The Gamma--Ray Burst catalog obtained with the Gamma Ray Burst Monitor aboard BeppoSAX

We report on the catalog of Gamma--Ray Bursts (GRBs) detected with the Gamma Ray Burst Monitor aboard the BeppoSAX satellite. It includes 1082 GRBs with 40--700 keV fluences in the range from $1.3\times 10^{-7}$ to $4.5\times 10^{-4}$ erg cm$^{-2}$, and with 40--700 keV peak fluxes from $3.7\times 10^{-8}$ to $7.0\times 10^{-5}$ erg cm$^{-2}$s$^{-1}$. We report in the catalog some relevant parameters of each GRB and discuss the derived statistical properties.Comment: 48 pages, 14 figures, 4 Tables. Accepted for publication in The Astrophysical Journal Supplemen

Repeatability of the European Standardized Method for Measuring Sound Reflection and Sound Insulation of Noise Barriers

The EN 1793-5 and EN 1793-6 standards have been in use for many years as a method for measuring the intrinsic characteristics of noise barriers installed along highways and railways. They require a sound source and a grid of microphones, to be placed near the barrier and in free field conditions, according to predetermined distances. In principle, small errors in positioning the sound source and microphone grid may affect the results obtained. An international round-robin test was carried out in 2012 to evaluate the repeatability and reproducibility of the method, but until now no studies have been carried out to evaluate and compare the repeatability of laboratory versus in-place measurements performed with the same equipment and its variance when an imperfect positioning of sound source and microphones is taken into account. In the present work, multiple series of sound reflection index and sound insulation index measurements performed on noise barriers of the same kind installed in the laboratory or along a highway are presented. The measurements were repeated in different ways: (1) in the laboratory, leaving the source and microphones unmoved to assess the repeatability of the results and of the measurement system under controlled conditions; (2) in the laboratory, repositioning for each measurement the source and microphone grid to assess the robustness of the method under real conditions but in a controlled environment; (3) in situ, along a highway open to traffic, repositioning for each measurement the source and microphone grid to assess the repeatability of the method under real conditions in a critical environment. In both reflection index and sound insulation index measurements, the standard deviation on single-number ratings in all cases examined is well below the value presented in EN 1793-5 and EN 1793-6, which was obtained from statistical analysis of the international round-robin test performed a dozen years ago, suggesting that expert operators with state-of-the art equipment can achieve much better results now

A Low-Cost System for Quick Measurements on Noise Barriers in Situ

This paper describes the development of a low-cost device for measuring the acoustic intrinsic characteristics of noise barriers. The system is based on the Teensy 4.1 microcontroller combined with a few other components. The measurements are carried out using a vertical linear microphone antenna housing 6 microphones and a lightweight loudspeaker, wireless connected to the main unit. Both the main system unit and the amplified loudspeaker are powered from normal 5 V USB battery packs, which are easily rechargeable and interchangeable. The system measures 6 impulse responses using an MLS signal and performs a series of calculations and frequency analyses to characterize the device under test, following a simplified version of the European standards EN 1793-5 and EN 1793-6 (commonly referred to as the ’Adrienne method’). One measurement takes few minutes, obtaining results comparable to those obtained with the Adrienne method, which requires a more complicated and heavy measuring equipment and is much more expensive and time consuming

SN/GRB connection: a statistical approach with BATSE and Asiago Catalogues

Recent observations suggest that some types of GRB are physically connected with SNe of type Ib/c. However, it has been pointed out by several authors that some GRBs could be associated also with other types of core-collapse SNe (type IIdw/IIn). On the basis of a comphrensive statistical study, which has made use of the BATSE and Asiago catalogues, we have found that: i) the temporal and spacial distribution of SNe-Ib/c is marginally correlated with that of the BATSE GRBs; ii) we do not confirm the existence of an association between GRBs and SNe-IIdw/IIn.Comment: Proceeding of the 4th workshop on Gamma Ray Bursts in the Afterglow Era, Rome, 2004; 4 page

Evidence for a long duration component in the prompt emission of short Gamma-Ray Bursts detected with BeppoSAX

A statistical study on the light curves of all the short Gamma-Ray Bursts detected with the Gamma Ray Burst Monitor (GRBM) aboard BeppoSAX is reported. Evidence for a very weak and long duration component associated with these events in the two 1 s counters of the GRBM (40-700 keV and >100 keV) is found. It starts a few tens of seconds before the burst and continues for about 30 s after the burst. The overall hardness of this component is comparable with that of the event itself. The detection of a signal before the onset time and the similar hardness are consistent with an interpretation of the long duration component in terms of prompt emission associated with short GRBs.Comment: 12 pages, 6 figures, accepted for publication in ApJ

A Burst and Simultaneous Short-Term Pulsed Flux Enhancement from the Magnetar Candidate 1E 1048.1-5937

We report on the 2004 June 29 burst detected from the direction of the Anomalous X-ray Pulsar (AXP) 1E 1048.1-5937 using the Rossi X-ray Timing Explorer (RXTE). We find a simultaneous increase of ~3.5 times the quiescent value in the 2-10 keV pulsed flux of 1E 1048.1-5937 during the tail of the burst which identifies the AXP as the burst's origin. The burst was overall very similar to the two others reported from the direction of this source in 2001. The unambiguous identification of 1E 1048.1-5937 as the burster here confirms it was the origin of the 2001 bursts as well. The epoch of the burst peak was very close to the arrival time of 1E 1048.1-5937's pulse peak. The burst exhibited significant spectral evolution with the trend going from hard to soft. During the 11 days following the burst, the AXP was observed further with RXTE, XMM-Newton and Chandra. Pre- and post-burst observations revealed no change in the total flux or spectrum of the quiescent emission. Comparing all three bursts detected thus far from this source we find that this event was the most fluent (>3.3x10^-8 erg/cm^2 in the 2-20 keV band), had the highest peak flux (59+/-9x10^-10 erg/s/cm^2 in the 2-20 keV band), and the longest duration (>699 s). The long duration of the burst differentiates it from Soft Gamma Repeater (SGR) bursts which have typical durations of ~0.1 s. Bursts that occur preferentially at pulse maximum, have fast-rises and long X-tails containing the majority of the total burst energy have been seen uniquely from AXPs. The marked differences between AXP and SGRs bursts may provide new clues to help understand the physical differences between these objects.Comment: 24 pages, 4 figures, submitted to the Astrophysical Journa

