arXiv subjects

Elena Jimenez Bailon

Publications and source records attributed to Elena Jimenez Bailon.

3 recordsLinked to original sources

arXiv2026

Hard X-ray Sources in Fermi UFOs

Identification and/or association of unidentified $γ$-ray sources with lower-energy counterparts represents a key challenge in modern astronomy, due to the relatively large positional uncertainty provided by $γ$-ray detectors. We selected Unidentified Fermi Objects (UFOs) positionally compatible with hard X-ray sources in the latest Palermo Swift-BAT hard X-ray Catalog and in the SRG/ART-XC all-sky X-ray survey Catalog, to identify lower-energy sources and possibly associate them to the UFOs. We found 17 UFOs with overlapping hard X-ray sources. We then collected soft X-ray data from Swift-XRT, Chandra-ACIS, XMM-Newton-EPIC, and eROSITA, identified 16 soft X-ray counterparts to the hard X-ray sources, and associate 15 with known astronomical objects, classified as: blazars/blazars candidates (2 sources), Seyfert galaxies (5 sources), X-ray binaries (2 sources), generic X-ray sources (1 source), cataclysmic variables (2 sources), and variable stars (3 sources). Blazars and Seyfert galaxies are likely lower-energy counterparts to the UFOs, since their mid-IR colors and broad-band spectral energy distributions suggest significant jetted, non-thermal emission. X-ray binaries can be potential lower-energy counterparts to the UFOs, since this class of sources has been already observed to emit $γ$-rays. The generic X-ray source has been proposed as a pulsar candidate, and we therefore suggest that it can be the lower-energy counterpart to the UFO. Cataclysmic variables have been suggested as potential $γ$-ray emitters so, if confirmed, the 2 sources classified as cataclysmic variables would represent the first $γ$-ray emitting sources of this kind. Finally, we consider the association of the 3 variable stars with the UFOs unlikely.

astro-ph.HE↗

arXiv2009

How complex is the obscuration in AGN? New clues from the Suzaku monitoring of the X-ray absorbers in NGC7582

We present the results of a Suzaku monitoring campaign of the Seyfert 2 galaxy, NGC7582. The source is characterized by very rapid (on timescales even lower than a day) changes of the column density of an inner absorber, together with the presence of constant components arising as reprocessing from a Compton-thick material. The best fitting scenario implies important modifications to the zeroth order view of Unified Models. While the existence of a pc-scale torus is needed in order to produce a constant Compton reflection component and an iron K$α$ emission line, in this Seyfert 2 galaxy this is not viewed along the line of sight. On the other hand, the absorption of the primary continuum is due to another material, much closer to the BH, roughly at the distance of the BLR, which can produce the observed rapid spectral variability. On top of that, the constant presence of a $10^{22}$ cm$^{-2}$ column density can be ascribed to the presence of a dust lane, extended on a galactic scale, as previously confirmed by Chandra. There is now mounting evidence that complexity in the obscuration of AGN may be the rule rather than the exception. We therefore propose to modify the Unification Model, adding to the torus the presence of two further absorbers/emitters. Their combination along the line of sight can reproduce all the observed phenomenology.

astro-ph.GA↗

arXiv2008

A BLR origin for the iron K$α$ line in NGC7213

The X-ray spectrum of NGC7213 is known to present no evidence for Compton reflection, a unique result among bright Seyfert 1s. The observed neutral iron K$α$ line, therefore, cannot be associated with a Compton-thick material, like the disc or the torus, but is due to Compton-thin gas, with the Broad Line Region (BLR) as the most likely candidate. To check this hypothesis, a long Chandra HETG observation, together with a quasi-simultaneous optical spectroscopic observation at the ESO NTT EMMI were performed. We found that the iron line is resolved with a FWHM=$2 400^{+1 100}_{-600}$ km/s, in perfect agreement with the value measured for the broad component of the H$α$, $2640^{+110}_{-90}$ km/s. Therefore, NGC7213 is the only Seyfert 1 galaxy whose iron K$α$ line is unambiguously produced in the BLR. We also confirmed the presence of two ionised iron lines and studied them in greater detail than before. The resonant line is the dominant component in the Fe XXV triplet, therefore suggesting an origin in collisionally ionised gas. If this is the case, the blueshift of around 1000 km/s of the two ionised iron lines could be the first measure of the velocity of a starburst wind from its X-ray emission.

astro-ph↗