scholarly journals Extended X-ray emission from the z = 4.26 radio galaxy 4C 63.20

2020 ◽  
Vol 498 (2) ◽  
pp. 1550-1559
Author(s):  
Kate Napier ◽  
Adi Foord ◽  
Elena Gallo ◽  
Gabriele Ghisellini ◽  
Edmund Hodges-Kluck ◽  
...  
Keyword(s):  
Radio Galaxy ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Radio Galaxies ◽  
Spectral Energy ◽  
Synchrotron Emission ◽  
Radio Flux ◽  
Microwave Background ◽  
X Ray ◽  
Inverse Compton

ABSTRACT We report on deep Chandra X-ray Telescope imaging observations of 4C 63.20, one of the few known radio galaxies at z > 3.5. The X-ray counterpart is resolved into a core plus two off-nuclear sources that (combined) account for close to 30 per cent of the total X-ray flux. Their morphology and orientation are consistent with a diffuse, lobe-like nature, albeit compact hotspots cannot be ruled out. The broad-band spectral energy distribution of 4C 63.20 can be reproduced with a jet model where the majority of the radio flux can be ascribed to synchrotron emission from the hotspots, whereas the (non-nuclear) X-ray emission is produced via inverse Compton (IC) off of cosmic microwave background (CMB) photons within the extended lobes. This scenario is broadly consistent with the expectation from highly magnetized lobes in a hotter CMB, and supports the view that IC/CMB may quench less extreme radio lobes at high redshifts.

scholarly journals Constraining X-ray emission in HBL blazars using multiwavelength observations

2020 ◽  
Vol 496 (2) ◽  
pp. 1295-1306
Author(s):  
Alicja Wierzcholska ◽  
Stefan J Wagner
Keyword(s):  
Spectral Energy Distribution ◽  
Broad Band ◽  
Neutral Hydrogen ◽  
High Energy ◽  
Host Galaxy ◽  
Spectral Energy ◽  
Additional Absorption ◽  
X Ray ◽  
Uv Excess ◽  
Survey Results

ABSTRACT The X-ray spectrum of extreme high-energy peaked BL Lac-type blazars is located in the synchrotron branch of the broad-band spectral energy distribution (SED), at energies below the peak. A joint fit of the extrapolated X-ray spectra together with a host galaxy template allows characterizing the synchrotron branch in the SED. The X-ray spectrum is usually characterized either with a pure or a curved power-law model. In the latter case, however, it is hard to distinguish an intrinsic curvature from excess absorption. In this paper, we focus on five well-observed blazars: 1ES 0229+200, PKS 0548−322, RX J 1136+6737, 1ES 1741+196, and 1ES 2344+514. We constrain the infrared to X-ray emission of these five blazars using a model that is characterized by the host galaxy, spectral curvature, absorption, and ultraviolet (UV) excess to separate these spectral features. In the case of four sources, namely 1ES 0229+200, PKS 0548−322, 1ES 1741+196, and 1ES 2344+514, the spectral fit with the atomic neutral hydrogen from the Leiden Argentina Bonn Survey results in a significant UV excess present in the broad-band SED. Such excess can be interpreted as an additional component, for example, a blue bump. However, in order to describe spectra of these blazars without such excess, additional absorption to the atomic neutral hydrogen from the Leiden Argentina Bonn Survey is needed.

scholarly journals Broad-band spectral energy distribution of the X-ray transient Swift J1745−26 from outburst to quiescence

2020 ◽  
Vol 637 ◽  
pp. A2
Author(s):  
Sylvain Chaty ◽  
Francis Fortin ◽  
Alicia López-Oramas
Keyword(s):  
Energy Distribution ◽  
Light Curve ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Spectral Energy ◽  
X Ray ◽  
Upper Limit ◽  
Spectral Break ◽  
Hard State ◽  
Low Mass

