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Fausto Vagnetti, Astrofisica,
Dipartimento di Fisica, Universita` di Roma Tor Vergata
via della Ricerca Scientifica, I-00133 ROMA, Italy
room E014
http://www.fisica.uniroma2.it/~vagnetti/          .
voice +39 06 7259 4426                          ~\_/]
fax +39 06 2023507                       d_| d_| /|\
fausto.vagnetti (at) roma2.infn.it      \------------/
[ currently in sabbatical leave at Universita` di Roma La Sapienza - Dipartimento di Fisica - 06 4991 2417 ]
CURRENT RESEARCH TOPICS
Ensemble X-ray variability of AGNs from serendipitous source catalogs
We study the ensemble structure function of two serendipitously selected AGN samples extracted from the catalogs of XMM-Newton and Swift, with redshift between ~0.2 and ~4.5, and X-ray luminosities, in the 0.5-4.5 keV band, between ~10^43 erg/s and ~10^46 erg/s. We find statistically consistent results for the two samples, with the SF described by a power law of the time lag, with slope ~ 0.1. We do not find evidence of the break in the SF, at variance with the case of lower luminosity AGNs. We confirm a strong anti-correlation of the variability with X-ray luminosity (Vagnetti et al 2011).

 		Variability and the X-ray/Optical ratio of AGNs
Analysis of the X-ray/Optical ratio for AGN samples extracted from the catalogs of serendipitous sources by XMM-Newton observations (XMMSSC, XMMOMSUSS), with simultaneous X-ray and UV data.  Study of the factors affecting the dispersion of the distribution. Variability accounts for ~30% of the total variance, while the remaining is due to intrinsic differences in the average alpha_ox values from source to source, or "inter-source dispersion" (Vagnetti et al 2010). Similar analysis on a low-redshift sample from Swift is in progress (Vagnetti et al in preparation). A new program is starting on the X-ray/UV data in the CDFS from the deep XMM-Newton survey by Comastri et al.
Broad Line Region size from echo-mapping of luminous QSOs
Study of the relation between luminosity and BLR size for AGNs, and its extension to high redshift and luminosity. Ongoing campaign of spectrophotometric monitoring of 4 luminous (L~10^47 erg s-1), intermediate redshift (1<z<4) quasars with the Cima Ekar 1.8m telescope since 2003. Continuum and emission line variability detected for the quasar PG 1247+268 (Trevese et al 2007).  Estimate of BLR size and black hole mass for the same quasar are in progress (Trevese et al. in preparation). Journal of the observations available on the echoweb page. 
Multi-year variability of CIV absorption in APM 08279+5255
Spectrophotometric monitoring of the high redshift (z.3.911) BALQSO APM 08279+5255, observed with the Asiago Cima Ekar 1.8m telescope in 21 epochs between 2003 and 2012. Measured a variation of the equivalent width of the BAL absorption on time scales from days to ~2.5 yr rest-frame. The general trend of logW variations versus the time interval tau between the observations resulting from our monitoring of a single object is similar to the ensemble of data collected from the literature referring to several QSOs, each observed a few times (Trevese et al, in preparation).
X-ray and optical Survey in Selected Area 57
Optical variability has been used in the SA57 to select low luminosity AGNs (LLAGNs)  appearing as "variable galaxies".  X-ray survey with XMM-Newton, catalogue of 140 X-ray sources, (Trevese et al 2007).  Optical follow-up spectroscopy of variable candidates and of X-ray sources, WHT and TNG telescopes (Trevese et al 2008).
Synergic selection of AGN candidates in supernova surveys
Variable AGN candidates can be selected in synergic analyses of surveys devoted to the search of supernovae.  Analysis of the data of the STRESS survey, in a field overlapping the Chandra Deep Field South (CDFS),  produced a sample of 132 variable AGN candidates (Trevese et al 2008).  Optical follow-up spectroscopy of the bright candidates,  ESO/NTT telescope (Boutsia et al 2009).