Constraints on the environment and energetics of the Broad-Line Ic SN2014ad from deep radio and X-ray observations

Broad-line type Ic Supernovae (BL-Ic SNe) are characterized by high ejecta velocity ($\gtrsim 10^4$ km s$^{-1}$) and are sometimes associated with the relativistic jets typical of long duration ($\gtrsim 2$ s) Gamma-Ray Bursts (L-GRBs). The reason why a small fraction of BL-Ic SNe harbor relativistic jets is not known. Here we present deep X-ray and radio observations of the BL-Ic SN2014ad extending from $13$ to $930$ days post explosion. SN2014ad was not detected at either frequency and has no observational evidence of a GRB counterpart. The proximity of SN2014ad ($d\sim 26$ Mpc) enables very deep constraints on the progenitor mass-loss rate $\dot{M}$ and on the total energy of the fast ejecta $E$. We consider two synchrotron emission scenarios for a wind-like circumstellar medium (CSM): (i) uncollimated non-relativistic ejecta, and (ii) off-axis relativistic jet. Within the first scenario our observations are consistent with GRB-less BL-Ic SNe characterized by a modest energy budget of their fast ejecta ($E \lesssim 10^{45}$ erg), like SNe 2002ap and 2010ay. For jetted explosions, we cannot rule out a GRB with $E \lesssim 10^{51}$ erg (beam-corrected) with a narrow opening angle ($\theta_j \sim 5^{\circ}$) observed moderately off-axis ($\theta_{\rm obs} \gtrsim 30^{\circ}$) and expanding in a very low CSM density ($\dot{M}$ $\lesssim 10^{-6}$ M$_{\odot}$ yr$^{-1}$). Our study shows that off-axis low-energy jets expanding in a low-density medium cannot be ruled out even in the most nearby BL-Ic SNe with extensive deep observations, and might be a common feature of BL-Ic SNe.Comment: 9 pages, 5 figures, accepted in Ap

Spectral catalogue of bright gamma-ray bursts detected with the BeppoSAX/GRBM

The emission process responsible for the so-called "prompt" emission of gamma-ray bursts is still unknown. A number of empirical models fitting the typical spectrum still lack a satisfactory interpretation. A few GRB spectral catalogues derived from past and present experiments are known in the literature and allow to tackle the issue of spectral properties of gamma-ray bursts on a statistical ground. We extracted and studied the time-integrated photon spectra of the 200 brightest GRBs observed with the Gamma-Ray Burst Monitor which flew aboard the BeppoSAX mission (1996-2002) to provide an independent statistical characterisation of GRB spectra. The spectra were fit with three models: a simple power-law, a cut-off power law or a Band function. The typical photon spectrum of a bright GRB consists of a low-energy index around 1.0 and a peak energy of the nuFnu spectrum E_p~240 keV in agreement with previous results on a sample of bright CGRO/BATSE bursts. Spectra of ~35% of GRBs can be fit with a power-law with a photon index around 2, indicative of peak energies either close to or outside the GRBM energy boundaries. We confirm the correlation between E_p and fluence, with a logarithmic dispersion of 0.13 around the power-law with index 0.21+-0.06. The low-energy and peak energy distributions are not yet explained in the current literature. The capability of measuring time-resolved spectra over a broadband energy range, ensuring precise measurements of parameters such as E_p, will be crucial for future experiments (abridged).Comment: 28 pages, 20 figures, 3 tables, accepted to A&

Broad band time-resolved E_{p,i}--L_{iso} correlation in GRBs

We report results of a systematic study of the broad band (2--2000 keV) time resolved prompt emission spectra of a sample of gamma-ray bursts (GRBs) detected with both Wide Field Cameras on board the \sax\ satellite and the \batse\ experiment on board CGRO. In this first paper, we study the time-resolved dependence of the intrinsic peak energy $E_{p,i}$ of the $E F(E)$ spectrum on the corresponding isotropic bolometric luminosity $L_{\rm iso}$. The $E_{p,i}$--$L_{\rm iso}$ relation or the equivalent relation between $E_{p,i}$ and the bolometric released energy $E_{iso}$, derived using the time averaged spectra of long GRBs with known redshift, is well established, but its physical origin is still a subject of discussion. In addition, some authors maintain that these relations are the result of instrumental selection effects. We find that not only a relation between the measured peak energy $E_p$ and the corresponding energy flux, but also a strong $E_{p,i}$ versus $L_{\rm iso}$ correlation are found within each burst and merging together the time resolved data points from different GRBs. We do not expect significant instrumental selection effects that can affect the obtained results, apart from the fact that the GRBs in our sample are sufficiently bright to perform a time-resolved spectroscopy and that they have known redshift. If the fundamental physical process that gives rise to the GRB phenomenon does not depend on its brightness, we conclude that the found $E_{p,i}$ versus $L_{\rm iso}$ correlation within each GRB is intrinsic to the emission process, and that the correlations discovered by Amati et al. and Yonetoku et al. are likely not the result of selection effects. We also discuss the properties of the correlations found.Comment: 27 pages,4 tables, 7 figure, accepted for publication in The Astrophysical Journa