On the Origin of the Dark Gamma-Ray Bursts

The origin of dark bursts - i.e. that have no observed afterglows in X-ray, optical/NIR and radio ranges - is unclear yet. Different possibilities - instrumental biases, very high redshifts, extinction in the host galaxies - are discussed and shown to be important. On the other hand, the dark bursts should not form a new subgroup of long gamma-ray bursts themselves.Comment: published in Nuovo Ciment

The Electrostatic Ion Beam Trap : a mass spectrometer of infinite mass range

We study the ions dynamics inside an Electrostatic Ion Beam Trap (EIBT) and show that the stability of the trapping is ruled by a Hill's equation. This unexpectedly demonstrates that an EIBT, in the reference frame of the ions works very similar to a quadrupole trap. The parallelism between these two kinds of traps is illustrated by comparing experimental and theoretical stability diagrams of the EIBT. The main difference with quadrupole traps is that the stability depends only on the ratio of the acceleration and trapping electrostatic potentials, not on the mass nor the charge of the ions. All kinds of ions can be trapped simultaneously and since parametric resonances are proportional to the square root of the charge/mass ratio the EIBT can be used as a mass spectrometer of infinite mass range

Comparing Star Formation on Large Scales in the c2d Legacy Clouds: Bolocam 1.1 mm Dust Continuum Surveys of Serpens, Perseus, and Ophiuchus

We have undertaken an unprecedentedly large 1.1 millimeter continuum survey of three nearby star forming clouds using Bolocam at the Caltech Submillimeter Observatory. We mapped the largest areas in each cloud at millimeter or submillimeter wavelengths to date: 7.5 sq. deg in Perseus (Paper I), 10.8 sq. deg in Ophiuchus (Paper II), and 1.5 sq. deg in Serpens with a resolution of 31", detecting 122, 44, and 35 cores, respectively. Here we report on results of the Serpens survey and compare the three clouds. Average measured angular core sizes and their dependence on resolution suggest that many of the observed sources are consistent with power-law density profiles. Tests of the effects of cloud distance reveal that linear resolution strongly affects measured source sizes and densities, but not the shape of the mass distribution. Core mass distribution slopes in Perseus and Ophiuchus (alpha=2.1+/-0.1 and alpha=2.1+/-0.3) are consistent with recent measurements of the stellar IMF, whereas the Serpens distribution is flatter (alpha=1.6+/-0.2). We also compare the relative mass distribution shapes to predictions from turbulent fragmentation simulations. Dense cores constitute less than 10% of the total cloud mass in all three clouds, consistent with other measurements of low star-formation efficiencies. Furthermore, most cores are found at high column densities; more than 75% of 1.1 mm cores are associated with Av>8 mag in Perseus, 15 mag in Serpens, and 20-23 mag in Ophiuchus.Comment: 32 pages, including 18 figures, accepted for publication in Ap

Principal-Component Analysis of Gamma-Ray Bursts’ Spectra

The principal-component analysis is a statistical method, which lowers the number of important variables in a data set. The use of this method for the bursts’ spectra and afterglows is discussed in this paper. The analysis indicates that three principal components are enough among the eight ones to describe the variablity of the data. The correlation between the spectral index α and the redshift suggests that the thermal emission component becomes more dominant at larger redshifts

INTEGRAL broadband spectroscopy of Vela X-1

The wind-accreting X-ray binary pulsar and cyclotron line source Vela X-1 has been observed extensively during INTEGRAL Core Program observations of the Vela region in June-July and November-December 2003. In the latter set of observations the source showed intense flaring -- see also Staubert et al. (2004), these proceedings. We present early results on time averaged and time resolved spectra, of both epochs of observations. A cyclotron line feature at ~53 keV is clearly detected in the INTEGRAL spectra and its broad shape is resolved in SPI spectra. The remaining issues in the calibration of the instruments do not allow to resolve the question of the disputed line feature at 20-25 keV. During the first main flare the average luminosity increases by a factor of \~10, but the spectral shape remains very similar, except for a moderate softening.Comment: Accepted for proceedings of 5th INTEGRAL Worksho

The F-GAMMA program: Multi-frequency study of Active Galactic Nuclei in the Fermi era. Program description and the first 2.5 years of monitoring

