We report here on the first multi-wavelength (MWL) campaign on the blazar TXS 1515-273, undertaken in 2019 and extending from radio to very-high-energy gamma rays (VHE). Up until now, this blazar had not been the subject of any detailed MWL observations. It has a rather hard photon index at GeV energies and was considered a candidate extreme high-synchrotronpeaked source. MAGIC observations resulted in the first-time detection of the source in VHE with a statistical significance of 7.6$\sigma$. The average integral VHE flux of the source is 6 $\pm$ 1% of the Crab nebula flux above 400 GeV. X-ray coverage was provided by Swift-XRT, XMMNewton, and NuSTAR. The long continuous X-ray observations were separated by $\sim$ 9 h, both showing clear hour scale flares. In the XMM-Newton data, both the rise and decay timescales are longer in the soft X-ray than in the hard X-ray band, indicating the presence of a particle cooling regime. The X-ray variability timescales were used to constrain the size of the emission region and the strength of the magnetic field. The data allowed us to determine the synchrotron peak frequency and classify the source as a flaring high, but not extreme, synchrotron peaked object. Considering the constraints and variability patterns from the X-ray data, we model the broad-band spectral energy distribution. We applied a simple one-zone model, which could not reproduce the radio emission and the shape of the optical emission, and a two-component leptonic model with two interacting components, enabling us to reproduce the emission from radio to VHE band.

BL Lac object

Crab Nebula

Spectral energy distribution

10.1093/mnras/stab1994

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Citations (6)

Multiwavelength monitoring of the BL Lacertae object PKS 2155-304. I - The IUE campaign

The Astrophysical Journal (1993)

C. M. Urry L. Maraschi R. Edelson Anuradha Koratkar Julian H. Krolik

view Abstract Citations (108) References (55) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multiwavelength Monitoring of the BL Lacertae Object PKS 2155-304. I. The IUE Campaign Urry, C. M. ; Maraschi, L. ; Edelson, R. ; Koratkar, A. ; Krolik, J. ; Madejski, G. ; Pian, E. ; Pike, G. ; Reichert, G. ; Treves, A. ; Wamsteker, W. ; Bohlin, R. ; Bregman, J. ; Brinkmann, W. ; Chiappetti, L. ; Courvoisier, T. ; Filippenko, A. V. ; Fink, H. ; George, I. M. ; Kondo, Y. ; Martin, P. G. ; Miller, H. R. ; O'Brien, P. ; Shull, J. M. ; Sitko, M. ; Szymkowiak, A. E. ; Tagliaferri, G. ; Wagner, S. ; Warwick, R. Abstract Daily monitoring of PKS 2155 - 304 with the IUE satellite throughout 1991 November has revealed dramatic, large-amplitude, rapid variations in the ultraviolet flux of this BL Lac object. Many smaller, rapid flares are superposed on a general doubling of the intensity. During the 5^d^ period when sampling was roughly continuous, the rapid flaring had an apparent quasi-periodic nature, with peaks repeating every ~0.7^d^. The short- and long-wavelength ultraviolet light curves are well correlated with each other, and with the optical light curve deduced from the Fine Error Sensor (FES) on IUE. The formal lag is zero, but the cross- correlation is asymmetric in the sense that the shorter wavelength emission leads the longer. The ultraviolet spectral shape varies a small but significant amount. The correlation between spectral shape and intensity is complicated; an increase in intensity is associated with spectral hardening, but lags behind the spectral change by ~1 day. The sign of the correlation is consistent with the nonthermal acceleration processes expected in relativistic plasmas, so that the present results are consistent with relativistic jet models, which can also account for quasi-periodic flaring. In contrast, currently proposed accretion disk models are strongly ruled out by the simultaneous optical and ultraviolet variability. Publication: The Astrophysical Journal Pub Date: July 1993 DOI: 10.1086/172864 arXiv: arXiv:astro-ph/9304003 Bibcode: 1993ApJ...411..614U Keywords: Accretion Disks; Active Galactic Nuclei; Active Galaxies; Bl Lacertae Objects; Iue; Light Curve; Ultraviolet Spectra; Astronomical Models; Blazars; Brightness Temperature; Relativistic Plasmas; Astrophysics; Astrophysics E-Print: 27 pages, plain TeX, STScI Preprint 714 full text sources arXiv | ADS | data products SIMBAD (3) NED (1) MAST (1) INES (1) Related Materials (3) Part 2: 1994A&A...288..433B Part 3: 1995ApJ...438..108C Part 4: 1995ApJ...438..120E

