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تسجيل مستخدم جديدThe 5th edition of the Roma-BZCAT. A short presentation
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The 5th edition of the Roma-BZCAT Multifrequency Catalogue of Blazars is available in a printed version and online at the ASDC website (http://www.asdc.asi.it/bzcat); it is also in the NED database. It presents several relevant changes with respect to the past editions which are briefly described in this paper.
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The 2nd edition of the Roma-BZCAT is available on line at the ASDC website (http://www.asdc.asi.it/bzcat) and in the NED database. In this short paper we describe the major updates from the first edition.
We present a new catalogue of blazars based on multi-frequency surveys and on an extensive review of the literature. Blazars are classified as BL Lacertae objects, as flat spectrum radio quasars or as blazars of uncertain/transitional type. Each obje
ct is identified by a root name, coded as BZB, BZQ and BZU for these three subclasses respectively, and by its coordinates. This catalogue is being built as a tool useful for the identification of the extragalactic sources that will be detected by present and future experiments for X and gamma-ray astronomy, like Swift, AGILE, Fermi-GLAST and Simbol-X. An electronic version is available from the ASI Science Data Center web site at http://www.asdc.asi.it/bzcat
In an optical monitoring program to characterize the variability properties of blazar, we observed 10 sources from the Roma-BZCAT catalogue for 26 nights in V and R bands during October 2014 to June 2015 with two telescopes located in India. The samp
le includes mainly newly discovered BL Lacs where the redshift of some sources are not known yet. We present the results of flux and color variations of the sample on intraday and short time scales obtained by using the power-enhanced F-test and the nested-ANOVA tests, along with their spectral behavior. We find significant intraday variability in the single FSRQ in our sample, having an amplitude of variation ~12%. Although a few of BL Lacs showed probable variation in some nights, none of them passes the variability tests at 99.9% significance level. We find that 78% of the sample showed significant negative colour--magnitude correlations i.e., a redder-when-brighter spectral evolution. Those which do not show strong or clear chromatism, predominantly exhibit a redder-when-brighter trends. Unlike on hourly timescales, the high synchrotron peaked (HSP) blazars in the sample (BZGJ0656+4237, BZGJ0152+0147 and BZBJ1728+5013) show strong flux variation on days to months timescales, where again we detect a decreasing trend of the spectral slope with brightness. We observe a global steepening of the optical spectrum with increasing flux on intranight timescale for the entire blazar sample. Non-variability in the BL Lacs in our sample could be resulted by distinct contribution from the disk as well as from other components in the studied energy range.
The AI City Challenge was created with two goals in mind: (1) pushing the boundaries of research and development in intelligent video analysis for smarter cities use cases, and (2) assessing tasks where the level of performance is enough to cause rea
l-world adoption. Transportation is a segment ripe for such adoption. The fifth AI City Challenge attracted 305 participating teams across 38 countries, who leveraged city-scale real traffic data and high-quality synthetic data to compete in five challenge tracks. Track 1 addressed video-based automatic vehicle counting, where the evaluation being conducted on both algorithmic effectiveness and computational efficiency. Track 2 addressed city-scale vehicle re-identification with augmented synthetic data to substantially increase the training set for the task. Track 3 addressed city-scale multi-target multi-camera vehicle tracking. Track 4 addressed traffic anomaly detection. Track 5 was a new track addressing vehicle retrieval using natural language descriptions. The evaluation system shows a general leader board of all submitted results, and a public leader board of results limited to the contest participation rules, where teams are not allowed to use external data in their work. The public leader board shows results more close to real-world situations where annotated data is limited. Results show the promise of AI in Smarter Transportation. State-of-the-art performance for some tasks shows that these technologies are ready for adoption in real-world systems.
We present optical observations of the Swift short-duration gamma-ray burst (GRB) GRB 161104A and its host galaxy at $z=0.793 pm 0.003$. We model the multiband photometry and spectroscopy with the stellar population inference code Prospector, and exp
lore the posterior using nested sampling. We find that the mass-weighted age $t_m = 2.12^{+0.23}_{-0.21}$~Gyr, stellar mass $log{(M/M_odot)} = 10.21 pm 0.04$, metallicity $log{(Z/Z_odot)} = 0.08^{+0.05}_{-0.06}$, dust extinction $A_V = 0.08^{+0.08}_{-0.05}$ mag, and the star formation rate $text{SFR} = 9.9 times 10^{-2} M_odot$~yr$^{-1}$. These properties, along with a prominent 4000 Angstrom break and optical absorption lines classify this host as an early-type, quiescent galaxy. Using Dark Energy Survey galaxy catalogues, we demonstrate that the host of GRB 161104A resides on the outskirts of a galaxy cluster at $zapprox 0.8$, situated $approx 1$ Mpc from the likely brightest cluster galaxy. We also present new modeling for 20 additional short GRB hosts ($approx33%$ of which are early-type galaxies), finding population medians of $log(M/M_odot) = 9.94^{+0.88}_{-0.98}$ and $t_m = 1.07^{+1.98}_{-0.67}$~Gyr ($68%$ confidence). We further find that the host of GRB 161104A is more distant, less massive, and younger than the four other short GRB hosts known to be associated with galaxy clusters. Cluster short GRBs have faint afterglows, in the lower $approx 11%$ ($approx 30%$) of observed X-ray (optical) luminosities. We place a lower limit on the fraction of short GRBs in galaxy clusters versus those in the field of $approx 5-13%$, consistent with the fraction of stellar mass $approx 10-20%$ in galaxy clusters at redshifts $0.1 leq z leq 0.8$.
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