Evidence for proton acceleration up to TeV energies based on VERITAS and Fermi-LAT observations of the Cas A SNR

We present a study of $\gamma$-ray emission from the core-collapse supernova remnant Cas~A in the energy range from 0.1GeV to 10TeV. We used 65 hours of VERITAS data to cover 200 GeV - 10 TeV, and 10.8 years of \textit{Fermi}-LAT data to cover 0.1-500 GeV. The spectral analysis of \textit{Fermi}-LAT data shows a significant spectral curvature around $1.3 \pm 0.4_{stat}$ GeV that is consistent with the expected spectrum from pion decay. Above this energy, the joint spectrum from \textit{Fermi}-LAT and VERITAS deviates significantly from a simple power-law, and is best described by a power-law with spectral index of $2.17\pm 0.02_{stat}$ with a cut-off energy of $2.3 \pm 0.5_{stat}$ TeV. These results, along with radio, X-ray and $\gamma$-ray data, are interpreted in the context of leptonic and hadronic models. Assuming a one-zone model, we exclude a purely leptonic scenario and conclude that proton acceleration up to at least 6 TeV is required to explain the observed $\gamma$-ray spectrum. From modeling of the entire multi-wavelength spectrum, a minimum magnetic field inside the remnant of $B_{\mathrm{min}}\approx150\,\mathrm{\mu G}$ is deduced.Comment: 33 pages, 9 Figures, 6 Table

Direct measurement of stellar angular diameters by the VERITAS Cherenkov Telescopes

The angular size of a star is a critical factor in determining its basic properties. Direct measurement of stellar angular diameters is difficult: at interstellar distances stars are generally too small to resolve by any individual imaging telescope. This fundamental limitation can be overcome by studying the diffraction pattern in the shadow cast when an asteroid occults a star, but only when the photometric uncertainty is smaller than the noise added by atmospheric scintillation. Atmospheric Cherenkov telescopes used for particle astrophysics observations have not generally been exploited for optical astronomy due to the modest optical quality of the mirror surface. However, their large mirror area makes them well suited for such high-time-resolution precision photometry measurements. Here we report two occultations of stars observed by the VERITAS Cherenkov telescopes with millisecond sampling, from which we are able to provide a direct measurement of the occulted stars' angular diameter at the $\leq0.1$ milliarcsecond scale. This is a resolution never achieved before with optical measurements and represents an order of magnitude improvement over the equivalent lunar occultation method. We compare the resulting stellar radius with empirically derived estimates from temperature and brightness measurements, confirming the latter can be biased for stars with ambiguous stellar classifications.Comment: Accepted for publication in Nature Astronom

Single-agent gemcitabine in pretreated patients with non-small-cell lung cancer: results of an Argentinean multicentre phase II trial

The activity and mild toxicity profile of single-agent gemcitabine therapy in untreated (chemonaive) patients with non-small-cell lung cancer (NSCLC) is well documented. This phase II trial was conducted to determine the objective tumour response rate and toxicity profile of single-agent gemcitabine in pretreated patients with NSCLC. Patients with histological evidence of advanced NCSLC stage IIIB or IV; at least one prior chemotherapy regimen including a platinum or taxane analogue; an Eastern Cooperative Oncology Group (ECOG) performance status of 0–2; clinically measurable disease; adequate bone marrow reserve; and adequate renal function; received 1000 mg m–2 gemcitabine administered over 30 min on days 1, 8 and 15 of a 28-day cycle defined as 3 weekly treatments followed by 1 week of rest. Twenty-nine patients were evaluated for efficacy and 32 for toxicity. One patient achieved a complete response and five patients had a partial response resulting in a total response rate of 20.6% (95% confidence interval (CI) 6–34). Median response duration was 7 months (range 4–11 months). Twelve (41%) patients reached stable disease after two cycles of therapy and 11 (38%) patients had disease progression. Median progression-free survival time was 3 months and median overall survival time was 5.5 months. Toxicity was generally mild (grades 0–2). Severe (grade 3 or 4) haematological toxicities included grade 3 anaemia in one patient and grade 3 thrombocytopenia in two patients. Severe non-haematological toxicities included one patient each with grade 3 liver transaminase elevations, nausea/vomiting and diarrhoea. This study confirms the activity and safety of single-agent gemcitabine in pretreated patients with advanced NSCLC who are refractory or sensitive to first-line therapy. © 1999 Cancer Research Campaig

