EGRET Observations of High‐Energy Gamma‐Ray Emission from Blazars: An Update

Mukherjee, R.; Bertsch, D. L.; Bloom, S. D.; Dingus, B. L.; Esposito, J. A.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Lin, Y. C.; Mayer‐Hasselwander, H. A.; McDonald, L. M.; Michelson, P. F.; Montigny, C. von; Mücke, A.; Nolan, P. L.; Pohl, M.; Reimer, O.; Schneid, E. J.; Sreekumar, P.; Thompson, D. J.

doi:10.1086/304851

Cited by 242 publications

(185 citation statements)

References 44 publications

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“…We expect, therefore, that gamma rays having energies greater than about 50 MeV are copiously produced in such an event. ON 231 is known to have been detected by EGRET (Mukherjee et al 1997), but unfortunately no data after 1995.5 are available.…”

Section: Discussionmentioning

confidence: 99%

Two-sided radio emission in ON 231 (W Comae)

Massaro

Mantovani

Fanti

et al. 2001

A&A

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Abstract. Recent radio images of the BL Lac object ON 231 (W Com, 1219+285) show remarkable new features in the source structure compared to those previously published. The images were obtained from observations made with the European VLBI Network plus MERLIN at 1.6 GHz and 5 GHz after the exceptional optical outburst occurred in Spring 1998. The up-to-date B band historic light curve of ON 231 is also presented together with the R band luminosity evolution in the period 1994-1999. We identify the source core in the radio images with the brightest component having the flattest spectrum. A consequence of this assumption is the existence of a two-sided emission in ON 231 not detected in previous VLBI images. A further new feature is a large bend in the jet at about 10 mas from the core. The emission extends for about 20 mas after the bend, which might be due to strong interaction with the environment surrounding the nucleus. We suggest some possible interpretations to relate the changes in the source structure with the optical and radio flux density variation in the frame of the unification model.

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Section: Discussionmentioning

confidence: 99%

Two-sided radio emission in ON 231 (W Comae)

Massaro

Mantovani

Fanti

et al. 2001

A&A

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“…The ⋆ E-mail: aditi@aries.res.in spectral energy distribution (SED) of blazars display two welldefined broad spectral components (Mukherjee et al 1997;Weekes 2003). Based on the location of these peaks, we have low energy peaked blazars (LBLs) whose first component peaks in near-IR (NIR)/optical while the second component usually peaks at GeV energies and high energy peaked blazars (HBLs) where first peak is in UV/X-rays while the second peak at TeV energies (Padovani & Giommi 1995, Abdo et al 2010.…”

Section: Introductionmentioning

confidence: 99%

Multiband optical variability studies of BL Lacertae

Agarwal¹,

Gupta²

2015

Monthly Notices of the Royal Astronomical Society

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We monitored BL Lacertae for 13 nights in optical B, V, R, and I bands during October and November 2014 including quasi-simultaneous observations in V and R bands using two optical telescopes in India. We have studied multi-band optical flux variations, colour variation and spectral changes in this blazar. Source was found to be active during the whole monitoring period and showed significant intraday variability on 3 nights in V and R filters while displayed hints of variability on 6 other dates in R passband and on 2 nights in V filter. From the colour-magnitude analysis of the source we found that the spectra of the target gets flatter as it becomes brighter on intra-night timescale. Using discrete correlation technique, we found that intraday light curves in both V and R filters are almost consistent and well correlated with each other. We also generated spectral energy distribution (SED) of the target using the B, V, R, and I data sets for all 13 nights which could help us investigate the physical process responsible for the observed variations in BL Lacertae objects. We also discuss possible physical causes of the observed spectral variability.

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“…The data obtained from the Compton Gamma Ray Observatory (CGRO) mission suggest that blazars-the subclass of active galactic nuclei (AGNs) that includes flat-spectrum radio quasars (FSRQs) and BL Lac objects-are strong -ray emitters (von Montigny et al 1995;Mukherjee et al 1997). In these objects, -ray radiation forms a distinctive spectral component clearly separated from another, lower-energy (synchrotron) component.…”

Section: Introductionmentioning

confidence: 99%

On the Nature of MeV Blazars

Sikora

Błażejowski

Moderski

et al. 2002

ApJ

103

102

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Broadband spectra of the flat-spectrum radio quasars (FSRQs) detected in the high-energy -ray band imply that there may be two types of such objects: those with steep -ray spectra, hereafter called MeV blazars, and those with flat -ray spectra, GeV blazars. We demonstrate that this difference can be explained in the context of the external radiation Compton (ERC) model using the same electron injection function. A satisfactory unification is reachable, provided that (1) spectra of GeV blazars are produced by internal shocks formed at the distances where cooling of relativistic electrons in a jet is dominated by Comptonization of broad emission lines, whereas spectra of MeV blazars are produced at the distances where cooling of relativistic electrons is dominated by Comptonization of near-IR radiation from hot dust, and (2) electrons are accelerated via a two-step process and their injection function takes the form of a double power law, with the break corresponding to the threshold energy for the diffusive shock acceleration. Direct predictions of our model are that, on average, variability timescales of the MeV blazars should be longer than variability timescales of the GeV blazars, and that both types of the blazar phenomenon can appear in the same object.

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EGRET Observations of High‐Energy Gamma‐Ray Emission from Blazars: An Update

Cited by 242 publications

References 44 publications

Two-sided radio emission in ON 231 (W Comae)

Two-sided radio emission in ON 231 (W Comae)

Multiband optical variability studies of BL Lacertae

On the Nature of MeV Blazars

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