To fully exploit the scientific potential of the Fermi mission, we initiated the F-GAMMA program. Between 2007 and 2015 it was the prime provider of complementary multi-frequency monitoring in the radio regime. We quantify the radio variability of gamma-ray blazars. We investigate its dependence on source class and examine whether the radio variability is related to the gamma-ray loudness. Finally, we assess the validity of a putative correlation between the two bands. The F-GAMMA monitored monthly a sample of about 60 sources at up to twelve radio frequencies between 2.64 and 228.39 GHz. We perform a time series analysis on the first 2.5-year dataset to obtain variability parameters. A maximum likelihood analysis is used to assess the significance of a correlation between radio and gamma-ray fluxes. We present light curves and spectra (coherent within ten days) obtained with the Effelsberg 100-m and IRAM 30-m telescopes. All sources are variable across all frequency bands with amplitudes increasing with frequency up to rest frame frequencies of around 60 - 80 GHz as expected by shock-in-jet models. Compared to FSRQs, BL Lacs show systematically lower variability amplitudes, brightness temperatures and Doppler factors at lower frequencies, while the difference vanishes towards higher ones. The time scales appear similar for the two classes. The distribution of spectral indices appears flatter or more inverted at higher frequencies for BL Lacs. Evolving synchrotron self-absorbed components can naturally account for the observed spectral variability. We find that the Fermi-detected sources show larger variability amplitudes as well as brightness temperatures and Doppler factors, than non-detected ones. Flux densities at 86.2 and 142.3 GHz correlate with 1 GeV fluxes at a significance level better than 3sigma, implying that gamma rays are produced very close to the mm-band emission region.Comment: Accepted for publication in section 4. Extragalactic astronomy of Astronomy and Astrophysics (18 pages, 9 figures

A large spin-up rate measured with INTEGRAL in the High Mass X-ray Binary Pulsar SAXJ2103.5+4545

The High Mass X-ray Binary Pulsar SAXJ2103.5+4545 has been observed with INTEGRAL several times during the last outburst in 2002-2004. We report a comprehensive study of all INTEGRAL observations, allowing a study of the pulse period evolution during the recent outburst. We measured a very rapid spin-up episode, lasting 130days, which decreased the pulse period by 1.8s. The spin-up rate, pdot=-1.5e-7 s/s, is the largest ever measured for SAXJ2103.5+4545, and it is among the fastest for an accreting pulsar. The pulse profile shows evidence for temporal variability, apparently not related to the source flux or to the orbital phase. The X-ray spectrum is hard and there is significant emission up to 150keV. A new derivation of the orbital period, based on RXTE data, is also reported.Comment: 8 pages, 7 figures, accepted for publication in A&

Common Cerambycid Pheromone components as attractants for Longhorn Beetles (Cerambycidae) breeding in ephemeral oak substrates in Northern Europe

Longhorn beetles are ecologically important insects in forest ecosystems as decomposers of woody substrates, microhabitat engineers, and as components of forest food webs. These species can be greatly affected both positively and negatively by modern forestry management practices, and should be monitored accordingly. Through headspace sampling, coupled gas chromatography-electroantennography, gas chromatography-mass spectrometry, and field bioassays, we identified two compounds, 2-methyl-1-butanol and 3-hydroxy-2-hexanone, that constitute aggregation-sex pheromone attractants of three cerambycid species which breed primarily in different types of fresh, recently dead oak wood in Northern Europe: Pyrrhidium sanguineum (L.), Phymatodes alni ssp. alni (L.), and Phymatodes testaceus (L.) (Cerambycinae: Callidiini). Analyses of headspace volatiles collected from live insects indicated that the male-produced aggregation-sex pheromone of P. sanguineum is a 1–15:100 blend of (R)-2-methyl-1-butanol and (R)-3-hydroxy-2-hexanone, whereas the corresponding ratios for P. alni were 70–110:100. In field bioassays, adult P. sanguineum and P. alni were significantly attracted to multiple blends with varying ratios of the two compounds. When tested individually, the compounds were minimally attractive. In contrast, adult P. testaceus exhibited nonspecific attraction to both of the individual compounds and to different blends, despite the hydroxyketone not being part of its pheromone, which consists of (R)-2-methyl-1-butanol alone. Overall, our results suggest that a blend of 50:100 of racemic 2-methyl-1-butanol and 3-hydroxy-2-hexanone is appropriate for parallel, cost-efficient pheromone-based monitoring of all three species. In particular, these species could serve as useful indicators of how modern forestry practices affect a whole guild of saproxylic insects that require ephemeral deadwood substrates for successful breeding