scholarly journals Multiwavelength analysis of the variability of the blazar 3C 273

2020 ◽  
Vol 497 (2) ◽  
pp. 2066-2077 ◽  
Author(s):  
S Fernandes ◽  
V M Patiño-Álvarez ◽  
V Chavushyan ◽  
E M Schlegel ◽  
J R Valdés
Keyword(s):  
Gamma Ray ◽  
Optical Emission ◽  
Time Frame ◽  
Accretion Disc ◽  
Light Curves ◽  
Time Range ◽  
Data Set ◽  
V Band ◽  
Spectrum Radio ◽  
Observed Behaviour

ABSTRACT We present multiwavelength light curves and polarimetric data of the Flat Spectrum Radio Quasar 3C 273 over 8 yr. The wavelength range of our data set extends from radio to gamma-rays. We found that the optical emission in this source is dominated by the accretion disc during the entire time-frame of study. We additionally find that in contrast with the observed behaviour in other blazars, 3C 273 does not show a correlation between the gamma-ray spectral index and the gamma-ray luminosity. Finally, we identified an anticorrelation between the 15 GHz and V-band light curves for the time-range JD245 = 4860–5760, which we speculate is the consequence of the inner part of the accretion disc falling into the black hole, followed by the ejection of a component into the jet.

scholarly journals The Optical Emission from Gamma-Ray Quasars

2003 ◽  
Vol 20 (2) ◽  
pp. 196-202 ◽  
Author(s):  
M. T. Whiting ◽  
P. Majewski ◽  
R. L. Webster
Keyword(s):  
Near Infrared ◽  
Gamma Ray ◽  
Optical Emission ◽  
Accretion Disc ◽  
Photometric Observations ◽  
Wide Range

AbstractWe present photometric observations of six radio-loud quasars that were detected by the COMPTEL gamma-ray telescope. The data encompass seven wavebands in the optical and near infrared. After correction for Galactic extinction, we find a wide range in optical slopes. Two sources are as blue as optically-selected quasars, and are likely to be dominated by the accretion disc emission, while three others show colours consistent with a red synchrotron component. We discuss the properties of the COMPTEL sample of quasars, as well as the implications our observations have for multiwavelength modelling of gamma-ray quasars.

scholarly journals GAMMA-RAY BURSTS — OBSERVATIONS

2010 ◽  
Vol 19 (06) ◽  
pp. 977-984
Author(s):  
N. GEHRELS ◽  
J. K. CANNIZZO
Keyword(s):  
Gamma Ray ◽  
Optical Emission ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Medium Energy ◽  
Host Galaxies ◽  
Data Set ◽  
Spectral Signatures ◽  
High Energy Emission ◽  
Combined Data

We are in an exciting period of discovery for gamma-ray bursts. The Swift observatory is detecting 100 bursts per year, providing arcsecond localizations and sensitive observations of the prompt and afterglow emission. The Fermi observatory is observing 250 bursts per year with its medium-energy GRB instrument and about 10 bursts per year with its high-energy LAT instrument. In addition, rapid-response telescopes on the ground are providing new capabilities to study optical emission during the prompt phase and spectral signatures of the host galaxies. The combined data set is enabling great advances in our understanding of GRBs including afterglow physics, short burst origin, and high-energy emission.

scholarly journals X-Ray Observations Of Stellar Flares

1983 ◽  
Vol 71 ◽  
pp. 255-272 ◽  
Author(s):  
Bernhard M. Haisch
Keyword(s):  
Optical Emission ◽  
Light Curves ◽  
Data Set ◽  
Time Resolved ◽  
X Ray ◽  
Uv Emission ◽  
Stellar Flares ◽  
History Of ◽  
Relationship Of ◽  
Lower Limits

ABSTRACTThe history of stellar X-ray flare observations prior to EINSTEIN is reviewed. X-ray light curves as measured by the IPC are then presented for all time resolved flare events discovered as of July 1982 in the EINSTEIN data set. These light curves are analyzed in terms of solar-like loop models to derive densities, temperatures, loop lengths, magnetic field strength lower limits, etc. The failure of the model to adequately represent the observations in the case of the YZ CMi flares is discussed. The relationship of X-ray to optical emission and X-ray to UV emission is considered from both an observational and a theoretical viewpoint. It is concluded that the characterization of a flare by a single, time averaged ratio, Lx /Lopt , is not physically significant.

scholarly journals Quasi-periodic behaviour in the optical and γ-ray light curves of blazars 3C 66A and B2 1633+38

