- ID:
- ivo://CDS.VizieR/J/A+AS/146/141
- Title:
- Intensive monitoring of OJ 287
- Short Name:
- J/A+AS/146/141
- Date:
- 03 Dec 2021 00:36:11
- Publisher:
- CDS
- Description:
- We present intensive optical, infrared, and radio monitoring observations of the BL Lac object OJ 287, taken between the years 1993-1998. Two large optical outbursts were detected at the predicted times in November 1994 and December 1995. The detection of these outbursts supports the binary black hole model for OJ 287. Optical and radio polarisation observations show large variability in the degree of polarisation and position angle, very similar to those observed during the 1983/84 outburst in OJ 287. The polarisation position angles show very similar behaviour during these observations, indicating that, at least, the magnetic field orientations in radio and optical bands are related in OJ 287. Optical and infrared light curves show continuous variability in time scales ranging from tens of minutes to years. In the radio bands we have observed some of the lowest ever measured flux levels. During the first optical outburst in November 1994 the observed radio flux was very low, but during the second optical outburst radio bands also showed high flux levels. This is a puzzling observation, which can hopefully be used for discriminating between different outburst models. On top of the large outbursts OJ 287 has displayed flaring activity in time scales from days to weeks and shorter time scale flickering.
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- ID:
- ivo://CDS.VizieR/J/ApJS/165/439
- Title:
- Interstellar scintillation at 2 and 8GHz
- Short Name:
- J/ApJS/165/439
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From 1979 to 1996 the Green Bank Interferometer was used by the Naval Research Laboratory to monitor the flux density from 146 compact radio sources at frequencies near 2 and 8GHz. We filter the light curves to separate intrinsic variations on times of a year or more from more rapid interstellar scintillation (ISS) on times of 550 days. Whereas the intrinsic variation at 2GHz is similar to that at 8GHz (although diminished in amplitude), the ISS variation is much stronger at 2 than at 8GHz. We characterize the ISS variation by an rms amplitude and a timescale and examine the statistics of these parameters for the 121 sources with significant ISS at 2GHz. We model the scintillations using the NE2001 Galactic electron model assuming the sources are brightness-limited.
- ID:
- ivo://CDS.VizieR/J/ApJ/732/116
- Title:
- IR spectra of {gamma}-ray bright blazars
- Short Name:
- J/ApJ/732/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A possible source of {gamma}-ray photons observed from the jets of blazars is inverse Compton scattering by relativistic electrons of infrared seed photons from a hot, dusty torus in the nucleus. We use observations from the Spitzer Space Telescope to search for signatures of such dust in the infrared spectra of four {gamma}-ray bright blazars, the quasars 4C 21.35, CTA102, and PKS 1510-089, and the BL Lacertae object ON231. The spectral energy distribution (SED) of 4C 21.35 contains a prominent infrared excess indicative of dust emission. After subtracting a non-thermal component with a power-law spectrum, we fit a dust model to the residual SED. The model consists of a blackbody with temperature ~1200K, plus a much weaker optically thin component at ~660K. The total luminosity of the thermal dust emission is 7.9+/-0.2x10^45^erg/s. If the dust lies in an equatorial torus, the density of infrared photons from the torus is sufficient to explain the {gamma}-ray flux from 4C 21.35 as long as the scattering occurs within a few parsecs of the central engine. We also report a tentative detection of dust in the quasar CTA102, in which the luminosity of the infrared excess is 7+/-2x10^45^erg/s. However, in CTA102 the far-infrared spectra are too noisy to detect the 10um silicate feature. Upper limits to the luminosity from thermal emission from dust in PKS 1510-089, and ON231, are 2.3x10^45^, and 6.6x10^43^erg/s, respectively. These upper limits do not rule out the possibility of inverse Compton upscattering of infrared photons to {gamma}-ray energies in these two sources.
- ID:
- ivo://CDS.VizieR/J/A+A/555/A2
- Title:
- J-band variability of AGN
- Short Name:
- J/A+A/555/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectral energy distribution and its variability are basic tools for understanding the physical processes operating in active galactic nuclei (AGN). In this paper we report the results of a one-year near infra red (NIR) and optical monitoring of a sample of 22 AGN known to be {gamma}-ray emitters, aimed at discovering correlations between optical and {gamma}-ray emission. We observed our objects with the Rapid Eye Mount (REM) telescope in J, H, K, and R bands nearly twice every month during their visibility window and derived light curves and spectral indexes. We also analyzed the {gamma}-ray data from the Fermi {gamma}-ray Space Telescope, making weekly averages.
