1,087 research outputs found
BeppoSAX observations of Seyfert 1s in the Piccinotti sample I: poorly studied sources
In this work we present the first of two papers devoted to the study of the
X-ray spectral characteristics of Seyfert 1 galaxies in the Piccinotti sample.
In particular we analyse here the BeppoSAX broad band (0.1-100 keV) data of 4
objects which, despite their X-ray brightness, have been historically poorly
studied due to their late identification with an AGN; these are H0111-149
(MKN1152), H0235-525 (ESO198-G24), H0557-385 (IRAS F05563-3820) and H1846-786
(IRAS F18389-7834). We have assumed for all the sources a baseline model which
includes a power law with an exponential cut-off plus a reflection component
and an iron K_alpha line; we have also searched for the presence of intrinsic
absorption and/or a soft excess component. Our analysis indicates the presence
of complex absorption in two objects (H0557-385 and H0111-149) best described
by a combination of two uniform absorbers, one cold and one warm. Only in one
source, H0557-385, a soft excess component has been measured. The primary
continuum is best described by a canonical power law (Gamma=1.7-2) with a high
energy cut-off in the range 40-130 keV. A cold reflection component is likely
present in all sources with values ranging from less than 0.6 to higher than 2.
In 3 out of 4 objects we find a cold iron line having equivalent width typical
of Seyfert 1s (100-200 eV).Comment: 6 pages, 2 figures, accepted for publication as a Research Note in
Astronomy and Astrophysic
Using X-ray catalogues to find counterparts to unassociated high-energy Fermi/LAT sources
The first Fermi Large Area Telescope (LAT) catalogue of sources (1FHL)
emitting at high energies (above 10 GeV) reports the details of 514 objects
detected in the first three years of the Fermi mission. Of these, 71 were
reported as unidentified in the 1FHL catalogue, although six are likely to be
associated with a supernova remnant (SNR), a Pulsar Wind Nebula (PWN) or a
combination of both, thereby leaving a list of 65 still unassociated objects.
Herein, we report a preliminary analysis on this sample of objects
concentrating on nine 1FHL sources, which were found to have a clear optical
extragalactic classification. They are all blazar, eight BL Lac and one flat
spectrum radio quasar, typically at redshift greater than 0.1.Comment: Proceedings of "Swift: 10 Years of Discovery", December 2-5 2014,
Rome, Italy, in Proceedings of Science (SWIFT 10
Unveiling the nature of three INTEGRAL sources through optical spectroscopy
The results of an optical spectroscopy campaign performed at the Astronomical
Observatory of Bologna in Loiano (Italy) on three hard X-ray sources detected
by INTEGRAL (IGR J17303-0601, IGR J18027-1455 and IGR J21247+5058) are
presented. These data have allowed a determination of the nature for two of
them, with IGR J17303-0601 being a low mass X-ray binary in the Galaxy and IGR
J18027-1455 a background Type 1 Seyfert galaxy at redshift z = 0.035. IGR
J21247+5058, instead, has a quite puzzling spectroscopic appearance, with a
broad, redshifted H_alpha complex superimposed onto a `normal' F/G-type
Galactic star continuum: these features, together with the spatially coincident
extended radio emission, might suggest a chance alignment between a relatively
nearby star and a background radio galaxy. These results underline the still
non-negligible importance of smaller telescopes in modern astrophysics.Comment: 4 pages, 2 figures. Accepted for publication in A&A Letter
Swift/XRT counterparts to unassociated Fermi high-energy LAT sources
We report the results from our analysis of a large set of archival data
acquired with the X-ray telescope (XRT) onboard Swift, covering the sky region
surrounding objects from the first Fermi Large Area Telescope (LAT) catalogue
of high-energy sources (1FHL), which still lack an association. Of the 23
regions analysed, ten did not show any evidence of X-ray emission, but 13 were
characterised by the presence of one or more objects emitting in the 0.3-10 keV
band. Only in a couple of cases is the X-ray counterpart located outside the
Fermi positional uncertainty, while in all other cases the associations found
are compatible with the high-energy error ellipses. All counterparts we found
have been studied in detail by means of a multi-waveband approach to evaluate
their nature or class; in most cases, we have been able to propose a likely or
possible association except for one Fermi source whose nature remains doubtful
at the moment. The majority of the likely associations are extragalactic in
nature, most probably blazars of the BL Lac type.Comment: 13 pages, 5 figures, 4 tables. Accepted for publication in A&
IGR J17488-2338: a newly discovered giant radio galaxy
We present the discovery of a large scale radio structure associated with IGR
J17488--2338, a source recently discovered by \emph{INTEGRAL} and optically
identified as a broad line AGN at redshift 0.24. At low frequencies, the source
properties are those of an intermediate-power FR II radio galaxy with a linear
size of 1.4\,Mpc. This new active galaxy is therefore a member of a class of
objects called Giant Radio Galaxies (GRGs), a rare type of radio galaxies with
physical sizes larger than 0.7\,Mpc; they represent the largest and most
energetic single entities in the Universe and are useful laboratories for many
astrophysical studies. Their large scale structures could be due either to
special external conditions or to uncommon internal properties of the source
central engine The AGN at the centre of IGR J17488--2338 has a black hole of
1.310 solar masses, a bolometric luminosity of
710erg\,s and an Eddington ratio of 0.3, suggesting that
it is powerful enough to produce the large structure observed in radio. The
source is remarkable also for other properties, among which its X-ray
absorption, at odds with its type 1 classification, and the presence of a
strong iron line which is a feature not often observed in radio galaxies.Comment: 4 pages, 3 figures, accepted for publication on Astronomy and
Astrophysic
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