1997/08/04 by Jules P. Halpern, J. P. Halpern, Michael Eracleous +3 · 1 citation
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1086/118602
To appear in the Astronomical Journal. 8 pages including figures (uses psfig.tex, also included)
arxiv created 1997/08/04 · openalex publication_date 1997/11/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/04
We obtained new ROSAT HRI and optical observations in the field of the Einstein X-ray source E 0336-248, which we use to identify it as a 19th magnitude BL Lacertae object at ζ=O.251 with L<SUB>x</SUB>=1X10<SUP>45</SUP> erg s<SUP>-1</SUP>. It is also a 14 mJy radio source at 20 cm. An emission-line galaxy at ζ = 0.043 that was previously considered a Seyfert identification for E 0336-248 is shown instead to be an unrelated, nonactive H II region galaxy that lies 78‧‧ from the X-ray source. The resolution of this historical case of mistaken identity illustrates that discoveries of non-AUN emission-line galaxies with high X-ray luminosity should be tested carefully. The properties of E 0336-248 are similar to those of other X-ray selected BL Lacs, including its location in an apparent group or cluster of galaxies. Somewhat unusual is the weak contribution of nonstellar optical light relative to the starlight in the spectrum of its host galaxy, which raises once again the possibility that even high-luminosity BL Lac objects may be difficult to identify in X-ray selected samples. We discuss a possible manifestation of this problem that appeared in the recent literature.