse Compton synchrotron emission are possible radiative mechanisms. underlying particle distributions also not well constrained, particularly the non-thermal contribution. In work, we employ GPU-accelerated general relativistic magnetohydrodynamics code H-AMR to perform a study...
We report on a successful, simultaneous observation and modeling of the sub-millimeter to near-infrared flare emission Sgr A* counterpart associated with super-massive black hole at Galactic center. Our is based observations that have been carried out 03 June, 2008 using NACO adaptive optics (AO) instrument ESO VLT LABOCA bolometer APEX telescope. Inspection light curves show sub-mm follows NIR delay 1.5+/-0.5 hours. explain by an adiabatic expansion source components.
Context. We report on new simultaneous observations and modeling of the millimeter, near-infrared, X-ray flare emission source Sagittarius A* (SgrA*) associated with super-massive (4 × 106 M⊙) black hole at Galactic center.
There are a number of faint compact infrared excess sources in the central stellar cluster Milky Way. Their nature and origin is unclear. In addition to several isolated objects this kind we find small but dense co-moving (IRS13N) about 3" west SgrA* just 0.5" north bright IRS13E WR O-type stars. Based on their color brightness, there two main possibilities: (1) they may be dust embedded stars older than few Myr, or (2) extremely young, dusty with ages less 1Myr. We present fist H- Ks-band...
We present a statistical analysis of the X-ray flux distribution Sgr A* from Chandra Observatory's 3 Ms Visionary Project (XVP) in 2012. Our indicates that observed can be decomposed into steady quiescent component, represented by Poisson process with rate $Q=(5.24\pm0.08)\times10^{-3}$ cts s$^{-1},$ and variable power law ($dN/dF\propto F^{-\xi},$ $\xi=1.92_{-0.02}^{+0.03}$). This slope matches our recently-reported flare luminosities. The variability may also described log-normal median...
We present a detailed analysis of the kinematics 112 stars that mostly comprise high velocity S-cluster and orbit super massive black hole SgrA* at center Milky Way. For 39 them orbital elements are known, for remainder we know proper motions. The distribution inclinations, motion flight directions deviate significantly from uniform which one expects if orientation orbits random. Across central arcseconds arranged in two almost edge on disks located position angle approximately +-45 o with...
<i>Context. <i/>We report on the results of new simulations near-infrared (NIR) observations Sagittarius A* (Sgr A*) counterpart associated with super-massive black hole at Galactic Center.<i>Aims. <i/>Our goal is to investigate and understand physical processes behind variability NIR flaring emission from Sgr A*. <i>Methods. <i/>The have been carried out using NACO adaptive optics (AO) instrument European Southern Observatory's Very Large Telescope CIAO camera Subaru telescope (13 june...
We report the detection of two-dimensional structure radio source associated with Galactic Center black hole, Sagittarius A*, obtained from Very Long Baseline Array (VLBA) observations at a wavelength 7mm. The intrinsic is modeled as an elliptical Gaussian major axis size 35.4 x 12.6 R_S in position angle 95 deg East North. This morphology can be interpreted context both jet and accretion disk models for emission. There supporting evidence large angular-scale multi-wavelength preferred near...
We present a statistical analysis of polarized near-infrared (NIR) light from Sgr A*, the radio source associated with supermassive black hole at center Milky Way. The observations have been carried out using adaptive optics instrument NACO VLT UT4 in infrared $K_\mathrm{s}$-band 2004 to 2012. Several flux excursions were observed during these years. Linear polarization 2.2 $\mu m$, its statistics and time variation, can be used constrain physical conditions accretion process onto this hole....
Abstract The star S0-2, which orbits the supermassive black hole (SMBH) in our Galaxy with a period of 16 years, provides strongest constraint on both mass SMBH and distance to Galactic center. S0-2 will soon provide first measurement relativistic effects near SMBH. We report limits binarity from radial velocity (RV) monitoring, has implications for understanding its origin robustness as probe central gravitational field. With 87 RV measurements, include 12 new observations that we present,...
We report on new modeling results based the mm- to X-ray emission of SgrA* counterpart associated with massive black hole at Galactic Center. Our is simultaneous observations carried out 07 July, 2004, using ESO NACO adaptive optics instrument and ACIS-I aboard Chandra Observatory as well SMA VLA. The revealed several flare events in all wavelength domains. Here we show that a combined synchrotron self-Compton (SSC) model followed by an adiabatic expansion source components can fully account...
We present the longest, by a factor of 2, near-infrared light curve from Sgr A*—the supermassive black hole in Galactic center. Achieved combining Keck and VLT data one common night, which fortuitously had simultaneous Chandra SMA data, this is used to address two outstanding problems. First, putative quasi-periodicity ~20 minutes reported groups using ESO's not confirmed observations. Second, while infrared mm regimes are thought be related based on time lags between curves wavelength...