Search For Optical Emission Research Articles

A Search for Optical Emission from Binary Black Hole Merger GW170814 with the Dark Energy Camera

Abstract Binary black hole (BBH) mergers found by the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo detectors are of immense scientific interest to the astrophysics community, but are considered unlikely to be sources of electromagnetic emission. To test whether they have rapidly fading optical counterparts, we used the Dark Energy Camera to perform an i-band search for the BBH merger GW170814, the first gravitational wave (GW) detected by three interferometers. The 87 deg2 localization region (at 90% confidence) centered in the Dark Energy Survey (DES) footprint enabled us to image 86% of the probable sky area to a depth of i ∼ 23 mag and provide the most comprehensive data set to search for electromagnetic (EM) emission from BBH mergers. To identify candidates, we perform difference imaging with our search images and with templates from pre-existing Dark Energy Survey (DES) images. The analysis strategy and selection requirements were designed to remove supernovae and to identify transients that decline in the first two epochs. We find two candidates, each of which is spatially coincident with a star or a high-redshift galaxy in the DES catalogs, and they are thus unlikely to be associated with GW170814. Our search finds no candidates associated with GW170814, disfavoring rapidly declining optical emission from BBH mergers brighter than i ∼ 23 mag (L optical ∼ 5 × 1041 erg s−1) 1–2 days after coalescence. In terms of GW sky map coverage, this is the most complete search for optical counterparts to BBH mergers to date.

A search for optical counterparts of hot spots in radio galaxies

The search for optical emission from radio hot spots has a long history but, up to now, only very few hot spots with optical synchrotron radiation have been detected. We embarked on a project to search for optical hot spot emission with VLT. We present the first results of near-infrared and optical imaging observations which detected synchrotron emission with a success rate of some 70%.

Extragalactic jets and their interaction with their environment

We describe three optical observational projects, each carried out in conjunction with studies at other wavelengths. These emphasize the usefulness of multifrequency studies in elucidating the nature of extragalactic jets. The first part concerns regions of optical line and continuum emission found at the sites of X-ray-radio knots in the inner 2 kpc of the Centaurus A jet. We show that these regions are physically associated with the jet and cite evidence for shock excitation within the emitting clumps. The full-spectrum continuum emission is attributed to the synchrotron process. Next we report the preliminary results of a search for optical emission in the fields of five radio jets. In the field of Abell 194 we find evidence for a jet-galaxy interaction. The optical-emission region known as Minkowski's Object is found to lie in the path of a radio jet. Spectroscopic investigation supports the view that it results from a burst of star formation, triggered by the impact of the jet on a cloud of material in its path. Last, we describe simultaneous multifrequency observations of the highly variable BL Lac object Mkn421. Dramatic changes in X-ray flux on time scales of weeks are not reproduced at other wavelengths. The X-ray variations are such that the lowest energy photons undergo the least change. These results allow some discrimination between the various theoretical jet models that have been proposed to describe the properties of BL Lacs. We also discuss possible interpretations for shorter time-scale (~10 000 s) variations with 10% amplitude, which were observed in X-ray light curves when the source was in an X-ray bright state.

Search for optical emission from cosmic gamma-ray bursts

view Abstract Citations (45) References (6) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Search for Optical Emission from Cosmic Gamma-Ray Bursts Grindlay, J. E. ; Wright, E. L. ; McCrosky, R. E. Abstract Long-exposure films are available for both times and regions of sky for several cosmic gamma-ray bursts. A visual magnitude of no more than 6 was set for optical emission from the well-observed May 14, 1972, event. The corresponding lower limit for the ratio of X-ray to optical energy flux in the burst is greater than 100. This may restrict solar-flare analogy models for the burst sources. Publication: The Astrophysical Journal Pub Date: September 1974 DOI: 10.1086/181604 Bibcode: 1974ApJ...192L.113G Keywords: Cosmic Rays; Gamma Rays; Light Emission; X Ray Astronomy; Astronomical Models; Photographic Film; Radiant Flux Density; Solar Flares; Space Radiation full text sources ADS |