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Pulsed Gamma Rays from the Original Millisecond and Black Widow Pulsars: A Case for Caustic Radio Emission?
Camilo, F.; Gargano, F.; Grove, J. E. +25 more
We report the detection of pulsed gamma-ray emission from the fast millisecond pulsars (MSPs) B1937+21 (also known as J1939+2134) and B1957+20 (J1959+2048) using 18 months of survey data recorded by the Fermi Large Area Telescope and timing solutions based on radio observations conducted at the Westerbork and Nançay radio telescopes. In addition, …
Accretion-related properties of Herbig Ae/Be stars. Comparison with T Tauris
Eiroa, C.; Montesinos, B.; Mora, A. +4 more
Context. The mass accretion rate M⊙;acc) is a key parameter that has not accurately been determined for a wide sample of Herbig Ae/Be (HAeBe) stars until recently.
Aims: We look for trends relating M⊙acc and the stellar ages (t), spectral energy distributions (SEDs), and disk masses for a sample of 38 HAeBe stars, compar…
On the masses of OJ287 black holes
Ciprini, S.; Lehto, H. J.; Valtonen, M. J.
Two multifrequency campaigns were carried out on OJ287 in 2005: in April when it was in its pre-outburst state, and in November during the main 12 yr cycle outburst. The wavelength coverage was from radio to X-rays. In the optical-to-ultraviolet range, the differential spectrum between the observations has a bremsstrahlung spectral shape, consiste…
Optical flux and spectral variability of blazars
Gupta, Alok C.; Wiita, Paul J.; Bachev, R. +9 more
We report the results of optical monitoring for a sample of 11 blazars including 10 BL Lacertae objects (BL Lacs) and one flat spectrum radio quasar (FSRQ). We have measured the multiband optical flux and colour variations in these blazars on intraday and short-term time-scales of months and have limited data for two more blazars. These photometri…
X-Ray and Multiwavelength Insights into the Nature of Weak Emission-line Quasars at Low Redshift
Brandt, W. N.; Hall, Patrick B.; Anderson, Scott F. +5 more
We report on the X-ray and multiwavelength properties of 11 radio-quiet quasars with weak or no emission lines identified by the Sloan Digital Sky Survey (SDSS) with redshift z = 0.4-2.5. Our sample was selected from the Plotkin et al. catalog of radio-quiet, weak-featured active galactic nuclei (AGNs). The distribution of relative X-ray brightnes…
A Sunyaev-Zel'dovich take on cluster radio haloes - I. Global scaling and bi-modality using Planck data
Basu, Kaustuv
Giant radio haloes in galaxy clusters are the primary evidence for the existence of relativistic particles (cosmic rays) and magnetic fields over Mpc scales. Observational tests for the different theoretical models explaining their powering mechanism have so far been obtained through X-ray selection of clusters, e.g. by comparing cluster X-ray lum…
Isotopic Ratios in Titan's Methane: Measurements and Modeling
Irwin, P. G. J.; Teanby, N. A.; Flasar, F. M. +10 more
The existence of methane in Titan's atmosphere (~6% level at the surface) presents a unique enigma, as photochemical models predict that the current inventory will be entirely depleted by photochemistry in a timescale of ~20 Myr. In this paper, we examine the clues available from isotopic ratios (12C/13C and D/H) in Titan's m…
The Spectrum of the Recycled PSR J0437-4715 and Its White Dwarf Companion
Pavlov, George G.; Kargaltsev, Oleg; Kaplan, David L. +4 more
We present extensive spectral and photometric observations of the recycled pulsar/white dwarf binary containing PSR J0437-4715, which we analyzed together with archival X-ray and gamma-ray data, to obtain the complete mid-infrared to gamma-ray spectrum. We first fit each part of the spectrum separately, and then the whole multi-wavelength spectrum…
The Magnetic Energy-Helicity Diagram of Solar Active Regions
Georgoulis, Manolis K.; Tziotziou, Kostas; Raouafi, Nour-Eddine
Using a recently proposed nonlinear force-free method designed for single-vector magnetograms of solar active regions, we calculate the instantaneous free magnetic energy and relative magnetic helicity budgets in 162 vector magnetograms corresponding to 42 different active regions. We find a statistically robust, monotonic correlation between the …
Rapid disappearance of a warm, dusty circumstellar disk
Zuckerman, B.; Murphy, Simon J.; Song, Inseok +3 more
Stars form with gaseous and dusty circumstellar envelopes, which rapidly settle into disks that eventually give rise to planetary systems. Understanding the process by which these disks evolve is paramount in developing an accurate theory of planet formation that can account for the variety of planetary systems discovered so far. The formation of …