We present Gran Telescopio CANARIAS CanariCam 8.7$mu$m imaging and 7.5-13$mu$m spectroscopy of six local systems known to host an active galactic nucleus (AGN) and have nuclear star formation. Our main goal is to investigate whether the molecules res
ponsible for the 11.3$mu$m polyclyclic aromatic hydrocarbon (PAH) feature are destroyed in the close vicinity of an AGN. We detect 11.3$mu$m PAH feature emission in the nuclear regions of the galaxies as well as extended PAH emission over a few hundred parsecs. The equivalent width (EW) of the feature shows a minimum at the nucleus but increases with increasing radial distances, reaching typical star-forming values a few hundred parsecs away from the nucleus. The reduced nuclear EW are interpreted as due to increased dilution from the AGN continuum rather than destruction of the PAH molecules. We conclude that at least those molecules responsible for the 11.3$mu$m PAH feature survive in the nuclear environments as close as 10pc from the AGN and for Seyfert-like AGN luminosities. We propose that material in the dusty tori, nuclear gas disks, and/or host galaxies of AGN is likely to provide the column densities necessary to protect the PAH molecules from the AGN radiation field.
We present mid-infrared (MIR) 8-13micron spectroscopy of the nuclear regions of the interacting galaxy Arp299 (IC694+NGC3690) obtained with CanariCam (CC) on the 10.4m Gran Telescopio Canarias (GTC). The high angular resolution (~0.3-0.6arcsec) of th
e data allows us to probe nuclear physical scales between 60 and 120pc, which is a factor of 10 improvement over previous MIR spectroscopic observations of this system. The GTC/CC spectroscopy displays evidence of deeply embedded Active Galactic Nucleus (AGN) activity in both nuclei. The GTC/CC nuclear spectrum of NGC3690/Arp299-B1 can be explained as emission from AGN-heated dust in a clumpy torus with both a high covering factor and high extinction along the line of sight. The estimated bolometric luminosity of the AGN in NGC3690 is 3.2(+/-0.6)x10^44 erg/s. The nuclear GTC/CC spectrum of IC694/Arp299-A shows 11.3micron polycyclic aromatic hydrocarbon (PAH) emission stemming from a deeply embedded (A_V~24mag) region of less than 120pc in size. There is also a continuum-emitting dust component. If associated with th putative AGN in IC694, we estimate that it would be approximately 5 times less luminous than the AGN in NGC3690. The presence of dual AGN activity makes Arp299 a good example to study such phenomenon in the early coalescence phase of interacting galaxies.
SDSS J120136.02+300305.5 was detected in an XMM-Newton slew from June 2010 with a flux 56 times higher than an upper limit from ROSAT, corresponding to Lx~3x10^44 ergs/s. It has the optical spectrum of a quiescent galaxy (z=0.146). Overall the X-ray
flux has evolved consistently with the canonical t^-5/3 model, expected for returning stellar debris from a tidal disruption event, fading by a factor ~300 over 300 days. In detail the source is very variable and became invisible to Swift between 27 and 48 days after discovery, perhaps due to self-absorption. The X-ray spectrum is soft but is not the expected tail of optically thick thermal emission. It may be fit with a Bremsstrahlung or double-power-law model and is seen to soften with time and declining flux. Optical spectra taken 12 days and 11 months after discovery indicate a deficit of material in the broad line and coronal line regions of this galaxy, while a deep radio non-detection implies that a jet was not launched during this event.
The data collected by XMM-Newton as it slews between pointings currently cover almost half the entire sky, and many familiar features and new sources are visible. The soft-band sensitivity limit of the Slew is close to that of the RASS, and a large-a
rea Slew-RASS comparison now provides the best opportunity for discovering extremely rare high-variability objects.
It has been demonstrated that active galactic nuclei are powered by gas accretion onto supermassive black holes located at their centres. The paradigm that the nuclei of inactive galaxies are also occupied by black holes was predicted long ago by the
ory. In the last decade, this conjecture was confirmed by the discovery of giant-amplitude, non-recurrent X-ray flares from such inactive galaxies and explained in terms of outburst radiation from stars tidally disrupted by a dormant supermassive black hole at the nuclei of those galaxies. Due to the scarcity of detected tidal disruption events, the confirmation and follow-up of each new candidate is needed to strengthen the theory through observational data, as well as to shed new light on the characteristics of this type of events. Two tidal disruption candidates have been detected with XMM-Newton during slew observations. Optical and X-ray follow-up, post-outburst observations were performed on these highly variable objects in order to further study their classification and temporal evolution. We show that the detected low-state X-ray emission for these two candidates has properties such that it must still be related to the flare. The X-ray luminosity of the objects decreases according to theoretical predictions for tidal disruption events. At present, optical spectra of the sources do not present any evident signature of the disruption event. In addition, the tidal disruption rate as derived from the XMM-Newton slew survey has been computed and agrees with previous studies.
