Multiwavelength Evidence for Quasi-periodic Modulation in the Gamma-ray Blazar PG 1553+113

We report for the first time a gamma-ray and multi-wavelength nearly-periodic oscillation in an active galactic nucleus. Using the Fermi Large Area Telescope (LAT) we have discovered an apparent quasi-periodicity in the gamma-ray flux (E >100 MeV) from the GeV/TeV BL Lac object PG 1553+113. The marginal significance of the 2.18 +/-0.08 year-period gamma-ray cycle is strengthened by correlated oscillations observed in radio and optical fluxes, through data collected in the OVRO, Tuorla, KAIT, and CSS monitoring programs and Swift UVOT. The optical cycle appearing in ~10 years of data has a similar period, while the 15 GHz oscillation is less regular than seen in the other bands. Further long-term multi-wavelength monitoring of this blazar may discriminate among the possible explanations for this quasi-periodicity.Comment: 8 pages, 5 figures. Accepted to The Astrophysical Journal Letters. Corresponding authors: S. Ciprini (ASDC/INFN), S. Cutini (ASDC/INFN), S. Larsson (Stockholm Univ/KTH), A. Stamerra (INAF/SNS), D. J. Thompson (NASA GSFC

System for detecting and estimating concentrations of gas or liquid analytes

A sensor system for detecting and estimating concentrations of various gas or liquid analytes. In an embodiment, the resistances of a set of sensors are measured to provide a set of responses over time where the resistances are indicative of gas or liquid sorption, depending upon the sensors. A concentration vector for the analytes is estimated by satisfying a criterion of goodness using the set of responses. Other embodiments are described and claimed

Search for extended gamma-ray emission from the Virgo galaxy cluster with Fermi-LAT

Galaxy clusters are one of the prime sites to search for dark matter (DM) annihilation signals. Depending on the substructure of the DM halo of a galaxy cluster and the cross sections for DM annihilation channels, these signals might be detectable by the latest generation of $\gamma$-ray telescopes. Here we use three years of Fermi Large Area Telescope (LAT) data, which are the most suitable for searching for very extended emission in the vicinity of nearby Virgo galaxy cluster. Our analysis reveals statistically significant extended emission which can be well characterized by a uniformly emitting disk profile with a radius of 3\deg that moreover is offset from the cluster center. We demonstrate that the significance of this extended emission strongly depends on the adopted interstellar emission model (IEM) and is most likely an artifact of our incomplete description of the IEM in this region. We also search for and find new point source candidates in the region. We then derive conservative upper limits on the velocity-averaged DM pair annihilation cross section from Virgo. We take into account the potential $\gamma$-ray flux enhancement due to DM sub-halos and its complex morphology as a merging cluster. For DM annihilating into $b\overline{b}$, assuming a conservative sub-halo model setup, we find limits that are between 1 and 1.5 orders of magnitude above the expectation from the thermal cross section for $m_{\mathrm{DM}}\lesssim100\,\mathrm{GeV}$. In a more optimistic scenario, we exclude $\langle \sigma v \rangle\sim3\times10^{-26}\,\mathrm{cm^{3}\,s^{-1}}$ for $m_{\mathrm{DM}}\lesssim40\,\mathrm{GeV}$ for the same channel. Finally, we derive upper limits on the $\gamma$-ray-flux produced by hadronic cosmic-ray interactions in the inter cluster medium. We find that the volume-averaged cosmic-ray-to-thermal pressure ratio is less than $\sim6\%$.Comment: 15 pages, 11 figures, 4 tables, accepted for publication in ApJ; corresponding authors: T. Jogler, S. Zimmer & A. Pinzk