Aims. We aim to analyse our study of the X-ray transient Swift J1745−26, using observations obtained from its outburst in September 2012, up to its decay towards quiescence in March 2013. Methods. We obtained optical and infrared observations, through override programme at ESO/VLT with FORS2 and ISAAC instruments, and added archival optical (VLT/VIRCAM), radio and X-ray (Swift) observations, to build the light curve and the broad-band spectral energy distribution (SED) of Swift J1745−26. Results. We show that, during its outburst and also during its decay towards quiescence, Swift J1745−26 SED can be adjusted, from infrared up to X-rays, by the sum of both a viscous irradiated multi-colour black body emitted by an accretion disc, and a synchrotron power law at high energy. In the radio domain, the SED arises from synchrotron emission from the jet. While our SED fitting confirms that the source remained in the low/hard state during its outburst, we determine an X-ray spectral break at frequency 3.1 ≤ νbreak ≤ 3.4 × 1014 Hz, and a radio spectral break at 1012 Hz ≤ νbreak ≤ 1013 Hz. We also show that the system is compatible with an absorption AV of ∼7.69 mag, lies within a distance interval of D ∼ [2.6 − 4.8] kpc with an upper limit of orbital period Porb = 11.3 h, and that the companion star is a late spectral type in the range K0–M0 V, confirming that the system is a low-mass X-ray binary. We finally plot the position of Swift J1745−26 on an optical-infrared – X-ray luminosity diagram: its localisation on this diagram is consistent with the source staying in the low-hard state during outburst and decay phases. Conclusions. By using new observations obtained at ESO/VLT with FORS2 and ISAAC, and adding archival optical (VLT/VIRCAM), radio and X-ray (Swift) observations, we built the light curve and the broad-band SED of Swift J1745−26, and we plotted its position on an optical-infrared – X-ray luminosity diagram. By fitting the SED, we characterized the emission of the source from infrared, via optical, up to X-ray domain, we determined the position of both the radio and X-ray spectral breaks, we confirmed that it remained in the low-hard state during outburst and decay phases, and we derived its absorption, distance interval, orbital period upper limit, and the late-type nature of companion star, confirming Swift J1745−26 is a low-mass X-ray binary.

scholarly journals A multiwavelength view of the open cluster NGC 2527: discovery of active stars

2020 ◽  
Vol 493 (4) ◽  
pp. 5565-5582
Author(s):  
Nevil Shah ◽  
K P Singh ◽  
Annapurni Subramaniam
Keyword(s):  
Binary Stars ◽  
Open Cluster ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Spectral Energy ◽  
Single Star ◽  
X Ray ◽  
Cluster Membership ◽  
Open Star ◽  
Combining Data

ABSTRACT Star clusters are ideal platforms for categorizing X-ray emitting stars and to study X-ray emission as a function of stellar age and activity. We present a comprehensive study of an open star cluster, NGC 2527, by combining data from XMM-UVOT-Gaia. Cluster membership of stars and their photometry are taken from Gaia and cross-matched with XMM and UVOT detections. We estimate the age of NGC 2527 as ∼630 Myr, reddening as E(B − V) = 0.13 mag, and a distance of 642 ± 30 pc using PARSEC isochrones. We detect five sub-subgiants and five bandgap stars, which defy single star evolution. We estimate the temperature, mass, radius, and luminosity of 53 single stars and 10 potential binary stars using a python code that fits single and composite Kurucz spectra to broad-band spectral energy distribution. Among the 12 X-ray emitting members, we find that five are potential RS CVn-type binaries, two are potential FK Comae type of red giant branch (RGB) stars, and five are main sequence (MS) stars with high coronal activity. Members with strong UV emission comprise one RGB star and several MS stars with UV excess suggestive of chromospheric activity. Based on comparison with other clusters, we tentatively suggest that X-ray luminosity of both RS CVn and contact binaries increases with age, suggesting that more active binaries are present in older clusters as compared to younger clusters. This study suggests possible presence of W UMa and FK Comae-type stars in younger (age ≃ 630 Myr) clusters.

scholarly journals The nature of the unassociated 2FGL sources

2014 ◽  
Vol 10 (S313) ◽  
pp. 91-92
Author(s):  
T. Pursimo ◽  
R. Ojha ◽  
E. Ferrara ◽  
F. Acero ◽  
H. Johnston ◽  
...  
Keyword(s):  
Spectral Energy Distribution ◽  
Low Frequency ◽  
Spectral Energy ◽  
High Frequency Peak ◽  
X Ray ◽  
Frequency Peak ◽  
Inverse Compton ◽  
Multi Wavelength ◽  
Error Circle

