- ID:
- ivo://CDS.VizieR/J/A+A/591/A21
- Title:
- Optical flux behaviour of Fermi blazars
- Short Name:
- J/A+A/591/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim at investigating the time-behaviour of a sample of gamma-ray blazars. We present the results from a 13 month-long optical photometry monitoring campaign of the blazars PKS0048-097, PKS0754+100, [HB89] 0827+243, PKS0851+202, PKS1253-055, PKS1510-089, PKS1749+096, PKS2230+114 and PKS2251+158. We analyse the variability of each object, focusing on different time-scales (long term, short term, and microvariability), in an attempt to achieve a statistical comparison of the results. After applying a geometric model to explain the variability results, we found that it is possible that a slight change in the direction of the jet generates the variations detected in some objects during this campaign.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/880/32
- Title:
- Optical/{gamma}-ray flares for Fermi-LAT blazars
- Short Name:
- J/ApJ/880/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Even with several thousand Fermi-Large Area Telescope (LAT) blazar detections, the {gamma}-ray emission mechanism is poorly understood. We explore correlated optical/{gamma}-ray flux variations for 178 Fermi-LAT blazars regularly monitored by the Katzman Automatic Imaging Telescope, the Small and Moderate Aperture Research Telescope System, and the Steward Observatory. Out of the 178 sources, 121 show a measurable (>1{sigma}) discrete correlation function peak. Using the derived time lags and Bayesian block light-curve decompositions, we measure the fraction of common and orphan flares between the two bands. After accounting for sampling and sensitivity limitations we quantify for the first time the true orphan flare rates of optical and {gamma}-ray flares: 54.5% of optical and 20% of {gamma}-ray flares are orphan events. Both the intraband temporal relation and the small orphan {gamma}-ray flare fraction point toward leptonic processes as the likely mechanisms for the high-energy emission. Motivated to discriminate between synchrotron self-Compton (SSC) and external-Compton dominance in individual sources, we use the flux-flux variations to determine the slope m of the log fopt-log f{gamma} dependence. The slope distribution suggests a bimodal population with high and intermediate synchrotron peak objects showing larger m than low synchrotron peak objects. We find that m is naturally decreased through pollution from the orphan (typically optical) flares and develop a method to statistically recover, given the sources' measured orphan flare rate, the intrinsic m. While source classes show composite behavior, the majority of BL Lac objects favor m=2, indicating an SSC origin for the {gamma}-rays. No preference for either m is found in flat spectrum radio quasars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/439/690
- Title:
- Optical/{gamma}-ray variability in blazars
- Short Name:
- J/MNRAS/439/690
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use optical data from the Palomar Transient Factory (PTF) and the Catalina Real-Time Transient Survey (CRTS) to study the variability of {gamma}-ray-detected and non-detected objects in a large population of active galactic nuclei selected from the Candidate Gamma-Ray Blazar Survey and Fermi Gamma-Ray Space Telescope catalogues. Our samples include 714 sources with PTF data and 1244 sources with CRTS data. We calculate the intrinsic modulation index to quantify the optical variability amplitude in these samples.
- ID:
- ivo://CDS.VizieR/J/A+A/531/A123
- Title:
- Optical light curve of PKS 2155-304
- Short Name:
- J/A+A/531/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The long-term optical light curve of PKS 2155-304 is assembled from archival data as well as from so-far unpublished observations mostly carried out with the ROTSE-III and the ASAS robotic telescopes. A forward folding technique is used to determine the best-fit parameters for a model of a power law with a break in the power spectral density function (PSD). The best-fit parameters are estimated using a maximum-likelihood method with simulated light curves in conjunction with the Lomb-Scargle periodogram and the first-order structure function (SF). In addition, a new approach based upon the so-called multiple fragments variance function (MFVF) is introduced and compared to the other methods. Simulated light curves have been used to confirm the reliability of these methods as well as to estimate the uncertainties of the best-fit parameters.
- ID:
- ivo://CDS.VizieR/J/A+A/529/A162
- Title:
- Optically selected BL Lac candidates polarimetry
- Short Name:
- J/A+A/529/A162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 195 polarimetric measurements of 182 BL Lac candidates from the SDSS taken with 3 different telescopes are presented. For each candidate the J2000 coordinates, its redshift, whether a source is listed in NED, the SDSS r-mag, the telescope for the observations used, the date of the observations, the exposure time for an individual exposure per position angle, the measured degree of polarization, the position angle and references to previous measurements of the sources are given. 13 objects have been observed twice. Here no entry for the coordinates is given. The redshifts, NED-listing and SDSS r-mags have been taken from Collinge et al. (2005, Cat. J/AJ/129/2542).
