We report results from an intensive multiwavelength campaign on the intermediate-frequency-peaked BL Lacertae object W Com (z = 0.102) during a strong outburst of very high energy gamma-ray emission in 2008 June. The very high energy gamma-ray signal was detected by VERITAS on 2008 June 7-8 with a flux F(>200 GeV) = (5.7 ± 0.6) × 10 −11 cm −2 s −1 , about three times brighter than during the discovery of gamma-ray emission from W Com by VERITAS in 2008 March. The initial detection of this flare by VERITAS at energies above 200 GeV was followed by observations in high-energy gamma rays (AGILE; E γ 100 MeV), X-rays (Swift and XMM-Newton), and at UV, and ground-based optical and radio monitoring through the GASP-WEBT consortium and other observatories. Here we describe the multiwavelength data and derive the spectral energy distribution of the source from contemporaneous data taken throughout the flare.

The results of 8-year R-band photopolarimetric data of blazar Mrk 421 collected from February 2008 to May 2016 are presented, along with extensive multiwavelength observations covering from radio to TeV γ-rays around the flares observed in May 2008, March 2010, and April 2013. The most important results are found in 2013 when the source displayed in the R-band a very high brightness state of 11.29 ± 0.03 mag (93.60 ± 1.53 mJy) on April 10th and a polarization degree of (11.00 ± 0.44)% on May 13th. The analysis of the optical data shows that the polarization variability is due to the superposition of two polarized components that might be produced in two distinct emitting regions. An intranight photopolarimetric variability study carried out over 7 nights after the 2013 April maximum found flux and polarization variations on the nights of April 14, 15, 16 and 19. In addition, the flux shows a minimum variability timescale of ∆ t =2.34±0.12 hours, and that the polarization degree presented variations of ∼ (1 -2) % in a timescale of ∆ t ∼ minutes. Also, a detailed analysis of the intranight data shows a coherence length of the large-scale magnetic field of l B 0.3 pc which is the same order of magnitude to the distance traveled by the relativistic shocks. This result suggests that there is a connection between the intranight polarimetric variations and spatial changes of the magnetic field. Analysis of the complete R-band data along with the historical optical light curve found for this object shows that Mrk 421 varies with a period of 16.26 ± 1.78 years.

Isolated cool white dwarf stars more often have strong magnetic fields than young, hotter white dwarfs, which has been a puzzle because magnetic fields are expected to decay with time but a cool surface suggests that the star is old. In addition, some white dwarfs with strong fields vary in brightness as they rotate, which has been variously attributed to surface brightness inhomogeneities similar to sunspots, chemical inhomogeneities and other magneto-optical effects. Here we describe optical observations of the brightness and magnetic field of the cool white dwarf WD 1953-011 taken over about eight years, and the results of an analysis of its surface temperature and magnetic field distribution. We find that the magnetic field suppresses atmospheric convection, leading to dark spots in the most magnetized areas. We also find that strong fields are sufficient to suppress convection over the entire surface in cool magnetic white dwarfs, which inhibits their cooling evolution relative to weakly magnetic and non-magnetic white dwarfs, making them appear younger than they truly are. This explains the long-standing mystery of why magnetic fields are more common amongst cool white dwarfs, and implies that the currently accepted ages of strongly magnetic white dwarfs are systematically too young.

Abstract. The San Pedro Mártir kinematic catalogue of galactic planetary nebulae provides spatially resolved, long-slit, Echelle spectra for about 600 planetary nebulae, representing 55 observing runs and about 4000 individual integrations to date in this first release. The project is ongoing and will continue adding spectra to the database. The data are presented wavelength calibrated and corrected for heliocentric motion. This is the most extensive and homogeneous single source of data concerning the internal kinematics of the ionized nebular material in planetary nebulae. The catalogue is available through the world wide web at http://kincatpn.astrosen.unam.mx and an article will a full description of the catalogue will soon appear in the RevMexAA.

No abstract