Civano, F.Elvis, M.Lanzuisi, G.Jahnke, K.Zamorani, G.Blecha, L.Bongiorno, A.Brusa, M.Comastri, A.Hao, H.Leauthaud, A.Loeb, A.Mainieri, V.Piconcelli, E.Salvato, M.Scoville, N.Trump, J.Vignali, C.Aldcroft, T.Bolzonella, M.Bressert, E.Finoguenov, A.Fruscione, A.Koekemoer, A. M.Cappelluti, N.Fiore, F.Giodini, S.Gilli, R.Impey, C. D.Lilly, S. J.Lusso, E.Puccetti, S.Silverman, J. D.Aussel, H.Capak, P.Frayer, D.Le Floch, E.McCracken, H. J.Sanders, D. B.Schiminovich, D.Taniguchi, Y.2019-09-242010Civano, F., M. Elvis, G. Lanzuisi, K. Jahnke, G. Zamorani, L. Blecha, A. Bongiorno, et al. 2010. “A RUNAWAY BLACK HOLE IN COSMOS: GRAVITATIONAL WAVE OR SLINGSHOT RECOIL?” The Astrophysical Journal 717 (1): 209–22. https://doi.org/10.1088/0004-637x/717/1/209.0004-637X1538-4357http://nrs.harvard.edu/urn-3:HUL.InstRepos:41393150We present a detailed study of a peculiar source detected in the COSMOS survey at z = 0.359. Source CXOC J100043.1+020637, also known as CID-42, has two compact optical sources embedded in the same galaxy. The distance between the two, measured in the HST/ACS image, is 0 ''.495 +/- 0 ''.005 that, at the redshift of the source, corresponds to a projected separation of 2.46 +/- 0.02 kpc. A large (similar to 1200 km s(-1)) velocity offset between the narrow and broad components of H beta has been measured in three different optical spectra from the VLT/VIMOS and Magellan/IMACS instruments. CID-42 is also the only X-ray source in COSMOS, having in its X-ray spectra a strong redshifted broad absorption iron line and an iron emission line, drawing an inverted P-Cygni profile. The Chandra and XMM-Newton data show that the absorption line is variable in energy by Delta E = 500 eV over four years and that the absorber has to be highly ionized in order not to leave a signature in the soft X-ray spectrum. That these features-the morphology, the velocity offset, and the inverted P-Cygni profile-occur in the same source is unlikely to be a coincidence. We envisage two possible explanations, both exceptional, for this system: (1) a gravitational wave (GW) recoiling black hole (BH), caught 1-10 Myr after merging; or (2) a Type 1/Type 2 system in the same galaxy where the Type 1 is recoiling due to the slingshot effect produced by a triple BH system. The first possibility gives us a candidate GW recoiling BH with both spectroscopic and imaging signatures. In the second case, the X-ray absorption line can be explained as a BAL-like outflow from the foreground nucleus (a Type 2 AGN) at the rearer one (a Type 1 AGN), which illuminates the otherwise undetectable wind, giving us the first opportunity to show that fast winds are present in obscured active galactic nuclei (AGNs), and possibly universal in AGNs.en-USJournal Article2019-09-2410.1088/0004-637X/717/1/209