E 0336-248 : A New BL Lac Object Found by an Old Einstein

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 z=0.251 with an X-ray luminosity of 10^45 erg/s. It is also a 14 mJy radio source at 20 cm. An emission-line galaxy at z=0.043 that was previously considered a Seyfert identification for E 0336-248 is shown instead to be an unrelated, non-active H II region galaxy that lies 78 arcseconds from the X-ray source. The resolution of this historical case of mistaken identity illustrates that discoveries of non-AGN 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.Comment: To appear in the Astronomical Journal. 8 pages including figures (uses psfig.tex, also included

Spectral Models for Low-luminosity Active Galactic Nuclei in LINERs: The Role of Advection-dominated Accretion and Jets

We perform an exploratory study of the physical properties of accretion flows and jets in low-luminosity active galactic nuclei (LLAGNs) by modeling the spectral energy distributions (SEDs) of 12 LLAGNs in low-ionization nuclear emission-line regions (LINERs). These SEDs we constructed from high-resolution radio, X-ray and optical/UV observations of the immediate vicinity of the black hole. We adopt a coupled accretion-jet model comprising an inner advection-dominated accretion flow (ADAF) and an outer standard thin disk. We present best-fit models in which either the ADAF or the jet dominate the X-ray emission. Six sources in our sample display an optical-UV excess with respect to ADAF and jet models; this excess can be explained as emission from the truncated disk with transition radii 30-225 Rs in four of them. In almost all sources the optical emission can also be attributed to unresolved, old stellar clusters with masses ~1E7-1E8 Msun. We find evidence for a correlation between the accretion rate and jet power and an anti-correlation between the radio-loudness and the accretion rate. We confirm previous findings that the radio emission is severely underpredicted by ADAF models and explained by the relativistic jet. We find evidence for a nonlinear relation between the X-ray and bolometric luminosities and a slight IR excess in the average model SED compared to that of quasars. We suggest that the hardness of the X-ray spectrum can be used to identify the X-ray emission mechanism and discuss directions for progress in understanding the origin of the X-rays.Comment: Accepted for publication in MNRAS. 27 pages, 22 figures. arXiv admin note: substantial text overlap with arXiv:1112.464

A Large Systematic Search for Recoiling and Close Supermassive Binary Black Holes

[ABRIDGED] We have carried out a systematic search for close supermassive black hole binaries among z < 0.7 SDSS quasars Such binaries are predicted by models of supermassive black hole and host galaxy co-evolution, therefore their census and population properties constitute an important test of these models. We used an automatic technique based on spectroscopic principal component analysis to search for broad H-beta lines that are displaced from the rest-frame of the quasar by more than 1,000 km/s This method can also yield candidates for rapidly recoiling black holes. Our search yielded 88 candidates, several of which were previously identified and discussed in the literature. The widths of the broad H-beta lines are typical among quasars but the shifts are extreme. We found a correlation between the peak offset and skewness of the broad H-beta profiles, which suggests that the profiles we have selected share a common physical explanation. The general properties of the narrow emission lines are typical of quasars. We carried out followup spectroscopic observations of 68 objects to search for changes in the peak velocities of the H-beta lines (the time interval in the observer's frame between the original and new observations is 1-10 yr). We measured significant changes in 14 objects, with resulting accelerations between -120 and +120 km/s/yr. We emphasize that interpretation of the offset broad emission lines as signatures of supermassive binaries is subject to many significant caveats. Many more followup observations over a long temporal baseline are needed to characterize the variability pattern of the broad lines and test that this pattern is indeed consistent with orbital motion. The possibility that some of the objects in this sample are rapidly recoiling black holes remains open as the available data do not provide strong constraints for this scenario.Comment: Submitted to the Astrophysical Journal Supplements on 10 June 2011. Version with large figures and full object list at: http://www2.astro.psu.edu/users/mce/preprints/SBHB.pdf (5 MB

Chandra detection of a parsec scale wind in the Broad Line Radio Galaxy 3C 382

We present unambiguous evidence for a parsec scale wind in the Broad-Line Radio Galaxy (BLRG) 3C 382, the first radio-loud AGN, with $R_{\rm L} = \log_{10}(f_{\rm 5GHz}/f_{4400})>1$, whereby an outflow has been measured with X-ray grating spectroscopy. A 118 ks Chandra grating (HETG) observation of 3C 382 has revealed the presence of several high ionization absorption lines in the soft X-ray band, from Fe, Ne, Mg and Si. The absorption lines are blue-shifted with respect to the systemic velocity of 3C 382 by -840\pm60 km/s and are resolved by Chandra with a velocity width of 340\pm70 km/s. The outflow appears to originate from a single zone of gas of column density $N_{\rm H} = 1.3 \times 10^{21}$ cm$^{-2}$ and ionization parameter $\log \xi = 2.45$. From the above measurements we calculate that the outflow is observed on parsec scales, within the likely range from 10-1000 pc, i.e., consistent with an origin in the Narrow Line Region.Comment: 11 pages, accepted for publication in Astrophysical Journal Letter