Pulsar Timing Constraints on the Fermi Massive Black-Hole Binary Blazar Population

Blazars are a sub-population of quasars whose jets are nearly aligned with the line-of-sight, which tend to exhibit multi-wavelength variability on a variety of timescales. Quasi-periodic variability on year-like timescales has been detected in a number of bright sources, and has been connected to the orbital motion of a putative massive black hole binary. If this were indeed the case, those blazar binaries would contribute to the nanohertz gravitational-wave stochastic background. We test the binary hypothesis for the blazar population observed by the \textit{Fermi} Gamma-Ray Space Telescope, which consists of BL Lacertae objects and flat-spectrum radio quasars. Using mock populations informed by the luminosity functions for BL Lacertae objects and flat-spectrum radio quasars with redshifts $z \le 2$, we calculate the expected gravitational wave background and compare it to recent pulsar timing array upper limits. The two are consistent only if a fraction $\lesssim 10^{-3}$ of blazars hosts a binary with orbital periods $<5$ years. We therefore conclude that binarity cannot significantly explain year-like quasi-periodicity in blazars.Comment: 5 pages, 4 figures, accepted by MNRAS Letter

Quasi-periodicities of BL Lac Objects

We review the reports of possible year-long quasi-periodicities of BL Lac objects in the $\gamma$-ray and optical bands, and present a homogeneous time analysis of the light curves of PKS2155$-$304, PG1553+113, and BL Lac. Based on results from a survey covering the entire Fermi $\gamma$-ray sky we have estimated the fraction of possible quasi-periodic BL Lac objects. We compared the cyclical behaviour in BL Lac objects with that derived from the search of possible optical periodicities in quasars, and find that at z$\lesssim$1 the cosmic density of quasi-periodic BL Lac objects is larger than that of quasi-periodic quasars. If the BL Lac quasi-periodicities were due to a supermassive binary black hole (SBBH) scenario, there could be a tension with the upper limits on the gravitational wave background measured by the pulsar timing array. The argument clearly indicates the difficulties of generally associating quasi-periodicities of BL Lac objects with SBBHs.Comment: In publication on A&A, 6 pages, 4 figure (11 plots). Minor corrections adde

Gamma-ray quasi-periodicities of blazars. A cautious approach

The availability of about a decade of uninterrupted sky monitoring by the Fermi satellite has made it possible to study long-term quasi-periodicities for high-energy sources. It is therefore not a surprise that for several blazars in the recent literature claims for such periodicities, with various level of confidence, have been reported. The confirmation of these findings could be of tremendous importance for the physical description of this category of sources and have consequences for the gravitational wave background interpretation. In this work, we carry out a temporal analysis of the Fermi light curves for several of the sources mentioned in recent literature by means of a homogeneous procedure and find that, globally, no strong cases for blazar year-long quasi-periodicities can be confirmed. The computed power spectral densities are all essentially consistent with being generated by red-noise only. We further discuss the meaning and the limitations of the present analysis

Gamma-Ray and Optical Oscillations in PKS 0537-441

We have considered the Fermi γ-ray light curve of the blazar PKS 0537-441 during a high state extending from 2008 August 10 to 2011 August 27. The periodogram exhibits a peak at T ∼ 280 days, with a significance of ∼99.7%. A peak of similar relevance at \frac{1}{2}T is found in the optical light curves. Considering the entire duration of the Fermi light curve 2008-2015, no significant peak is revealed, while the optical one remains meaningful. Comparing with recent observations of PKS 2155-304 and PG 1553+113 it seems that month-year oscillations can characterize some blazars. Month-scale oscillations can also show up only during phases of enhanced or bursting emission, such as in the case of PKS 0537-441

VizieR Online Data Catalog: VRIJHK photometry of 3C 279 (Sandrinelli+, 2016)

The starting point of the present investigation is the VRIJHK photometric observations obtained with the robotic Rapid Eye Mounting telescope (REM) at La Silla, which are described in detail in Sandrinelli et al. 2014 (cat. J/A+A/562/A79). We add to the data available in the above mentioned paper the REM photometry of 3C 279 (see Table2), which is unpublished thus far. (2 data files)

Quasi-periodicities at Year-like Timescales in Blazars

We searched for quasi-periodicities on year-like timescales in the light curves of six blazars in the optical—near-infrared bands and we made a comparison with the high energy emission. We obtained optical/NIR light curves from Rapid Eye Mounting photometry plus archival Small & Moderate Aperture Research Telescope System data and we accessed the Fermi light curves for the γ-ray data. The periodograms often show strong peaks in the optical and γ-ray bands, which in some cases may be inter-related. The significance of the revealed peaks is then discussed, taking into account that the noise is frequency dependent. Quasi-periodicities on a year-like timescale appear to occur often in blazars. No straightforward model describing these possible periodicities is yet available, but some plausible interpretations for the physical mechanisms causing periodic variabilities of these sources are examined

