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Register a new userA comparison of X-ray photon indices among the narrow and broad-line Seyfert 1 galaxies
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We present a detailed comparative systematic study using a sample of 221 Narrow-line Seyfert 1 (NLSy1) galaxies in comparison to a redshift matched sample of 154 Broad-line Seyfert 1 (BLSy1) galaxies based on their observations using ROSAT and/or XMM-Newton telescopes in soft X-ray band (0.1-2.0 keV). A homogeneous analysis is carried out to estimate their soft X-ray photon indices ($Gamma^{s}_{X}$) and its correlations with other parameters of nuclear activities such as Eddington ratios (R$_mathrm{Edd}$), bolometric luminosities (L$_mathrm{bol}$), black hole masses (M$_mathrm{BH}$) and the widths of the broad component of H$beta$ lines (FWHM(H$beta$)). In our analysis, we found clear evidence of the difference in the $Gamma^{s}_{X}$ and R$_mathrm{Edd}$ distributions among NLSy1 and BLSy1 galaxies, with steeper $Gamma^{s}_{X}$ and higher R$_mathrm{Edd}$ for the former. Such a difference also exists in the spectral indices distribution in hard X-ray ($Gamma^{h}_{X}$), based on the analysis of 53 NLSy1 and 46 BLSy1 galaxies in the 2-10 keV energy band. The difference in R$_mathrm{Edd}$ distributions does exist even after applying the average correction for the difference in the inclination angle of NLSy1 and BLSy1 galaxies. We also estimated R$_mathrm{Edd}$, based on SED fitting of 34 NLSy1 and 30 BLSy1 galaxies over the 0.3-10 keV energy band and found that results are still consistent with R$_mathrm{Edd}$ estimates based on the optical bolometric luminosity. Our analysis suggests that the higher R$_mathrm{Edd}$ in NLSy1 is responsible for its steeper X-ray spectral slope compared to the BLSy1, consistent with the disc-corona model as proposed for the luminous AGNs.
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We use publicly available XMM-Newton data to systematically compare the hard X-ray photon indices, $Gamma_{rm 2-10 keV}$ and the iron K$alpha$ emission lines of narrow-line (NL) and broad-line Seyfert 1 (BLS1) galaxies. We compile a flux-limited ($f_{rm 2-10 keV} geq 1 times 10^{-12}$ erg s$^{-1}$ cm$^{-2}$) sample including 114 radio-quiet objects, with the 2-10 keV luminosity ranging from 10$^{41}$ to 10$^{45}$ erg s$^{-1}$. Our main results are: 1) NLS1s and BLS1s show similar luminosity distributions; 2) The weighted mean of $Gamma_{rm 2-10 keV}$ of NLS1s, BLS1s and the total sample is $2.04pm0.04$, $1.74pm0.02$, $1.84pm0.02$, respectively; a significant anti-correlation between ga and FWHMH$beta$ suggests that $Gamma_{rm 2-10 keV} > 2.0$ may be taken to indicate X-ray luminous NLS1 type; 3) The 6.4 keV narrow iron K$alpha$ lines from NLS1s are generally weaker than that from BLS1s; this would indicate a smaller covering factor of the dusty tori in NLS1s, if the line emission originates from the inner boundary region of the dusty torus in an AGN; 4) all the broadened iron K$alpha$ lines with intrinsic width $sigma>0.5$ keV correspond to FWHMhb $leq 4000 ~kms$.