AbstractThe majority of Fermi-LAT detected (2FGL) sources are AGN, mostly blazars. However, the second largest category in the 2FGL are unassociated sources (~30% or 575 sources), whose multi-wavelength counterpart is either inconclusive or absent. Follow-up observations and archival data at X-ray, optical, and radio frequencies suggest that many unassociated 2FGL sources are strong candidates to be AGN. Typical observed characteristics of 2FGL detected AGN include variability at all frequencies and a spectral energy distribution (SED) with two “bumps”; a low-frequency synchrotron peak in the radio to optical/X-ray region and a high-frequency peak, possibly due to synchrotron self-Compton or Inverse Compton processes, that extends up to TeV energies. We present optical follow-up observations of a sample of Fermi unassociated sources with one or more potential X-ray counterparts detected within the LAT error circle.

scholarly journals The first broad-band X-ray view of the narrow-line Seyfert 1 Ton S180

2020 ◽  
Vol 497 (2) ◽  
pp. 2352-2370 ◽  
Author(s):  
G A Matzeu ◽  
E Nardini ◽  
M L Parker ◽  
J N Reeves ◽  
V Braito ◽  
...  
Keyword(s):  
Thermal Emission ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Outer Part ◽  
Spectral Energy ◽  
X Rays ◽  
Narrow Line ◽  
X Ray ◽  
Extreme Uv ◽  
Reflection Grating

ABSTRACT We present joint XMM–Newton and NuSTAR observations of the ‘bare’ narrow-line Seyfert 1 Ton S180 (z = 0.062), carried out in 2016 and providing the first hard X-ray view of this luminous galaxy. We find that the 0.4–30 keV band cannot be self-consistently reproduced by relativistic reflection models, which fail to account simultaneously for the soft and hard X-ray emission. The smooth soft excess prefers extreme blurring parameters, confirmed by the nearly featureless nature of the Reflection Grating Spectrometer (RGS) spectrum, while the moderately broad Fe K line and the modest hard excess above 10 keV appear to arise in a milder gravity regime. By allowing a different origin of the soft excess, the broad-band X-ray spectrum and overall spectral energy distribution (SED) are well explained by a combination of (a) direct thermal emission from the accretion disc, dominating from the optical to the far/extreme UV; (b) Comptonization of seed disc photons by a warm (kTe ∼ 0.3 keV) and optically thick (τ ∼ 10) corona, mostly contributing to the soft X-rays; (c) Comptonization by a standard hot ($kT_{\rm \mathrm{ e}}\gtrsim 100$ keV) and optically thin (τ < 0.5) corona, responsible for the primary X-ray continuum; and (d) reflection from the mid/outer part of the disc. The two coronae are suggested to be rather compact, with $R_{\rm hot}\lesssim R_{\rm warm}\lesssim 10\, r_{\rm g}$. Our SED analysis implies that Ton S180 accretes at super-Eddington rates. This is a key condition for the launch of a wind, marginal (i.e. 3.1σ significance) evidence of which is indeed found in the RGS spectrum.

scholarly journals An obscured AGN population hidden in the VIPERS galaxies: identification through spectral energy distribution decomposition

2020 ◽  
Vol 495 (2) ◽  
pp. 1853-1873
Author(s):  
E Pouliasis ◽  
G Mountrichas ◽  
I Georgantopoulos ◽  
A Ruiz ◽  
M Yang ◽  
...  
Keyword(s):  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Galactic Nuclei ◽  
Spectral Energy ◽  
X Ray ◽  
Star Forming ◽  
Star Forming Regions ◽  
Redshift Survey ◽  
Selection Of

