Search results for "telescope"
showing 10 items of 499 documents
Black hole lightning due to particle acceleration at subhorizon scales
2015
Supermassive black holes with masses of millions to billions of solar masses are commonly found in the centers of galaxies. Astronomers seek to image jet formation using radio interferometry, but still suffer from insufficient angular resolution. An alternative method to resolve small structures is to measure the time variability of their emission. Here, we report on gamma-ray observations of the radio galaxy IC 310 obtained with the MAGIC telescopes revealing variability with doubling time scales faster than 4.8 min. Causality constrains the size of the emission region to be smaller than 20\% of the gravitational radius of its central black hole. We suggest that the emission is associated …
Alternative single-reference coupled cluster approaches for multireference problems: the simpler, the better.
2011
We report a general implementation of alternative formulations of single-reference coupled cluster theory (extended, unitary, and variational) with arbitrary-order truncation of the cluster operator. These methods are applied to compute the energy of Ne and the equilibrium properties of HF and C(2). Potential energy curves for the dissociation of HF and the BeH(2) model computed with the extended, variational, and unitary coupled cluster approaches are compared to those obtained from the multireference coupled cluster approach of Mukherjee et al. [J. Chem. Phys. 110, 6171 (1999)] and the internally contracted multireference coupled cluster approach [F. A. Evangelista and J. Gauss, J. Chem. …
ARES I: WASP-76 b, A Tale of Two HST Spectra
2020
We analyse the transmission and emission spectra of the ultra-hot Jupiter WASP-76b, observed with the G141 grism of the Hubble Space Telescope's Wide Field Camera 3 (WFC3). We reduce and fit the raw data for each observation using the open-source software Iraclis before performing a fully Bayesian retrieval using the publicly available analysis suite TauRex 3. Previous studies of the WFC3 transmission spectra of WASP-76 b found hints of titanium oxide (TiO) and vanadium oxide (VO) or non-grey clouds. Accounting for a fainter stellar companion to WASP-76, we reanalyse this data and show that removing the effects of this background star changes the slope of the spectrum, resulting in these vi…
First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
2019
We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at 1.3 mm wavelength. These images show a prominent ring with a diameter of ~40 μas, consistent with the size and shape of the lensed photon orbit encircling the "shadow" of a supermassive black hole. The ring is persistent across four observing nights and shows enhanced brightness in the south. To assess the reliability of these results, we implemented a two-stage imaging procedure. In the first stage, four teams, each blind to the others' work, produced images of M87 using both an established method (CLEAN) and a newer technique (regularized maximum likelihood). This stage allowed us to av…
The Second Flight of the Sunrise Balloon-borne Solar Observatory: Overview of Instrument Updates, the Flight, the Data, and First Results
2017
S. K. Solanki et. al.
Monitoring the Morphology of M87* in 2009-2017 with the Event Horizon Telescope
2020
All authors: Wielgus, Maciek; Akiyama, Kazunori; Blackburn, Lindy; Chan, Chi-kwan; Dexter, Jason; Doeleman, Sheperd S.; Fish, Vincent L.; Issaoun, Sara; Johnson, Michael D.; Krichbaum, Thomas P.; Lu, Ru-Sen; Pesce, Dominic W.; Wong, George N.; Bower, Geoffrey C.; Broderick, Avery E.; Chael, Andrew; Chatterjee, Koushik; Gammie, Charles F.; Georgiev, Boris; Hada, Kazuhiro Loinard, Laurent; Markoff, Sera; Marrone, Daniel P.; Plambeck, Richard; Weintroub, Jonathan; Dexter, Matthew; MacMahon, David H. E.; Wright, Melvyn; Alberdi, Antxon; Alef, Walter; Asada, Keiichi; Azulay, Rebecca; Baczko, Anne-Kathrin; Ball, David; Baloković, Mislav; Barausse, Enrico; Barrett, John; Bintley, Dan; Boland, Wilf…
Multiband RadioAstron space VLBI imaging of the jet in quasar S5 0836+710
2019
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.-- Open Access funding provided by Max Planck Society.
Detection of Intrinsic Source Structure at ~3 Schwarzschild Radii with Millimeter-VLBI Observations of SAGITTARIUS A*
2018
We report results from very long baseline interferometric (VLBI) observations of the supermassive black hole in the Galactic center, Sgr A*, at 1.3 mm (230 GHz). The observations were performed in 2013 March using six VLBI stations in Hawaii, California, Arizona, and Chile. Compared to earlier observations, the addition of the APEX telescope in Chile almost doubles the longest baseline length in the array, provides additional {\it uv} coverage in the N-S direction, and leads to a spatial resolution of $\sim$30 $\mu$as ($\sim$3 Schwarzschild radii) for Sgr A*. The source is detected even at the longest baselines with visibility amplitudes of $\sim$4-13% of the total flux density. We argue th…
Relativistic beaming and gamma-ray brightness of blazars
2009
We investigate the dependence of gamma-ray brightness of blazars on intrinsic properties of their parsec-scale radio jets and the implication for relativistic beaming. By combining apparent jet speeds derived from high-resolution VLBA images from the MOJAVE program with millimetre-wavelength flux density monitoring data from Metsahovi Radio Observatory, we estimate the jet Doppler factors, Lorentz factors, and viewing angles for a sample of 62 blazars. We study the trends in these quantities between the sources which were detected in gamma-rays by the Fermi Large Area Telescope (LAT) during its first three months of science operations and those which were not detected. The LAT-detected blaz…
BALDONE 1.2M TELESCOPE PLATE ARCHIVE - HIDDEN RESERVES OF THE FON PROJECT
2018
The plate archive of the 1.2 m Baldone telescope (Latvia) has approximately 780 and 4660 astronegatives exposed in 1967-1993 in the U (ZU21 + UG1 filter plates) and V (A600N + ZS17 filter films) closed to Johnson system U and V passbands. Digitization of astronegatives is carried out using the Epson Expression 10000XL scanner, the scanning mode is 1200 or 2400 dpi, each field covers 19 square degrees of sky. The plates and films are scanned at the Baldone Observatory, processing of digitized scans is carried out by the observers in Baldone, at the Research Institute "Mykolaiv Astronomical Observatory" and at the Main Astronomical Observatory of the National Academy of Sciences of Ukraine. …