2020 ◽  
Vol 492 (4) ◽  
pp. 5524-5539 ◽  
Author(s):  
J Otero-Santos ◽  
J A Acosta-Pulido ◽  
J Becerra González ◽  
C M Raiteri ◽  
V M Larionov ◽  
...  
Keyword(s):  
Light Curve ◽  
Confidence Level ◽  
Light Curves ◽  
Data Set ◽  
Spectrum Radio ◽  
Periodic Behaviour ◽  
Optical Light Curve ◽  
Emission Models ◽  
Γ Ray ◽  
Radio Quasar

ABSTRACT We report on quasi-periodic variability found in two blazars included in the Steward Observatory Blazar Monitoring data sample: the BL Lac object 3C 66A and the Flat Spectrum Radio Quasar B2 1633+38. We collect optical photometric and polarimetric data in V and R bands of these sources from different observatories: St. Petersburg University, Crimean Astrophysical Observatory, WEBT–GASP, Catalina Real-Time Transient Survey, Steward Observatory, STELLA Robotic Observatory, and Katzman Automatic Imaging Telescope. In addition, an analysis of the γ-ray light curves from Fermi–LAT is included. Three methods are used to search for any periodic behaviour in the data: the Z-transform Discrete Correlation Function, the Lomb–Scargle periodogram and the Weighted Wavelet Z-transform. We find pieces of evidence of possible quasi-periodic variability in the optical photometric data of both sources with periods of ∼3 yr for 3C 66A and ∼1.9 yr for B2 1633+38, with significances between 3σ and 5σ. Only B2 1633+38 shows evidence of this behaviour in the optical polarized data set at a confidence level of 2σ–4σ. This is the first reported evidence of quasi-periodic behaviour in the optical light curve of B2 1633+38. Also, a hint of quasi-periodic behaviour is found in the γ-ray light curve of B2 1633+38 with a confidence level ≥2σ, while no periodicity is observed for 3C 66A in this energy range. We propose different jet emission models that could explain the quasi-periodic variability and the differences found between these two sources.

scholarly journals On the distribution of fluxes of gamma-ray blazars: hints for a stochastic process?

2020 ◽  
Vol 497 (1) ◽  
pp. 1294-1300
Author(s):  
F Tavecchio ◽  
G Bonnoli ◽  
G Galanti
Keyword(s):  
Temporal Variability ◽  
Stochastic Equation ◽  
Gamma Ray ◽  
Rotational Energy ◽  
Accretion Disc ◽  
Light Curves ◽  
Differential Distribution ◽  
Predicted Probability ◽  
Stochastic Term ◽  
Γ Ray

ABSTRACT We examine a model for the observed temporal variability of powerful blazars in the γ-ray band in which the dynamics is described in terms of a stochastic differential equation, including the contribution of a deterministic drift and a stochastic term. The form of the equation is motivated by the current astrophysical framework, accepting that jets are powered through the extraction of the rotational energy of the central supermassive black hole mediated by magnetic fields supported by a so-called magnetically arrested accretion disc. We apply the model to the γ-ray light curves of several bright blazars and we infer the parameters suitable to describe them. In particular, we examine the differential distribution of fluxes (dN/dFγ) and we show that the predicted probability density function for the assumed stochastic equation naturally reproduces the observed power-law shape at large fluxes $\mathrm{ d}N/\mathrm{ d}F_{\gamma } \propto F_{\gamma }^{-\alpha }$ with α > 2.

scholarly journals Multiwavelength variability analysis of the FSRQ 3C 279

2014 ◽  
Vol 10 (S313) ◽  
pp. 89-90
Author(s):  
V. Patiño-Álvarez ◽  
V. Chavushyan ◽  
J. León-Tavares ◽  
A. Carramiñana ◽  
L. Carrasco ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Near Infrared ◽  
Gamma Ray ◽  
Activity Period ◽  
V Band ◽  
Spectrum Radio ◽  
Polarization Spectra ◽  
Multiwavelength Variability ◽  
Radio Quasar ◽  
Optical Flare

AbstractWe present a multifrequency analysis of the variability in the flat-spectrum radio quasar 3C 279 from 2008 to 2014. Our multiwavelength dataset includes gamma-ray data from Fermi/LAT (Abdo et al. 2009), observations in 1mm from SMA (Gurwell et al. 2007), Near Infrared from OAGH (Carramiñana & Carrasco 2009) and SMARTS (Bonning et al. 2012); optical V band from the Steward Observatory (Smith et al. 2009) and SMARTS; optical spectra from OAGH (Patiño-Álvarez et al. 2013) and the Steward Observatory; and polarization spectra from the Steward Observatory. The light curves are shown in Fig. 1. Six out of seven optical activity periods identified within our dataset show clear counterparts in mm, NIR and gamma-rays, however, the late 2011 - early 2012 optical flare does not have a counterpart in the GeV regime. In this contribution, we discuss the flaring evolution of 3C 279 and speculate about the production of the anomalous activity period.

