H-alpha monitoring of OJ 287 in 2005-08

TL;DR

This study monitored the BL Lac object OJ 287 over several years, detecting new emission lines and analyzing the properties of the H-alpha line, revealing its stability and lower luminosity compared to past observations and other active galactic nuclei.

Contribution

First detection of multiple narrow emission lines in OJ 287 during 2005-08, with analysis of H-alpha line properties showing stability over time.

Findings

Detected five narrow emission lines, including H-alpha, during 2005-08.

H-alpha luminosity was about ten times lower than in 1984.

H-alpha line width remained consistent with previous measurements.

Abstract

We present the results of H-alpha monitoring of the BL Lac object OJ 287 with the VLT during seven epochs in 2005-08. We were able to detect five previously undetected narrow emission lines, 6548,6583[NII], 6563H-alpha$ and 6716,6731[SII] during at least one of the epochs and a broad H-alpha feature during two epochs. The broad H-alpha luminosity was a factor ~10 lower in 2005-08 than in 1984 when the line was previously detected and a factor ~10 lower than what is observed in quasars and Seyfert galaxies at the same redshift. The data are consistent with no change in the position or luminosity of the H-alpha line in 2005-08. The width of the H-alpha line was 4200 +- 500 km/s, consistent with the width in 1984.