Jayant Abhir

Last Name

Abhir

First Name

Jayant

ORCID

0000-0001-8215-4377

Organisational unit

08823 - Biland, Adrian (Tit.-Prof.)

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Publications 1 - 10 of 32

The variability patterns of the TeV blazar PG 1553 + 113 from a decade of MAGIC and multiband observations
MAGIC Collaboration; Abe, H.; Abhir, Jayant; et al. (2024)
Monthly Notices of the Royal Astronomical Society
PG 1553 + 113 is one of the few blazars with a convincing quasi-periodic emission in the gamma-ray band. The source is also a very high energy (VHE; >100 GeV) gamma-ray emitter. To better understand its properties and identify the underlying physical processes driving its variability, the MAGIC Collaboration initiated a multiyear, multiwavelength monitoring campaign in 2015 involving the OVRO 40-m and Medicina radio telescopes, REM, KVA, and the MAGIC telescopes, Swift and Fermi satellites, and the WEBT network. The analysis presented in this paper uses data until 2017 and focuses on the characterization of the variability. The gamma-ray data show a (hint of a) periodic signal compatible with literature, but the X-ray and VHE gamma-ray data do not show statistical evidence for a periodic signal. In other bands, the data are compatible with the gamma-ray period, but with a relatively high p-value. The complex connection between the low- and high-energy emission and the non-monochromatic modulation and changes in flux suggests that a simple one-zone model is unable to explain all the variability. Instead, a model including a periodic component along with multiple emission zones is required.
Standardised formats and open-source analysis tools for the MAGIC telescopes data
The MAGIC Collaboration; Abe, Shotaro; Abhir, Jayant; et al. (2024)
Journal of High Energy Astrophysics
Instruments for gamma-ray astronomy at Very High Energies (E>100GeV) have traditionally derived their scientific results through proprietary data and software. Data standardisation has become a prominent issue in this field both as a requirement for the dissemination of data from the next generation of gamma-ray observatories and as an effective solution to realise public data legacies of current-generation instruments. Specifications for a standardised gamma-ray data format have been proposed as a community effort and have already been successfully adopted by several instruments. We present the first production of standardised data from the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes. We converted 166h of observations from different sources and validated their analysis with the open-source software Gammapy. We consider six data sets representing different scientific and technical analysis cases and compare the results obtained analysing the standardised data with open-source software against those produced with the MAGIC proprietary data and software. Aiming at a systematic production of MAGIC data in this standardised format, we also present the implementation of a database-driven pipeline automatically performing the MAGIC data reduction from the calibrated down to the standardised data level. In all the cases selected for the validation, we obtain results compatible with the MAGIC proprietary software, both for the manual and for the automatic data productions. Part of the validation data set is also made publicly available, thus representing the first large public release of MAGIC data. This effort and this first data release represent a technical milestone toward the realisation of a public MAGIC data legacy.
Multiwavelength characterization of two flaring blazars: insight into the emission region of intermediate-synchrotron-peaked BL Lacs
Loporchio, Serena; Bonnoli, Giacomo; Cerasole, Davide; et al. (2024)
PoS: Proceedings of Science ~ Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023)
The blazars B2 1811+31 and GB6 J1058+2817 were found to be in flaring state during 2020 and 2021, respectively. The high states of the sources were registered by the Fermi-LAT at energies below 100 GeV, triggering observations at higher energies with the MAGIC telescopes, in the UV/X rays with the Swift satellite and with ground-based radio and optical telescopes. The observations in the very-high-energy (VHE, 100 GeV < E < 100 TeV) gamma-ray band led to the first detection of both sources in this energy range. A long-term gamma-ray lightcurve was derived using Fermi-LAT data, identifying the time intervals in which the two sources persisted in a quiet state. Archival data collected in the radio to X-ray wavelengths showed that the two sources exhibited intermediate-synchrotron-peaked BL Lac behaviors in their low states, rather rare sources in the TeV sky. The high state of the two sources was deeply investigated thanks to the coverage provided by multi-wavelength (MWL) observational campaigns. In this contribution, we present the results of the gamma-ray observations which are included in a MWL observational campaign organized on these sources during their high-states. We discuss the flare spectral properties and temporal variability. In the high-energy gamma band, sub-daily-scale variability and strong spectral hardening give evidence for compact emission regions responsible for the radiative output at high energies during the flare.
Leptonic and lepto-hadronic time-dependent spectral modeling of VER J0521+211 during the large outburst of February-March 2020
Nievas Rosillo, Mireia; Artero, Manuel; Fallah Ramazani, Vandad; et al. (2024)
PoS: Proceedings of Science ~ Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023)
