56 research outputs found

    MAGIC and H.E.S.S. detect VHE gamma rays from the blazar OT081 for the first time: a deep multiwavelength study

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    https://pos.sissa.it/395/815/pdfPublished versio

    Pseudorapidity densities of charged particles with transverse momentum thresholds in pp collisions at √ s = 5.02 and 13 TeV

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    The pseudorapidity density of charged particles with minimum transverse momentum (pT) thresholds of 0.15, 0.5, 1, and 2 GeV/c is measured in pp collisions at the center of mass energies of √s=5.02 and 13 TeV with the ALICE detector. The study is carried out for inelastic collisions with at least one primary charged particle having a pseudorapidity (η) within 0.8pT larger than the corresponding threshold. In addition, measurements without pT-thresholds are performed for inelastic and nonsingle-diffractive events as well as for inelastic events with at least one charged particle having |η|2GeV/c), highlighting the importance of such measurements for tuning event generators. The new measurements agree within uncertainties with results from the ATLAS and CMS experiments obtained at √s=13TeV.

    Multiwavelength Picture of the Blazar S5 0716+714 during Its Brightest Outburst

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    S5 0716+714 is a well known BL Lac object, and one of the brightest and most active blazars. The discovery in the Very High Energy band (VHE, E > 100 GeV) by MAGIC happened in 2008. In January 2015, the source went through the brightest optical state ever observed, triggering MAGIC follow-up and a VHE detection with ∼ 13σ significance (ATel ♯6999 ). Rich multiwavelength coverage of the flare allowed us to construct the broad-band spectral energy distribution of S5 0716+714 during its brightest outburst. In this work, we will present the preliminary analysis of MAGIC and Fermi-LAT data of the flaring activity in January and February 2015 for the HE (0.1 < HE < 300 GeV) and VHE band, together with radio (Metsähovi, OVRO, VLBA, Effelsberg), sub-millimeter (SMA), optical (Tuorla, Perkins, Steward, AZT-8+ST7, LX-200, Kanata), X-ray and UV (Swift-XRT and UVOT), in the same time-window and discuss the time variability of the multiwavelength light curves during this impressive outburst.</p

    Emission-line Variability during a Nonthermal Outburst in the Gamma-Ray Bright Quasar 1156+295

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    This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.We present multi-epoch optical spectra of the γ-ray bright blazar 1156+295 (4C +29.45, Ton 599) obtained with the 4.3 m Lowell Discovery Telescope. During a multiwavelength outburst in late 2017, when the γ-ray flux increased to 2.5 × 10−6 phot cm−2 s−1 and the quasar was first detected at energies ≥100 GeV, the flux of the Mg ii λ2798 emission line changed, as did that of the Fe emission complex at shorter wavelengths. These emission-line fluxes increased along with the highly polarized optical continuum flux, which is presumably synchrotron radiation from the relativistic jet, with a relative time delay of ≲2 weeks. This implies that the line-emitting clouds lie near the jet, which points almost directly toward the line of sight. The emission-line radiation from such clouds, which are located outside the canonical accretion-disk related broad-line region, may be a primary source of seed photons that are up-scattered to γ-ray energies by relativistic electrons in the jet. © 2022. The Author(s). Published by the American Astronomical Society.This research was supported in part by NASA Fermi guest investigator program grants 80NSSC19K1504 and 80NSSC20K1565. We thank A. Tchekhovskoy for discussion of possible origins of the variable line-emitting clouds. These results made use of the Lowell Discovery Telescope (LDT) at Lowell Observatory. Lowell Observatory is a private, non-profit institution dedicated to astrophysical research and public appreciation of astronomy, and operates the LDT in partnership with Boston University, the University of Maryland, the University of Toledo, Northern Arizona University and Yale University. This study was based in part on observations conducted using the 1.8 m Perkins Telescope Observatory (PTO) in Arizona, which is owned and operated by Boston University. I.A. acknowledges financial support from the Spanish "Ministerio de Ciencia e Innovación" (MCINN) through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofísica de Andalucía-CSIC (SEV-2017-0709). Acquisition and reduction of the MAPCAT data were supported in part by MICINN through grants AYA2016-80889-P and PID2019-107847RB-C44. The MAPCAT observations were carried out at the German-Spanish Calar Alto Observatory, which is jointly operated by Junta de Andalucía and Consejo Superior de Investigaciones Científicas. Data from the Steward Observatory spectropolarimetric monitoring project were used; this program was supported by Fermi Guest Investigator grants NNX08AW56G, NNX09AU10G, NNX12AO93G, and NNX15AU81G. C.C. acknowledges support from the European Research Council (ERC) under the European Union Horizon 2020 research and innovation program under the grant agreement No. 771282.Peer reviewe

