- ID:
- ivo://CDS.VizieR/J/AJ/150/67
- Title:
- Optical photometry for 1ES 1959+650
- Short Name:
- J/AJ/150/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the 1.56m telescope at Shanghai Observatory, China, we present the photometric results of 1ES 1959+650, which cover from 2006 June 11 to 2014 July 31. The maximum variabilities are {Delta}m_V|max_=1.74+/-0.02mag in the V band, {Delta}m_R|max_=0.97+/-0.02mag in the R band, and {Delta}m_I/max_=1.15+/-0.03mag in the I band. During the monitoring period, we obtain intraday variabilities on 2009 September 2 (JD2455077) and 2009 September 3 (JD2455078). On 2009 September 2, the intraday variabilities are {Delta}m_V_=0.36+/-0.08mag within 1.56hr, {Delta}m_R_=0.21+/-0.04mag within 23minutes, and {Delta}m_I_=0.53+/-0.03mag within 45minutes. On 2009 September 3, the intraday variabilities are {Delta}m_V_=0.40+/-0.10mag within 27minutes, {Delta}m_R_=0.48+/-0.04mag within 3.24hr, and {Delta}m_I_=0.68+/-0.06mag within 3.72hr. The two intraday variabilities occur in 24hr, which may occur in the same variable phase. Other results show that (1) no quasi-periodicity is found in the long-term light curve and (2) the correlations between the brightness and the spectrum show obvious anti-correlation, {alpha}=-(0.18+/-0.02)F_V_+(2.33+/-0.12), with the correlation coefficient r=-0.74 and the chance probability p<0.01%.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/402/2087
- Title:
- Optical polarization of OJ 287 in 2005-2009
- Short Name:
- J/MNRAS/402/2087
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- OJ287 is a BL Lac object at redshift z=0.306 that has shown double-peaked bursts at regular intervals of ~12yr during the last ~40yr. We analyse optical photopolarimetric monitoring data from 2005-2009, during which the latest double-peaked outburst occurred. The aim of this study is twofold: firstly, we aim to analyse variability patterns and statistical properties of the optical polarization light-curve. We find a strong preferred position angle in optical polarization. The preferred position angle can be explained by separating the jet emission into two components: an optical polarization core and chaotic jet emission. The optical polarization core is stable on time scales of years and can be explained as emission from an underlying quiescent jet component. The chaotic jet emission sometimes exhibits a circular movement in the Stokes plane. We find six such events, all on the timescales of 10-20days. We interpret these events as a shock front moving forwards and backwards in the jet, swiping through a helical magnetic field. Secondly, we use our data to assess different binary black hole models proposed to explain the regularly appearing double-peaked bursts in OJ287. We compose a list of requirements a model has to fulfil to explain the mysterious behaviour observed in OJ287. The list includes not only characteristics of the light-curve but also other properties of OJ287, such as the black hole mass and restrictions on accretion flow properties. We rate all existing models using this list and conclude that none of the models is able to explain all observations. We discuss possible new explanations and propose a new approach to understanding OJ287. We suggest that both the double-peaked bursts and the evolution of the optical polarization position angle could be explained as a sign of resonant accretion of magnetic field lines, a 'magnetic breathing' of the disc.
- ID:
- ivo://CDS.VizieR/J/A+A/545/A68
- Title:
- Optical spectrum of the blazar PKS 0447-439
- Short Name:
- J/A+A/545/A68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- PKS 0447-439 is one of the BL Lacertae objects that have been detected at very high energy. There has been a recent report of a lower limit of z>=1.246 for the redshift of this blazar, challenging the current paradigm in which very high-energy {gamma}-rays cannot freely propagate in the z>~1 universe. In this research note, we present a new MagE/Magellan spectrum of PKS 0447-439 with exquisite signal-to-noise (S/N>150 at 6500{AA}). Our analysis confirms the presence of the previously-reported absorption line at 6280{AA}, which we identify, however, with a known telluric absorption, invalidating the claim that this blazar lies at z>1. Since no other extragalactic spectral features are detected, we cannot establish a redshift based on our spectrum.
- ID:
- ivo://CDS.VizieR/J/ApJ/537/101
- Title:
- Optical Study for blazars. I.
- Short Name:
- J/ApJ/537/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric observations of AGNs are important to construct light curves and to study variability behavior over different timescales. In this paper, the historical optical data compiled from the published literature are presented in tabular form as an optical database for 28 radio-selected BL Lacertae objects. Maximum optical variations are found and compared with the infrared ones. The faintest, brightest, and averaged magnitudes are presented for individual object. The variation is found correlated with polarization. The light curves are shown in figures along with the relation between color index and magnitude. For the color-magnitude relation, two objects, 0735+178 and 0537-441, show evidence that the color index increases with magnitude, indicating that the spectrum flattens when the source brightens, while three objects (0219+428, 1514-241, 2200+420) show the opposite behavior; an object, 0235+164, shows a brightness-dependent color index- magnitude correlation, while the rest of the objects do not show any clear tendency.
