- ID:
- ivo://CDS.VizieR/J/MNRAS/448/1541
- Title:
- Spectral parameters for Mrk 335 and Ark 564
- Short Name:
- J/MNRAS/448/1541
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive flux-resolved spectral analysis of the bright narrow-line Seyfert 1 AGNs, Mrk 335 and Ark 564 using observations by XMM-Newton satellite. The mean and the flux-resolved spectra are fitted by an empirical model consisting of two Comptonization components, one for the low-energy soft excess and the other for the high-energy power law. A broad iron line and a couple of low-energy edges are required to explain the spectra. For Mrk 335, the 0.3-10 keV luminosity relative to the Eddington value, L_X_/L_Edd_, varied from 0.002 to 0.06. The index variation can be empirically described as {Gamma}=0.6log_10_L_X_/L_Edd_+3.0 for 0.005<L_X_/L_Edd_<0.04. At L_X_/L_Edd_~0.04 the spectral index changes and then continues to follow {Gamma}=0.6log_10_L_X_/L_Edd_+2.7, i.e. on a parallel track. We confirm that the result is independent of the specific spectral model used by fitting the data in the 3-10 keV band by only a power law and an iron line. For Ark 564, the index variation can be empirically described as {Gamma}=0.2log_10_L_X_/L_Edd_+2.7 with a significantly large scatter as compared to Mrk 335. Our results indicate that for Mrk 335, there may be accretion disc geometry changes which lead to different parallel tracks. These changes could be related to structural changes in the corona or enhanced reflection at high flux levels. There does not seem to be any homogeneous or universal relationship for the X-ray index and luminosity for different AGNs or even for the same AGN.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/699/L139
- Title:
- Spectral parameters of SNe Ia
- Short Name:
- J/ApJ/699/L139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the observables of 158 relatively normal Type Ia supernovae (SNe Ia) by dividing them into two groups in terms of the expansion velocity inferred from the absorption minimum of the SiII{lambda}6355 line in their spectra near B-band maximum brightness. One group ("Normal") consists of normal SNe Ia populating a narrow strip in the SiII velocity distribution, with an average expansion velocity <{nu}>=10600+/-400km/s near B maximum; the other group ("HV") consists of objects with higher velocities, {nu}>~11800km/s. Compared with the Normal group, the HV one shows a narrower distribution in both the peak luminosity and the luminosity decline rate {Delta}m_15_. In particular, their B-V colors at maximum brightness are found to be on average redder by ~0.1mag, suggesting that they either are associated with dusty environments or have intrinsically red B-V colors. The HV SNe Ia are also found to prefer a lower extinction ratio RV~1.6 (versus ~2.4 for the Normal ones). Applying such an absorption-correction dichotomy to SNe Ia of these two groups remarkably reduces the dispersion in their peak luminosity from 0.178mag to only 0.125mag.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A136
- Title:
- Spectral properties for Fluorine-like Ions
- Short Name:
- J/A+A/645/A136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The primary motivation of this paper is to provide accurate atomic properties of F-like ions with Z=20-30, including energy levels, line strengths, static dipole polarizabilities, and lifetimes. In addition, a detailed analysis is also carried out to explore the convergence and uncertainties of our results. Large-scale B-spline relativistic configuration interaction calculations are carried out to generate the atomic properties of F-like ions. The radial parts of one-electron Dirac orbitals are obtained from the relativistic self-consistent field procedure in which the Breit Interaction and QED corrections (vacuum polarization and self-energy terms) are also included. A numerical method, called Emu CI, is adopted to decrease the size of CI matrix significantly without loss of much accuracy. Energy levels and line strengths for electric-dipole (E1), electric-quadrupole (E2), and magnetic-dipole (M1) transitions are provided for the 250 lowest levels of each system, showing a good agreement with available theoretical and experimental information. The static dipole polarizabilities and lifetimes for the ten lowest states are also reported. A statement for the convergence and uncertainties of our results is presented.
