Photometrically Triggered Keck Spectroscopy of Fermi BL Lac Objects

Abstract

We report on Keck spectra of ten Fermi blazars. J0622+3326, previously unobserved, is shown to be a flat-spectrum radio quasar at redshift z=1.062. The others are known BL Lac-type objects that have resisted previous attempts to secure redshifts. Using a photometric monitoring campaign with the 0.76 m Katzman Automatic Imaging Telescope at Lick Observatory, we identified epochs when the relativistic jet emission was fainter than usual, thus triggering the Keck spectroscopy. This strategy gives improved sensitivity to stars and ionized gas in the host galaxy, thereby providing improved redshift constraints for seven of these sources.

7 pages; Accepted to AJ

References in corpus (3)

• CGRaBS: An All-Sky Survey of Gamma-Ray Blazar Candidates
• The Sedentary Survey of Extreme High Energy Peaked BL Lacs III. Results from Optical Spectroscopy
• Spectroscopy of Optically Selected BL Lac Objects and their gamma-ray emission

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