* Astronomy

Blobrana · L

RE: Fast radio bursts

Blobrana · L

FRB 121102

Blobrana · L

RE: Fast radio bursts

Blobrana · L

Title: A mechanism for fast radio bursts
Author: Gustavo E. Romero, Maria Victoria del Valle, Florencia L. Vieyro

Fast radio bursts are mysterious transient sources likely located at cosmological distances. The derived brightness temperatures exceed by many orders of magnitude the self-absorption limit of incoherent synchrotron radiation, implying the operation of a coherent emission process. We propose a radiation mechanism for fast radio bursts where the emission arises from collisionless Bremsstrahlung in strong plasma turbulence excited by relativistic electron beams. We discuss possible astrophysical scenarios in which this process might operate. The emitting region is a turbulent plasma hit by a relativistic jet, where Langmuir plasma waves produce a concentration of intense electrostatic soliton-like regions (cavitons). The resulting radiation is coherent and, under some physical conditions, can be polarised and have a power-law distribution in energy. We obtain radio luminosities in agreement with the inferred values for fast radio bursts. The timescale of the radio flare in some cases can be extremely fast, of the order of 10^-3 s. The mechanism we present here can explain the main features of fast radio bursts and is plausible in different astrophysical sources, such as gamma-ray bursts and some Active Galactic Nuclei.

Read more (69kb, PDF)

Blobrana · L

Title: Fast radio bursts: the observational case for a Galactic origin
Author: Dan Maoz, Abraham Loeb, Yossi Shvartzvald, Monika Sitek, Michael Engel, Flavien Kiefer, Marcin Kiraga, Amir Levi, Tsevi Mazeh, Michal Pawlak, R. Michael Rich, Lukasz Wyrzykowski

There are by now ten published detections of fast radio bursts (FRBs), single bright GHz-band millisecond pulses of unknown origin. Proposed explanations cover a broad range from exotic processes at cosmological distances to atmospheric and terrestrial sources. Loeb et al. have previously suggested that FRB sources could be nearby flare stars, and pointed out the presence of a W-UMa-type contact binary within the beam of one out of three FRB fields that they examined. Using time-domain optical photometry and spectroscopy, we now find possible flare stars in additional FRB fields, with one to three such cases among eight FRB fields studied. We evaluate the chance probabilities of these possible associations to be in the range 0.1% to 9%, depending on the input assumptions. Further, we re-analyse the probability that two FRBs recently discovered 3 years apart within the same radio beam are unrelated. Contrary to other claims, we conclude with 99% confidence that the two events are from the same repeating source. The different dispersion measures between the two bursts then rule out a cosmological origin for the dispersion measure, but are consistent with the flare-star scenario with a varying plasma blanket between bursts. Finally, we review some theoretical objections that have been raised against a local flare-star FRB origin, and show that they are incorrect.

Read more (130kb, PDF)

Blobrana · L

Title: Fast Radio Bursts: Collisions between Neutron Stars and Asteroids/Comets
Author: J. J. Geng, Y. F. Huang

Fast radio bursts (FRBs) are newly discovered radio transient sources. Their high dispersion measures indicate a cosmological origin. But due to the lack of observational data in other wavelengths, their progenitors still remain unclear. Here we suggest the collisions between neutron stars and asteroids/comets as a promising mechanism for FRBs. During the impact process, a hot plasma fireball will form after the material of the small body penetrates into the neutron star surface. The ionized matter inside the fireball will then expand along the magnetic field lines. Coherent radiation from the thin shell at the top of the fireball will account for the observed FRBs. Our scenario can reasonably explain the main features of FRBs, such as their durations, luminosities, and the event rate. We argue that for a single neutron star, FRBs are not likely to happen repeatedly in a foreseeable time span since such impacts are of low probability. We predict that faint X-ray afterglows should be associated with FRBs, which may be detected by future rapid follow-up observations of FRBs.

Read more (311kb, PDF)

Blobrana · L

Cosmic Radio Burst Caught Red-Handed

A team of astronomers using twelve telescopes from around the world, and in space, have for the first time captured a fast radio burst happening live.
The achievement will help scientists trap more bursts in the future, which could offer insight into the evolution of the universe. University of Manchester academics working from Jodrell Bank were members of the team, led by Emily Petroff from the Swinburne University of Technology in Melbourne, Australia, that captured the burst using the Parkes radio telescope located in eastern Australia.
Read more

Blobrana · L

Arecibo captures its first 'fast radio burst'

The Arecibo Observatory has captured one of the most fleeting, mysterious and rare deep-space events - a so-called "fast radio burst" (FRB) that lasted a mere three one-thousandths of a second. Cornell, McGill University and other astronomers report this peculiar event today (July 10) in the Astrophysical Journal.
Read more

Blobrana · L

Radio-burst discovery deepens astrophysics mystery

The discovery of a split-second burst of radio waves using the Arecibo radio telescope in Puerto Rico provides important new evidence of mysterious pulses that appear to come from deep in outer space.
The findings by an international team of astronomers led by Laura Spitler from the Max Planck Institute for Radio Astronomy in Bonn, Germany are published on July 10 in the online issue of The Astrophysical Journal. They mark the first time that a so-called "fast radio burst" has been detected in the Northern hemisphere of the sky.
Read more