Rodrigo Nemmen
A5042493197- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Dark Matter and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- Astronomy and Astrophysical Research
- Particle Detector Development and Performance
- Neutrino Physics Research
- Stellar, planetary, and galactic studies
- Relativity and Gravitational Theory
- Astrophysics and Star Formation Studies
- Particle physics theoretical and experimental studies
- Particle Accelerators and Free-Electron Lasers
- Astronomical Observations and Instrumentation
- Cosmology and Gravitation Theories
- Black Holes and Theoretical Physics
- Adaptive optics and wavefront sensing
- Heat Transfer Mechanisms
- Mechanics and Biomechanics Studies
- Plant Water Relations and Carbon Dynamics
- Statistics Education and Methodologies
- Solar and Space Plasma Dynamics
- Astro and Planetary Science
Universidade de São Paulo
2015-2024
Kavli Institute for Particle Astrophysics and Cosmology
2023-2024
Stanford University
2023-2024
TU Dortmund University
2023
University of Łódź
2023
University of Turku
2023
Niels Brock
2023
University of Copenhagen
2023
Main Astronomical Observatory
2023
Taras Shevchenko National University of Kyiv
2023
The γ-ray sky can be decomposed into individually detected sources, diffuse emission attributed to the interactions of Galactic cosmic rays with gas and radiation fields, a residual all-sky component commonly called isotropic background (IGRB). IGRB comprises all extragalactic emissions too faint or resolved in given survey, as well any foregrounds that are approximately isotropic. first measurement Large Area Telescope (LAT) on board Fermi Gamma-ray Space (Fermi) used 10 months sky-survey...
The dwarf spheroidal satellite galaxies of the Milky Way are some most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack astrophysical backgrounds, widely considered be among promising targets for indirect detection via $\ensuremath{\gamma}$ rays. Here we report on $\ensuremath{\gamma}$-ray observations 25 based 4 years Fermi Large Area Telescope (LAT) data. None significantly detected in rays, present flux upper limits between 500 MeV GeV. We...
The Fermi bubbles are two large structures in the gamma-ray sky extending to 55° above and below Galactic center. We analyze 50 months of Large Area Telescope data between 100 MeV 500 GeV 10° latitude derive spectrum morphology bubbles. thoroughly explore systematic uncertainties that arise when modeling diffuse emission through separate approaches. is well described by either a log parabola or power law with an exponential cutoff. exclude simple more than 7σ significance. cutoff has index...
The fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Gamma-ray Space Telescope Large Area (4LAC) between 2008 August 4 and 2016 2 contains 2863 objects located at high Galactic latitudes (|b|>10{\deg}). It includes 85% more sources than previous 3LAC based on years data. AGNs represent least 79% high-latitude in Fermi-Large Source Catalog (4FGL), which covers energy range from 50 MeV to 1 TeV. In addition, 344 gamma-ray are found low latitudes. Most 4LAC blazars (98%),...
The existence of ionized X-ray absorbing layers gas along the line sight to nuclei Seyfert galaxies is a well established observational fact. This material systematically outflowing and shows large range in parameters. However, its actual nature dynamics are still not clear. In order gain insights into these important issues we performed literature search for papers reporting parameters soft warm absorbers (WAs) 35 type 1 Seyferts compared their properties those ultra-fast outflows (UFOs)...
Weakly interacting massive particles (WIMPs) are a theoretical class of that excellent dark matter candidates. WIMP annihilation or decay may produce essentially monochromatic γ rays detectable by the Fermi Large Area Telescope (LAT) against astrophysical γ-ray emission Galaxy. We have searched for spectral lines in energy range 5–300 GeV using 3.7 years data, reprocessed with updated instrument calibrations and an improved dispersion model compared to previous Fermi-LAT Collaboration line...
We have produced the next generation of quasar spectral energy distributions (SEDs), essentially updating work Elvis et al. (1994) by using high-quality data obtained with several space and ground-based telescopes, including NASA's Great Observatories. present an atlas SEDs 85 optically bright, non-blazar quasars over electromagnetic spectrum from radio to X-rays. The heterogeneous sample includes 27 radio-quiet 58 radio-loud quasars. Most objects quasi-simultaneous ultraviolet-optical...
