Studying the WIGM During Outburst Phases of Nearby AGNs

Nicastro F.$^1$, Fiore F.$^2$, and Elvis M.$^1$

$^1$ Harvard-Smithsonian Center for Astrophysics, Cambridge, USA\newline
$^2$ Osservatorio Astronomico di Monteporzio, Rome, Italy

2-10 keV fluxes higher than 40 mCrab are frequently reached by beamed 
(and less frequently by non-beamed) nearby AGNs during their outburst 
phases. These exceptional phases can be easily triggered now by the 
RossiXTE-ASM and, in the near-future, and with much higher sensitivity, 
by MAXI. High resolution X-ray spectroscopy follow-ups (as now possible 
with Chandra and XMM-Newton) of such high-state AGNs would allow one not 
only to study in great detail the gaseous AGN environment and to strongly 
constrain the mechanisms responsible for the nuclear emission, but also to 
X-ray-ing very efficiently random line of sights in the sky to search for 
evidences of intervening Warm-to-hot Intergalactic Medium (WIGM) in the 
local Universe. The most efficient way to probe the existence of this medium 
and to study its physical and dynamical properties is in fact through the 
detection of resonant absorption lines from highly ionized metals in the 
X-ray spectra of bright, preferably intrinsically featureless, background 
sources.

In this contribute we then propose to use the X-ray all sky monitors to
trigger outburst phases of nearby AGNs, and demonstrate that moderate
exposure (i.e. 100 ks) Chandra or XMM-Newton follow-ups of these sources 
will allow to detect and study the WIGM. As already probed by the XTE-ASM 
lightcurves of these AGNs, these outburst phases can last for several days, 
up to weeks. Using these sources, in these states would then also allow to 
relax the severe constraint of having the high-resolution detectors on-source 
within few hours from the trigger event.