General
Los núcleos activos de galaxias (AGN por sus siglas en inglés) se caracterizan por una potente emisión proveniente de una región muy compacta (sólo pocos pcs) en el centro de la galaxia. Los "blazars" son una categoría de AGNs, caracterizados por mostrar una alta luminosidad en un amplio rango de frecuencia, desde radio a altas energías (rayos X y gamma), y también variabilidad extrema y alta polarización en el visible, infrarrojo cercano y radiosondas. La distribución espectral de energía muestra dos máximos: uno a baja frecuencia, de radio al optico, y a veces rayos X; y el de alta frecuencia de rayos X a gamma. El escenario más aceptado para explicar estas propiedades sugiere que la emisión proviene de un chorro de partículas aceleradas a velocidades relativístas, muy alineados con la linea de visión y originandose en las proximidades de un agujero negro supermasivo. En estas condiciones, la emisión del chorro es fuertemente amplificada y facilmente supera la del resto de la galaxia.
Hoy en día, un numero considerable de "blazars" está siendo monitorizado diariamente por los observatorios espaciales de altas energías, Fermi y AGILE. Los "blazars" también destacan en radiación gamma de muy alta energía, donde llevan a cabo las observaciones los telescopios Cherenkov desde Tierra. Por tanto, programas de seguimiento simultáneo son necesarios para aprender mas acerca del comportamiento impredecible en este tipo de AGNs, igualmente que para entender en más detalle los procesos físicos que tienen lugar.
En este proyecto se cubren dos aspectos: por una parte, se pretende proporcionar observaciones de seguimiento en los rangos visibles e infrarrojos usando los telescopios disponibles en los Observatorios del Teide y del Roque de los Muchachos. Esta obseraciones se llevan a cabo dentro del marco de una colaboración más extensa, la GASP-WEBT, que incluye alrededor de otros 30 observatorios. Esta es la unica forma de capturar todas las fases (subida, pico y caida) de los aumentos de flujo, o fulguraciones, que son criticas para los modelos teoricos para las altas energias. Por otra parte, se analizarán largas series temporales (varios años) tomadas en diferentes rangos de energia, buscando correlaciones entre bandas y también cualquier tipo de variaciones periodicas que puedan indicar precesión del chorro, presencia de un sistema binario de agujeros negros o cualquier otro mecanismo. Igualmente se analizarán distintos tipos de fulguraciones que debido a lo impredecible que aparecen se hará en terminos estadisticos.
Miembros
Resultados
- Se confirma que la morfología de la galaxia huésped del núcleo activo Pks 1502+036 corresponde a un tipo elíptico (D'Ammando et al 2018). Este núcleo activo es un potente emisor de radiación gamma lo cual implica que debe albergar un agujero negro muy masivo, contrario al tipo morfológico asociado con la clasificación espectroscopica de la galaxia.
- Primera medida del desplazamiento al rojo del blazar PGC 2402248 a partir de espectroscopia obtenida con OSIRIS en el GTC (Becerra et al, 2018, ATel 11621). Este objeto había sido detectado previamente por MAGIC como fuerte emisor en rayos gamma extremos (E >100GeV)
- El análisis de curvas de luz en el rango visible para dos "blazars" revela un comportamiento periódico, con una cadencia de pocos años.
Actividad científica
Publicaciones relacionadas
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Extreme photometric and polarimetric variability of blazar S4 0954+65 at its maximum optical and γ-ray brightness levelsIn 2022 the BL Lac object S4 0954+65 underwent a major variability phase, reaching its historical maximum brightness in the optical and γ-ray bands. We present optical photometric and polarimetric data acquired by the Whole Earth Blazar Telescope (WEBT) Collaboration from 2022 April 6 to July 6. Many episodes of unprecedented fast variability wereRaiteri, C. M. et al.
Fecha de publicación:
122023 -
A Reemerging Bright Soft X-Ray State of the Changing-look Active Galactic Nucleus 1ES 1927+654: A Multiwavelength View1ES1927+654 is a nearby active galactic nucleus (AGN) that has shown an enigmatic outburst in optical/UV followed by X-rays, exhibiting strange variability patterns at timescales of months to years. Here we report the unusual X-ray, UV, and radio variability of the source in its postflare state (2022 January-2023 May). First, we detect an increaseGhosh, Ritesh et al.
