RESUMO
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.
RESUMO
The Kuiper belt is a collection of small bodies (Kuiper belt objects, KBOs) that lie beyond the orbit of Neptune and which are believed to have formed contemporaneously with the planets. Their small size and great distance make them difficult to study. KBO 55636 (2002 TX(300)) is a member of the water-ice-rich Haumea KBO collisional family. The Haumea family are among the most highly reflective objects in the Solar System. Dynamical calculations indicate that the collision that created KBO 55636 occurred at least 1 Gyr ago. Here we report observations of a multi-chord stellar occultation by KBO 55636, which occurred on 9 October 2009 ut. We find that it has a mean radius of 143 +/- 5 km (assuming a circular solution). Allowing for possible elliptical shapes, we find a geometric albedo of in the V photometric band, which establishes that KBO 55636 is smaller than previously thought and that, like its parent body, it is highly reflective. The dynamical age implies either that KBO 55636 has an active resurfacing mechanism, or that fresh water-ice in the outer Solar System can persist for gigayear timescales.
RESUMO
Sick Building Syndrome has been reported with increasing frequency during recent years. Buildings that have sustained water damage harbor various molds, some of which may be toxic. Students and staff at Central Middle School in Murfreesboro, Tennessee, reported symptoms similar to those associated with Sick Building Syndrome. Upon investigation, investigators noted that a black fungal growth occurred throughout the building on wet cellulose ceiling tiles. Fungal growth of this type is consistent with the genus Stachybotrys. Stachybotrys spores contain macrocyclic trichothecenes, which may cause harm when inhaled or ingested. Bulk sampling of the black mold was initiated, and the samples were cultured in a moist chamber. Testing of the samples confirmed the presence of Stachybotrys spp., a finding that implies that air sampling procedures should ensue. Professional remediation of this potentially hazardous fungal contaminant is therefore recommended.
