scholarly journals First Results of Optical Monitoring of 3C 390.3

1997 ◽  
Vol 159 ◽  
pp. 163-164
Author(s):  
M. Dietrich ◽  
P.T. O’Brien ◽  
K. M. Leighly
Keyword(s):  
Time Scales ◽  
Broad Band ◽  
Emission Lines ◽  
High Temporal Resolution ◽  
Line Profiles ◽  
X Ray ◽  
First Results ◽  
Long Time ◽  
Flux Measurements ◽  
Calar Alto

In late autumn 1994, the International AGN Watch started a multiwavelength monitoring campaign on 3C 390.3, the first radio-loud AGN to be selected for high temporal-resolution monitoring from the radio domain to X-ray energies. This AGN is is of particular interest since significant variations have been observed on both short and long time scales in both the line fluxes and line profiles (Barr et al. 1980, Veilleux & Zheng 1991).In the optical, spectroscopic data and broad-band flux measurements in B, V, R, and I were obtained. The brightness of 3C 390.3 was calculated relative to the stars in the field. The R magnitudes are based on observations recorded at Calar Alto, Spain, in 1994 December. Generally, AGN spectra are intercalibrated using narrow forbidden emission lines since these lines can be taken as constant on time scales of decades (Peterson 1993). Since the [O III] λλ4959, 5007 flux is variable on time scales of several months (Zheng et al. 1995), these lines were studied in detail. We found that they were constant within ~2% during 1995 (Dietrich et al. 1996). The spectra were therefore intercalibrated by using the narrow forbidden emission lines. 3C 390.3 was also observed with IUE for 14 months (O’Brien et al. 1996) and with ROSAT for nine months in 1995 (Leighly et al. 1996). Radio data were also obtained during a 3-month MERLIN campaign.

scholarly journals Review of GRANAT Observations of AGNs

1994 ◽  
Vol 159 ◽  
pp. 63-72 ◽  
Author(s):  
E. Churazov ◽  
M. Gilfanov ◽  
A. Finoguenov ◽  
R. Sunyaev ◽  
M. Chernyakova ◽  
...  
Keyword(s):  
Time Scales ◽  
Gamma Ray ◽  
Broad Band ◽  
Band 3 ◽  
X Rays ◽  
X Ray ◽  
X Ray Background

Brief review of AGNs observations in the X-ray / soft gamma-ray bands with the orbital observatory GRANAT is presented.For three well known bright objects (3C273, NGC4151 and Cen A) broad band (3 keV–few hundreds keV) spectra have been obtained. Imaging capabilities allowed accurate (several arcminutes) identification of these objects with sources of hard X-rays.The spectrum of NGC4151 above ≈ 50 keV was found to be much steeper than that in most of the previous observations, while in standard X-ray band the spectrum agrees with observed previously. The comparison of the observed spectra with that of the X-Ray Background (XRB) indicates that sources similar to NGC4151 could reproduce the shape of XRB spectrum in 3–60 keV band.Cen A was observed in the very low state during most of observations in 1990–1993, except for two observations in 1991. The variability of the hard X-ray flux has been detected on the time scales of several days.

scholarly journals Magnetic fields in O-type stars measured with FORS 1 at the VLT

2008 ◽  
Vol 4 (S259) ◽  
pp. 381-382
Author(s):  
Swetlana Hubrig ◽  
M. Schöller ◽  
R. S. Schnerr ◽  
I. Ilyin ◽  
H. F. Henrichs ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Massive Stars ◽  
Emission Lines ◽  
X Ray ◽  
Wind Variability ◽  
Thermal Radio ◽  
Wide Range ◽  
Long Time ◽  
Hα Emission ◽  
Chemical Peculiarity

AbstractThe presence of magnetic fields in O-type stars has been suspected for a long time. The discovery of such fields would explain a wide range of well documented enigmatic phenomena in massive stars, in particular cyclical wind variability, Hα emission variations, chemical peculiarity, narrow X-ray emission lines and non-thermal radio/X-ray emission. Here we present the results of our studies of magnetic fields in O-type stars, carried out over the last years.

scholarly journals Simple noise estimates and pseudoproxies for the last 21k years

