...
Saturday, June 1
Giovanni Cozzolongo - "Clustering analysis of Fermi-LAT unidentified point sources"
| Expand |
|---|
|
| Abstract: In this work we study clustering of unassociated Fermi-LAT sources and search for counterpart extended sources in TeV energies. The goal is to determine whether an extended source model is preferred compared to a cluster of point-like sources. The work is motivated by prior observations of extended TeV gamma-ray sources, such as HESS J1813-178, and their GeV counterparts. In the case of HESS J1813-178, two unidentified Fermi-LAT point sources were detected in the region. Subsequent multiwavelength analysis combining TeV and GeV data showed that a single extended source is a better description of the emission in this region than two point-like sources. |
...
| Expand |
|---|
|
| Abstract: The dual-mirrored Schwarzschild-Couder Telescope is a proposed medium-sized telescope candidate for the Cherenkov Telescope Array’s southern site (in Paranal, Chile). The Schwarzschild-Couder design has an energy range of 100 GeV to 10 TeV and a field of view of 8°. A prototype Schwarzschild-Couder Telescope (pSCT) has been built next to VERITAS at the Fred Lawrence Whipple Observatory and was inaugurated in January 2019. The initial camera had 1,600 pixels instrumented (out of the full 11,328) spanning a 2.7° field of view. Based on observations in 2020, the partially instrumented camera detected gamma-ray emission from the Crab Nebula at a significance of 8.6σ. The pSCT camera is undergoing an upgrade, both to improve its performance and to instrument the full 11,328 pixel camera. I will present the process and status of the camera upgrade. |
Agostina Filócomo - "In search of evidence of flares in T Tauri stars as gamma-ray emitters"
| Expand |
|---|
|
| Abstract: NGC 2071 is a star-forming region positionally correlated with three unidentified gamma-ray sources detected by the Fermi satellite telescope. According to a preliminary model, T Tauri stars could produce gamma-ray emission under specific conditions. We performed a spectral and temporal analysis of the Fermi data to determine whether the detected emission was caused by flares occurring in T Tauri stars. We found that the gamma-ray source can only be detected in the first two years of observations at energies above 100 GeV. In addition, a variability analysis reveals that the expected frequency of events is compatible with flare activity with a minimum X-ray energy of 5 × 1037 erg. These observational results impose, for the first time, a substantial constraint on the energetic of flares in T Tauri stars that could explain the origin of unknown gamma-ray sources in star-forming regions. |
...
Tuesday, June 4 Part 2
Rafael Diaz - "Studying VHE variability and flare for blazar B2 1811+31"
...
| Expand |
|---|
|
| Abstract: The blazar 4C 31.03 has bee reported by Fermi-LAT for exhibiting a major 𝛾- ray outburst at the beginning of 2023 after a prolonged quiescent phase. We performed a comprehensive study of this extraordinary outbreak in temporal and multi-wavelength aspects. From the statistical analysis of the 𝛾gamma-ray lightcurves using Bayesian blocks, we identified 3 epochs of prominent flares. The variability analysis performed using a 12 hour binned 𝛾gamma-ray lightcurve resulted the shortest timescale of 5.453 hours. The highest energy of gamma-ray photons found from the source during the active phase is ∼ 82 GeV. Subsequently, using the transparency of gamma-rays against pair production and light crossing time argument, we could obtain the minimum jet Doppler factor as ∼ 17 and the upper limit on emission region size to be∼1016cm. The broadband spectral energy distribution study performed using synchrotron, SSC and EC emission processes supports the external Compton scattering of IR photons as the likely mechanism for the 𝛾gamma-ray emission from the source. The results of our analysis support the scenario of the emission site in 4C 31.03, being located beyond the Broad line region from the central black-hole. The long-term 𝛾gamma-ray flux distribution depicts a double log-normal variability, indicating that two distinct flux states are active in this energy band. The index distribution also reveals a two distinct variability pattern and hints that the 𝛾gamma-ray spectrum can be more precisely described by two photon indices. |
Krishna Teja Vedula - "Study of Blazar Polarization in Gamma Rays with COSI"
| Expand |
|---|
|
| Abstract: The Compton Spectrometer and Imager (COSI) Mission, slated for launch in 2027 is focused on bridging the MeV gap in gamma-ray observations. COSI employs innovative polarimetric data collection methods using Compton scattering which puts it in a very unique position in addressing the challenging MeV range. The cutting-edge technology and analytical tools employed by COSI, including MEGAlib and Python-based frameworks which are being built on the same principles and frameworks as the Fermi Tools, underscore its potential to revolutionize the understanding of blazars, contributing to the elucidation of particle acceleration mechanisms, magnetic field order, and turbulence in extragalactic gamma-ray objects. Preliminary blazar analyses for COSI depend upon spectra from the Fermi mission. |
...
