We are carrying out a program of high signal to noise optical spectroscopy of BL Lacs with unknown or tentative redshift. Here we report some preliminary results. New redshifts are measured for PKS0754+100 (z=0.266) and 1ES0715-259 (z=0.464) . From lineless spectra of PG1553+113 and PKS1722+119 we set a lower limit of z>0.3 for both sources. In two cases (UM493 and 1620+103) stellar spectra indicate a wrong classification.
@article{arxiv.astro-ph/0210016,
title = {Spectroscopy of BL Lac Objects: new redshifts and mis-identified sources},
author = {N. Carangelo and R. Falomo and J. Kotilainen and A. Treves and M. -H. Ulrich},
journal= {arXiv preprint arXiv:astro-ph/0210016},
year = {2007}
}
Comments
4 pages; Conference proceeding "High Energy Blazar Astronomy", Tuorla Observatory, Finland, 17-21 June 2002; to be published in the PASP conference series