English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The third Fermi source catalog lists 3033 gamma-ray sources above $4\sigma$significance. More than 30% are classified as either unidentified/unassociatedGamma-ray sources (UGSs), with about 20% classified as Blazar candidates ofuncertain types (BCUs). To confirm the blazar-like nature of candidatecounterparts of UGSs and BCUs, we started in 2012 an optical spectroscopicfollow up campaign. We report here the spectra of 36 targets with observationsfrom the Observatorio Astron\'omico Nacional San Pedro M\'artir, the SouthernAstrophysical Research Observatory, the Kitt Peak National Observatory and theNorthern Optical Telescope, between 2016 and 2017. We confirm the BL Lac natureof 23 sources, and the flat spectrum radio quasar nature of other 7 ones. Wealso provide redshift estimates for 19 out of these 30 confirmations, with onlyone being a lower limit due to spectral features ascribable to interveningsystems along the line of sight. As in previous analyses, the largest fractionof now-classified BCUs belong to the class of BL Lac objects, that appear to bethe most elusive class of active galactic nuclei. One of the BL Lacs identifiedin this work, associated with 3FGL J2213.6-4755, lies at a redshift of$z>$1.529, making it one of the few distant gamma-ray BL Lac objects.

astrophysics and space science

Optical spectroscopic observations of gamma-ray blazar candidates VIII:  the 2016-2017 follow up campaign carried out at SPM, NOT, KPNO and SOAR  telescopes