DEEP MORPHOLOGICAL and SPECTRAL STUDY of the SNR RCW 86 with FERMI-LAT

RCW 86 is a young supernova remnant (SNR) showing a shell-type structure at several wavelengths and is thought to be an efficient cosmic-ray (CR) accelerator. Earlier \textit{Fermi} Large Area Telescope results reported the detection of $\gamma$-ray emission coincident with the position of RCW 86 but its origin (leptonic or hadronic) remained unclear due to the poor statistics. Thanks to 6.5 years of data acquired by the \textit{Fermi}-LAT and the new event reconstruction Pass 8, we report the significant detection of spatially extended emission coming from RCW 86. The spectrum is described by a power-law function with a very hard photon index ($\Gamma = 1.42 \pm 0.1_{\rm stat} \pm 0.06_{\rm syst}$) in the 0.1--500 GeV range and an energy flux above 100 MeV of ($2.91$ $\pm$ $0.8_{\rm stat}$ $\pm$ $0.12_{\rm syst}$) $\times$ $10^{-11}$ erg cm$^{-2}$ s$^{-1}$. Gathering all the available multiwavelength (MWL) data, we perform a broadband modeling of the nonthermal emission of RCW 86 to constrain parameters of the nearby medium and bring new hints about the origin of the $\gamma$-ray emission. For the whole SNR, the modeling favors a leptonic scenario in the framework of a two-zone model with an average magnetic field of 10.2 $\pm$ 0.7 $\mu$G and a limit on the maximum energy injected into protons of 2 $\times$ 10$^{49}$ erg for a density of 1 cm$^{-3}$. In addition, parameter values are derived for the North-East (NE) and South-West (SW) regions of RCW 86, providing the first indication of a higher magnetic field in the SW region.The Fermi LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l’Energie Atomique and the Centre National de la Recherche Scientifique / Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d’Études Spatiales in France. GD and EG are members of CIC-CONICET (Argentina), LD is Fellow of CONICET (Argentina). They are supported through grants from CONICET and ANPCyT (Argentina). We acknowledge to Estela Reynoso and Anne Green who collaborated in the first stages of the HI data acquisition and preocessing.This is the author accepted manuscript. It first appeared from the Institute of Physics via http://dx.doi.org/10.3847/0004-637X/819/2/9

Localization and Broadband Follow-Up of the Gravitational-Wave Transient GW150914

A gravitational-wave (GW) transient was identified in data recorded by the Advanced Laser InterferometerGravitational-wave Observatory (LIGO) detectors on 2015 September 14. The event, initially designated G184098and later given the name GW150914, is described in detail elsewhere. By prior arrangement, preliminary estimatesof the time, significance, and sky location of the event were shared with 63 teams of observers covering radio,optical, near-infrared, X-ray, and gamma-ray wavelengths with ground- and space-based facilities. In this Letter wedescribe the low-latency analysis of the GW data and present the sky localization of the first observed compactbinary merger. We summarize the follow-up observations reported by 25 teams via private Gamma-rayCoordinates Network circulars, giving an overview of the participating facilities, the GW sky localizationcoverage, the timeline, and depth of the observations. As this event turned out to be a binary black hole merger,there is little expectation of a detectable electromagnetic (EM) signature. Nevertheless, this first broadbandcampaign to search for a counterpart of an Advanced LIGO source represents a milestone and highlights the broadcapabilities of the transient astronomy community and the observing strategies that have been developed to pursueneutron star binary merger events. Detailed investigations of the EM data and results of the EM follow-upcampaign are being disseminated in papers by the individual teams

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Insights into the mode of action of tannin-based feed additives in broiler chickens: looking for connections with the plasma metabolome and caecal microbiota