scholarly journals Temporal analysis of an unprecedented data set for the gamma-ray blazar 1ES 1215+303: Fermi-LAT and VERITAS light curves spanning ten years

2017 ◽  
Author(s):  
Janeth Valverde ◽  
Deirdre Horan ◽  
Giuliana Noto ◽  
Reshmi Mukherjee ◽  
Denis Bernard ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Temporal Analysis ◽  
Light Curves ◽  
Data Set

Can Precessing Jets Explain the Light Curves of Gamma‐Ray Bursts?

1999 ◽  
Vol 520 (2) ◽  
pp. 666-679 ◽  
Author(s):  
Simon F. Portegies Zwart ◽  
Chang‐Hwan Lee ◽  
Hyun Kyu Lee
Keyword(s):  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Light Curves

scholarly journals SuperWASP variable stars: classifying light curves using citizen science

2021 ◽  
Vol 502 (1) ◽  
pp. 1299-1311
Author(s):  
Heidi B Thiemann ◽  
Andrew J Norton ◽  
Hugh J Dickinson ◽  
Adam McMaster ◽  
Ulrich C Kolb
Keyword(s):  
Variable Stars ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Data Set ◽  
Resultant Data ◽  
Sky Survey ◽  
Short Period ◽  
Contact Binaries ◽  
Analysis Of Results

ABSTRACT We present the first analysis of results from the SuperWASP variable stars Zooniverse project, which is aiming to classify 1.6 million phase-folded light curves of candidate stellar variables observed by the SuperWASP all sky survey with periods detected in the SuperWASP periodicity catalogue. The resultant data set currently contains >1 million classifications corresponding to >500 000 object–period combinations, provided by citizen–scientist volunteers. Volunteer-classified light curves have ∼89 per cent accuracy for detached and semidetached eclipsing binaries, but only ∼9 per cent accuracy for rotationally modulated variables, based on known objects. We demonstrate that this Zooniverse project will be valuable for both population studies of individual variable types and the identification of stellar variables for follow-up. We present preliminary findings on various unique and extreme variables in this analysis, including long-period contact binaries and binaries near the short-period cut-off, and we identify 301 previously unknown binaries and pulsators. We are now in the process of developing a web portal to enable other researchers to access the outputs of the SuperWASP variable stars project.

scholarly journals Light-curve properties of SN 2017fgc and HV SNe Ia

2021 ◽  
Vol 502 (3) ◽  
pp. 4112-4124
Author(s):  
Umut Burgaz ◽  
Keiichi Maeda ◽  
Belinda Kalomeni ◽  
Miho Kawabata ◽  
Masayuki Yamanaka ◽  
...  
Keyword(s):  
Light Curve ◽  
Near Infrared ◽  
Light Curves ◽  
Normal Velocity ◽  
External Effects ◽  
Band Maximum ◽  
Bolometric Luminosity ◽  
V Band ◽  
Photometric And Spectroscopic Observations ◽  
Type Ia

ABSTRACT Photometric and spectroscopic observations of Type Ia supernova (SN) 2017fgc, which cover the period from −12 to + 137 d since the B-band maximum are presented. SN 2017fgc is a photometrically normal SN Ia with the luminosity decline rate, Δm15(B)true  = 1.10 ± 0.10 mag. Spectroscopically, it belongs to the high-velocity (HV) SNe Ia group, with the Si ii λ6355 velocity near the B-band maximum estimated to be 15 200 ± 480 km s−1. At the epochs around the near-infrared secondary peak, the R and I bands show an excess of ∼0.2-mag level compared to the light curves of the normal velocity (NV) SNe Ia. Further inspection of the samples of HV and NV SNe Ia indicates that the excess is a generic feature among HV SNe Ia, different from NV SNe Ia. There is also a hint that the excess is seen in the V band, both in SN 2017fgc and other HV SNe Ia, which behaves like a less prominent shoulder in the light curve. The excess is not obvious in the B band (and unknown in the U band), and the colour is consistent with the fiducial SN colour. This might indicate that the excess is attributed to the bolometric luminosity, not in the colour. This excess is less likely caused by external effects, like an echo or change in reddening but could be due to an ionization effect, which reflects an intrinsic, either distinct or continuous, difference in the ejecta properties between HV and NV SNe Ia.

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