8 research outputs found
Multi-band optical variability of a newly discovered twelve blazars sample from 2013-2019
Here we present the first optical photometric monitoring results of a sample
of twelve newly discovered blazars from the ICRF - Gaia CRF astrometric link.
The observations were performed from April 2013 until August 2019 using eight
telescopes located in Europe. For a robust test for the brightness and colour
variability, we use Abbe criterion and F-test. Moreover, linear fittings are
performed to investigate the relation in the colour-magnitude variations of the
blazars. Variability was confirmed in the case of 10 sources; two sources,
1429+249 and 1556+335 seem to be possibly variable. Three sources (1034+574,
1722+119, and 1741+597) have displayed large amplitude brightness change of
more than one magnitude. We found that the seven sources displayed
bluer-when-brighter variations, and one source showed redder-when-brighter
variations. We briefly explain the various AGN emission models which can
explain our results.Comment: 14 pages, 8 figures, 11 tables, 6 supplement figures can be provided
on request, MNRAS in pres
Intra-night optical flux and polarization variability of BL~Lacertae during its 2020 2021 high state
In this work, we report the presence of rapid intra-night optical variations
in both -- flux and polarization of the blazar BL Lacertae during its
unprecedented 2020--2021 high state of brightness. The object showed
significant flux variability and some color changes, but no firmly detectable
time delays between the optical bands. The linear polarization was also highly
variable in both -- polarization degree and angle (EVPA). The object was
observed from several observatories throughout the world, covering in a total
of almost 300 hours during 66 nights. Based on our results, we suggest, that
the changing Doppler factor of an ensemble of independent emitting regions,
travelling along a curved jet that at some point happens to be closely aligned
with the line of sight can successfully reproduce our observations during this
outburst. This is one of the most extensive variability studies of the optical
polarization of a blazar on intra-night timescales.Comment: 23 pages,7 figures, 5 Tables (2 as appendix). Accepted for
publication in MNRA
Multi-band optical variability of a newly discovered twelve blazars sample from 2013-2019
International audienceHere we present the first optical photometric monitoring results of a sample of twelve newly discovered blazars from the ICRF - Gaia CRF astrometric link. The observations were performed from April 2013 until August 2019 using eight telescopes located in Europe. For a robust test for the brightness and colour variability, we use Abbe criterion and F-test. Moreover, linear fittings are performed to investigate the relation in the colour-magnitude variations of the blazars. Variability was confirmed in the case of 10 sources; two sources, 1429+249 and 1556+335 seem to be possibly variable. Three sources (1034+574, 1722+119, and 1741+597) have displayed large amplitude brightness change of more than one magnitude. We found that the seven sources displayed bluer-when-brighter variations, and one source showed redder-when-brighter variations. We briefly explain the various AGN emission models which can explain our results
A Complete Bank of Optical Images of the ICRF QSOs
International audienceWe have been developing a systematic effort to collect good quality images of the optical counterpart of ICRF sources, in particular for those that have been regularly radio surveyed either for future implementation at high frequencies and/or those that will be the link sources between the ICRF and the Gaia CRF. Observations have been taken at the LNA/Brazil, CASLEO/Argentina, NOT/Spain, LFOA/Austria, Rozhen/Bulgária, and ASV/Serbia. In complement images were collected from the SDSS. As a step to implement such image data bank and make it publicly available through the IERS service we present its description, that comprises for each source the number of measurements, filter, pixel scale, size of field, and seeing at each observation. The photometry analysis is centered on the morphology, since there remain still cases in which the host galaxy is overwhelming, and many cases in which the host asks for a non-stellar PSF modeling. On basis of the neighbor stars we assign magnitudes and variability whenever possible. Finally, assisted by previous literature, the redshift and luminosity are used to derive astrophysical quantities, in special the absolute magnitude, SED and spectral index. Moreover, since Gaia will not obtain direct images of the observed sources, the morphology and magnitude becomes useful as templates onto which assembling and interpreting the one-dimensional and uncontinuous line spread function samplings that will be delivered by Gaia for each QSO
A Complete Bank of Optical Images of the ICRF QSOs
We have been developing a systematic effort to collect good quality images of the optical counterpart of ICRF sources, in particular for those that have been regularly radio surveyed either for future implementation at high frequencies and/or those that will be the link sources between the ICRF and the Gaia CRF. Observations have been taken at the LNA/Brazil, CASLEO/Argentina, NOT/Spain, LFOA/Austria, Rozhen/Bulgária, and ASV/Serbia. In complement images were collected from the SDSS. As a step to implement such image data bank and make it publicly available through the IERS service we present its description, that comprises for each source the number of measurements, filter, pixel scale, size of field, and seeing at each observation. The photometry analysis is centered on the morphology, since there remain still cases in which the host galaxy is overwhelming, and many cases in which the host asks for a non-stellar PSF modeling. On basis of the neighbor stars we assign magnitudes and variability whenever possible. Finally, assisted by previous literature, the redshift and luminosity are used to derive astrophysical quantities, in special the absolute magnitude, SED and spectral index. Moreover, since Gaia will not obtain direct images of the observed sources, the morphology and magnitude becomes useful as templates onto which assembling and interpreting the one-dimensional and uncontinuous line spread function samplings that will be delivered by Gaia for each QSO