2018 ◽  
Author(s):  
Oliver Bothe ◽  
Sebastian Wagner ◽  
Eduardo Zorita
Keyword(s):  
Time Scales ◽  
Ice Cores ◽  
Noise Model ◽  
Climate Simulation ◽  
High Temporal Resolution ◽  
Model Code ◽  
Proxy Records ◽  
Noise Characteristics ◽  
Spatial Differences ◽  
Long Time

Abstract. Climate reconstructions are means to extract the signal from uncertain paleo-observations, i.e. proxies. It is essential to evaluate these to understand and quantify their uncertainties. Similarly, comparing climate simulations and proxies requires approaches to bridge the, e.g., temporal and spatial differences between both and address their specific uncertainties. One way to achieve these two goals are so called pseudoproxies. These are surrogate proxy records within, e.g., the virtual reality of a climate simulation. They in turn depend on an understanding of the uncertainties of the real proxies, i.e. the noise-characteristics disturbing the original environmental signal. Common pseudoproxy approaches so far concentrated on data with high temporal resolution from, e.g., tree-rings or ice-cores over the last approximately 2,000 years. Here we provide a simple but flexible noise model for potentially low-resolution sedimentary climate proxies for temperature on millennial time-scales, the code for calculating a set of pseudoproxies from a simulation and, for one simulation, the pseudoproxies themselves. The noise model considers the influence of other environmental variables, a dependence on the climate state, a bias due to changing seasonality, modifications of the archive (e.g., bioturbation), potential sampling variability, and a measurement error. Model, code, and data should allow to develop new ways of comparing simulation data with proxies on long time-scales. Code and data are available at https://doi.org/10.17605/OSF.IO/ZBEHX.

scholarly journals Optical Emission Lines and the X-Ray Properties of Type 1 Seyfert Galaxies

2011 ◽  
Vol 20 (3) ◽  
pp. 442-447
Author(s):  
G. La Mura ◽  
S. Ciroi ◽  
V. Cracco ◽  
D. Ilić ◽  
L. Č. Popović ◽  
...  
Keyword(s):  
Structural Model ◽  
Optical Emission ◽  
Seyfert Galaxies ◽  
Emission Lines ◽  
Line Profiles ◽  
Energy Bands ◽  
X Ray ◽  
Line Region ◽  
Spectral Components

Abstract In this contribution we report on the study of the optical emission lines and X-ray spectra of a sample of Type 1 AGNs, collected from the SDSS database and observed by the XMM-Newton satellite. Using different instruments onboard XMM, we identify the spectral components of the soft and hard energy bands (in the range from 0.3 keV to 10 keV). The properties of the X-ray continuum and of the Fe Kα line feature are related to the optical broad emission line profiles and intensity ratios. The resulting picture of emission, absorption and reflection processes is interpreted by means of a structural model of the broad line region, developed on the basis of independent optical and radio observations.

scholarly journals Non-thermal particle effects on the Hα and Hβ line profiles in the 18 August 2002 solar flare

2008 ◽  
Vol 26 (10) ◽  
pp. 2975-2982 ◽  
Author(s):  
L. K. Kashapova ◽  
P. Kotrč ◽  
Yu. A. Kupryakov
Keyword(s):  
Diagnostic Tool ◽  
Broad Band ◽  
Line Center ◽  
Thermal Processes ◽  
Line Profiles ◽  
Thermal Electron ◽  
X Ray ◽  
Line Intensity Ratio ◽  
Electron Contribution ◽  
The Difference

Abstract. We present results of the 18 August 2002 flare analysis as an example for developing a diagnostic tool for thermal and non-thermal processes in chromospheric lines. Taking into account the hard X-ray (HXR) emission, we attempted to derive the Hα and Hβ line properties which were caused by the non-thermal electron contribution and could be useful for diagnostic purposes. The flare itself was a sequence of harder and softer bursts in HXR and we investigated three flare kernels associated with them. Two of the kernels appeared simultaneously. This phase of the flare could be observed in a broad band of wavelengths (HXR, UV, optical and microwaves). Kernel 1 did not clearly coincide with any HXR source but its intensity increased with the HXR flux rise. The flare kernel~3 did not show any significant response in microwaves, however, the related HXR flux was comparable with the flux of the previous kernels. We carried out an analysis of the difference between the Hα/Hβ profile rate in the line center at the distance of 0.5 Å from the line center. Only kernel 2 showed parameter fluctuations that were related to HXR flux evolution. The supposition of the non-thermal electron effect on the Hα/Hβ profile ratio was confirmed only at the kernel connected with the 25–50 keV HXR source. We found further confirmation that the Hα/Hβ line intensity ratio could be used as a diagnostic tool for non-thermal electron presence.

