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Stars erupt with flares for the same reason the sun does. Around active regions of the star's atmosphere, magnetic fields become twisted and distorted. Much like winding up a rubber band, these allow the fields to accumulate energy. Eventually a process called magnetic reconnection destabilizes the fields, resulting in the explosive release of the stored energy we see as a flare. The outburst emits radiation across the electromagnetic spectrum, from radio waves to visible, ultraviolet and X-ray light.
At 5:07 p.m. EDT on April 23, the rising tide of X-rays from DG CVn's superflare triggered Swift's Burst Alert Telescope (BAT). Within several seconds of detecting a strong burst of radiation, the BAT calculates an initial position, decides whether the activity merits investigation by other instruments and, if so, sends the position to the spacecraft. In this case, Swift turned to observe the source in greater detail, and, at the same time, notified astronomers around the globe that a powerful outburst was in progress.
We present an up-to-date catalog of pulsating binaries, i.e. the binary and multiple stellar systems containing pulsating components, along with a statistics on them. Compared to the earlier compilation by Soydugan et al.(2006a) of 25 δ Scuti-type `oscillating Algol-type eclipsing binaries' (oEA) plus 197 candidates,the recent collection of 74 oEA by Liakos et al.(2012), and the collection of Cepheids in binaries by Szabados (2003a), both the types of pulsating variables and binaries are now extended. The total numbers of pulsating binary/multiple stellar systems have increased to be 501 as of 2014 September 16, among which 262+ are oscillating eclipsing binaries and the oEA containing δ Scuti components are updated to be 93. The catalog is intended to be a collection of various pulsating binary stars across the Hertzsprung-Russell diagram. We reviewed the open questions, advances and prospects connecting pulsation/oscillation and binarity. The observational implication of binary systems with pulsating components, to stellar evolution theories is also addressed. In addition, a catalog consisting of 434 confirmed Algol-type eclipsing binaries (EA) is provided for reference.
Deep mid-infrared (10-20 $\mu$m) images with sub-arcsec resolution were obtained for two Herbig Be stars, MWC 1080 and HD 259431, to probe their immediate environments. Our goal is to understand the origin of the diffuse nebulosities observed around these two very young objects. By analyzing our new mid-IR images and comparing them to published data at other wavelengths, we demonstrate that the well extended emission around MWC 1080 traces neither a disk nor an envelope, but rather the surfaces of a cavity created by the outflow from MWC 1080A, the primary star of the MWC 1080 system. In the N-band images, the filamentary nebulosities trace the hourglass-shaped gas cavity wall out to $\sim$0.15 pc. This scenario reconciles the properties of the MWC 1080 system revealed by a wide range of observations. Our finding confirms that the environment around MWC 1080, where a small cluster is forming, is strongly affected by the outflow from the central Herbig Be star. Similarities observed between the two subjects of this study suggest that the filamentary emission around HD 259431 may arise from a similar outflow cavity structure, too.
Authors: Dan Li, Naibí Mariñas, Charles M. Telesco
T Tauri stars are a class of variable stars, named for their prototype T Tauri, discovered in 1852. T Tauri stars have been known for decades as relatively normal, medium-sized, extremely young main-sequence stars. At one point, some 4.5 billion years ago, our Sun was a T Tauri star. T Tauri stars are thought to be surrounded by protoplanetary disks, containing the raw materials to build both rocky and gaseous planets. Though nearly invisible in optical light, these disks shine in both infrared and millimeter-wavelength light.
Some T Tauri stars emit infrared radiation in unexpected ways. Those stars were the focus of this study, led by astronomer Colette Salyk at the National Optical Astronomical Observatory (NOAO) in Tucson, Arizona. Many T Tauri stars have been thought to have extremely powerfulstellar winds – predicted by astronomers, but never clearly detected – and Salyk and her team proposed that, for some T Tauri stars, the winds may be emanating from within the stars’ protoplanetary disks. They say these winds could have important implications for planet formation, potentially robbing the disk of some of the gas required for the formation of giant Jupiter-like planets, or stirring up the disk and causing the building blocks of planets to change location entirely.