GeV Emission in the Region of the Supernova Remnant G51.26+0.11

The supernova remnant G51.26+0.11 was recently discovered and little is known about its properties and environment. Using data from the Fermi Large Area Telescope we study the GeV emission seen in the direction of G51.26+0.11 to constrain the origin of the gamma rays and their possible relation to this supernova remnant or to a star-forming region. We also search for emission from molecular gas in the region that could provide dense material for the production of gamma rays. By modeling the multiwavelength spectrum of G51.26+0.11 from radio to gamma rays we derive the properties of the particle populations that could produce the emission in several possible scenarios. We rule out the star-forming regions (such as G051.010+00.060) seen nearby as the origin of the GeV emission. The correspondence seen between the gamma-ray and radio morphologies supports a scenario in which G51.26+0.11 is the cause of the gamma rays. The flat spectral energy distribution observed at GeV energies is best fit by hadronic or inverse Compton emission, while a bremsstrahlung model cannot properly account for the radio fluxes under a simple one-zone scenario. A pulsar wind nebula origin of the high-energy photons cannot be ruled out or confirmed.Universidad de Costa Rica/[112-B8-267]/UCR/Costa RicaNational Science Foundation/[AST-9800334]/NSF/Estados UnidosNational Science Foundation/[AST-0098562]/NSF/Estados UnidosNational Science Foundation/[AST-0100793]/NSF/Estados UnidosNational Science Foundation/[AST-0228993]/NSF/Estados UnidosNational Science Foundation/[AST-0507657]/NSF/Estados UnidosUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Físic

Fermi-LAT detection of G118.4+37.0: a supernova remnant in the Galactic halo seen around the Calvera pulsar

The discovery of a non-thermal radio ring of low surface brightness about one degree in diameter has been recently reported around the location in the sky of the Calvera pulsar, at a high Galactic latitude. The radio properties point to it likely being a new supernova remnant (SNR), G118.4+37.0. We report an analysis of almost 14 yr of observations of this region by the γ-ray Large Area Telescope onboard the Fermi satellite. We detect extended GeV emission consistent with the size and location of the radio source, which confirms the presence of relativistic particles. The spectrum of the high-energy emission is fully compatible with an origin in the same relativistic particles producing the radio emission. These features and its similarities to other isolated SNRs establish this source as the remnant of a supernova. A simple model of the non-thermal emission from radio to GeV energies resulting from leptonic emission from electrons produced by the SNR is presented. G118.4+37.0 and other similar isolated remnants could be part of a radio-dim SNR population evolving in low density environments showing hard GeV emission of leptonic origin. Future deeper surveys in radio and γ-rays could discover new members of the group.Universidad de Costa Rica/[112-B8-267]/UCR/Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Físic

Non-thermal emission from young supernova remnants: Implications on cosmic ray acceleration

For a long time, supernova remnants have been thought to constitute the main source of galactic cosmic rays. Plausible mechanisms have been proposed through which these objects would be able to transfer some of their energy to charged particles. Detailed studies of SNRs, particularly allowed by the spectral and spatial resolution obtained with telescopes such as the Chandra X-Ray Observatory, have permitted us to understand some of the properties of high-energy particles within these objects and their interactions with their environment. In the first part of this work, the basic concepts of particle acceleration in SNRs are outlined, and the main observational tools available today for studying high-energy phenomena in astrophysics are mentioned briefly. In the second part, a study of non-thermal emission from the young SNR Cassiopeia A is presented. Through the use of a very deep one million-second Chandra observation of this remnant, the spectral evolution across non-thermal filaments near the forward shock was studied. A consistent hardening of the spectrum towards the exterior of the remnant was found and explained via a model developed that takes into account particle diffusion, plasma advection and radiation losses. The role of particle diffusion was studied and its effect on the photon spectral index quantified. In the model, the diffusion is included as a fraction of Bohm-type diffusion, which is consistent with the data. The model also allowed an estimation of the electron distribution, the magnetic field and its orientation, as well as the level of magnetic turbulence. In the third part, a multi-wavelength study of two young SNRs is presented. Multi-wavelength modeling of spectral energy distributions (SED) may hold the key to disentangle the nature and content of cosmic rays within these objects. The first model shown presents state of the art measurements gathered for Cassiopeia A, and the modeling is based partly on the results presented in the second part. The good quality SED shown at gamma ray energies was obtained from observations by the VERITAS array and the recently-launched Fermi telescope. It is found that the leptonic emission expected from the different electron populations observed in this remnant can account for the observed flux at TeV energies but fails to account for the SED at GeV energies where instead a hadronic population responsible for pion-zero production is proposed to explain the data, constituting evidence for ion acceleration in Cassiopeia A. A similar treatment was followed for data from Tycho\u27s SNR and the multi-wavelength modeling of this source is presented. The radio to X-ray data can be well explained with one population of electrons, and the gamma ray fluxes observed at TeV energies are compatible with leptonic emission expected from non-thermal Bremsstrahlung and Inverse Compton scattering processes when adopting a magnetic field value which corresponds to a lower limit allowed by the data. Results indicating a possible detection of this source at GeV energies are shown. The flux measured at these energies, if confirmed to be associated with Tycho\u27s SNR, would be compatible, similarly to the case of Cassiopeia A\u27s SED, with hadronic emission and a higher field