scholarly journals New measurements of the cyclotron line energy in Cen X-3

2020 ◽  
Vol 500 (3) ◽  
pp. 3454-3461
Author(s):  
Gunjan Tomar ◽  
Pragati Pradhan ◽  
Biswajit Paul
Keyword(s):  
Broad Band ◽  
Resonant Scattering ◽  
High Energy ◽  
Emission Lines ◽  
Power Law Model ◽  
Pulse Profile ◽  
Line Energy ◽  
X Ray ◽  
Cyclotron Absorption ◽  
Cyclotron Line

ABSTRACT We report results from the analysis of data from two observations of the accreting binary X-ray pulsar Cen X-3 carried out with the broad-band X-ray observatories Suzaku and NuSTAR. The pulse profile is dominated by a broad single peak and show some energy dependence with two additional weak pulse peaks at energies below 15 and 25 keV, respectively. The broad-band X-ray spectrum for 0.8–60.0 keV for Suzaku  and 3.0–60.0 keV for NuSTAR is fitted well with high-energy cut-off power-law model along with soft-excess, multiple iron emission lines and a cyclotron absorption. The cyclotron line energy is found to be $30.29^{+0.68}_{-0.61}$ and $29.22^{+0.28}_{-0.27}$ keV, respectively, in the Suzaku  and NuSTAR  spectra. We make a comparison of these two measurements with four previous measurements of Cyclotron Resonant Scattering Feature (CRSF) in Cen X-3  obtained with Ginga, BeppoSAX,  and RXTE. We find no evidence for a dependence of the CRSF on luminosity. Except for one CRSF measurement with BeppoSAX , the remaining measurements are consistent with a CRSF energy in the range of 29.5–30.0 keV over a luminosity range of 1.1–5.4 × 1037 erg s−1 different from several other sources that show considerable CRSF variation in the same luminosity range.

scholarly journals X-ray photolysis of CH3COCH3 ice: implications for the radiation effects of compact objects towards astrophysical ices

2020 ◽  
Vol 498 (1) ◽  
pp. 689-701 ◽  
Author(s):  
G A Carvalho ◽  
S Pilling
Keyword(s):  
Cross Section ◽  
Time Scales ◽  
Chemical Equilibrium ◽  
Radiation Effects ◽  
Broad Band ◽  
Compact Objects ◽  
X Rays ◽  
Formation Cross Section ◽  
X Ray ◽  
Molecular Abundances

ABSTRACT In this study, we employed broad-band X-rays (6–2000 eV) to irradiate the frozen acetone CH3COCH3, at the temperature of 12 K, with different photon fluences up to 2.7 × 1018 photons cm−2. Here, we consider acetone as a representative complex organic molecule (COM) present on interstellar ice grains. The experiments were conduced at the Brazilian Synchrotron facility (LNLS/CNPEN) employing infrared spectroscopy (FTIR) to monitor chemical changes induced by radiation in the ice sample. We determined the effective destruction cross-section of the acetone molecule and the effective formation cross-section for daughter species. Chemical equilibrium, obtained for fluence 2 × 1018 photons cm−2, and molecular abundances at this stage were determined, which also includes the estimates for the abundance of unknown molecules, produced but not detected, in the ice. Time-scales for ices, at hypothetical snow line distances, to reach chemical equilibrium around several compact and main-sequence X-ray sources are given. We estimate time-scales of 18 d, 3.6 and 1.8 months, 1.4 × 109–6 × 1011 yr, 600 and 1.2 × 107 yr, and 107 yr, for the Sun at 5 au, for O/B stars at 5 au, for white dwarfs at 1 LY, for the Crab pulsar at 2.25 LY, for Vela pulsar at 2.25 LY, and for Sagittarius A* at 3 LY, respectively. This study improves our current understanding about radiation effects on the chemistry of frozen material, in particular, focusing for the first time, the effects of X-rays produced by compact objects in their eventual surrounding ices.

