Next Article in Journal / Special Issue
The Structure and Propagation of the Misaligned Jet M87
Previous Article in Journal
Using the Outskirts of Galaxy Clusters to Determine Their Mass Accretion Rate
Previous Article in Special Issue
Conical Stream of the Two-Sided Jets in NGC 4261 over the Range of 103–109 Schwarzschild Radii
Open AccessArticle

A New Statistical Approach to the Optical Spectral Variability in Blazars

Instituto de Astrofisica de Canarias-Spain, La Laguna E38205, Spain
Dpto de Astrofisica, University La Laguna-Spain, La Laguna E38206, Spain
INAF-Osservatorio Astrofisico di Torino, Pino Torinese (TO) 10025, Italy
Author to whom correspondence should be addressed.
Academic Editors: Jose L. Gómez, Alan P. Marscher and Svetlana G. Jorstad
Galaxies 2017, 5(1), 1;
Received: 29 September 2016 / Revised: 14 December 2016 / Accepted: 15 December 2016 / Published: 28 December 2016
(This article belongs to the Special Issue Blazars through Sharp Multi-wavelength Eyes)
We present a spectral variability study of a sample of about 25 bright blazars, based on optical spectroscopy. Observations cover the period from the end of 2008 to mid 2015, with an approximately monthly cadence. Emission lines have been identified and measured in the spectra, which permits us to classify the sources into BL Lac-type or FSRQs, according to the commonly used EW limit. We have obtained synthetic photometry and produced colour-magnitude diagrams which show different trends associated with the object classes: generally, BL Lacs tend to become bluer when brighter and FSRQs become redder when brighter, although several objects exhibit both trends, depending on brightness. We have also applied a pattern recognition algorithm to obtain the minimum number of physical components which can explain the variability of the optical spectrum. We have used NMF (Non-Negative Matrix Factorization) instead of PCA (Principal Component Analysis) to avoid un-realistic negative components. For most targets we found that 2 or 3 meta-components are enough to explain the observed spectral variability. View Full-Text
Keywords: emission lines; optical spectroscopy; light curves emission lines; optical spectroscopy; light curves
Show Figures

Figure 1

MDPI and ACS Style

Acosta-Pulido, J.A.; Castro Segura, N.; Carnerero, M.I.; Raiteri, C.M. A New Statistical Approach to the Optical Spectral Variability in Blazars. Galaxies 2017, 5, 1.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

Search more from Scilit
Back to TopTop