After the All-Sky Automated Survey for SuperNovae (ASAS-SN) discovered a significant brightening of the inner region of NGC 2617, we began a ∼ 70 day photometric and spectroscopic monitoring campaign from the X-ray through near-infrared (NIR) wavelengths. We report that NGC 2617 went through a dramatic outburst, during which its X-ray flux increased by over an order of magnitude followed by an increase of its optical/ultraviolet (UV) continuum flux by almost an order of magnitude. NGC 2617, classified as a Seyfert 1.8 galaxy in 2003, is now a Seyfert 1 due to the appearance of broad optical emission lines and a continuum blue bump. Such "changing look Active Galactic Nuclei (AGN)" are rare and provide us with important insights about AGN physics. Based on the Hβ line width and the radius-luminosity relation, we estimate the mass of central black hole to be (4 ± 1) × 10 7 M ⊙ . When we crosscorrelate the light curves, we find that the disk emission lags the X-rays, with the lag becoming longer as we move from the UV (2 − 3 days) to the NIR (6 − 9 days). Also, the NIR is more heavily temporally smoothed than the UV. This can largely be explained by a simple model of a thermally emitting thin disk around a black hole of the estimated mass that is illuminated by the observed, variable X-ray fluxes.
Las Cumbres Observatory Global Telescope (LCOGT) is a young organization
dedicated to time-domain observations at optical and (potentially) near-IR
wavelengths. To this end, LCOGT is constructing a world-wide network of
telescopes, including the two 2m Faulkes telescopes, as many as 17 x 1m
telescopes, and as many as 23 x 40cm telescopes. These telescopes initially
will be outfitted for imaging and (excepting the 40cm telescopes) spectroscopy
at wavelengths between the atmospheric UV cutoff and the roughly 1-micron limit
of silicon detectors. Since the first of LCOGT's 1m telescopes are now being
deployed, we lay out here LCOGT's scientific goals and the requirements that
these goals place on network architecture and performance, we summarize the
network's present and projected level of development, and we describe our
expected schedule for completing it. In the bulk of the paper, we describe in
detail the technical approaches that we have adopted to attain the desired
performance. In particular, we discuss our choices for the number and location
of network sites, for the number and sizes of telescopes, for the
specifications of the first generation of instruments, for the software that
will schedule and control the network's telescopes and reduce and archive its
data, and for the structure of the scientific and educational programs for
which the network will provide observations.Comment: 59 pages, 9 figures, 4 tables. AAS Latex v5.2. Accepted for
publication in Pub. Astr. Soc. Pacifi
We analyze a ∆V ∼ −9 magnitude flare on the newly identified M8 dwarf SDSS J022116.84+194020.4 (hereafter SDSSJ0221) detected as part of the All-Sky Automated Survey for Supernovae (ASAS-SN). Using infrared and optical spectra, we confirm that SDSSJ0221 is a relatively nearby (d∼76 pc) M8 dwarf with strong quiescent Hα emission. Based on kinematics and the absence of features consistent with low-gravity (young) ultracool dwarfs, we place a lower limit of 200 Myr on the age of SDSSJ0221. When modeled with a simple, classical flare light-curve, this flare is consistent with a total U -band flare energy E U ∼ 10 34 erg, confirming that the most dramatic flares are not limited to warmer, more massive stars. Scaled to include a rough estimate of the emission line contribution to the V band, we estimate a blackbody filling factor of ∼10-30% during the flare peak and ∼0.5-1.6% during the flare decay phase. These filling factors correspond to flare areas that are an order of magnitude larger than those measured for most mid-M dwarf flares.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.