Presencia de enfermedades en majadas caprinas de las quebradas áridas de Jujuy y Salta

Una encuesta transversal ad hoc se llevó a cabo en 40 unidades productoras familiares (UPF) de las áridas en las provincias de Jujuy y Salta, con el objetivo de describir la presencia de enfermedades en sus majadas caprinas. Se recabaron datos del manejo general y sanitario en particular. Se procesaron sueros para el diagnóstico de brucelosis por las pruebas tamiz del antígeno bufferado en placa (BPA) y confirmadas por polarización fluorecente (FPA), para paratuberculosis (PTBC), artritis-encefalitis (CAEV), chlamydiosis, herpesvirus caprino tipo 1 (CaHV-1), fiebre Q y toxoplasmosis se utilizó ELISA indirecto y para leptospirosis microaglutinación. Se determinaron los valores de Cu2+, Zn2+, Mg2+ y Ca2+ sérico por espectofotómetría de absorción atómica. En heces, se realizó el recuento de huevos de helmintos por gramo (hpg) y la diferenciación de géneros por coprocultivo.Las UPF tuvieron en promedio 91,4±75 caprinos (sin contar cabritos), siendo el 80,9% cabras madres. La cría fue extensiva con encierre nocturno y la alimentación de la majada se basó mayormente en el pastoreo de los cerros y de cultivos y rastrojos. La parición se concentró en dos períodos, uno principal en abril-julio y una segunda parición de menor número de cabras ubicada en octubre-diciembre. El 92,3% de los productores desparasitaba en forma rutinaria toda la majada con ivermectina, albendazole o closantel y el 71,8 % trataba los piojos. En un 61,5% de las UPF se inyectaba mineralizantes-vitamínicos a toda la majada y en solo un 15,4% se vacunaba contra enfermedades clostridiales. El promedio de la tasa de mortalidad anual por majada fue del 14,2±11%. En el 86,4% de las UPF se registró la ocurrencia de abortos, y de estos el 42,9% presentó retención de placenta. El promedio intramajada de abortos comunicados fue del 8,6±8,5%. El 75% de las UPF declaró tener ectima contagioso, aunque solo el 22% dijo que era grave. Se registraron un 30,4% cuadros de muertes agudas probablemente por infecciones clostridiales. En el 72,7% de las UPF se registraron problemas de mastitis. El porcentaje de UPF con seroprevalencia positiva a brucelosis, leptospirosis, paratuberculosis, toxoplasmosis, clamidiosis, CpHV-1, CAEV y fiebre Q fue respectivamente de 0%, 25%, 50%, 42,8%, 88,8%, 85,7%, 12,5% y 0%. Las UPF destacaron la importancia de los piojos (Linognathus spp.: 87%). Los promedios de los hpg fueron en abril-mayo, julio-agosto y septiembre-noviembre respectivamente de 407, 332 y 59 con Haemonchus y en menor medida Trichostrongylus como nematodes predominantes. En el 76% de las UPF se diagnosticó Fasciolosis. El 30,8% de las UPF describió la presencia a la faena de quistes hidatídicos. En un 31% de las majadas se describió bocio. Los promedios por UPF de cobre, zinc, magnesio y calcio séricos fueron respectivamente 0,48 ±0,10 ppm, 0,73±0,16 ppm, 2,4±0,47mg/d y 7,25±2,25 mg/dl. Se describieron casos de timpanismo espumoso (43,5%), muertes (36%) atribuidas por los propietarios a la ingesta de ñusco, mio mio y sunchillo y un 38,1% de las UPF dijeron padecer casos de intoxicación con cegadera (Heterophyllaea pustulata). Un 66,7% de los propietarios declararon tener problemas de pérdidas de animales en el monte a causa mayormente de pumas. Estos primeros resultados en cuanto a mortandad y presencia de enfermedades y zoonosis, muestran la importancia de llevar a cabo estudios más específicos respecto de la salud de las majadas para incrementar la producción y el bienestar general de las familias productoras.Fil: Suarez, V. H.. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Dodero, Ana Mariela. Instituto Nacional de Tecnología Agropecuaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Nievas, J. D.. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Martinez, G. M.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Salta-Jujuy. Estación Experimental Agropecuaria Salta; ArgentinaFil: Bertoni, E. A.. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Salatin, A. O.. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Viñabal, A. E.. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Grossberger, G.. No especifíca;Fil: Brihuega, Bibiana. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas; ArgentinaFil: Romera, Sonia. Instituto Nacional de Tecnología Agropecuaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pinto, G.. Instituto Nacional de Tecnología Agropecuaria; Argentin