This study assessed the effects of three tannin-based feed additives on the productive performance, foot-pad conditions, plasma metabolome, and caecal microbiota of meat-type chickens. A total of 2,340 male broilers were divided into 4 treatments (9 replicates each) fed either a commercial basal diet (CON) or the basal diet supplemented with one of the three tested products (A, B, or C) up to 49 days. According to manufacturers\u2019 instructions, product A was added to the basal diet at 0.3% from 0 to 49 d, while B and C at 0.13% from 0 to 21 d and 0.12% from 22 to 49 d. Compared to CON, tannin-supplemented birds consumed less feed (6.59 vs. 6.37, 6.49, and 6.35 kg, for CON vs. A, B, and C, respectively; p <.001) and reached a lower slaughter weight (3,599 vs. 3,494, 3,546, and 3,472 g, for CON vs. A, B, and C, respectively; p <.05). Feed conversion ratio (FCR) was not affected by the tannin supplementations, except for the starter phase when CON exhibited lower FCR than the other groups (p <.01). The observed differences in the plasma metabolome between CON and treated groups might indicate an impaired energy metabolism of tannin-supplemented chickens. The significant reduction in the caecal microbial diversity and short-chain fatty acid producer bacteria can also be related to the depressed performance of tannin-fed chickens. In contrast to earlier findings, pododermatitis was unaffected by our treatments. Further dose-response studies can help better exploit tannin-based additives in broiler diets

The Imaging X-ray Polarimetry Explorer (IXPE): Technical Overview

The Imaging X-ray Polarimetry Explorer (IXPE) will expand the information space for study of cosmic sources, by adding linear polarization to the properties (time, energy, and position) observed in x-ray astronomy. Selected in 2017 January as a NASA Astrophysics Small Explorer (SMEX) mission, IXPE will be launched into an equatorial orbit in 2021. The IXPE mission will provide scientifically meaningful measurements of the x-ray polarization of a few dozen sources in the 2-8 keV band, including polarization maps of several x-ray-bright extended sources and phase-resolved polarimetry of many bright pulsating x-ray sources

Phosphorus supply affects zinc uptake in wheat plant

La contribución de los flujos unidireccionales de zinc (Zn) a la absorción neta de este catión divalente fue estudiada en plantas de trigo (Triticum aestivum L.) cultivadas en hidroponia con dos niveles de fósforo (0,05 y 5 mol P. m-3). Los resultados obtenidos muestran que, en niveles de P y Zn no limitantes del crecimiento, tanto la absorción como el transporte neto de Zn al vástago se incrementaron al aumentar la concentración externa de P. La mayor absorción neta de Zn en el suministro más alto de P fue atribuido al aumento del influjo, junto con un descenso del cociente eflujo:influjo. Estos resultados muestran que el nivel de suministro de P es capaz de modular ambos flujos unidireccionales de Zn. Por otro lado, el seguimiento del influjo de Zn, tras cambiar la concentración externa de P desde 5 a 0,05 mol m-3 de P, y viceversa, puso en evidencia un patrón consistente con la idea de que el flujo de entrada de Zn es modulado por el fósforo presente en las raíces. Se discute la posibilidad de que la fracción de P acumulada en el citoplasma radical sea la responsable de esta forma de regulación, en condiciones de suministro óptimo de ambos nutrientes.The effect of phosphorus (P) supply on net uptake and unidirectional zinc (Zn) fluxes was studied in 21 day old wheat plants (Triticum aestivum L.) grown in nutrient solution. The supply both P and Zn were in the range in which did not limit plant growth. The higher the level of P supply the higher both net Zn uptake and net Zn translocation to the shoot. The enhanced net uptake of Zn at 5 mol m-3 P relative to that measured at 0.05 mol m-3 P, was due to a higher Zn-influx added to a lower ratio between the efflux and influx of Zn. Thus, our results showed that the level of P supply modulats the long term regulation of both unidirectional Zn-fluxes. The short term response of Zn-influx when changing the external level of P supply from 5 to 0.05 mol. m-3, and vice versa, is consistent with the idea that an endogenous effect of P is involved in such a regulation. The possibility is discussed of P-concentration in root cytoplasm modulating Zn-influx in plants with supraoptimum P and Zn supplies.Universidad Nacional de La Plata (UNLP) - Facultad de Ciencias Agrarias y Forestales (FCAF