- ID:
- ivo://CDS.VizieR/J/AN/340/437
- Title:
- Optical variability of blazars
- Short Name:
- J/AN/340/437
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The analysis of blazars' parameters from BZCAT leads to a conclusion that they do not have the same properties. The preliminary criterion to include an object in the catalog was the strong radio emission; however, two type of radio sources were selected: BL Lacertae (BLL) objects and Flat Spectrum Radio Quasars (FSRQ). As a number of properties are typical of blazars (strong radio emission, optical variability, continuum optical spectra, polarization, high luminosity, etc.), using the optical data, we investigate them to clarify which property plays the most significant role in their classification as blazars. We found that 60% of blazars have optical variability. We use a technique developed based on POSS1 and POSS2 photometry and group the variability into extreme, strong, medium, and low classes. In the optical range, 51 blazars have powerful variability (extreme variables), and 126 are high variables. In addition, 63% of blazars have detected radiation in X-ray and 28% have detected radiation in gamma rays. We give the average statistical characteristics of blazars based on our analysis and calculations.
- ID:
- ivo://CDS.VizieR/J/AJ/157/95
- Title:
- Optical variability of OJ 287 in 2016-2017
- Short Name:
- J/AJ/157/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a recent multiband optical photometric and polarimetric observational campaign of the blazar OJ 287 that was carried out during 2016 September-2017 December. We employed nine telescopes in Bulgaria, China, Georgia, Japan, Serbia, Spain, and the United States. We collected over 1800 photometric image frames in BVRI bands and over 100 polarimetric measurements over ~175 nights. In 11 nights with many quasi-simultaneous multiband (V, R, I) observations, we did not detect any genuine intraday variability in flux or color. On longer timescales, multiple flaring events were seen. Large changes in color with respect to time and in a color-magnitude diagram were seen, and while only a weak systematic variability trend was noticed in color with respect to time, the color-magnitude diagram shows a bluer-when-brighter trend. Large changes in the degree of polarization and substantial swings in the polarization angle were detected. The fractional Stokes parameters of the polarization showed a systematic trend with time in the beginning of these observations, followed by chaotic changes and then an apparently systematic variation at the end. These polarization changes coincide with the detection and duration of the source at very high energies as seen by VERITAS. The spectral index shows a systematic variation with time and V-band magnitude. We briefly discuss possible physical mechanisms that could explain the observed flux, color, polarization, and spectral variability.
- ID:
- ivo://CDS.VizieR/J/AJ/129/1818
- Title:
- Photometry of S5 0716+714
- Short Name:
- J/AJ/129/1818
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical monitoring of S5 0716+714 was performed with a 60/90 Schmidt telescope in 2003 November and December and 2004 January for studying the variability of the object on short timescales. Because of the high brightness of the source, we could carry out quasi-simultaneous measurements in three bands with a temporal resolution of about 20min by using one single telescope.
- ID:
- ivo://CDS.VizieR/J/ApJS/192/12
- Title:
- Photometry of the blazar PKS 0537-441
- Short Name:
- J/ApJS/192/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a large collection of photometric data on the blazar PKS 0537-441 in the VRIJHK bands taken in 2004-2009. At least three flare-like episodes with months duration and >3mag amplitude are apparent. The spectral energy distribution is consistent with a power law, and no indication of a thermal component is found. We searched for short timescale variability, and an interesting event was identified in the J band, with a duration of ~25 minutes.
- ID:
- ivo://CDS.VizieR/J/A+A/541/A160
- Title:
- Planck + X/{gamma} observations of blazars
- Short Name:
- J/A+A/541/A160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard X-ray, and {gamma}-ray bands, with additional 5GHz flux-density limits to ensure a good probability of a Planck detection. We compare our results to those of a companion paper presenting simultaneous Planck and multi-frequency observations of 104 radio-loud northern active galactic nuclei selected at radio frequencies. While we confirm several previous results, our unique data set allows us to demonstrate that the selection method strongly influences the results, producing biases that cannot be ignored.
- ID:
- ivo://CDS.VizieR/J/AZh/71/717
- Title:
- Polarimetric Observations of BL Lac
- Short Name:
- J/AZh/71/717
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper continues publications that report the results of photoelectric polarization measurements of the blazar BL Lac. Earlier, we published observational data obtained over the period 1969-1982 (Hagen-Torn et al., 1984AZh....61..925H). Here, we discuss the observations over the period 1983-1991.