BL Lac object

Ultraviolet

ROSAT

10.1086/172864

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Citations (79)

Variability of the BL Lacertae objects PKS 2155 - 304 and OJ 287 in the far-ultraviolet

The Astrophysical Journal (1986)

L. Maraschi A. Treves G. Tagliaferri E. G. Tanzi

view Abstract Citations (34) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Variability of the BL Lacertae Objects PKS 2155-304 and OJ 287 in the Far-Ultraviolet Maraschi, L. ; Tagliaferri, G. ; Tanzi, E. G. ; Treves, A. Abstract All the ultraviolet spectra of the two bright BL Lacertae objects PKS 2155 - 304 and OJ 287 taken with the International Ultraviolet Explorer in the period 1978-1984 are examined. For each spectrum the best-fitting power law is determined and a correlation between spectral slope and intensity is searched for. The correlation, if present, is weak. This is discussed in terms of models of the continuum emission of active galactic nuclei. Publication: The Astrophysical Journal Pub Date: May 1986 DOI: 10.1086/164200 Bibcode: 1986ApJ...304..637M Keywords: Bl Lacertae Objects; Far Ultraviolet Radiation; Galactic Nuclei; Periodic Variations; Spectrum Analysis; Ultraviolet Spectra; Active Galactic Nuclei; Astronomical Models; Continuous Spectra; Emission Spectra; Iue; Radiant Flux Density; Spectral Energy Distribution; Astrophysics; BL LACERTAE OBJECTS; ULTRAVIOLET: SPECTRA full text sources ADS | data products SIMBAD (2) NED (2) MAST (1) INES (1)

Ultraviolet

Spectral energy distribution

BL Lac object

10.1086/164200

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Citations (9)

Deep observation of the NGC 1275 region with MAGIC: search of diffuseγ-ray emission from cosmic rays in the Perseus cluster

Astronomy and Astrophysics (2016)

M. L. Ahnen S. Ansoldi L. A. Antonelli P. Antoranz A. Babić

Clusters of galaxies are expected to be reservoirs of cosmic rays (CRs) that should produce diffuse gamma-ray emission due to their hadronic interactions with the intra-cluster medium. The nearby Perseus cool-core cluster, identified as the most promising target to search for such an emission, has been observed with the MAGIC telescopes at very-high energies (VHE, E>100 GeV) for a total of 253 hr from 2009 to 2014. The active nuclei of NGC 1275, the central dominant galaxy of the cluster, and IC 310, lying at about 0.6$^\circ$ from the centre, have been detected as point-like VHE gamma-ray emitters during the first phase of this campaign. We report an updated measurement of the NGC 1275 spectrum, which is well described by a power law with a photon index of $3.6\pm0.2_{stat}\pm0.2_{syst}$ between 90 GeV and 1.2 TeV. We do not detect any diffuse gamma-ray emission from the cluster and set stringent constraints on its CR population. In order to bracket the uncertainties over the CR spatial and spectral distributions, we adopt different spatial templates and power-law spectral indexes $\alpha$. For $\alpha=2.2$, the CR-to-thermal pressure within the cluster virial radius is constrained to be below 1-2%, except if CRs can propagate out of the cluster core, generating a flatter radial distribution and releasing the CR-to-thermal pressure constraint to <20%. Assuming that the observed radio mini-halo of Perseus is generated by secondary electrons from CR hadronic interactions, we can derive lower limits on the central magnetic field, $B_0$, that depend on the CR distribution. For $\alpha=2.2$, $B_0\gtrsim5-8 \mu$G, which is below the 25 $\mu$G inferred from Faraday rotation measurements, whereas, for $\alpha\lesssim2.1$, the hadronic interpretation of the diffuse radio emission is in contrast with our gamma-ray flux upper limits independently of the magnetic field strength.