So Different Yet Similar Gamma-ray bursts (GRBs) are associated with the collapse of stars into black holes. Blazars a class active galaxies powered by accretion onto central holes masses million to billion times that Sun. Nemmen et al. (p. 1445 ) show that, despite tremendous differences in luminosity and hole mass, relativistic jets produced GRBs blazars follow same correlation between kinetic power carried accelerated particles energy radiated away jet, suggesting there may be single...
We perform an exploratory study of the physical properties accretion flows and jets in low-luminosity active galactic nuclei (LLAGNs) by modeling spectral energy distributions (SEDs) 12 LLAGNs low-ionization nuclear emission-line regions (LINERs). These SEDs we constructed from high-resolution radio, X-ray optical/UV observations immediate vicinity black hole. adopt a coupled accretion-jet model comprising inner advection-dominated flow (ADAF) outer standard thin disk. present best-fit...
Current theories predict relativistic hadronic particle populations in clusters of galaxies addition to the already observed leptons. In these scenarios interactions give rise neutral pions which decay into γ rays that are potentially observable with Large Area Telescope (LAT) on board Fermi space telescope. We present a joint likelihood analysis searching for spatially extended γ-ray emission at locations 50 galaxy four years Fermi-LAT data under assumption universal cosmic-ray (CR) model...
The Fermi Large Area Telescope (LAT) observed two bright X-class solar flares on 2012 March 7, and detected gamma-rays up to 4 GeV. We both during the impulsive temporally-extended emission phases, with above 100 MeV lasting for approximately 20 hours. Accurate localization of gamma-ray production site(s) coincide active region from which X-ray emissions associated these originated. Our analysis >100 shows a relatively rapid monotonic decrease in flux first hour phase, much slower, almost...
We present the detections of 19 solar flares detected in high-energy gamma rays (above 100 MeV) with Fermi Large Area Telescope (LAT) during its first four years operation. Interestingly, all are associated fairly fast Coronal Mass Ejections (CMEs) and not powerful X-ray flares. then describe detailed temporal, spatial spectral characteristics two long-lasting events: 2011 March 7 flare, a moderate (M3.7) impulsive flare followed by slowly varying gamma-ray emission over 13 hours, June M2.5...
We search for evidence of dark matter (DM) annihilation in the isotropic gamma-ray background (IGRB) measured with 50 months Fermi Large Area Telescope (LAT) observations. An improved theoretical description cosmological DM signal, based on two complementary techniques and assuming generic weakly interacting massive particle (WIMP) properties, renders more precise predictions compared to previous work. More specifically, we estimate cosmologically-induced intensity have an uncertainty a...
Long-term monitoring of PSR J2021+4026 in the heart Cygnus region with Fermi Large Area Telescope unveiled a sudden decrease flux above 100 MeV over timescale shorter than week. The "jump" was near MJD 55850 (2011 October 16), decreasing from (8.33 ± 0.08) × 10−10 erg cm−2 s−1 to (6.86 0.13) s−1. Simultaneously, frequency spindown rate increased (7.8 0.1) 10−13 Hz (8.1 Significant (>5σ) changes pulse profile and marginal (<3σ) emission spectrum occurred at same time. There is also evidence...
We present a model for the accretion flow around supermassive black hole in LINER nucleus of NGC 1097 which fits optical to X-ray spectral energy distribution (SED). The segment SED is based on observations with Chandra X-Ray Observatory, are reported here first time. inner part modeled as radiatively inefficient (RIAF) and outer standard thin disk. value transition radius (~225 Schwarzschild radii) between RIAF disk was obtained from our previous fitting double-peaked Balmer emission line...
In this paper, we present a new implementation of feedback due to active galactic nuclei (AGN) in cosmological simulations galaxy formation. We assume that fraction jet energy, which is generated by an AGN, transferred the surrounding gas as thermal energy. Combining theoretical model mass accretion on black holes with multiphase description star-forming gas, self-consistently follow evolution both galaxies and their central holes. The novelty our consider two distinct modes: standard...