Narrow-line Seyfert,1 galaxies (NLS1s) with very small broad-line widths (say, FWHM(hb) $la $ 1200,kms) represent the extreme type of Seyfert,1 galaxies that have small black hole masses (mbh) and/or high Eddington ratios (redd). Here we study the X-ray properties of a homogeneously and optically selected sample of 13 such objects, termed as very narrow line Seyfert,1 galaxies (VNLS1s), using archival xmm data. It is found that the Fe K$alpha$ emission line is at most weak in these objects. A soft X-ray excess is ubiquitous, with the thermal temperatures falling within a strict range of 0.1--0.2,keV. Our result highlights the puzzling independence of the thermal temperature by extending the relations to even smaller FWHM(hb), i.e., smaller mbh ($sim 10^6$ msun) and/or higher redd. The excess emission can be modeled by a range of viable models, though the disk reflection and Comptonization models generally give somewhat better fits over the smeared absorption and the $p$-free models. At the Eddington ratios around unity and above, the X-ray spectral slopes in the 2--10,keV band are systematically flatter than the Risaliti et al.s predictions of the relationship with redd suggested previously. Short timescale (1--2 hours) X-ray variability is common, which, together with the variability amplitude computed for some of the objects, are supportive of the scenario that NLS1s are indeed AGN with relatively small mbh.
It is arguably in the X-ray regime that Narrow-line Seyfert 1 galaxies (NLS1s) exhibit the most extreme behaviour. Spectral complexity, rapid and large amplitude flux variations, and exceptional spectral variability are well known characteristics. However, NLS1s are not eccentric, but form a continuous sequence with typical Seyfert 1 galaxies. Understanding the extreme behaviour displayed by NLS1s will provide insight to the general AGN phenomenon. In this review, I will examine some of the important NLS1 X-ray discoveries over the past twenty years. I will then explore recent work that looks at the nature of the primary X-ray source (i.e. the corona) in NLS1s, demonstrating how the corona can be compact, dynamic, and in some cases consistent with collimated outflow. X-ray observations of NLS1s will be key in determining the nature of the corona, resolving the disc-jet connection, and determining the origin of the radio loud/quiet dichotomy in AGN.
We report on radio-to-gamma-ray observations during 2011 May-September of PMN J0948+0022, the first narrow-line Seyfert 1 (NLSy1) galaxy detected in gamma-rays by Fermi-LAT. Strong variability was observed in gamma-rays, with two flaring periods peaking on 2011 June 20 and July 28. The variability observed in optical and near-infrared seems to have no counterpart in gamma-rays. This different behaviour could be related to a bending and inhomogeneous jet or a turbulent extreme multi-cell scenario. The radio spectra showed a variability pattern typical of relativistic jets. The XMM spectrum shows that the emission from the jet dominates above 2 keV, while a soft X-ray excess is evident in the low-energy part of the X-ray spectrum. Models where the soft emission is partly produced by blurred reflection or Comptonisation of the thermal disc emission provide good fits to the data. The X-ray spectral slope is similar to that found in radio-quiet NLSy1, suggesting that a standard accretion disc is present, as expected from the high accretion rate. Except for the soft X-ray excess, unusual in jet-dominated AGNs, PMN J0948+0022 shows all characteristics of the blazar class.
We studied optical variability (OV) of a large sample of narrow-line Seyfert 1 (NLSy1) and broad-line Seyfert 1 (BLSy1) galaxies with z<0.8 to investigate any differences in their OV properties. Using archival optical V-band light curves from the Catalina Real Time Transient Survey that span 5-9 years and modeling them using damped random walk, we estimated the amplitude of variability. We found NLSy1 galaxies as a class show lower amplitude of variability than their broad-line counterparts. In the sample of both NLSy1 and BLSy1 galaxies, radio-loud sources are found to have higher variability amplitude than radio-quiet sources. Considering only sources that are detected in the X-ray band, NLSy1 galaxies are less optically variable than BLSy1 galaxies. The amplitude of variability in the sample of both NLSy1 and BLSy1 galaxies is found to be anti-correlated with Fe II strength but correlated with the width of the H-beta line. The well-known anti-correlation of variability-luminosity and the variability-Eddington ratio is present in our data. Among the radio-loud sample, variability amplitude is found to be correlated with radio-loudness and radio-power suggesting jets also play an important role in the OV in radio-loud objects, in addition to the Eddington ratio, which is the main driving factor of OV in radio-quiet sources.
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