The soft X-ray spectrum of NGC 4051 in its low state: a CLOUDY approach

The physical properties of the line emitting material in AGNs can be derived from well known line ratio diagnostics related to H-like and He-like ion transitions. Here, we show how to get this information (size, location and geometry of the emitting clouds) by a fit procedure of the overall observed spectrum with theoretical models developed by using the photoionization code CLOUDY. Application to NGC 4051 in its low flux state is shown

Observing circumnuclear photoionized gas in high resolution spectra of Seyfert 1 Galaxies

I will present XMM-Newton-RGS observations of the Seyfert 1 Galaxies Mrk 335 and NGC 4051 that unveiled an emission line-rich spectrum during a low flux state of the AGN continuum.Line ratio diagnostics from H-like and He-like ions indicate that the emission lines arise in X-ray photoionized plasma. The physical properties of the line emitting material were derived using the CLOUDY photoionization code. Although the properties of the plasma cannot be uniquely determined, we found that the density of the X-ray photoionized gas in Mrk 335 is constrained at 99% c.l. to 10^9-10^{11} cm^{-3}, placing the gas within the inner edge of the optical Broad Line Region. For NGC 4051, the density and the location of the plasma are instead consistent with outer region of the AGN. I will briefly present other Seyfert 1 sources where X-ray photoionized emission lines possibly arise in the Broad Line Region and I will review the implication of these findings in a broader context

Suzaku broad-band observations of the Seyfert 1 galaxies Mrk 509 and Mrk 841

Context. Markarian 509 and Markarian 841 are two bright Seyfert 1 galaxies with X-ray spectra characterised by a strong soft excess and a variable Fe Kα line, as shown by several X-ray observatories in the past. Aims: We report an analysis and modelling of new Suzaku observations of these sources, taken between April and November, 2006, for Mrk 509, and between January and July, 2007, for Mrk 841, for a total exposure time of ≈ 100 ks each. Data from XIS and HXD/PIN instruments, going from 0.5 to 60 keV, represent the highest spectral resolution simultaneous broad-band X-ray spectrum for these objects, and provide the strongest constraints yet on the origin of the soft excess emission. Methods: We fitted the broad-band spectrum of both sources with a double Comptonisation model, adding neutral reflection from distant material and a two-phase warm absorber. We then studied the two competing models developed to explain the soft excess in terms of atomic processes: a blurred ionised disc reflection and an ionised absorption by a high velocity material. Results: When fitting the data in the 3-10 keV range with a power law spectrum, and extrapolating this result to low energies, a soft excess is clearly observed below 2 keV, although its strength is weak compared to previous observations of both sources. A moderate hard excess is seen at energies higher than 10 keV, together with a neutral Fe Kα narrow emission line at E0 ≈ 6.4 keV and a broad Fe emission line. For Mrk 509, the broad Fe emission line is required in all the three physical models to ensure a good fit to the data: this finding suggests that the blurred reflection model correctly describes the soft excess, but that it underestimates the broad Fe emission line. For the smeared absorption model, this suggests instead that the continuum spectrum absorbed by the outflowing gas should indeed contain a reflected component. For Mrk 841, all three models that we tested provide a good fit to the data, and we cannot rule out any of them. A broad emission line is required in the double Comptonisation and smeared absorption models, while the blurred reflection model consistently fits the broad-band spectrum, without adding any extra emission-line component

Search for Gamma-Ray and Neutrino Coincidences Using HAWC and ANTARES Data

In the quest for high-energy neutrino sources, the Astrophysical Multimessenger Observatory Net- work (AMON) has implemented a new search by combining data from the High Altitude Water Cherenkov (HAWC) observatory and the Astronomy with a Neutrino Telescope and Abyss environ- mental RESearch (ANTARES) neutrino telescope. Using the same analysis strategy as in a previous detector combination of HAWC and IceCube data, we perform a search for coincidences in HAWC and ANTARES events that are below the threshold for sending public alerts in each individual detector. Data were collected between July 2015 and February 2020 with a livetime of 4.39 years. Over this time period, 3 coincident events with an estimated false-alarm rate of $< 1$ coincidence per year were found. This number is consistent with background expectations