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92023 -
Variability and evolution of the optical polarization of a sample of gamma-ray blazarsWe present a polarization variability analysis of a sample of 26 γ-ray blazars monitored by the Steward Observatory between 2008 and 2018 in the optical band. We investigate the properties and long-term variability of their optical polarization, searching for differences between blazar types. We observe that BL Lac objects are typically lessOtero-Santos, J. et al.
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82023 -
Multimessenger Characterization of Markarian 501 during Historically Low X-Ray and γ-Ray ActivityWe study the broadband emission of Mrk 501 using multiwavelength observations from 2017 to 2020 performed with a multitude of instruments, involving, among others, MAGIC, Fermi's Large Area Telescope (LAT), NuSTAR, Swift, GASP-WEBT, and the Owens Valley Radio Observatory. Mrk 501 showed an extremely low broadband activity, which may help to unravelAbe, H. et al.
Fecha de publicación:
62023 -
Multiwavelength observations of the extraordinary accretion event AT2021lwxWe present observations from X-ray to mid-infrared wavelengths of the most energetic non-quasar transient ever observed, AT2021lwx. Our data show a single optical brightening by a factor >100 to a luminosity of 7 × 10 45 erg s -1 and a total radiated energy of 1.5 × 10 53 erg, both greater than any known optical transient. The decline is smooth andWiseman, P. et al.
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72023 -
The optical behaviour of BL Lacertae at its maximum brightness levels: a blend of geometry and energeticsIn 2021 BL Lacertae underwent an extraordinary activity phase, which was intensively followed by the Whole Earth Blazar Telescope (WEBT) Collaboration. We present the WEBT optical data in the BVRI bands acquired at 36 observatories around the world. In mid-2021 the source showed its historical maximum, with R = 11.14. The light curves display manyRaiteri, C. M. et al.
Fecha de publicación:
62023 -
Follow-up Survey for the Binary Black Hole Merger GW200224_222234 Using Subaru/HSC and GTC/OSIRISThe LIGO/Virgo detected a gravitational wave (GW) event, named GW200224_222234 (also known as S200224ca) and classified as a binary-black hole coalescence, on 2020 February 24. Given its relatively small localization skymap (71 deg 2 for a 90% credible region; revised to 50 deg 2 in GWTC-3), we performed target-of-opportunity observations using theOhgami, Takayuki et al.
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42023 -
Disentangling the nature of the prototype radio weak BL Lac. Contemporaneous multifrequency observations of WISE J141046.00+740511.2Context. The γ-ray emitting source WISE J141046.00+740511.2 has been associated with a Fermi-LAT detection by crossmatching with Swift/XRT data. It has shown all the canonical observational characteristics of a BL Lac source, including a power-law, featureless optical spectrum. However, it was only recently detected at radio frequencies and itsMarchesini, E. J. et al.
Fecha de publicación:
22023 -
Long-term multi-wavelength study of 1ES 0647+250Context. The BL Lac object 1ES 0647+250 is one of the few distant γ-ray emitting blazars detected at very high energies (VHEs; ≳100 GeV) during a non-flaring state. It was detected with the MAGIC telescopes during a period of low activity in the years 2009−2011 as well as during three flaring activities in the years 2014, 2019, and 2020, with theMAGIC Collaboration et al.
Fecha de publicación:
22023 -
Multiwavelength periodicity search in a sample of γ-ray bright blazarsWe present the results of a long-term periodicity search in a sample of γ-ray blazars within a multiwavelength context. These blazars have been selected from the Steward Observatory sample as part of its optical monitoring program between 2008 and 2018. We study 15 sources with a temporal coverage in their optical total and polarized emissionOtero-Santos, J. et al.
Fecha de publicación:
22023 -
Rapid quasi-periodic oscillations in the relativistic jet of BL LacertaeBlazars are active galactic nuclei (AGN) with relativistic jets whose non-thermal radiation is extremely variable on various timescales 1-3. This variability seems mostly random, although some quasi-periodic oscillations (QPOs), implying systematic processes, have been reported in blazars and other AGN. QPOs with timescales of days or hours areJorstad, S. G. et al.
