Optical and infrared photometry of the blazar PKS0537-441

We present a large collection of photometric data on the Blazar PKS 0537-441 in the VRIJHK bands taken in 2004-2009. At least three flare-like episodes with months duration, and >3 mag amplitude are apparent. The spectral energy distribution is consistent with a power law, and no indication of a thermal component is found. We searched for short time scale variability, and an interesting event was identified in the J band, with a duration of ~25 minutes.Comment: 10 pages, 3 figures, in press in ApJ

Gain variations as induced by the diffuse night sky background: the ASTRI-Horn experience

ASTRI-Horn is the prototype of the nine telescopes that form the ASTRI Mini-Array, under construction at the Teide Observatory in Spain, devoted to observe the sky above 10 TeV. It adopts an innovative optical design based on a dual-mirror Schwarzschild-Couder configuration, and the camera, composed by a matrix of monolithic multipixel silicon photomultipliers (SiPMs) is managed by ad-hoc tailored front-end electronics based on a peak-detector operation mode. During the Crab Nebula campaign in 2018-2019, ASTRI-Horn was affected by gain variations induced by high levels of night sky background. This paper reports the work performed to detect and quantify the effects of these gain variations in shower images. The analysis requested the use of simultaneous observations of the night sky background flux in the wavelength band 300-650 nm performed with the auxiliary instrument UVscope, a calibrated multi-anode photomultiplier working in single counting mode. As results, a maximum gain reduction of 15% was obtained, in agreement with the value previously computed from the variance of the background level in each image. This ASTRI-Horn gain reduction was caused by current limitation of the voltage supply. The analysis presented in this paper provides a method to evaluate possible variations in the nominal response of SiPMs when scientific observations are performed in the presence of high night sky background as in dark or gray conditions.Comment: 14 pages, 8 figures -- Submitted to Journal of Instrumentation (JINST) peer review on 10 November 202

Muon calibration of the ASTRI-Horn telescope: preliminary results

Astri-Horn is a Small-Sized Telescope (SST) for very-high energy gamma-ray astronomy installed in Italy at the INAF "M.C. Fracastoro" observing station (Mt. Etna, Sicily). The ASTRI-Horn telescope is characterized by a dual-mirror optical system and a curved focal surface covered by SiPM sensors managed by a innovative fast front-end electronics. Dedicated studies were performed to verify the feasibility of the calibration through muons on the relatively small size of the primary mirror (~4 m diameter), as in the case of larger Cherenkov telescopes. A number of tests were performed using simulations of the atmospheric showers with the CORSIKA package and of the telescope response with a dedicated simulator. In this contribution we present a preliminary analysis of muon events detected by ASTRI-Horn during the regular scientific data taking performed in December 2018 and March 2019. These muon events validate the results obtained with the simulations and definitively confirm the feasibility of calibrating the ASTRI-Horn SST telescope with muons.Comment: Proceedings of the 36th International Cosmic Ray Conference, Madison, Wisconsin, USA, 24 July-1 August 201

A randomized phase II study comparing sequential versus simultaneous chemo-radiotherapy in patients with unresectable locally advanced squamous cell cancer of the head and neck

Background: Single-modality radiotherapy is still considered standard treatment for patients with locally advanced unresectable cancer of the head and neck. As treatment outcome is poor, attempts to integrate chemotherapy into the overall management of these patients are ongoing. Patients and methods: A randomized study was undertaken to compare a sequential with a simultaneous chemoradiotherapy program. Between February 1986 and February 1991, 93 eligible patients with locally advanced unresectable cancer of the head and neck were stratified by WHO PS, T and N class and primary site and then randomized to receive either three courses of neoadjuvant chemotherapy with cisplatin (100 mg/m2 i.v. d 1) and 5-fluorouracil 1000 mg/m2/days 1-5 by continuous i.v. infusion every 3 weeks prior to definitive conventional radiotherapy of 65-70 Gy (sequential treatment), or cisplatin 100 mg/m2 on days 1, 22, 43 given simultaneously for the duration of the same conventional radiotherapy (simultaneous treatment). Results: At the end of the entire treatment 18 complete responses (47%) in the sequential-treatment arm and 18 (41%) in the simultaneous treatment arm were obtained. No statistically significant differences in the 5-yr progression-free survival, in the median time to loco-regional and distant progression and in the 5-yr overall survival were observed. Leukopenia was more frequent in the simultaneous than in the sequential arm (p = 0.03), whereas alopecia (p = 0.008) and phlebitis (p < 0.0001) were more frequent in the sequential-treatment arm. A better compliance was associated with the concomitant treatment, with 87% of the patients completing the entire radiotherapy program versus 63% of those in the sequential arm (p = 0.01). Conclusions: In the present study, the two treatment arms showed similar activity (complete response, progression-free and overall survival rates). Compliance to treatment was better in the concomitant arm. These data suggest that concomitant chemo-radiation therapy might be considered an option in unresectable locally advanced cancer of the head and neck. Phase III studies are needed in order to establish the superiority of this combination of cisplatin and radiotherapy versus radiotherapy alone

UVscope and its application aboard the ASTRI-Horn telescope

UVscope is an instrument, based on a multi-pixel photon detector, developed to support experimental activities for high-energy astrophysics and cosmic ray research. The instrument, working in single photon counting mode, is designed to directly measure light flux in the wavelengths range 300-650~nm. The instrument can be used in a wide field of applications where the knowledge of the nocturnal environmental luminosity is required. Currently, one UVscope instrument is allocated onto the external structure of the ASTRI-Horn Cherenkov telescope devoted to the gamma-ray astronomy at very high energies. Being co-aligned with the ASTRI-Horn camera axis, UVscope can measure the diffuse emission of the night sky background simultaneously with the ASTRI-Horn camera, without any interference with the main telescope data taking procedures. UVscope is properly calibrated and it is used as an independent reference instrument for test and diagnostic of the novel ASTRI-Horn telescope.Comment: Published (Open Access) in "Experimental Astronomy

Expected performance of the ASTRI-SST-2M telescope prototype

ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) is an Italian flagship project pursued by INAF (Istituto Nazionale di Astrofisica) strictly linked to the development of the Cherenkov Telescope Array, CTA. Primary goal of the ASTRI program is the design and production of an end-to-end prototype of a Small Size Telescope for the CTA sub-array devoted to the highest gamma-ray energy region. The prototype, named ASTRI SST-2M, will be tested on field in Italy during 2014. This telescope will be the first Cherenkov telescope adopting the double reflection layout in a Schwarzschild-Couder configuration with a tessellated primary mirror and a monolithic secondary mirror. The collected light will be focused on a compact and light-weight camera based on silicon photo-multipliers covering a 9.6 deg full field of view. Detailed Monte Carlo simulations have been performed to estimate the performance of the planned telescope. The results regarding its energy threshold, sensitivity and angular resolution are shown and discussed.Comment: In Proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at arXiv:1307.223