    Studying the Extreme Behaviour of 1ES 2344+51.4

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    The BL Lac type object 1ES 2344+51.4 (redshift z = 0.044) was one of the first sources to be included in the extreme high-peaked BL Lac (EHBL) family. EHBLs are characterised by a broadband spectral energy distribution (SED) featuring the synchrotron peak above ∼ 1017 Hz. From previous studies of 1ES 2344+51.4 in the very-high-energy (VHE, >100 GeV) gamma-ray range, its inverse Compton (IC) peak is expected around 200 GeV. 1ES 2344+51.4 was first detected in the VHE range by Whipple in 1995 during a very bright outburst showing around 60% of the flux of the Crab Nebula above 350 GeV. In 1996, during another flare in the X-ray band, observations with Beppo-SAX revealed a large 0.1-10 keV flux variability on timescales of a few hours and an impressive frequency shift of the synchrotron peak to above 1018 Hz. Later on, this extreme behaviour of the source motivated several multiwavelength campaigns, during most of which the source appeared to be in a low state and showing no clear signs of “extremeness”. In August 2016, FACT detected 1ES 2344+51.4 in a high state and triggered multiwavelength observations. The VHE observations show a flux level similar to the historical maximum of 1995. The combination of MAGIC, FACT, and Fermi-LAT spectra provides an unprecedented characterisation of the IC peak. It is the first time that simultaneous HE and VHE data are presented for this object during a flaring episode. We find an atypically hard spectrum in the VHE γ-rays as well as a hard X-ray spectrum, revealing a renewed extreme behaviour.ISSN:1824-803

    MAGIC and H.E.S.S. detect VHE gamma rays from the blazar OT081 for the first time: a deep multiwavelength study

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    OT 081 is a luminous blazar well known for its variability in many energy bands. The very-high-energy (VHE; E >100 GeV) gamma-ray emission from the source was discovered by MAGIC and H.E.S.S. during flaring activity in July 2016, after a trigger from the Large Area Telescope (LAT) onboard the Fermi satellite. By analysing the multiwavelength light curves andthe broadband spectral energy distribution (SED), we study the activity of the source and investigate four individual states of activity in the window from MJD 57575 to 57602. The intrinsic gamma-ray spectrum can be described by a power law with spectral indices of 3.27 ± 0.44(MAGIC)and 3.39 ± 0.58(H.E.S.S.) over energy ranges 60–300 GeV and 120–500 GeV, respectively. The combined contemporaneous high-energy (HE;E >100 MeV) through VHE SED shows curvatureand can be described by a log-parabola shape. A simple one-zone synchrotron self-Compton (SSC)model is not sufficient to describe the broadband SED. The presence of broad emission lines in the optical spectrum of the source challenges the categorisation of OT 081 as a BL Lac and, together with the emission scenarios tested, points to the possibility that the source is transitional in nature between a BL Lac and a flat-spectrum radio quasar.ISSN:1824-803

    Optical Emission and Particle Acceleration in a Quasi-stationary Component in the Jet of OJ 287