10.1051/0004-6361/201527846

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Citations (51)

Two temperature spherical accretion onto a black hole: The X and gamma ray spectrum

Monica Colpi L. Maraschi A. Treves

Black-body radiation

Accretion disc

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On the nebulosity surrounding the BL Lacertae object PKS 2155 - 304

The Astrophysical Journal (1991)

R. Falomo E. Giraud J. L. Melnick L. Maraschi E. G. Tanzi

view Abstract Citations (39) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On the Nebulosity Surrounding the BL Lacertae Object PKS 2155-304 Falomo, R. ; Giraud, E. ; Maraschi, L. ; Melnick, J. ; Tanzi, E. G. ; Treves, A. Abstract High-resolution imaging of the bright BL Lacertae object PKS 2155 - 304 reveals a symmetric nebulosity extending up to 15" from the nucleus and confirms the presence of a faint galaxy located ~4'' away from the nucleus. We show that the redshift of z = 0.117, previously attributed to the BL Lac object, pertains in fact to the companion galaxy. The radial brightness profile of the surrounding nebulosity is consistent with that of an elliptical galaxy of effective radius of 4.5'' which, assuming an absolute magnitude typical of luminous ellipticals, puts the object at z~0.1. The field of PKS 2155-304 appears to be rich in galaxies, one of which is at z = 0.116. A scenario in which the BL Lac object is hosted by a giant elliptical (M_v_~ - 22.5), which is the brightest member of a group of galaxies, is suggested by our observations. Publication: The Astrophysical Journal Pub Date: October 1991 DOI: 10.1086/186175 Bibcode: 1991ApJ...380L..67F Keywords: Astronomical Spectroscopy; Bl Lacertae Objects; Elliptical Galaxies; Nebulae; Astronomical Observatories; Brightness Distribution; Charge Coupled Devices; Astrophysics; BL LACERTAE OBJECTS; GALAXIES: INDIVIDUAL ALPHANUMERIC: PKS 2155-304 full text sources ADS | data products SIMBAD (4) NED (1)

BL Lac object

Absolute magnitude

10.1086/186175

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Citations (22)

THE JUNE 2008 FLARE OF MARKARIAN 421 FROM OPTICAL TO TeV ENERGIES

The Astrophysical Journal (2008)

I. Donnarumma V. Vittorini S. Vercellone E. Del Monte M. Feroci

We present optical, X-ray, high energy ($\lessapprox 30$ GeV) and very high energy ($\gtrapprox 100$ GeV; VHE) observations of the high-frequency peaked blazar Mrk 421 taken between 2008 May 24 and June 23. A high energy $\gamma$-ray signal was detected by AGILE with \sqrt{TS}=4.5 on June 9--15, with $F(E>100 \mathrm{MeV})= 42^{+14}_{-12}\times 10^{-8}$ photons cm$^{-2}$ s$^{-1}$. This flaring state is brighter than the average flux observed by EGRET by a factor of $\sim$3, but still consistent with the highest EGRET flux. In hard X-rays (20-60 keV) SuperAGILE resolved a 5-day flare (June 9-15) peaking at $\sim$ 55 mCrab. SuperAGILE, RXTE/ASM and Swift/BAT data show a correlated flaring structure between soft and hard X-rays. Hints of the same flaring behavior are also detected in the simultaneous optical data provided by the GASP-WEBT. A Swift/XRT observation near the flaring maximum revealed the highest 2-10 keV flux ever observed from this source, of 2.6 $\times 10^{-9}$ erg cm$^{-2}$ s$^{-1}$ (i.e. > 100 mCrab). A peak synchrotron energy of $\sim$3 keV was derived, higher than typical values of $\sim$0.5-1 keV. VHE observations with MAGIC and VERITAS on June 6-8 show the flux peaking in a bright state, well correlated with the X-rays. This extraordinary set of simultaneous data, covering a twelve-decade spectral range, allowed for a deep analysis of the spectral energy distribution as well as of correlated light curves. The $\gamma$-ray flare can be interpreted within the framework of the synchrotron self-Compton model in terms of a rapid acceleration of leptons in the jet.

