Discovery of Dramatic Optical Variability in SDSS J1100+4421: A Peculiar Radio-loud Narrow-line Seyfert 1 Galaxy?
Tanaka, M; Morokuma, T; Itoh, R; Akitaya, H; Tominaga, N; Saito, Y; Stawarz, L; Tanaka, Y, T; Gandhi, P; Ali, G; Aoki, T; Contreras, C; Doi, M; Essam, A; Hamed, G; Hsiao, E. Y; Iwata, I; Kawabata, K. S; Kawai, N; Kikuchi, Y; Kobayashi, N; Kuroda, D; Maehara, H; Matsumoto, E; Mazzali, P. A; Minezaki, T; Mito, H; Miyata, T; Miyazaki, S; Mori, K; Moritani, Y; Morokuma-Matsui, Kana; Morrell, N; Nagao, T; Nakada, Y; Nakata, F; Noma, C; Ohsuga, K; Okada, N; Phillips, M. M; Pian, E; Richmond, M. W; Sahu, D. K; Sako, S; Sarugaku, Y; Shibata, T; Soyano, T; Stritzinger, M. D; Tachibana, Y; Taddia, F; Takaki, K; Takey, Ali; Tarusawa, K; Ui, T; Ukita, N; Urata, Y; Walker, E. S; Yoshii, T
Date:
2014-10-01
Abstract:
We present our discovery of dramatic variability in SDSS J1100+4421 by the high-cadence transient survey Kiso Supernova Survey. The source brightened in the optical by at least a factor of three within about half a day. Spectroscopic observations suggest that this object is likely a narrow-line Seyfert 1 galaxy (NLS1) at z = 0.840, however, with unusually strong narrow emission lines. The estimated black hole mass of ~107 M ☉ implies bolometric nuclear luminosity close to the Eddington limit. SDSS J1100+4421 is also extremely radio-loud, with a radio loudness parameter of R sime 4 × 102-3 × 103, which implies the presence of relativistic jets. Rapid and large-amplitude optical variability of the target, reminiscent of that found in a few radio- and γ-ray-loud NLS1s, is therefore produced most likely in a blazar-like core. The 1.4 GHz radio image of the source shows an extended structure with a linear size of about 100 kpc. If SDSS J1100+4421 is a genuine NLS1, as suggested here, this radio structure would then be the largest ever discovered in this type of active galaxies.
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