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    We analyze the linear polarization of the relativistic jet in BL Lacertae object OJ 287 as revealed by multi-epoch Very Long Baseline Array images at 43 GHz and monitoring observations at optical bands. The electric-vector position angle of the optical polarization matches that at 43 GHz at locations that are often in the compact millimeter-wave >core> or, at other epochs, coincident with a bright, quasi-stationary emission feature ∼0.2 mas (∼0.9 pc projected on the sky) downstream from the core. This implies that electrons with high enough energies to emit optical synchrotron and γ-ray inverse Compton radiation are accelerated both in the core and at the downstream feature, the latter of which lies ≥10 pc from the central engine. The polarization vector in the stationary feature is nearly parallel to the jet axis, as expected for a conical standing shock capable of accelerating electrons to GeV energies.© 2018. The American Astronomical Society. All rights reserved..The authors thank Dr. Ioannis Myserlis for a critical review of a draft of this manuscript. The authors acknowledge financial support by MEXT/JSPS Grant-in-Aid for Scientific Research on Innovative Areas (No. 25120007). M.S. was supported during this study by a JSPS Postdoctoral Fellowship for Research Abroad. The research at Boston University was supported in part by National Science Foundation grant AST-1615796 and NASA Fermi Guest Investigator Program grants NNX14AQ58G and 80NSSC17K0649. The St. Petersburg University team acknowledges support from Russian Science Foundation grant 17-12-01029. I.A. acknowledges support by a Ramon y Cajal grant of the Ministerio de Economia y Competitividad (MINECO) of Spain. The research at the IAA-CSIC was supported in part by the MINECO through grants AYA2016-80889-P, AYA2013-40825-P, and AYA2010-14844; and by the regional government of Andalucia through grant P09-FQM-4784. Calar Alto Observatory is jointly operated by the Max-Planck-Institut fur Astronomie and the IAA-CSIC. The VLBA is an instrument of the Long Baseline Observatory (LBO). The LBO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Data from the Steward Observatory spectro-polarimetric monitoring project were used. This program was supported by Fermi Guest Investigator grants NNX08AW56G, NNX09AU10G, NNX12AO93G, and NNX15AU81G

    Multiwavelength behaviour of the blazar 3C 279: Decade-long study from γ -ray to radio