Probing the origin of 4FGL J0822.8–4207: cosmic ray illumination from the SNR Puppis A and the Herbig-Haro object HH219

4FGL J0822.8–4207 is a point source found in the 4FGL-DR2 catalogue by the gamma-ray observatory Fermi-LAT and has no known association. We carry out X-ray observations of 4FGL J0822.8–4207 to help understand its nature. We explore two scenarios for the origin of 4FGL J0822.8–4207 . In the first case, we study the possibility that cosmic rays from the supernova remnant (SNR) Puppis A, seen nearby in the sky, reach the dense gas at the location of the source and produce the gamma-rays through inelastic proton–proton collisions. We apply a standard model for particle diffusion in the interstellar medium and derive the required physical parameters. We find that this scenario for the gamma-rays is possible if the gas is located at a distance that is not higher than ∼40 pc from Puppis A, unless the SNR is older than 7 kyr or the diffusion coefficient is higher than typical Galactic values, and relatively low-energy cosmic rays are currently escaping from the SNR. In the second scenario, we consider the protostellar jet HH219 as the origin of the GeV source and find the very interesting possibility that particles could be accelerated up to energies of at least several TeV in HH219. This would make this system the first known of its kind to produce gamma-ray emission extending up to hundreds of GeV without any apparent cut-off and an excellent laboratory to study the process of particle acceleration.Universidad de Costa Rica/[112-B8-267]/UCR/Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Físic

Analysis of Fermi-LAT observations, UHECRs and neutrinos from the radio galaxy Centaurus B

Centaurus B (Cen B) is one of the closest and brightest radio-loud galaxy in the southern sky. This radio galaxy, proposed as a plausible candidate for accelerating ultra-high-energy cosmic rays (UHECRs), is near the highest-energy neutrino event reported (IC35) in the High-Energy Starting Events catalog. Pierre Auger observatory reported the highest energy comic rays during 10 years of collecting data with some of them around this source. In this paper, the analysis of the gamma-ray spectrum and the light curve above 200 MeV is presented with nine years of cumulative Fermi-LAT data around Cen B . Taking into consideration the multi-wavelength observations carried out about this radio galaxy, leptonic and hadronic scenarios are introduced in order to fit the spectral energy distribution, assuming that the gamma-ray flux is produced in a region close to the core and in the extended lobes. Using the best-fit values found, several physics properties of this radio galaxy are derived. Furthermore, a statistical analysis of the cosmic ray distribution around Cen B is performed, finding that this distribution is not different from the background at a level of significance of 5%. Considering the UHECR event associated to this source by Moskalenko et al. [1] and extrapolating its luminosity to low energies, we do not find enough evidence to associate the highest-energy neutrino event (IC35) with this radio galaxy.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de FísicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones Espaciales (CINESPA

Synthesis and characterization of Cu(II) containing PMMA co-polymer for optical applications

Homogenous, transparent, greenish blue Cu(II) containing PMMA co-polymer disks were prepared through the radical polymerization of the Cu(II) methac rylate, MMA and HMA using AIBN as an initiator. The dependence of the absorbance and transmittance spectra with the Cu(II) methacrylate concentration was investi gated in the visible range (420–750 nm). From the trans mittance measurements the refractive index and extinction coefficient spectral dependence were calculated by appli cation of an inversion approach. To further characterize this co-polymer a thermogram was performed. The overall behavior of this material suggests its possible use as a standard solution for Spectroscopy Equipment Calibration and as a selective optical filter.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de QuímicaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencia e Ingeniería de Materiales (CICIMA)UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Físic

HAWC and Fermi-LAT detection of extended emission from the unidentified source 2HWC J2006+341

The discovery of the TeV point source 2HWC J2006+341 was reported in the second HAWC gamma-ray catalog. We present a follow-up study of this source here. The TeV emission is best described by an extended source with a soft spectrum. At GeV energies, an extended source is significantly detected in Fermi-LAT data. The matching locations, sizes, and spectra suggest that both gamma-ray detections correspond to the same source. Different scenarios for the origin of the emission are considered and we rule out an association to the pulsar PSR J2004+3429 due to extreme energetics required, if located at a distance of 10.8 kpc.Universidad de Costa Rica/[112-B9-171]/UCR/Costa RicaUniversidad de Costa Rica/[112-B6-509]/UCR/Costa RicaUniversidad de Costa Rica/[829-B5-198]/UCR/Costa RicaUCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Físic

The High-Altitude water cherenkov (HAWC) observatory in México: The primary detector

The High-Altitude Water Cherenkov (HAWC) observatory is a second-generation continuously operated, wide field-of-view, TeV gamma-ray observatory. The HAWC observatory and its analysis techniques build on experience of the Milagro experiment in using ground-based water Cherenkov detectors for gamma-ray astronomy. HAWC is located on the Sierra Negra volcano in México at an elevation of 4100 meters above sea level. The completed HAWC observatory principal detector (HAWC) consists of 300 closely spaced water Cherenkov detectors, each equipped with four photomultiplier tubes to provide timing and charge information to reconstruct the extensive air shower energy and arrival direction. The HAWC observatory has been optimized to observe transient and steady emission from sources of gamma rays within an energy range from several hundred GeV to several hundred TeV. However, most of the air showers detected are initiated by cosmic rays, allowing studies of cosmic rays also to be performed. This paper describes the characteristics of the HAWC main array and its hardware.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Físic