- ID:
- ivo://CDS.VizieR/J/A+A/573/A81
- Title:
- Spectral properties of energetic GRBs
- Short Name:
- J/A+A/573/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the time-resolved spectral properties of energetic gamma-ray bursts (GRBs) with good high-energy photon statistics observed by the Gamma-Ray Burst Monitor (GBM) onboard the Fermi Gamma-Ray Space Telescope. We aim to constrain in detail the spectral properties of GRB prompt emission on a time-resolved basis and to discuss the theoretical implications of the fitting results in the context of various prompt emission models. Our sample comprises eight GRBs observed by the Fermi GBM in its first five years of mission, with 1keV-1MeV fluence f>1.0x10^-4^erg/cm2 and a signal-to-noise ratio level of S/N>=10.0 above 900keV. We performed a time-resolved spectral analysis using a variable temporal binning technique according to optimal S/N criteria, resulting in a total of 299 time-resolved spectra. We performed Band function fits to all spectra and obtained the distributions for the low-energy power-law index {alpha}, the high-energy power-law index {beta}, the peak energy in the observed {nu}F_{nu}_ spectrum E_p_, and the difference between the low- and high-energy power-law indices {Delta}s={alpha}-{beta}. We also applied a physically motivated synchrotron model, which is a triple power-law with constrained power-law indices and a blackbody component, to test the prompt emission for consistency with a synchrotron origin and obtain the distributions for the two break energies E_b,1_ and E_b,2_, the middle segment power-law index {beta}, and the Planck function temperature kT.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A21
- Title:
- Spectral properties of 438 GRBs
- Short Name:
- J/A+A/530/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the spectral analysis of the public data of 438 gamma ray bursts (GRBs) detected by the Fermi Gamma ray Burst Monitor (GBM) up to March 2010. For 432 bursts we could fit the time-integrated spectrum. In 318 cases we could reliably constrain the peak energy E^obs^_peak_ of their {nu}F{nu} spectrum by analyzing their time-integrated spectrum between 8keV and 35MeV. Eighty percent of these spectra are fitted by a power-law with an exponential cutoff, and the remaining with the Band function. Among these 318 GRBs, 274 belong to the long GRB class and 44 to the short.
- ID:
- ivo://CDS.VizieR/J/ApJS/232/17
- Title:
- Spectral properties of magnetar bursts
- Short Name:
- J/ApJS/232/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our broadband (2-250keV) time-averaged spectral analysis of 388 bursts from SGR J1550-5418, SGR 1900+14, and SGR 1806-20 detected with the Rossi X-ray Timing Explorer (RXTE) here and as a database in a companion web-catalog. We find that two blackbody functions (BB+BB), the sum of two modified blackbody functions (LB+LB), the sum of a blackbody function and a power-law function (BB+PO), and a power law with a high-energy exponential cutoff (COMPT) all provide acceptable fits at similar levels. We performed numerical simulations to constrain the best fitting model for each burst spectrum and found that 67.6% of burst spectra with well-constrained parameters are better described by the Comptonized model. We also found that 64.7% of these burst spectra are better described with the LB+LB model, which is employed in the spectral analysis of a soft gamma repeater (SGR) for the first time here, than with the BB+BB and BB+PO models. We found a significant positive lower bound trend on photon index, suggesting a decreasing upper bound on hardness, with respect to total flux and fluence. We compare this result with bursts observed from SGR and AXP (anomalous X-ray pulsar) sources and suggest that the relationship is a distinctive characteristic between the two. We confirm a significant anticorrelation between burst emission area and blackbody temperature, and find that it varies between the hot and cool blackbody temperatures differently than previously discussed. We expand on the interpretation of our results in the framework of a strongly magnetized neutron star.