Long-term multi-wavelength variability and correlation study of Markarian 421 from 2007 to 2009

We study the multi-band variability and correlations of the TeV blazar Mrk 421 on year time scales, which can bring additional insight on the processes responsible for its broadband emission. We observed Mrk 421 in the very high energy (VHE) gamma-ray range with the Cherenkov telescope MAGIC-I from March 2007 to June 2009 for a total of 96 hours of effective time after quality cuts. The VHE flux variability is quantified with several methods, including the Bayesian Block algorithm, which is applied to data from Cherenkov telescopes for the first time. The 2.3 year long MAGIC light curve is complemented with data from the Swift/BAT and RXTE/ASM satellites and the KVA, GASP-WEBT, OVRO, and Mets\"ahovi telescopes from February 2007 to July 2009, allowing for an excellent characterisation of the multi-band variability and correlations over year time scales. Mrk 421 was found in different gamma-ray emission states during the 2.3 year long observation period. Flares and different levels of variability in the gamma-ray light curve could be identified with the Bayesian Block algorithm. The same behaviour of a quiet and active emission was found in the X-ray light curves measured by Swift/BAT and the RXTE/ASM, with a direct correlation in time. The behaviour of the optical light curve of GASP-WEBT and the radio light curves by OVRO and Mets\"ahovi are different as they show no coincident features with the higher energetic light curves and a less variable emission. The fractional variability is overall increasing with energy. The comparable variability in the X-ray and VHE bands and their direct correlation during both high- and low-activity periods spanning many months show that the electron populations radiating the X-ray and gamma-ray photons are either the same, as expected in the Synchrotron-Self-Compton mechanism, or at least strongly correlated, as expected in electromagnetic cascades.Comment: Corresponding authors: Ann-Kristin Overkemping ([email protected]), Marina Manganaro ([email protected]), Diego Tescaro ([email protected]), To be published in Astronomy&Astrophysics (A&A), 12 pages, 9 figure

MAGIC detection of short-term variability of the high-peaked BL Lac object 1ES 0806+524

The high-frequency-peaked BL Lac (HBL) 1ES 0806+524 (z = 0.138) was discovered in VHE $\gamma$ rays in 2008. Until now, the broad-band spectrum of 1ES 0806+524 has been only poorly characterized, in particular at high energies. We analysed multiwavelength observations from $\gamma$ rays to radio performed from 2011 January to March, which were triggered by the high activity detected at optical frequencies. These observations constitute the most precise determination of the broad-band emission of 1ES 0806+524 to date. The stereoscopic MAGIC observations yielded a $\gamma$-ray signal above 250 GeV of $(3.7 \pm 0.7)$ per cent of the Crab Nebula flux with a statistical significance of 9.9 $\sigma$. The multiwavelength observations showed significant variability in essentially all energy bands, including a VHE $\gamma$-ray flare that lasted less than one night, which provided unprecedented evidence for short-term variability in 1ES 0806+524. The spectrum of this flare is well described by a power law with a photon index of $2.97 \pm 0.29$ between $\sim$150 GeV and 1 TeV and an integral flux of $(9.3 \pm 1.9)$ per cent of the Crab Nebula flux above 250 GeV. The spectrum during the non-flaring VHE activity is compatible with the only available VHE observation performed in 2008 with VERITAS when the source was in a low optical state. The broad-band spectral energy distribution can be described with a one-zone Synchrotron Self Compton model with parameters typical for HBLs, indicating that 1ES 0806+524 is not substantially different from the HBLs previously detected.Comment: 12 pages, 8 figures, 3 tables, accepted 2015 April 20 for publication in Monthly Notices of the Royal Astronomical Society Main Journa