Flare

Spectral energy distribution

10.1088/0004-637x/691/1/l13

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Citations (100)

Coordinated UV and optical observations of the AM Herculis object E1405-451 in the high and low states

The Astrophysical Journal (1984)

L. Maraschi A. Treves E. G. Tanzi M. Mouchet A. Lauberts

view Abstract Citations (28) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Coordinated UV and optical observations of the AM Herculis object E 1405-451 in thehigh and low sta Maraschi, L. ; Treves, A. ; Tanzi, E. G. ; Mouchet, M. ; Lauberts, A. ; Motch, C. ; Bonnet Bidaud, J. M. ; Phillips, M. M. Abstract Simultaneous UV and optical observations of the magnetic white dwarf binary E1405-451 taken in February 1983, March, and April are reported. In March the source was found in a low state analogous to those observed in AM Her. In this state the ultraviolet spectrum of E1405-451 can be interpreted as the emission from a hot white dwarf/T = 26,500 K, R = 3 x 10 to the 8th x (d/100 pc) cm, and the R and I magnitudes can be accounted for by a Roche lobe filling secondary, of spectral type between M3 V and M8 V at a distance between 50 and 200 pc. Emission from a residual accretion column may still be present. In the high state, the UV continuum is described by a power law, F-gamma varies as gamma to the power-alpha with alpha = 1.9, while the optical and infrared magnitudes lie above the extrapolation of this power law. Subtracting the emission of the white dwarf and of the secondary from the overall energy distribution in the high state, the residual spectrum seems to contain two components. A steep one, emerging shortward of 2000 A, could be associated with a hot polar cap; a flatter one, between 2000 and 6000 A, rapidly decreasing in the infrared, could be due to cyclotron radiation. Publication: The Astrophysical Journal Pub Date: October 1984 DOI: 10.1086/162494 Bibcode: 1984ApJ...285..214M Keywords: Binary Stars; Cataclysmic Variables; Magnetic Stars; Ultraviolet Spectra; White Dwarf Stars; X Ray Sources; Blue Stars; Continuous Spectra; Emission Spectra; Hot Stars; Iue; Spectral Energy Distribution; Stellar Radiation; Stellar Spectrophotometry; Astrophysics full text sources ADS | data products SIMBAD (2) MAST (1) INES (1)

Spectral energy distribution

Ultraviolet

Cataclysmic variable star

10.1086/162494

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Broad band spectral study of the BeppoSAX observation of NGC 3783

Memorie della Societa Astronomica Italiana (2001)

Alessandra De Rosa L. Piro P. Grandi F. Fiore Francesco Haardt

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Multiwavelength observations of the February 1996 high-energy flare in the blazar 3C 279

AIP conference proceedings (1997)

A. E. Wehrle E. Pian C. M. Urry L. Maraschi G. Ghisellini

We report CGRO, RXTE, ASCA, ROSAT, IUE, HST and ground-based observations of a large flare in 3C 279 in February 1996. X-rays and γ-rays peaked simultaneously (within one day). We show simultaneous spectral energy distributions prior to and near the flare peak. The γ-ray flare was the brightest ever observed in this source.

Flare

ROSAT

High energy

10.1063/1.53954

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