The high-synchrotron-peaked blazar VER J0521+211 was discovered in 2009 by VERITAS and is located at an unknown distance. In February 2020, the VERITAS collaboration alerted the multi-messenger community of an ongoing flare from the source, followed by a multi-frequency monitoring campaign led by MAGIC, covering energies from radio to very-high-energy (VHE, E>100GeV) which allowed to observe the source in VHE for 6 consecutive nights. Out of these observations, a statistical upper limit to the source redshift at z<0.243 was set using Fermi-LAT and MAGIC data, a value consistent with lower limits derived from optical spectroscopy. The modeling of the broadband spectral energy distribution (SED) and its night-wise evolution is also presented using two types of models: i) a leptonic two-zone synchrotron-self-Compton scenario; ii) a lepto-hadronic one-zone scenario. Both scenarios allow to reproduce the observed SEDs and their night-wise evolution, and have implications on optical polarization and production of neutrinos. For the first scenario, optical polarimetry measurements were compared with the predictions from the evolution of the two-zones. For the second scenario, limits on the production of neutrinos and enhanced photon emission at ultra-high-energies (E>100TeV) from π⁰ decay were computed.
Defining the data legacy of the MAGIC telescopes: adopting a standardised data format and open-source analysis tools
Nigro, Cosimo; MAGIC Collaboration; Abe, Hyuga; et al. (2024)
PoS: Proceedings of Science ~ Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023)
Very-high-energy (VHE, E>100GeV) gamma-ray telescopes have traditionally conducted science with proprietary data and software. After two decades of operations, they have accumulated thousands of hours of observations whose full scientific exploitation cannot be accomplished by the restricted group of scientists operating these instruments. The advent of a new generation of open gamma-ray observatories and, at the same time, the forthcoming end of their scientific operations, call for the realisation of public archives of their observations. With the objective to facilitate the exchange and dissemination of data from current- and next-generation gamma-ray instruments, the "Data formats for gamma-ray astronomy" (GADF) initiative was formed to provide an open and standardised format for gamma-ray astronomical data. In this contribution, we present the effort to produce data of the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes in this standardised format. A total of 150 hours of observations of different sources were converted to the GADF format and then validated by analysing them with the open-source software Gammapy and comparing the results obtained against those produced with the MAGIC proprietary software, MARS. The effort to standardise and validate the Magic data in an open and shared format constitute the first fundamental milestone towards the realisation of its public data legacy.
Long term study of the blazar S5 0716+714: investigating a turbulent jet at all wavelengths
Podobnik, Franjo; Manganaro, Marina; Jormanainen, Jenni; et al. (2024)
PoS: Proceedings of Science ~ Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023)
The blazar S5 0716+714 is an intermediate BL Lacertae object remarkable for its variability in many energy bands. It was discovered by MAGIC in the very-high-energy (VHE) gamma-ray range in 2008. Later in 2015 an impressive electric vector polarization angle (EVPA) swing was detected in connection with a multiwavelength flaring event including the VHE gamma-ray band. This generated interest in further studies of the jet of this source and its electromagnetic emission at all wavelengths. Since then, MAGIC has monitored the source in coordination with other observatories and here we present the long-term study using data from 2015 to 2022 in a MWL context. The data set also includes the extraordinary flaring activity of 2017, so far the historical maximum detected for this source in the optical and VHE gamma-ray band.
Prospects for a survey of the galactic plane with the Cherenkov Telescope Array
The CTA Consortium; Abe, Shinsuke; Abhir, Jayant; et al. (2024)
Journal of Cosmology and Astroparticle Physics
Approximately one hundred sources of very-high-energy (VHE) gamma rays are known in the Milky Way, detected with a combination of targeted observations and surveys. A survey of the entire Galactic Plane in the energy range from a few tens of GeV to a few hundred TeV has been proposed as a Key Science Project for the upcoming Cherenkov Telescope Array Observatory (CTAO). This article presents the status of the studies towards the Galactic Plane Survey (GPS). We build and make publicly available a sky model that combines data from recent observations of known gamma-ray emitters with state-of-the-art physically-driven models of synthetic populations of the three main classes of established Galactic VHE sources (pulsar wind nebulae, young and interacting supernova remnants, and compact binary systems), as well as of interstellar emission from cosmic-ray interactions in the Milky Way. We also perform an optimisation of the observation strategy (pointing pattern and scheduling) based on recent estimations of the instrument performance. We use the improved sky model and observation strategy to simulate GPS data corresponding to a total observation time of 1620 hours spread over ten years. Data are then analysed using the methods and software tools under development for real data. Under our model assumptions and for the realisation considered, we show that the GPS has the potential to increase the number of known Galactic VHE emitters by almost a factor of five. This corresponds to the detection of more than two hundred pulsar wind nebulae and a few tens of supernova remnants at