Osservatorio Astronomico Armenzano

The decline of stenoecious species and the development of euryoecious species are causing a flattening of communities, which gradually lose their peculiar characteristics ending up being more and more similar among themselves and causing a general loss of biodiversity. Amongst the various causes of this phenomenon, known as ‘functional homogenization’ (FH), lies the urbanization which is responsible for the alteration of semi natural and natural environment. The environmental transformation is also affecting Umbria (a region in the centre of Italy) where in recent years there has been a significant intensification of this phenomenon. The purpose of the study is to verify whether FH is also happening in this region by analyzing the community of breeding birds to a regional level. Starting from a sample of 1,696 bird watching stations covered between 2001 and 2014, using the software TRIM it was possible to analyze the trend of 132 bird species classified as specialists and generalists in terms of habitat-selection. Furthermore, for each year taken into account it has been calculated the value of Community Specialization Index (CSI – Filippi-Codaccioni et al., 2010), an indicator of the importance of specialist species within the whole regional bird community. Finally, it was considered the degree of difference amongst the bird communities from different parts of the region (subdivided into 102 UTM squares each covering an area of 100 km2) using the average Euclidean distance (AED) between the various squares which was calculated based on the levels of abundance of the different species. The presence of FH would have implied the following: a tendency of increase of generalist species, a decrease of the specialists, a CSI reduction, a AED reduction. During the period considered it was observed that there was an increase of over half (50.7%) of generalist species, whereas just 23.2% was declining. Amongst the specialists, the declining species were equal to those increased (12.7%). Although there was an increment of the generalist species, the indexes CSI and AED did not show any significant trend (Spearman test). Overall, our findings do not describe the occurrence of a homogenization process in the last decade of the regional bird community as a whole.

ABSTRACT We report on 18 months of multiwavelength observations of the blazar 3C 454.3 (Crazy Diamond) carried out in the period 2007 July–2009 January. In particular, we show the results of the AGILE campaigns which took place on 2008 May–June, 2008 July–August, and 2008 October–2009 January. During the 2008 May–2009 January period, the source average flux was highly variable, with a clear fading trend toward the end of the period, from an average γ-ray flux F E>100 MeV ≳ 200 × 10−8 photons cm−2 s−1 in 2008 May–June, to F E>100 MeV ∼ 80 × 10−8 photons cm−2 s−1 in 2008 October–2009 January. The average γ-ray spectrum between 100 MeV and 1 GeV can be fit by a simple power law, showing a moderate softening (from ΓGRID ∼ 2.0 to ΓGRID ∼ 2.2) toward the end of the observing campaign. Only 3σ upper limits can be derived in the 20–60 keV energy band with Super-AGILE, because the source was considerably off-axis during the whole time period. In 2007 July–August and 2008 May–June, 3C 454.3 was monitored by Rossi X-ray Timing Explorer (RXTE). The RXTE/Proportional Counter Array (PCA) light curve in the 3–20 keV energy band shows variability correlated with the γ-ray one. The RXTE/PCA average flux during the two time periods is F 3-20 keV = 8.4 × 10−11 erg cm−2 s−1, and F 3-20 keV = 4.5 × 10−11 erg cm−2 s−1, respectively, while the spectrum (a power law with photon index ΓPCA = 1.65 ± 0.02) does not show any significant variability. Consistent results are obtained with the analysis of the RXTE/High-Energy X-Ray Timing Experiment quasi-simultaneous data. We also carried out simultaneous Swift observations during all AGILE campaigns. Swift/XRT detected 3C 454.3 with an observed flux in the 2–10 keV energy band in the range (0.9–7.5) × 10−11 erg cm−2 s−1 and a photon index in the range ΓXRT = 1.33–2.04. In the 15–150 keV energy band, when detected, the source has an average flux of about 5 mCrab. GASP-WEBT monitored 3C 454.3 during the whole 2007–2008 period in the radio, millimeter, near-IR, and optical bands. The observations show an extremely variable behavior at all frequencies, with flux peaks almost simultaneous with those at higher energies. A correlation analysis between the optical and the γ-ray fluxes shows that the γ-optical correlation occurs with a time lag of τ = −0.4+0.6 −0.8 days, consistent with previous findings for this source. An analysis of 15 GHz and 43 GHz VLBI core radio flux observations in the period 2007 July–2009 February shows an increasing trend of the core radio flux, anti-correlated with the higher frequency data, allowing us to derive the value of the source magnetic field. Finally, the modeling of the broadband spectral energy distributions for the still unpublished data, and the behavior of the long-term light curves in different energy bands, allow us to compare the jet properties during different emission states, and to study the geometrical properties of the jet on a time-span longer than one year.

We report the gamma-ray activity from the intermediate BL Lac S5 0716+714 during observations acquired by the AGILE satellite in September and October 2007. These detections of activity were contemporaneous with a period of intense optical activity, which was monitored by GASP-WEBT. This simultaneous optical and gamma-ray coverage allows us to study in detail the light curves, time lags, gamma-ray photon spectrum, and Spectral Energy Distributions (SEDs) during different states of activity. AGILE observed the source with its two co-aligned imagers, the Gamma-Ray Imaging Detector (GRID) and the hard X-ray imager (Super-AGILE), which are sensitive to the 30 MeV-50 GeV and 18-60 keV energy ranges, respectively. Observations were completed in two different periods, the first between 2007 September 4-23, and the second between 2007 October 24-November 1. Over the period 2007 September 7-12, AGILE detected gamma-ray emission from the source at a significance level of 9.6-sigma with an average flux (E>100 MeV) of (97 +/- 15) x 10^{-8} photons cm^{-2} s^{-1}, which increased by a factor of at least four within three days. No emission was detected by Super-AGILE for the energy range 18-60 keV to a 3-sigma upper limit of 10 mCrab in 335 ksec. In October 2007, AGILE repointed toward S5 0716+714 following an intense optical flare, measuring an average flux of (47 +/- 11) x 10^{-8} photons cm^{-2} s^{-1} at a significance level of 6.0-sigma. The gamma-ray flux of S5 0716+714 detected by AGILE is the highest ever detected for this blazar and one of the most intense gamma-ray fluxes detected from a BL Lac object. The SED of mid-September appears to be consistent with the synchrotron self-Compton (SSC) emission model, but only by including two SSC components of different variabilities.

Aims.A huge multiwavelength campaign targeting the blazar AO 0235+164 was organized by the Whole Earth Blazar Telescope (WEBT) in 2003–2005 to study the variability properties of the source.