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    We report the results of decade-long (2008-2018) γ -ray to 1 GHz radio monitoring of the blazar 3C 279, including GASP/WEBT, Fermi and Swift data, as well as polarimetric and spectroscopic data. The X-ray and γ -ray light curves correlate well, with no delay ≳ 3 h, implying general cospatiality of the emission regions. The γ -ray-optical flux-flux relation changes with activity state, ranging from a linear to amore complex dependence. The behaviour of the Stokes parameters at optical and radio wavelengths, including 43 GHz Very Long Baseline Array images, supports either a predominantly helical magnetic field or motion of the radiating plasma along a spiral path. Apparent speeds of emission knots range from 10 to 37c, with the highest values requiring bulk Lorentz factors close to those needed to explain γ -ray variability on very short time-scales. The MgII emission line flux in the 'blue' and 'red' wings correlates with the optical synchrotron continuum flux density, possibly providing a variable source of seed photons for inverse Compton scattering. In the radio bands, we find progressive delays of the most prominent light-curve maxima with decreasing frequency, as expected from the frequency dependence of the τ= 1 surface of synchrotron self-absorption. The global maximum in the 86 GHz light curve becomes less prominent at lower frequencies, while a local maximum, appearing in 2014, strengthens toward decreasing frequencies, becoming pronounced at ∼5 GHz. These tendencies suggest different Doppler boosting of stratified radio-emitting zones in the jet. © 2020 The Author(s).We thank the referee for attentive reading and comments that helped to improve presentation of the manuscript. The data collected by the WEBT collaboration are stored in the WEBT archive at the Osservatorio Astrofisico di Torino -INAF (ht tp://www.oato.inaf.it/blazars/webt/); for questions regarding their availability, please contact the WEBT President Massimo Villata([email protected]).TheSt.Petersburg University team acknowledges support from Russian Science Foundation grant 17-12-01029. The research at BU was supported in part by National Science Foundation grant AST-1615796 and NASA Fermi Guest Investigator grants 80NSSC17K0649, 80NSSC19K1504, and 80NSSC19K1505. The PRISM camera at Lowell Observatory was developed by K. Janes et al. at BU and Lowell Observatory, with funding from the NSF, BU, and Lowell Observatory. The emission-line observations made use of the DCT at Lowell Observatory, supported by Discovery Communications, Inc., BU, the University of Maryland, the University of Toledo, and Northern Arizona University. The VLBA is an instrument of the National Radio Astronomy Observatory. The National Radio Astronomy Observatory is a facility of the US NSF, operated under cooperative agreement by Associated Universities, Inc. This research has used data from the UMRAO which was supported by the University of Michigan; research at this facility was supported by NASA under awards NNX09AU16G, NNX10AP16G, NNX11AO13G, and NNX13AP18G, and by the NSF under award AST-0607523. The Steward Observatory spectropolarimetric monitoring project was supported by NASA Fermi Guest Investigator grants NNX08AW56G, NNX09AU10G, NNX12AO93G, and NNX15AU81G. The Torino group acknowledges financial contribution from agreement ASI-INAF n.2017-14-H.0 and from contract PRIN-SKA-CTA-INAF 2016. I.A. acknowledges support by a Ramon y Cajal grant (RYC-2013-14511) of the 'Ministerio de Ciencia, Innovacion, y Universidades (MICIU)' of Spain and from MCIU through the 'Center of Excellence Severo Ochoa' award for the Instituto de Astrofisica de Andalucia-CSIC (SEV-20170709). Acquisition and reduction of the POLAMI and MAPCAT data were supported by MICIU through grant AYA2016-80889-P. The POLAMI observations were carried out at the IRAM 30-m Telescope, supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). The MAPCAT observations were carried out at theGerman-Spanish Calar Alto Observatory, jointly operated by the Max-Plank-Institut fur Astronomie and the Instituto de Astrofisica de Andalucia-CSIC. The study is based partly on data obtained with the STELLA robotic telescopes in Tenerife, an AIP facility jointly operated by AIP and IAC. The OVRO 40-m monitoring program is supported in part by NASA grants NNX08AW31G, NNX11A043G, and NNX14AQ89G, and NSF grants AST-0808050 and AST-1109911. TH was supported by the Academy of Finland projects 317383 and 320085. AZT-24 observations were made within an agreement between Pulkovo, Rome and Teramo observatories. The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. The Abastumani team acknowledges financial support by the Shota Rustaveli National Science Foundation under contract FR/217950/16. r This research was partially supported by the Bulgarian National Science Fund of the Ministry of Education and Science under grants DN 081/2016, DN 18-13/2017, KP-06-H28/3 (2018), and KP-06-PN38/1 (2019), Bulgarian National Science Programme 'Young Scientists and Postdoctoral Students 2019', Bulgarian National Science Fund under grant DN18-10/2017 and National RI Roadmap Projects DO1-157/28.08.2018 and DO1-153/28.08.2018 of the Ministry of Education and Science of the Republic of Bulgaria. GD and OV gratefully acknowledge observing grant support from the Institute of Astronomy and Rozhen National Astronomical Observatory via bilateral joint research project `Study of ICRF radio-sources and fast variable astronomical objects' (head -G. Damljanovic). This work was partly supported by the National Science Fund of the Ministry of Education and Science of Bulgaria under grant DN 08-20/2016, and by project RD-08-37/2019 of the University of Shumen. This work is a part of projects nos 176011, 176004, and 176021, supported by theMinistry of Education, Science and Technological Development of the Republic of Serbia. MGM acknowledges support through the Russian Government Program of Competitive Growth of Kazan Federal University. The Astronomical Observatory of the Autonomous Region of the Aosta Valley (OAVdA) is managed by the Fondazione Clement Fillietroz-ONLUS, which is supported by the Regional Government of the Aosta Valley, the Town Municipality of Nus and the 'Unite des Communes vald 'otainesMont-Emilius'. The research at the OAVdA was partially funded by several `Research and Education' annual grants from Fondazione CRT. This article is partly based on observations made with the IAC80 and TCS telescopes operated by the Instituto de Astrofisica de Canarias in the Spanish Observatorio del Teide on the island of Tenerife. A part of the observations were carried out using theRATAN-600 scientific equipment (SAO of the Russian Academy of Sciences)
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