The mechanisms that produce and power relativistic jets are fundamental open questions in black hole (BH) astrophysics. In order to constrain these mechanisms, we analyze the energy efficiency of jet production 'eta' based on archival Chandra observations 27 nearby, low-luminosity active galactic nuclei. We obtain as ratio power, inferred from energetics powered X-ray emitting cavities, BH mass accretion rate Mdot_BH. standard assumption estimating Mdot_BH is all gas Bondi radius 'r_B' makes...
The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space routinely detects highly dust-absorbed, reddened, and MeV-peaked flat spectrum radio quasar PKS 1830-211 (z=2.507). Its apparent isotropic gamma-ray luminosity (E>100 MeV) averaged over $\sim$ 3 years of observations peaking 2010 October 14/15 at 2.9 X 10^{50} erg s^{-1}, makes it among brightest high-redshift blazars. No published model with a single lens can account for all observed characteristics this complex system. Based...
We reanalyze the prompt emission of two brightest Fermi GRBs (080916C and 090926A) with a new model composed 3 components: (i) thermal-like component--approximated black body (BB)--interpreted as jet photosphere magnetized relativistic outflow, (ii) non-thermal Band function--interpreted synchrotron radiation in an optically thin region above either from internal shocks or magnetic field dissipation, (iii) extra power law (PL) extending low to high energies likely inverse Compton origin,...
The power of jets from black holes are expected to depend on both the spin hole and structure accretion disk in region last stable orbit. We investigate these dependencies using two different physical models for jet power: classical Blandford-Znajek (BZ) model a hybrid developed by Meier. In BZ case, powered magnetic fields directly threading spinning while model, energy is extracted as well via anchored flow inside outside hole's ergosphere. takes advantage strengths Blandford-Payne...
Broad (~10,000 km/s), double-peaked emission-line profiles of Balmer lines emitted by active galactic nuclei (AGN) are thought to originate in the outer parts an accretion disk surrounding a nuclear supermassive black hole (SMBH), at R~1000 gravitational radii and most frequently observed spectra low-luminosity AGN (LLAGN) radio-galaxies. In present paper we argue that broad also other Type 1 AGN, such as Seyfert galaxies, suggesting inner part broad-line region (BLR) is disk. We use Palomar...
The discovery of rapidly variable Very High Energy (VHE; E > 100 GeV) gamma-ray emission from 4C +21.35 (PKS 1222+216) by MAGIC on 2010 June 17, triggered the high activity detected Fermi Large Area Telescope (LAT) in energy (HE; MeV) gamma-rays, poses intriguing questions location emitting region this flat spectrum radio quasar. We present multifrequency data collected centimeter to VHE during investigate properties source and discuss a possible model. first hint detection at was observed...
A variety of large-scale diffuse radio structures have been identified in many clusters with the advent new state-of-the-art facilities astronomy. Among these structures, mini-halos are found central regions cool core clusters. Their origin is still unknown and they challenging to discover; less than thirty published date. Based on VLA observations, we confirmed mini-halo massive strong cluster PKS 0745$-$191 ($z=0.1028$) discovered one MACS J1447.4+0827 ($z=0.3755$). Furthermore, using a...
We present an analysis of historical multi-wavelength emission the Changing Look (CL) Active Galactic Nucleus (AGN) in NGC 2992, covering epochs ranging from 1978 to 2021, as well new X-ray and optical spectra. The galaxy presents multiple Seyfert type transitions 2 intermediate-type, losing regaining its H$α$ BEL recurrently. In X-rays, source shows intrinsic variability with absorption corrected luminosity varying by a factor $\sim$ 40. rule out tidal disruption events or variable...
Bolometric corrections based on the optical-to-ultraviolet continuum spectrum of quasars are widely used to quantify their radiative output, although such estimates affected by a myriad uncertainties, as generally unknown line-of-sight angle central engine. In order shed light these issues, we investigate state-of-the-art models Hubeny et al. that describe thin accretion discs and include relativistic effects. We explore bolometric function mass rates, black hole masses viewing angles,...