- ID:
- ivo://CDS.VizieR/J/MNRAS/473/4436
- Title:
- Spectral properties of 441 radio pulsars
- Short Name:
- J/MNRAS/473/4436
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the spectral properties of 441 pulsars observed with the Parkes radio telescope near the centre frequencies of 728, 1382 and 3100MHz. The observations at 728 and 3100MHz were conducted simultaneously using the dual-band 10-50cm receiver. These high-sensitivity, multifrequency observations provide a systematic and uniform sample of pulsar flux densities. We combine our measurements with spectral data from the literature in order to derive the spectral properties of these pulsars. Using techniques from robust regression and information theory, we classify the observed spectra in an objective, robust and unbiased way into five morphological classes: simple or broken power law, power law with either low- or high-frequency cut-off and log-parabolic spectrum. While about 79 per cent of the pulsars that could be classified have simple power-law spectra, we find significant deviations in 73 pulsars, 35 of which have curved spectra, 25 with a spectral break and 10 with a low-frequency turn-over. We identify 11 gigahertz-peaked spectrum (GPS) pulsars, with 3 newly identified in this work and 8 confirmations of known GPS pulsars; 3 others show tentative evidence of GPS, but require further low-frequency measurements to support this classification. The weighted mean spectral index of all pulsars with simple power-law spectra is -1.60+/-0.03. The observed spectral indices are well described by a shifted log-normal distribution. The strongest correlations of spectral index are with spin-down luminosity, magnetic field at the light-cylinder and spin-down rate. We also investigate the physical origin of the observed spectral features and determine emission altitudes for three pulsars.
- ID:
- ivo://CDS.VizieR/J/ApJ/832/108
- Title:
- Spectral properties of Type Ic & Ic-bl SNe
- Short Name:
- J/ApJ/832/108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first systematic investigation of spectral properties of 17 Type Ic Supernovae (SNe Ic), 10 broad-lined SNe Ic (SNe Ic-bl) without observed gamma-ray bursts (GRBs), and 11 SNe Ic-bl with GRBs (SN-GRBs) as a function of time in order to probe their explosion conditions and progenitors. Using a number of novel methods, we analyze a total of 407 spectra, which were drawn from published spectra of individual SNe as well as from the densely time-sampled spectra of Modjaz+ (2014, J/AJ/147/99). In order to quantify the diversity of the SN spectra as a function of SN subtype, we construct average spectra of SNe Ic, SNe Ic-bl without GRBs, and SNe Ic-bl with GRBs. We find that SN 1994I is not a typical SN Ic, contrasting the general view, while the spectra of SN 1998bw/GRB 980425 are representative of mean spectra of SNe Ic-bl. We measure the ejecta absorption and width velocities using a new method described here and find that SNe Ic-bl with GRBs, on average, have quantifiably higher absorption velocities, as well as broader line widths than SNe without observed GRBs. In addition, we search for correlations between SN-GRB spectral properties and the energies of their accompanying GRBs. Finally, we show that the absence of clear He lines in optical spectra of SNe Ic-bl, and in particular of SN-GRBs, is not due to them being too smeared-out due to the high velocities present in the ejecta. This implies that the progenitor stars of SN-GRBs are probably free of the He-layer, in addition to being H-free, which puts strong constraints on the stellar evolutionary paths needed to produce such SN-GRB progenitors at the observed low metallicities.
- ID:
- ivo://CDS.VizieR/J/A+A/285/812
- Title:
- Spectral properties of X-ray extragal. sources
- Short Name:
- J/A+A/285/812
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/ApJ/434/54
- Title:
- Spectral properties of X-ray-selected AGNs
- Short Name:
- J/ApJ/434/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We survey the broadband spectral properties of ~500 X-ray-selected active galactic nuclei (AGNs) observed with the Einstein Observatory. Included in this survey are the ~450 AGNs in the Extended Medium Sensitivity Survey of Gioia et al. (1990ApJS...72..567G) and the ~50 AGNs in the Ultrasoft Survey of Cordova et al. (1992ApJS...81..661C). We present a revised version of the latter sample, based on the post publication discovery of a software error in the Einstein Rev-1b processing. We find that the mean spectral index of the AGNs between 0.1 and 0.6keV is softer, and the distribution of indices wider, than previous estimates based on analyses of the X-ray spectra of optically selected AGNs. A subset of these AGNs exhibit flux variability, some on timescales as short as 0.05-days. A correlation between radio and hard X-ray luminosity is confirmed, but the data do not support a correlation between the radio and soft X-ray luminosities, or between radio loudness and soft X-ray spectral slope. Evidence for physically distinct soft and hard X-ray components is found, along with the possibility of a bias in previous optically selected samples toward selection of AGNs with flatter X-ray spectra.