Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe soft excess of the NLS1 galaxy Mrk 359 studied with an XMM-Newton-NuSTAR monitoring campaign
70
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
XMM-Newton and NuSTAR multiple exposures allow us to disentangle the different emission components of active galactic nuclei (AGNs) and to study the evolution of their different spectral features. In this work, we present the timing and spectral properties of five simultaneous XMM-Newton and NuSTAR observations of the Narrow Line Seyfert 1 galaxy Mrk 359. We aim to provide the first broadband spectral modeling of Mrk 359 describing its emission spectrum from the UV up to the hard X-rays. To do this, we performed temporal and spectral data analysis, characterising the amplitude and spectral changes of the Mrk 359 time series and computing the 2-10 keV normalised excess variance. The spectral broadband modelling assumes the standard hot Comptonising corona and reflection component, while for the soft excess we tested two different models: a warm, optically thick Comptonising corona (the two-corona model) and a reflection model in which the soft-excess is the result of a blurred reflected continuum and line emission (the reflection model). High and low flux states were observed during the campaign. The former state has a softer spectral shape, while the latter shows a harder one. The photon index is in the 1.75-1.89 range, and only a lower limit to the hot-corona electron temperature can be found. A constant reflection component, likely associated with distant matter, is observed. Regarding the soft excess, we found that among the reflection models we tested, the one providing the better fit (reduced $chi^2$=1.14) is the high-density one. However, a significantly better fit (reduced $chi^2$=1.08) is found by modelling the soft excess with a warm Comptonisation model. The present analysis suggests the two-corona model as the best scenario for the optical-UV to X-ray emission spectrum of Mrk 359.
rate research
Read More
We present XMM-Newton observations of Mrk 359, the first Narrow Line Seyfert 1 galaxy discovered. Even among NLS1s, Mrk 359 is an extreme case with extraordinarily narrow optical emission lines. The XMM-Newton data show that Mrk 359 has a significant soft X-ray excess which displays only weak absorption and emission features. The (2-10) keV continuum, including reflection, is flatter than the typical NLS1, with Gamma approximately 1.84. A strong emission line of equivalent width approximately 200 eV is also observed, centred near 6.4 keV. We fit this emission with two line components of approximately equal strength: a broad iron-line from an accretion disc and a narrow, unresolved core. The unresolved line core has an equivalent width of approximately 120 eV and is consistent with fluorescence from neutral iron in distant reprocessing gas, possibly in the form of a `molecular torus. Comparison of the narrow-line strengths in Mrk 359 and other low-moderate luminosity Seyfert 1 galaxies with those in QSOs suggests that the solid angle subtended by the distant reprocessing gas decreases with increasing AGN luminosity.
We test the two-corona accretion scenario for active galactic nuclei in the case of the `bare Seyfert 1 galaxy HE 1143-1810. We perform a detailed study of the broad-band UV--X-ray spectral properties and of the short-term variability. We present results of a joint XMM-Newton and NuSTAR monitoring of the source, consisting of 5x20 ks observations, each separated by 2 days, performed in December 2017. The source is variable in flux among the different observations, and a correlation is observed between the UV and X-ray emission. Moderate spectral variability is observed in the soft band. The time-averaged X-ray spectrum exhibits a cut-off at $sim 100$ keV consistent with thermal Comptonization. We detect an iron K$alpha$ line consistent with being constant during the campaign and originating from a mildly ionized medium. The line is accompanied by a moderate, ionized reflection component. A soft excess is clearly present below 2 keV and is well described by thermal Comptonization in a `warm corona with a temperature of $sim 0.5$ keV and a Thomson optical depth of $sim 17-18$. For the hot hard X-ray emitting corona, we obtain a temperature of $sim 20$ keV and an optical depth of $sim 4$ assuming a spherical geometry. A fit assuming a jet-emitting disc (JED) for the hot corona also provides a nice description of the broad-band spectrum. In this case, the data are consistent with an accretion rate varying between $sim 0.7$ and $sim 0.9$ in Eddington units and a transition between the outer standard disc and the inner JED at $sim 20$ gravitational radii. The broad-band high-energy data agree with an accretion flow model consisting of two phases: an outer standard accretion disc with a warm upper layer, responsible for the optical--UV emission and the soft X-ray excess, and an inner slim JED playing the role of a hard X-ray emitting hot corona.