ABSTRACT The detection of X-ray emission constitutes a reliable and efficient tool for the selection of active galactic nuclei (AGNs), although it may be biased against the most heavily absorbed AGNs. Simple mid-infrared (IR) broad-band selection criteria identify a large number of luminous and absorbed AGNs, yet again host contamination could lead to non-uniform and incomplete samples. Spectral energy distribution (SED) decomposition is able to decouple the emission from the AGN versus that from star-forming regions, revealing weaker AGN components. We aim to identify the obscured AGN population in the VIMOS Public Extragalactic Redshift Survey in the Canada–France–Hawaii Telescope Legacy Survey W1 field through SED modelling. We construct SEDs for 6860 sources and identify 160 AGNs at a high confidence level using a Bayesian approach. Using optical spectroscopy, we confirm the nature of ∼85 per cent of the AGNs. Our AGN sample is highly complete (∼92 per cent) compared to mid-IR colour-selected AGNs, including a significant number of galaxy-dominated systems with lower luminosities. In addition to the lack of X-ray emission (80 per cent), the SED fitting results suggest that the majority of the sources are obscured. We use a number of diagnostic criteria in the optical, IR, and X-ray regimes to verify these results. Interestingly, only 35 per cent of the most luminous mid-IR-selected AGNs have X-ray counterparts suggesting strong absorption. Our work emphasizes the importance of using SED decomposition techniques to select a population of type II AGNs, which may remain undetected by either X-ray or IR colour surveys.

Is TOL 1326--379 a Prototype of $\gamma$-ray Emitting FR0 Radio Galaxy?

2021 ◽  
Author(s):  
Wen-Jing Fu ◽  
Hai-Ming Zhang ◽  
Jin Zhang ◽  
Yun-Feng Liang ◽  
Su Yao ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Radio Galaxy ◽  
Spectral Energy Distribution ◽  
Average Energy ◽  
Spectral Energy ◽  
Observation Data ◽  
X Ray ◽  
Upper Limit ◽  
The One ◽  
Radiation Physic

Abstract With the possible spacial association to the Fermi/LAT source 3FGL J1330.0--3818, TOL 1326--379 may be the first one that is identified as a $\gamma$-ray emitting Fanaroff--Riley type 0 radio galaxy (FR0 RG). We analyze the $\sim$12 yr Fermi/LAT observation data of this $\gamma$-ray source and examine its association to TOL 1326--379. We show that the $\gamma$-ray source (named as J1331.0--3818) is tentatively detected with a TS value of 28.7, 3FGL J1330.0--3818 is out of the 95\% containment of J1331.0--3818, and their positions are spatially separated with 0.2$\degr$. 4FGL J1331.3--3818 falls into the 68\% containment of J1331.0--3818, suggesting that our result agrees with that reported in the Fourth Fermi LAT Source Catalog. TOL 1326--379 is out of the 95\% containment of J1331.0--3818, and their positions are spatially separated with 0.4$\degr$, indicating that the association between J1331.0--3818 and TOL 1326--379 is quite ambiguous. However, we do not find other possible potential radio and X-ray counterparts within the circle centered at J1331.0--3818 with a radius of 0.4$\degr$. The spectral energy distribution (SED) of TOL 1326--379 shows a bimodal feature as seen in the $\gamma$-ray emitting RGs. We fit the SED with the one-zone leptonic model and find that the average energy spectrum of J1331.0--3818 agrees with the model prediction. Assuming that J1331.0--3818 is an unidentified $\gamma$-ray source, we derive the upper-limit of the $\gamma$-ray flux for TOL 1326--379. It is not tight enough to exclude this possibility. Based on these analysis results, we cautiously argue that the $\gamma$-ray source J1331.0--3818 is associated with TOL 1326--379 and its jet radiation physic is similar to those $\gamma$-ray emitting RGs.