Fecha de publicación:
92022 -
ASTRI Mini-Array core science at the Observatorio del TeideThe ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) Project led by the Italian National Institute for Astrophysics (INAF) is developing and will deploy at the Observatorio del Teide a mini-array (ASTRI Mini-Array) composed of nine telescopes similar to the small-size dual-mirror Schwarzschild-Couder telescope (ASTRI-Horn) currentlyVercellone, S. et al.
Fecha de publicación:
82022 -
A Radio, Optical, UV, and X-Ray View of the Enigmatic Changing-look Active Galactic Nucleus 1ES 1927+654 from Its Pre- to Postflare StatesThe nearby Type II active galactic nucleus (AGN) 1ES 1927+654 went through a violent changing-look (CL) event beginning 2017 December during which the optical and UV fluxes increased by four magnitudes over a few months, and broad emission lines newly appeared in the optical/UV. By 2018 July, the X-ray coronal emission had completely vanished, onlyLaha, Sibasish et al.
Fecha de publicación:
52022 -
A statistical study of the optical spectral variability in gamma-ray blazarsBlazars optical emission is generally dominated by relativistic jets, although the host galaxy, accretion disc, and broad-line region (BLR) may also contribute significantly. Disentangling their contributions has been challenging for years due to the dominance of the jet. To quantify the contributions to the spectral variability, we use theOtero-Santos, J. et al.
Fecha de publicación:
42022 -
Investigation of the correlation patterns and the Compton dominance variability of Mrk 421 in 2017Aims: We present a detailed characterisation and theoretical interpretation of the broadband emission of the paradigmatic TeV blazar Mrk 421, with a special focus on the multi-band flux correlations. Methods: The dataset has been collected through an extensive multi-wavelength campaign organised between 2016 December and 2017 June. The instrumentsMAGIC Collaboration et al.
Fecha de publicación:
112021 -
Optical spectral characterization of the gamma-ray blazars S4 0954+65, TXS 1515-273, and RX J0812.0+0237The study of gamma-ray blazars is usually hindered due to the lack of information on their redshifts and on their low-energy photon fields. This information is key to understand the effect on the gamma-ray absorption due to either extragalactic background light and/or intrinsic absorption and emission processes. All this information has also anBecerra González, J. et al.
Fecha de publicación:
72021 -
The complex variability of blazars: time-scales and periodicity analysis in S4 0954+65Among active galactic nuclei, blazars show extreme variability properties. We here investigate the case of the BL Lac object S4 0954+65 with data acquired in 2019-2020 by the Transiting Exoplanet Survey Satellite (TESS) and by the Whole Earth Blazar Telescope (WEBT) Collaboration. The 2-min cadence optical light curves provided by TESS during threeRaiteri, C. M. et al.
Fecha de publicación:
72021 -
The dual nature of blazar fast variability: Space and ground observations of S5 0716+714Blazar S5 0716+714 is well-known for its short-term variability, down to intraday time-scales. We here present the 2-min cadence optical light curve obtained by the TESS space telescope in 2019 December-2020 January and analyse the object fast variability with unprecedented sampling. Supporting observations by the Whole Earth Blazar TelescopeRaiteri, C. M. et al.
Fecha de publicación:
22021 -
Multiwavelength Variability of BL Lacertae Measured with High Time ResolutionIn an effort to locate the sites of emission at different frequencies and physical processes causing variability in blazar jets, we have obtained high time-resolution observations of BL Lacertae over a wide wavelength range: with the Transiting Exoplanet Survey Satellite (TESS) at 6000-10000 Å with 2 minute cadence; with the Neil Gehrels SwiftWeaver, Z. R. et al.
Fecha de publicación:
92020 -
An intermittent extreme BL Lac: MWL study of 1ES 2344+514 in an enhanced stateExtreme high-frequency BL Lacs (EHBL) feature their synchrotron peak of the broad-band spectral energy distribution (SED) at ν s ≥ 10 17 Hz. The BL Lac object 1ES 2344+514 was included in the EHBL family because of its impressive shift of the synchrotron peak in 1996. During the following years, the source appeared to be in a low state withoutMAGIC Collaboration et al.
Fecha de publicación:
62020
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