(Abridged) Soft and hard X-ray excesses, compared to the continuum power-law shape between ~2-10 keV, are common features observed in the spectra of active galactic nuclei (AGN) and are associated with the accretion disc-corona system around the supermassive black hole. However, the dominant process at work is still highly debated and has been proposed to be either relativistic reflection or Comptonisation. We aim to characterise the main X-ray spectral physical components from the bright bare Broad Line Seyfert 1 AGN Mrk 110, and the physical process(es) at work in its disc-corona system viewed almost face-on. We perform the X-ray broad-band spectral analysis thanks to two simultaneous XMM-Newton and NuSTAR observations performed on November 16-17 2019 and April 5-6 2020, we also use for the spectral analysis above 3 keV the deep NuSTAR observation obtained in January 2017. The broad-band X-ray spectra of Mrk 110 are characterised by the presence of a prominent and absorption-free smooth soft X-ray excess, moderately broad OVII and FeKalpha emission lines and a lack of a strong Compton hump. The continuum above ~3keV is very similar at both epochs, while some variability (stronger when brighter) is present for the soft X-ray excess. A combination of soft and hard Comptonisation by a warm and hot corona, respectively, plus mildly relativistic disc reflection reproduce the broadband X-ray continuum very well. The inferred warm corona temperature, kT_warm~0.3 keV, is similar to the values found in other sub-Eddington AGN, whereas the hot corona temperature, kT_hot~21-31 keV (depending mainly on the assumed hot corona geometry), is found to be in the lower range of the values measured in AGN.
We present a detailed spectral analysis of the joint XMM-Newton and NuSTAR observations of the active galactic nuclei (AGN) in the Seyfert 1.5 Galaxy ESO 362-G18. The broadband ($0.3mbox{--}79$ keV) spectrum shows the presence of a power-law continuum with a soft excess below $2$ keV, iron K$alpha$ emission ($sim 6.4$ keV), and a Compton hump (peaking at $sim 20$ keV). We find that the soft excess can be modeled by two different possible scenarios: a warm ($kT_mathrm{e}sim0.2$ keV) and optically thick ($tausim34$) Comptonizing corona; or with relativistically-blurred reflection off a high-density ($log{[n_mathrm{e}/mathrm{cm}^{-3}]}>18.3$) inner disk. These two models cannot be easily distinguished solely from their fit statistics. However, the low temperature ($kT_mathrm{e}sim20$ keV) and the thick optical depth ($tausim5$) of the hot corona required by the warm corona scenario are uncommon for AGNs. We also fit a hybrid model, which includes both disk reflection and a warm corona. Unsurprisingly, as this is the most complex of the models considered, this provides the best fit, and more reasonable coronal parameters. In this case, the majority of the soft excess flux arises in the warm corona component. However, based on recent simulations of warm coronae, it is not clear whether such a structure can really exist at the low accretion rates relevant for ESO 362-G18 ($dot{m}sim0.015$). This may therefore argue in favor of a scenario in which the soft excess is instead dominated by the relativistic reflection. Based on this model, we find that the data would require a compact hot corona ($hsim3,R_mathrm{Horizon}$) around a highly spinning ($a_star>0.927$) black hole.
We report the discovery of RX J2317.8-4422 in an extremely low X-ray flux state by the Neil Gehrels Swift observatory in 2014 April/May. In total, the low-energy X-ray emission dropped by a factor 100. We have carried out multi-wavelength follow-up observations of this Narrow-Line Seyfert 1 galaxy. Here we present observations with Swift, XMM-Newton, and NuSTAR in October and November 2014 and further monitoring observations by Swift from 2015 to 2018. Compared with the beginning of the Swift observations in 2005, in the November 2014 XMM and NuSTAR observation RX J2317--4422.8 dropped by a factor of about 80 in the 0.3-10 keV band. While the high-state Swift observations can be interpreted by a partial covering absorption model with a moderate absorption column density of $N_H=5.4times 10^{22}$ cm$^{-2}$ or blurred reflection, due to dominating background at energies above 2 keV the low-state XMM data can not distinguish between different multi-component models and were adequately fit with a single power-law model. We discuss various scenarios like a long-term change of the accretion rate or absorption as the cause for the strong variability seen in RX J2317.8--4422.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