average integral fluxes one order of magnitude lower than in the existing sample above 1 TeV, therefore opening the possibility to perform unprecedented population studies. The GPS also has the potential to provide new VHE detections of binary systems and pulsars, to confirm the existence of a hypothetical population of gamma-ray pulsars with an additional TeV emission component, and to detect bright sources capable of accelerating particles to PeV energies (PeVatrons). Furthermore, the GPS will constitute a pathfinder for deeper follow-up observations of these source classes. Finally, we show that we can extract from GPS data an estimate of the contribution to diffuse emission from unresolved sources, and that there are good prospects of detecting interstellar emission and statistically distinguishing different scenarios. Thus, a survey of the entire Galactic plane carried out from both hemispheres with CTAO will ensure a transformational advance in our knowledge of Galactic VHE source populations and interstellar emission.
Evidence of hadronic origin of the gamma-ray emission from the nova RS Oph by the MAGIC telescopes
Green, David M.; Fallah Ramazani, Vandad; Leone, Francesco; et al. (2024)
PoS: Proceedings of Science ~ Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023)
RS Ophiuchi (RS Oph) is a symbiotic recurrent nova that shows eruptive events roughly every 15 years. On August 8th, 2021, RS Oph erupted with its latest outburst. This event was detected by a wide range of multi-wavelength (MWL) instruments from radio up to very-high-energy (VHE) gamma rays. The MAGIC telescopes followed up on optical and high-energy triggers and initiated an observation campaign from August 9th till September 1st. RS Oph is the first nova detected in the VHE gamma-ray energy range. We report on the detection of VHE gamma rays at a significant level of 13.2σ during the first 4 days of RS Oph with the MAGIC telescopes. We combine the VHE emission detected by MAGIC with optical and high energy observations and conclude RS Oph accelerated hadrons during its eruption. We will present the MWL modeling revealing this hadronic emission, and its further implications for Galactic cosmic-rays.
Highlights of Galactic Science with the MAGIC telescopes
Strzys, Marcel C.; MAGIC Collaboration; Abe, Hyuga; et al. (2024)
PoS: Proceedings of Science ~ Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023)
There are several types of Galactic sources that can potentially accelerate charged particles up to GeV and TeV energies. These accelerated particles can produce Very High Energy (E>100 GeV) gamma-ray emission through different non-thermal processes such as inverse Compton scattering of ambient photon fields by accelerated electrons or pion decay after proton-proton collisions. Here we present highlight results of observations with the MAGIC telescopes on Galactic sources: millisecond pulsars, supernova remnants (SNRs), pulsar wind nebulae (PWNe), novae and binary systems. In particular, we present the promising PeVatron candidate SNR G106.3+2.7 containing an energetic PWN named Boomerang. Also, in the ongoing search for new source classes we looked for very-high-energy emission from the millisecond pulsar PSR J0218+4232 that has long been considered as one of the best candidates. Furthermore, we present the observations during an exceptionally bright X-ray outburst from the low mass X-ray binary MAXI J1820+070. Finally, we highlight the MAGIC results of the first nova detected at VHEs: RS Ophiuchi, a recurrent symbiotic nova located in the Milky Way. The detection with the MAGIC telescopes proves a hadronic origin of the the gamma-ray emission, and helps in understanding the contribution of novae to the cosmic-ray budget.
First characterization of the emission behavior of Mrk 421 from radio to very high-energy gamma rays with simultaneous X-ray polarization measurements
Abe, S.; Abhir, Jayant; Acciari, Victor Abelardo; et al. (2024)
Astronomy & Astrophysics
Aims: We have performed the first broadband study of Mrk 421 from radio to TeV gamma rays with simultaneous measurements of the X-ray polarization from IXPE. Methods: The data were collected as part of an extensive multiwavelength campaign carried out between May and June 2022 using MAGIC, Fermi-LAT, NuSTAR, XMM-Newton, Swift, and several optical and radio telescopes to complement IXPE data. Results: During the IXPE exposures, the measured 0.2–1 TeV flux was close to the quiescent state and ranged from 25% to 50% of the Crab Nebula without intra-night variability. Throughout the campaign, the very high-energy (VHE) and X-ray emission are positively correlated at a 4σ significance level. The IXPE measurements reveal an X-ray polarization degree that is a factor of 2–5 higher than in the optical/radio bands; that implies an energy-stratified jet in which the VHE photons are emitted co-spatially with the X-rays, in the vicinity of a shock front. The June 2022 observations exhibit a rotation of the X-ray polarization angle. Despite no simultaneous VHE coverage being available during a large fraction of the swing, the Swift-XRT monitoring reveals an X-ray flux increase with a clear spectral hardening. This suggests that flares in high synchrotron peaked blazars can be accompanied by a polarization angle rotation, as observed in some flat spectrum radio quasars. Finally, during the polarization angle rotation, NuSTAR data reveal two contiguous spectral hysteresis loops in opposite directions (clockwise and counterclockwise), implying important changes in the particle acceleration efficiency on approximately hour timescales.

Publications 1 - 10 of 32

Jayant Abhir

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