Overdensity of galaxies in the environment of quasar pairs

We report on a study of the galaxy environments of low redshift physical quasars pairs. We selected 20 pairs having projected separation -1. Using Sloan Digital Sky Survey images, we evaluated the galaxy overdensity around these quasars in pairs and then compare it with that of a sample of isolated quasars with same redshift and luminosity. It is found that on average there is a systematic larger overdensity of galaxies around quasars in pairs with respect to that of isolated quasars. This may represent a significant link between nuclear activity and galaxy environment. However, at odds with that, the closest quasar pairs seem to inhabit poorer environments. Implications of present results and perspectives for future work are briefly discussed

Quasi-periodicities of BL Lacertae objects

We review the reports of possible year-long quasi-periodicities of BL Lac objects in the gamma-ray and optical bands, and present a homogeneous time analysis of the light curves of PKS2155-304, PG1553+113, and BL Lac. Based on results from a survey covering the entire Fermi gamma-ray sky we have estimated the fraction of possible quasi-periodic BL Lac objects. We compared the cyclical behaviour in BL Lac objects with that derived from the search of possible optical periodicities in quasars, and find that at z less than or similar to 1 the cosmic density of quasi-periodic BL Lac objects is larger than that of quasi-periodic quasars. If the BL Lac quasi-periodicities were due to a supermassive binary black hole (SBBH) scenario, there could be a tension with the upper limits on the gravitational wave background measured by the pulsar timing array. The argument clearly indicates the difficulties of generally associating quasi-periodicities of BL Lac objects with SBBHs

Morpho-chemical characterization of new confectionery sunflower (Helianthus annuus L.) genotypes from Argentina

Argentina is the world’s leading exporter of confectionery sunflower. This work characterized the morphometric and nutritional composition of sunflower seeds from new confectionery genotypes. Average morphometric variables per seed were: weight 0.11 and 0.06 g with and without achene, respectively; length 15.2 mm; and width 8.50 mm, with most calibers greater than 9.51 mm. Proximate analysis indicated that seeds without shell were an important source of lipids (49 %), as well as proteins (28 %), carbohydrates (11 %), and minerals (4.8 % ashes). Fatty acid composition showed that polyunsaturated fatty acids were the major components (56 %), followed by monounsaturated ones (34 %), and saturated ones (11 %). The mid-oleic genotype developed by INTA showed significantly greater oleic acid (47 %) and lower linoleic acid (42 %) than the commercial hybrid. Proteic composition showed 33 % of essential amino acids (EAA) while fiber and sugars represented 3.9 % and 7.3 % respectively; macroelements such as K, Mg and Ca, and microelements such as Mn, Fe, Cu, Zn, Se, Co, Mo and Na. New confectionery sunflower hybrids developed by INTA stand out for their high quality in edible oil, proteins and essential components, all very valuable for the food industry.Argentina es el principal exportador mundial de girasol confitero. Este trabajo caracterizó la composición morfométrica y nutricional de nuevos genotipos de girasol confitero. Las variables morfométricas promedio por semilla fueron: peso 0,11 g y 0,06 g, con y sin aquenio respectivamente; longitud 15,2 mm; ancho 8,50 mm; la mayoría de calibres superiores a 9,51 mm. El análisis composicional indicó que las semillas sin cáscara aportan 49 % de lípidos, 28 % de proteínas, 11 % de carbohidratos y 4,8 % de minerales. La composición de ácidos grasos mostró que los poliinsaturados fueron los componentes principales (56 %), seguidos de los monoinsaturados (34 %) y los saturados (11 %). El genotipo medio oleico presentó porcentaje de ácido oleico significativamente mayor (47 %) y porcentaje de ácido linoleico menor (42 %) que el híbrido comercial. La composición de proteínas fue de 33 % de aminoácidos esenciales (AAE); fibra y azúcares de 3,9 % y 7,3 %, respectivamente; macroelementos K, Mg y Ca, y microelementos Mn, Fe, Cu, Zn, Se, Co, Mo y Na. Los nuevos híbridos de girasol confitero desarrollados por INTA se destacan por la alta calidad del aceite, proteínas y componentes esenciales, todos estos de importancia para la industria alimenticia.Fil: Sandrinelli Tesán, Rebeca. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Alvarez, D.. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Silva, M. P.. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Aguilar, R.. Instituto Nacional de Tecnología Agropecuaria; ArgentinaFil: Pazos, A.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Agroindustria. Instituto de Tecnología de Alimentos; ArgentinaFil: Balzarini, Monica Graciela. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Unidad de Fitopatología y Modelización Agrícola - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Unidad de Fitopatología y Modelización Agrícola; ArgentinaFil: Martínez, María José. Instituto Nacional de Tecnología Agropecuaria; Argentin