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Title: Short timescale photometric and polarimetric behavior of two BL Lacertae type objects

Abstract

Context. Blazars are astrophysical sources whose emission is dominated by non-thermal processes, typically interpreted as synchrotron and inverse Compton emission. Although the general picture is rather robust and consistent with observations, many aspects are still unexplored. Aims. Polarimetric monitoring can offer a wealth of information about the physical processes in blazars. Models with largely different physical ingredients can often provide almost indistinguishable predictions for the total flux, but usually are characterized by markedly different polarization properties. We explore, with a pilot study, the possibility to derive structural information about the emitting regions of blazars by means of a joint analysis of rapid variability of the total and polarized flux at optical wavelengths. Methods. Short timescale (from tens of seconds to a couple of minutes) optical linear polarimetry and photometry for two blazars, BL Lacertae and PKS 1424+240, was carried out with the PAOLO polarimeter at the 3.6 m Telescopio Nazionale Galileo. Several hours of almost continuous observations were obtained for both sources. Results. Our intense monitoring allowed us to draw strongly different scenarios for BL Lacertae and PKS 1424+240, with the former characterized by intense variability on time-scales from hours to a few minutes and the latter practically constant inmore » total flux. Essentially the same behavior is observed for the polarized flux and the position angle. The variability time-scales turned out to be as short as a few minutes, although involving only a few percent variation of the flux. The polarization variability time-scale is generally consistent with the total flux variability. Total and polarized flux appear to be essentially uncorrelated. However, even during our relatively short monitoring, different regimes can be singled out. Conclusions. No simple scenario is able to satisfactorily model the very rich phenomenology exhibited in our data. As a result, detailed numerical simulations show that the emitting region should be characterized by some symmetry, and the inclusion of turbulence for the magnetic field may constitute the missing ingredient for a more complete interpretation of the data.« less

Authors:
 [1];  [2];  [1];  [2];  [1];  [3];  [4];  [5];  [1];  [6];  [7];  [8];  [7];  [9];  [9];  [10];  [7];  [11];  [12];  [13] more »;  [14];  [14];  [1] « less
  1. Istituto Nazionale di Astrofisica (INAF), Merate (Italy)
  2. Univ. degli Studi dell' Insubria, Como (Italy); Istituto Nazionale di Astrofisica (INAF), Merate (Italy)
  3. Univ. degli Studi dell' Insubria, Como (Italy); Univ. degli Studi di Milano-Bicocca, Milano (Italy)
  4. Ohio Univ., Athens, OH (United States); Los Alamos National Lab., Los Alamos, NM (United States)
  5. Ministerio da Ciencia, Tecnologia e Inovacao (MCTI), Rio de Janiero (Brazil)
  6. North-West University, Potchefstroom (South Africa); Ohio Univ., Athens, OH (United States)
  7. Fundacion Galileao Galilei - INAF, Canary Islands (Spain)
  8. Istituto Nazionale di Astrofisica (INAF), Bologna (Italy); Univ. di Bologna, Bologna (Italy)
  9. Univ. di Catania, Catania (Italy)
  10. Univ. of Turku (Finland); Univ. of Oulu (Finland)
  11. Fundacion Galileao Galilei - INAF, Canary Islands (Spain); INAF/Instituto di Astrofisica Spaziale e Fisica Cosmica Milano, Milano (Italy)
  12. Università di Padova and INFN, Padova (Italy)
  13. Univ. of Geneva, Versoix (Switzerland)
  14. INAF/Osservatorio Astrofisico di Torino, Pino Torinse (Italy)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1221161
Report Number(s):
LA-UR-15-20163
Journal ID: ISSN 0004-6361; PII: aa25674-15; TRN: US1500724
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Astronomy and Astrophysics
Additional Journal Information:
Journal Volume: 578; Journal ID: ISSN 0004-6361
Publisher:
EDP Sciences
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; Polarization; BL Lacertae objects; PKS; 1424+240