A disc reflection model for ultra-soft narrow-line Seyfert 1 galaxies

2020 ◽  
Vol 498 (3) ◽  
pp. 3888-3901
Author(s):  
Jiachen Jiang ◽  
Luigi C Gallo ◽  
Andrew C Fabian ◽  
Michael L Parker ◽  
Christopher S Reynolds
Keyword(s):  
Thermal Emission ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Continuum Emission ◽  
Spectral Energy ◽  
Narrow Line ◽  
Ionization State ◽  
X Ray ◽  
Reflection Model ◽  
Photon Index

ABSTRACT We present a detailed analysis of the XMM–Newton observations of five narrow-line Seyfert 1 galaxies (NLS1s). They all show very soft continuum emission in the X-ray band with a photon index of Γ ≳ 2.5. Therefore, they are referred to as ‘ultra-soft’ NLS1s in this paper. By modelling their optical/UV–X-ray spectral energy distribution (SED) with a reflection-based model, we find indications that the disc surface in these ultra-soft NLS1s is in a higher ionization state than other typical Seyfert 1 AGN. Our best-fitting SED models suggest that these five ultra-soft NLS1s have an Eddington ratio of λEdd = 1–20 assuming available black hole mass measurements. In addition, our models infer that a significant fraction of the disc energy in these ultra-soft NLS1s is radiated away in the form of non-thermal emission instead of the thermal emission from the disc. Due to their extreme properties, X-ray observations of these sources in the iron band are particularly challenging. Future observations, e.g. from Athena, will enable us to have a clearer view of the spectral shape in the iron band and thus distinguish the reflection model from other interpretations of their broad-band spectra.

scholarly journals On the X-Ray Emission from the Powerful Radio galaxies

1996 ◽  
Vol 175 ◽  
pp. 407-408
Author(s):  
G. Brunetti ◽  
G. Setti ◽  
A. Comastri
Keyword(s):  
Radiation Flux ◽  
Background Radiation ◽  
Radio Galaxies ◽  
X Rays ◽  
Microwave Background ◽  
X Ray ◽  
Near Ir ◽  
Inverse Compton ◽  
Microwave Background Radiation ◽  
Low Sensitivity

There is a growing evidence that radio loud quasars and powerful FR II radio galaxies belong to the same population. While X-ray observations of low redshift radio galaxies generally support the unified scheme relating the FR II radio galaxies to the radio quasars, nevertheless detailed studies of the X-ray properties of distant radio galaxies are made difficult due to both the low sensitivity of X-ray-satellites and to the emission of the hot intracluster gas in which they are normally embedded. We point out that significant fluxes of X-rays are produced in the strong radio galaxies by the Inverse Compton (IC) process. In the framework of the unified scheme the radio galaxies are pervaded both by an intense radiation flux from the misdirected hidden quasar and the cosmic microwave background radiation flux (CMB). From the standpoint of IC computation the far and near-IR emissions of the hidden quasar are of particular importance.

scholarly journals A new hard X-ray-selected sample of extreme high-energy peaked BL Lac objects and their TeV gamma-ray properties

2019 ◽  
Vol 486 (2) ◽  
pp. 1741-1762 ◽  
Author(s):  
L Foffano ◽  
E Prandini ◽  
A Franceschini ◽  
S Paiano
Keyword(s):  
Spectral Properties ◽  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Spectral Energy ◽  
X Rays ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lac

ABSTRACT Extreme high-energy peaked BL Lac objects (EHBLs) are an emerging class of blazars with exceptional spectral properties. The non-thermal emission of the relativistic jet peaks in the spectral energy distribution (SED) plot with the synchrotron emission in X-rays and with the gamma-ray emission in the TeV range or above. These high photon energies may represent a challenge for the standard modelling of these sources. They are important for the implications on the indirect measurements of the extragalactic background light, the intergalactic magnetic field estimate, and the possible origin of extragalactic high-energy neutrinos. In this paper, we perform a comparative study of the multiwavelength spectra of 32 EHBL objects detected by the Swift-BAT telescope in the hard X-ray band and by the Fermi-LAT telescope in the high-energy gamma-ray band. The source sample presents uniform spectral properties in the broad-band SEDs, except for the TeV gamma-ray band where an interesting bimodality seems to emerge. This suggests that the EHBL class is not homogeneous, and a possible subclassification of the EHBLs may be unveiled. Furthermore, in order to increase the number of EHBLs and settle their statistics, we discuss the potential detectability of the 14 currently TeV gamma-ray undetected sources in our sample by the Cherenkov telescopes.

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