- ID:
- ivo://CDS.VizieR/J/AJ/139/390
- Title:
- Optically selected BL Lac objects from SDSS-DR7
- Short Name:
- J/AJ/139/390
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 723 optically selected BL Lac candidates from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) spectroscopic database encompassing 8250deg^2^ of sky; our sample constitutes one of the largest uniform BL Lac samples yet derived. Each BL Lac candidate has a high-quality SDSS spectrum from which we determine spectroscopic redshifts for ~60% of the objects. Redshift lower limits are estimated for the remaining objects utilizing the lack of host galaxy flux contamination in their optical spectra; we find that objects lacking spectroscopic redshifts are likely at systematically higher redshifts.
- ID:
- ivo://CDS.VizieR/J/ApJS/185/511
- Title:
- Optical microvariability of S5 0716+714
- Short Name:
- J/ApJS/185/511
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We monitored the BL Lac object S5 0716+714 in the optical band during 2008 October and December and 2009 February with a best temporal resolution of about 5 minutes in the BVRI bands. Four fast flares were observed with amplitudes ranging from 0.3 to 0.75mag. The source remained active during the whole monitoring campaign, showing microvariability in all days except for one. The overall variability amplitudes are {Delta}B~0.89, {Delta}V~0.80, {Delta}R~0.73, and {Delta}I~0.51mag. Typical timescales of microvariability range from 2 to 8hr. The overall V-R color index ranges from 0.37 to 0.59. Strong bluer-when-brighter chromatism was found on internight timescales. However, a different spectral behavior was found on intranight timescales. A possible time lag of ~11 minutes between B and I bands was found on one night. The shock-in-jet model and geometric effects can be applied to explain the source's intranight behavior.
- ID:
- ivo://CDS.VizieR/J/ApJ/522/846
- Title:
- Optical monitoring of GeV loud blazars
- Short Name:
- J/ApJ/522/846
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical monitoring between 1994 February and 1997 December of 10 gamma-ray-loud blazars included in our blazar monitoring program. Most of the monitored objects show significant rapid variations. The typical minimum variability timescale in the optical range is about 1 hour. We have analyzed the relationships between optical variability and gamma-ray variability, and discussed theoretical models for the gamma-rayloud blazar emission.
- ID:
- ivo://CDS.VizieR/J/A+AS/132/361
- Title:
- Optical observations of eight BL Lacs
- Short Name:
- J/A+AS/132/361
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical data in the Johnson's BV and Cousins' R bands are presented for eight X-ray selected BL Lacertae objects that have recently been pointed by the Satellite per Astronomia X `Beppo'(BeppoSAX). The observations were done with the 1.05m telescope of the Torino Astronomical Observatory and the observational periods include, or are close to, the satellite pointings. These data provide optical information on sources that have been rarely observed in the optical band. Moreover, they can be compared to the X-ray ones for a better understanding of the emission properties of these objects. Variability on short time scales (a few days) was found for MS 0317.0+1834, 1ES 0347-121, and MS 0737.9+7441. For a description of the (RI)c photometric system, see e.g. the General Catalog of Photometric Data <GCPD/54>
- ID:
- ivo://CDS.VizieR/J/AJ/155/90
- Title:
- 1996-2009 optical photometric monitoring for 3C 66A
- Short Name:
- J/AJ/155/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 3C 66A is one of the most interesting blazars and one of our monitoring objects carried out with the 1.56 m telescope at Sheshan station, Shanghai Astronomical Observatory (ShAO). It has been monitored since 1996 December 11. In the present work, we show its optical light curves during the period of 1996 December 11-2009 December 28. From our observations, we found that the largest variations in the V, R, and I bands are {Delta}V=1.840+/-0.065, {Delta}R=1.898+/-0.069 mag, and {Delta}I=1.659+/-0.047 mag, respectively. Intra-day variabilities are found in the three bands: in the V band, an A=17.7% brightness increase over {Delta}T=47.5 minutes on JD 2455119, and an A=46.27% brightness increase over {Delta}T=271.4 minutes on JD 2454816; in the R band, an A=47.09% brightness increase over {Delta}T=23.18 minutes on JD 2454004, and an A=38.11% brightness increase over {Delta}T=87.98 minutes on JD 2453995; and in the I band, an A=13.2% brightness decrease over {Delta}T=38.44 minutes on JD 2453995, and an A=92.8% brightness decrease over {Delta}T=344.02 minutes on JD 2454818. For micro-variability, we found that R variability leads I variability by 25.92+/-1.09 minutes. When the periodicity analysis methods, with the red noise being considered, are adopted to the V, R, and I observations, we can find that the periodogram to the V data is consistent with red noise, except for 1 CLEANest peak corresponding to the timescale of 696.0+/-182.0 days, those to the R data are 653.0+/-171.0 and 156.0+/-17.0 days; and those to the I data are 801.0+/-207.0 and 156.0+/-15.0 days, respectively.