| Expand |
|---|
|
| Abstract: Blazars are active galactic nuclei with relativistic jets pointing towards our line of sight. These sources are the most powerful persistent gamma-ray emitters in the Universe, and can be classified by the frequency of their synchrotron peak emission from low to extreme synchrotron peak blazars at frequencies larger than 10 is an ongoing observational challenge in gamma-ray astrophysics. In this pioneering search, we will systematically look for the most extreme of these blazars, by finding a transition between a synchrotron peak and the inverse Compton region that could lie at the GeV energy range, where the Large Area Telescope on board the Fermi Gamma-ray Space Telescope is most sensitive. Our results will allows us to understand the recurrence, time-scales, and energetics of these events, which are expected to happen in flares, and their role in the blazar sequence. |
Laenita De Jonge - "Study of the hadronic synchrotron mirror model for orphan flares in blazars - Application to 3C279"
| Expand |
|---|
|
| Abstract: Blazars are a class of Active Galactic Nuclei (AGN), found in the centres of elliptical galaxies, that are radio loud and have a small angle between the jet and the observer’s line of sight. In some cases, flaring events in one frequency band are not accompanied by flaring in other bands. Such events are called orphan flares. The causes of this variability and conditions in and location of the high energy emission region are not completely understood. As a possible explanation for rapid orphan gamma-ray variability, the hadronic synchrotron mirror model has been suggested in previous work. A TeV orphan flare was observed on the 28th of January 2018 by the H.E.S.S. observatory from 3C 279. A primary flare was observed 11 days earlier by Fermi-LAT. The hadronic synchrotron mirror model, is applied to this flare. A study is done using the SED and multi-wavelength light curve results to see which parameters provide the best fit and to draw conclusions about the radiation mechanism that caused this orphan flare. A search for neutrino emission is also conducted to establish if orphan flares are a possible source. |
...
| Expand |
|---|
|
| Abstract: Long term periodicity in gamma-ray Blazar light curves could be linked to the innermost zone of the complex structure of AGN, like possible presence of binary system of supermassive black holes, or it could shed light on the origin of gamma-rays emission. The work analyses 1525 sources, whose 14 years light curves come from the Fermi LAT Light Curve Repository (LCR), making use of Lomb-Scargle Periodogram (LSP) and wavelet weighted Z transform (WWZ), to express the significance we performed simulations using the Emmanoulopoulos algorithm. All the available possibilities for the light curves in the LCR, such as different temporal samplings and the use of photon flux and energy flux, are taken into account in order to ensure more reliable results. We found out high significance periodicity in less than 1% of the sources considered, and in few other sources hints of possible periodicity. Our results are compliant with the findings of recent literature focused on searches of periodic modulation in AGNs. |
Olive Zhang - "Search for anisotropic pair halos associated with blazar jets"
| Expand |
|---|
|
| Abstract: Magnetic fields found in the galaxies are believed to grow from weaker “seed” fields whose origin is still unknown. The weaker “seed” fields might be preserved in the interstellar medium. However, its strength is too weak to be measured by traditional methods such as the Faraday rotation and Zeeman effect. Pair halos around the blazar jets might provide a way to measure the strength of the intergalactic magnetic field (IGMF). Because the IGMFs deflect the charged particles produced by TeV photons emitted by the blazars, extended GeV gamma-rays will develop around the projected jet direction. We propose to use Fermi-LAT data to look at certain high-synchrotron-peaked BL lacs (HBLs) and intermediate-synchrotron-peaked BL Lacs (IBLs) objects and search for any anisotropic pair halos. |
Thursday, June 6
Eliza Neights - "Studying GRBs Using COSI"
| Expand |
|---|
|
| Abstract: Gamma-ray bursts (GRBs) are energetic phenomena that serve as probes for extreme physics, but their emission mechanisms, jet geometry, and magnetic field structure are not well understood and require new detection capabilities. The Compton Spectrometer and Imager (COSI) is a gamma-ray space telescope set to launch in 2027 that aims to further our understanding of GRBs, in addition to studying positron annihilation and nucleosynthesis in the Galaxy. COSI’s wide field-of-view, excellent energy resolution, sub-degree localizations, and polarization capabilities may reveal insight into GRB prompt emission. In this presentation, I will give a brief overview of the COSI mission and discuss the GRB science it enables. |
...