Limits to dark matter annihilation cross-section from a combined analysis of MAGIC and Fermi-LAT observations of dwarf satellite galaxies

We present the first joint analysis of gamma-ray data from the MAGIC Cherenkov telescopes and the Fermi Large Area Telescope (LAT) to search for gamma-ray signals from dark matter annihilation in dwarf satellite galaxies. We combine 158 hours of Segue 1 observations with MAGIC with 6-year observations of 15 dwarf satellite galaxies by the Fermi-LAT. We obtain limits on the annihilation cross-section for dark matter particle masses between 10 GeV and 100 TeV - the widest mass range ever explored by a single gamma-ray analysis. These limits improve on previously published Fermi-LAT and MAGIC results by up to a factor of two at certain masses. Our new inclusive analysis approach is completely generic and can be used to perform a global, sensitivity-optimized dark matter search by combining data from present and future gamma-ray and neutrino detectors.Comment: 19 pages, 3 figures. V2: Few typos corrected and references added. Matches published version JCAP 02 (2016) 03

Investigating the peculiar emission from the new VHE gamma-ray source H1722+119

The MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes observed the BL Lac object H1722+119 (redshift unknown) for six consecutive nights between 2013 May 17 and 22, for a total of 12.5 h. The observations were triggered by high activity in the optical band measured by the KVA (Kungliga Vetenskapsakademien) telescope. The source was for the first time detected in the very high energy (VHE, $E > 100$ GeV) $\gamma$-ray band with a statistical significance of 5.9 $\sigma$. The integral flux above 150 GeV is estimated to be $(2.0\pm 0.5)$ per cent of the Crab Nebula flux. We used contemporaneous high energy (HE, 100 MeV $< E < 100$ GeV) $\gamma$-ray observations from Fermi-LAT (Large Area Telescope) to estimate the redshift of the source. Within the framework of the current extragalactic background light models, we estimate the redshift to be $z = 0.34 \pm 0.15$. Additionally, we used contemporaneous X-ray to radio data collected by the instruments on board the Swift satellite, the KVA, and the OVRO (Owens Valley Radio Observatory) telescope to study multifrequency characteristics of the source. We found no significant temporal variability of the flux in the HE and VHE bands. The flux in the optical and radio wavebands, on the other hand, did vary with different patterns. The spectral energy distribution (SED) of H1722+119 shows surprising behaviour in the $\sim 3\times10^{14} - 10^{18}$ Hz frequency range. It can be modelled using an inhomogeneous helical jet synchrotron self-Compton model.Comment: 12 pages, 5 figures, 2 table

Multi-Wavelength Observations of the Blazar 1ES 1011+496 in Spring 2008

The BL Lac object 1ES 1011+496 was discovered at Very High Energy gamma-rays by MAGIC in spring 2007. Before that the source was little studied in different wavelengths. Therefore a multi-wavelength (MWL) campaign was organized in spring 2008. Along MAGIC, the MWL campaign included the Metsahovi radio observatory, Bell and KVA optical telescopes and the Swift and AGILE satellites. MAGIC observations span from March to May, 2008 for a total of 27.9 hours, of which 19.4 hours remained after quality cuts. The light curve showed no significant variability. The differential VHE spectrum could be described with a power-law function. Both results were similar to those obtained during the discovery. Swift XRT observations revealed an X-ray flare, characterized by a harder when brighter trend, as is typical for high synchrotron peak BL Lac objects (HBL). Strong optical variability was found during the campaign, but no conclusion on the connection between the optical and VHE gamma-ray bands could be drawn. The contemporaneous SED shows a synchrotron dominated source, unlike concluded in previous work based on nonsimultaneous data, and is well described by a standard one zone synchrotron self Compton model. We also performed a study on the source classification. While the optical and X-ray data taken during our campaign show typical characteristics of an HBL, we suggest, based on archival data, that 1ES 1011+496 is actually a borderline case between intermediate and high synchrotron peak frequency BL Lac objects.Comment: 13 pages, accepted for publication in MNRA