Results 21 to 30 of about 148 (122)

MOMO. VI. Multifrequency Radio Variability of the Blazar OJ 287 from 2015 to 2022, Absence of Predicted 2021 Precursor-flare Activity, and a New Binary Interpretation of the 2016/2017 Outburst

open access: yesThe Astrophysical Journal, 2023
Based on our dedicated Swift monitoring program, MOMO, OJ 287 is one of the best-monitored blazars in the X-ray–UV–optical regime. Here, we report results from our accompanying, dense, multifrequency (1.4–44 GHz) radio monitoring of OJ 287 between 2015 ...
S. Komossa   +14 more
doaj   +1 more source

A Search for Pulsars around Sgr A* in the First Event Horizon Telescope Data Set

open access: yesThe Astrophysical Journal, 2023
In 2017 the Event Horizon Telescope (EHT) observed the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), at a frequency of 228.1 GHz ( λ = 1.3 mm).
Pablo Torne   +284 more
doaj   +1 more source

IXPE and Multiwavelength Observations of Blazar PG 1553+113 Reveal an Orphan Optical Polarization Swing

open access: yesThe Astrophysical Journal Letters, 2023
The lower-energy peak of the spectral energy distribution of blazars has commonly been ascribed to synchrotron radiation from relativistic particles in the jets.
Riccardo Middei   +121 more
doaj   +1 more source

X-Ray Polarization of BL Lacertae in Outburst

open access: yesThe Astrophysical Journal Letters, 2023
We report the first >99% confidence detection of X-ray polarization in BL Lacertae. During a recent X-ray/ γ -ray outburst, a 287 ks observation (2022 November 27–30) was taken using the Imaging X-ray Polarimetry Explorer (IXPE), together with ...
Abel L. Peirson   +130 more
doaj   +1 more source

El profe Justo

open access: yesEntretextos, 2021
Así llamaban, llaman y seguirán llamando sus discípulos, que fueron muchos, al profe- sor emérito de la Universidad de La Guajira, de la que también fue rector ejemplar, a quien en vida respondía al nombre de Francisco Justo Pérez van-Leenden.
Amylkar Acosta Medina
doaj  

Polarimetric Geometric Modeling for mm-VLBI Observations of Black Holes

open access: yesThe Astrophysical Journal Letters, 2023
The Event Horizon Telescope (EHT) is a millimeter very long baseline interferometry (VLBI) array that has imaged the apparent shadows of the supermassive black holes M87* and Sagittarius A*.
Freek Roelofs   +282 more
doaj   +1 more source

First M87 Event Horizon Telescope Results. IX. Detection of Near-horizon Circular Polarization

open access: yesThe Astrophysical Journal Letters, 2023
Event Horizon Telescope (EHT) observations have revealed a bright ring of emission around the supermassive black hole at the center of the M87 galaxy. EHT images in linear polarization have further identified a coherent spiral pattern around the black ...
The Event Horizon Telescope Collaboration   +283 more
doaj   +1 more source

The Event Horizon Telescope Image of the Quasar NRAO 530

open access: yesThe Astrophysical Journal, 2023
We report on the observations of the quasar NRAO 530 with the Event Horizon Telescope (EHT) on 2017 April 5−7, when NRAO 530 was used as a calibrator for the EHT observations of Sagittarius A*.
Svetlana Jorstad   +269 more
doaj   +1 more source

Millimeter Light Curves of Sagittarius A* Observed during the 2017 Event Horizon Telescope Campaign

open access: yesThe Astrophysical Journal Letters, 2022
The Event Horizon Telescope (EHT) observed the compact radio source, Sagittarius A* (Sgr A*), in the Galactic Center on 2017 April 5–11 in the 1.3 mm wavelength band.
Maciek Wielgus   +266 more
doaj   +1 more source

Comparison of Polarized Radiative Transfer Codes Used by the EHT Collaboration

open access: yesThe Astrophysical Journal, 2023
Interpretation of resolved polarized images of black holes by the Event Horizon Telescope (EHT) requires predictions of the polarized emission observable by an Earth-based instrument for a particular model of the black hole accretion system.
Ben S. Prather   +273 more
doaj   +1 more source

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