We analyze a ΔV ∼ −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. 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 EU ∼ 1034 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.
The Las Cumbres Observatory Global Telescope Network comprises nine 1-meter and two 2-meter telescopes, all robotic and dynamically scheduled, at five sites spanning the globe. Instrumentation includes optical imagers and low-dispersion spectrographs. A suite of high-dispersion, high-stability spectrographs is being developed for deployment starting late this year. The network has been designed and built to allow regular monitoring of time-variable or moving objects with any cadence, as well as rapid response to external alerts. Our intent is to operate it in a totally integrated way, both in terms of scheduling and in terms of data quality. The unique attributes of the LCOGT network make it different enough from any existing facility that alternative approaches to optimize science productivity can be considered. The LCOGT network V1.0 began full science operations this year. It is being used in novel ways to undertake investigations related to supernovae, microlensing events, solar system objects, and exoplanets. The network’s user base includes a number of partners, who are providing resources to the collaboration. A key project program brings together many of these partners to carry out large projects. In the long term, our vision is to operate the network as a part of a time-domain system, in which pre-planned monitoring observations are interspersed with autonomously detected and classified events from wide-area surveys.
After the All-Sky Automated Survey for SuperNovae discovered a significant brightening of the inner region of NGC 2617, we began a similar to 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 (AGNs)" are rare and provide us with important insights about AGN physics. Based on the H beta line width and the radius-luminosity relation, we estimate the mass of central black hole (BH) to be (4 +/- 1) x 10(7)M(circle dot). When we cross-correlate 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 BH of the estimated mass that is illuminated by the observed, variable X-ray fluxes.
The optical light generated simultaneously with x-rays and gamma rays during a gamma-ray burst (GRB) provides clues about the nature of the explosions that occur as massive stars collapse. We report on the bright optical flash and fading afterglow from powerful burst GRB 130427A. The optical and >100-megaelectron volt (MeV) gamma-ray flux show a close correlation during the first 7000 seconds, which is best explained by reverse shock emission cogenerated in the relativistic burst ejecta as it collides with surrounding material. At later times, optical observations show the emergence of emission generated by a forward shock traversing the circumburst environment. The link between optical afterglow and >100-MeV emission suggests that nearby early peaked afterglows will be the best candidates for studying gamma-ray emission at energies ranging from gigaelectron volts to teraelectron volts.