- ID:
- ivo://CDS.VizieR/J/AJ/104/28
- Title:
- JHKL photometry of BL Lac Objects
- Short Name:
- J/AJ/104/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Homogeneous J, H, K, L, photometry of 42 BL Lacertae objects is presented. The observations cover a period of 3 yr with a typical time interval of 6 months.
- ID:
- ivo://CDS.VizieR/J/A+AS/98/393
- Title:
- 1Jy BL Lac Objects: Observational Data
- Short Name:
- J/A+AS/98/393
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Direct imaging and spectroscopic data are reported for the complete sample of 34 BL Lac objects selected from the 1Jy source catalogue (see Cat. <VIII/5>). A short description of each individual object is given along with a general discussion of the features observed in the optical spectra, the optical morphologies, and the environments of the BL Lac objects.
- ID:
- ivo://CDS.VizieR/J/MNRAS/401/1240
- Title:
- Light curves of flat-spectrum radio sources
- Short Name:
- J/MNRAS/401/1240
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Calibrated data for 143 flat-spectrum extragalactic radio sources are presented at a wavelength of 850um covering a 5-yr period from 2000 April. The data, obtained at the James Clerk Maxwell Telescope using the Submillimetre Common-User Bolometer Array (SCUBA) camera in pointing mode, were analysed using an automated pipeline process based on the Observatory Reduction and Acquisition Control - Data Reduction (ORAC-DR) system. This paper describes the techniques used to analyse and calibrate the data, and presents the data base of results along with a representative sample of the better-sampled light curves. A re-analysis of previously published data from 1997 to 2000 is also presented. The combined catalogue, comprising 10493 flux density measurements, provides a unique and valuable resource for studies of extragalactic radio sources.
- ID:
- ivo://CDS.VizieR/J/AJ/130/1389
- Title:
- Linear polarization of AGN jets at 15GHz
- Short Name:
- J/AJ/130/1389
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present first-epoch, milliarcsecond-scale linear polarization images at 15GHz of 133 jets associated with active galactic nuclei (AGNs) from the MOJAVE (Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments) survey. MOJAVE is a long-term observational program to study the structure and evolution of relativistic outflows in AGNs. The sample consists of all known AGNs with Galactic latitude |b|>2.5{deg}, J2000.0 declination greater than -20{deg} and correlated 15GHz Very Long Baseline Array (VLBA) flux density exceeding 1.5Jy (2Jy for sources below the celestial equator) at any epoch during the period 1994-2003.
- ID:
- ivo://CDS.VizieR/J/A+A/381/757
- Title:
- List of extra-galactic radio jets
- Short Name:
- J/A+A/381/757
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 1 lists 661 radio sources with detected radio jets known to us prior to the end of December 2000
- ID:
- ivo://CDS.VizieR/J/A+A/620/A185
- Title:
- Long-term optical monitoring of TeV Blazars
- Short Name:
- J/A+A/620/A185
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ten years of R-band monitoring data of 31 northern blazars which were either detected at very high-energy (VHE) gamma rays or listed as potential VHE gamma-ray emitters. The data comprise 11820 photometric data points in the R-band obtained in 2002-2012. We analyzed the light curves by determining their power spectral density (PSD) slopes assuming a power-law dependence with a single slope beta and a Gaussian probability density function (PDF). We used the multiple fragments variance function (MFVF) combined with a forward-casting approach and likelihood analysis to determine the slopes and perform extensive simulations to estimate the uncertainties of the derived slopes. We also looked for periodic variations via Fourier analysis and quantified the false alarm probability through a large number of simulations. Comparing the obtained PSD slopes to values in the literature, we find the slopes in the radio band to be steeper than those in the optical and gamma rays. Our periodicity search yielded one target, Mrk 421, with a significant (p<5%) period. Finding one significant period among 31 targets is consistent with the expected false alarm rate, but the period found in Mrk 421 is very strong and deserves further consideration.