Citation Formats

Covino, S., Baglio, M. C., Foschini, L., Sandrinelli, A., Tavecchio, F., Treves, A., Zhang, H., Barres de Almeida, U., Bonnoli, G., Böttcher, M., Cecconi, M., D’Ammando, F., di Fabrizio, L., Giarrusso, M., Leone, F., Lindfors, E., Lorenzi, V., Molinari, E., Paiano, S., Prandini, E., Raiteri, C. M., Stamerra, A., and Tagliaferri, G. Short timescale photometric and polarimetric behavior of two BL Lacertae type objects. United States: N. p., 2015. Web. doi:10.1051/0004-6361/201525674.
Covino, S., Baglio, M. C., Foschini, L., Sandrinelli, A., Tavecchio, F., Treves, A., Zhang, H., Barres de Almeida, U., Bonnoli, G., Böttcher, M., Cecconi, M., D’Ammando, F., di Fabrizio, L., Giarrusso, M., Leone, F., Lindfors, E., Lorenzi, V., Molinari, E., Paiano, S., Prandini, E., Raiteri, C. M., Stamerra, A., & Tagliaferri, G. Short timescale photometric and polarimetric behavior of two BL Lacertae type objects. United States. doi:10.1051/0004-6361/201525674.
Covino, S., Baglio, M. C., Foschini, L., Sandrinelli, A., Tavecchio, F., Treves, A., Zhang, H., Barres de Almeida, U., Bonnoli, G., Böttcher, M., Cecconi, M., D’Ammando, F., di Fabrizio, L., Giarrusso, M., Leone, F., Lindfors, E., Lorenzi, V., Molinari, E., Paiano, S., Prandini, E., Raiteri, C. M., Stamerra, A., and Tagliaferri, G. Fri . "Short timescale photometric and polarimetric behavior of two BL Lacertae type objects". United States. doi:10.1051/0004-6361/201525674. https://www.osti.gov/servlets/purl/1221161.
@article{osti_1221161,
title = {Short timescale photometric and polarimetric behavior of two BL Lacertae type objects},
author = {Covino, S. and Baglio, M. C. and Foschini, L. and Sandrinelli, A. and Tavecchio, F. and Treves, A. and Zhang, H. and Barres de Almeida, U. and Bonnoli, G. and Böttcher, M. and Cecconi, M. and D’Ammando, F. and di Fabrizio, L. and Giarrusso, M. and Leone, F. and Lindfors, E. and Lorenzi, V. and Molinari, E. and Paiano, S. and Prandini, E. and Raiteri, C. M. and Stamerra, A. and Tagliaferri, G.},
abstractNote = {Context. Blazars are astrophysical sources whose emission is dominated by non-thermal processes, typically interpreted as synchrotron and inverse Compton emission. Although the general picture is rather robust and consistent with observations, many aspects are still unexplored. Aims. Polarimetric monitoring can offer a wealth of information about the physical processes in blazars. Models with largely different physical ingredients can often provide almost indistinguishable predictions for the total flux, but usually are characterized by markedly different polarization properties. We explore, with a pilot study, the possibility to derive structural information about the emitting regions of blazars by means of a joint analysis of rapid variability of the total and polarized flux at optical wavelengths. Methods. Short timescale (from tens of seconds to a couple of minutes) optical linear polarimetry and photometry for two blazars, BL Lacertae and PKS 1424+240, was carried out with the PAOLO polarimeter at the 3.6 m Telescopio Nazionale Galileo. Several hours of almost continuous observations were obtained for both sources. Results. Our intense monitoring allowed us to draw strongly different scenarios for BL Lacertae and PKS 1424+240, with the former characterized by intense variability on time-scales from hours to a few minutes and the latter practically constant in total flux. Essentially the same behavior is observed for the polarized flux and the position angle. The variability time-scales turned out to be as short as a few minutes, although involving only a few percent variation of the flux. The polarization variability time-scale is generally consistent with the total flux variability. Total and polarized flux appear to be essentially uncorrelated. However, even during our relatively short monitoring, different regimes can be singled out. Conclusions. No simple scenario is able to satisfactorily model the very rich phenomenology exhibited in our data. As a result, detailed numerical simulations show that the emitting region should be characterized by some symmetry, and the inclusion of turbulence for the magnetic field may constitute the missing ingredient for a more complete interpretation of the data.},
doi = {10.1051/0004-6361/201525674},
journal = {Astronomy and Astrophysics},
number = ,
volume = 578,
place = {United States},
year = {Fri Jun 05 00:00:00 EDT 2015},
month = {Fri Jun 05 00:00:00 EDT 2015}
}

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  • The results are given of polarimetric and photometric observations of the BL Lac objects OI 090.4 over the period 1979-1982 and B2 1418 + 54 over the period 1980-1982. For both objects it was noted that there was variability on a time scale of from several years to several days. The comparison of the polarimetric parameters indicates the existence of a preferred direction of polarization both for B2 1418 + 54 (theta /sub O/ = 120/sup 0/), and for OI 090.4 (theta /sub O/ = 50/sup 0/), which points to a stable magnetic field. For OI 090.4 it was observedmore » that there was a certain dependence of the polarization parameters on the wavelength.« less
  • Results are presented on a systematic analysis of more than 200 X-ray observations on 36 BL Lac objects, obtained from the Exosat archive, providing further strong evidence that the population of currently known BL Lac objects can be divided into two subclasses, Q-BL Lacs and X-BL Lacs. The subclass Q-BL Lacs includes most of the classical radio-discovered BL objects which are characterized by a continuum energy distribution, from radio to X-rays, similar to that of flat-radio-spectrum QSOs, highly polarized quasars, and optically violent variable QSOs. The subclass X-BL Lacs includes all the BL Lac objects which were detected in high-frequencymore » surveys (i.e., optical and X-ray). This subclass is characterized by a very smooth energy distribution from radio to X-rays, which is often considered to be the signature of synchrotron emission. 96 refs.« less
  • Two 16th magnitude BL Lac objects, H1101 - 232 and H1426 + 428, have been discovered. Each is a persistent and relatively bright X-ray source. A 2.7 percent linear polarization is measured in the optical emission or H101 - 232. The X-ray identification of H1426 + 428 is confirmed in an Exosat observation. The X-ray spectrum is well-modeled by a power law with an energy index of 1.19. Both BL Lac objects exhibit high f(x)/f(opt) ratios and they show a distinct resemblance to other X-ray selected BL Lac objects. The host galaxies are about 18th mag with angular diameters ofmore » about 20 arcsec and each may be the dominant member of a cluster of galaxies. Additional wide-slit spectroscopy reveals faint absorption features with redshifts of 0.129 for H1426 + 428 and 0.186 for H1101 - 232. The implied X-ray and optical luminosities exceed 10 to the 45th ergs/s for both BL Lac nuclei, assuming isotropic emission. 37 refs.« less
  • This paper reports on the soft X-ray (0.15-2.8 keV) observations of two BL Lacertae-type objects, viz., Mrk 421 and Mrk 501. The observations were made with the low-energy detectors on the HEAO 1 satellite during the period 1977 August-1978 December. Steep, soft X-ray power-law spectra with photon index Gamma = 3 are found for both Mrk 421 and Mrk 501. The power-law models are found to give a significantly better fit than the thermal models to the observed pulse-height spectra of Mrk 421 and Mrk 501. Day-to-day soft X-ray (0.25 keV band) intensity variations are observed only in Mrk 501.more » No significant change is found in Gamma from both the BL Lac objects during the period of observations. However, the sum of all the X-ray observations from 1976 until 1980 can be understood in terms of two spectral components of variable intensity to account for the X-ray emission observed between 0.15 and 20 keV from Mrk 421 and Mrk 501. 24 references.« less