scholarly journals He I λ 10 830 Å in the transmission spectrum of HD209458 b

2019 ◽  
Vol 629 ◽  
pp. A110 ◽  
Author(s):  
F. J. Alonso-Floriano ◽  
I. A. G. Snellen ◽  
S. Czesla ◽  
F. F. Bauer ◽  
M. Salz ◽  
...  
Keyword(s):  
Close Relation ◽  
Emission Lines ◽  
Resolving Power ◽  
Velocity Change ◽  
X Ray ◽  
Transiting Planets ◽  
Upper Limits ◽  
Extreme Uv ◽  
Calar Alto ◽  
Excess Absorption

Context. Recently, the He I triplet at 10 830 Å was rediscovered as an excellent probe of the extended and possibly evaporating atmospheres of close-in transiting planets. This has already resulted in detections of this triplet in the atmospheres of a handful of planets, both from space and from the ground. However, while a strong signal is expected for the hot Jupiter HD 209458 b, only upper limits have been obtained so far. Aims. Our goal is to measure the helium excess absorption from HD 209458 b and assess the extended atmosphere of the planet and possible evaporation. Methods. We obtained new high-resolution spectral transit time-series of HD 209458 b using CARMENES at the 3.5 m Calar Alto telescope, targeting the He I triplet at 10 830 Å at a spectral resolving power of 80 400. The observed spectra were corrected for stellar absorption lines using out-of-transit data, for telluric absorption using the MOLECFIT software, and for the sky emission lines using simultaneous sky measurements through a second fibre. Results. We detect He I absorption at a level of 0.91 ± 0.10% (9 σ) at mid-transit. The absorption follows the radial velocity change of the planet during transit, unambiguously identifying the planet as the source of the absorption. The core of the absorption exhibits a net blueshift of 1.8 ± 1.3 km s−1. Possible low-level excess absorption is seen further blueward from the main absorption near the centre of the transit, which could be caused by an extended tail. However, this needs to be confirmed. Conclusions. Our results further support a close relation between the strength of planetary absorption in the helium triplet lines and the level of ionising, stellar X-ray, and extreme-UV irradiation.

scholarly journals X-ray variability in LINERs

2013 ◽  
Vol 9 (S304) ◽  
pp. 399-402
Author(s):  
Josefa Masegosa ◽  
Lorena Hernández-García ◽  
Isabel Márquez ◽  
Omaira González-Martín
Keyword(s):  
Active Galactic Nuclei ◽  
Time Scales ◽  
Galactic Nuclei ◽  
Spectral Variability ◽  
X Ray ◽  
Line Region ◽  
Variability Pattern ◽  
Long Time ◽  
Public Archives

AbstractOne of the most important features in active galactic nuclei (AGN) is the variability of their emission. Variability has been discovered at X-ray, UV, and radio frequencies on time scales from hours to years. Among the AGN family and according to theoretical studies, Low-Ionization Nuclear Emission Line Region (LINER) nuclei would be variable objects on long time scales. Our purpose is to investigate spectral X-ray variability in LINERs and to understand the nature of these kinds of objects, as well as their accretion mechanism. Chandra and XMM–Newton public archives were used to compile X-ray spectra of LINER nuclei at different epochs with time scales of years. To search for variability we fit all the spectra from the same object with a set of models, in order to identify the parameters responsible for the variability pattern. We found that long term spectral variability is very common, with variations mostly related to hard energies (2-10 keV). These variations are due to changes in the soft excess, and/or changes in the absorber, and/or intrinsic variations of the source.

scholarly journals Optical variability of X-ray selected blazars

2006 ◽  
Vol 2 (S238) ◽  
pp. 399-400 ◽  
Author(s):  
Omar M. Kurtanidze ◽  
Maria G. Nikolashvili ◽  
Givi N. Kimeridze ◽  
Lorand A. Sigua ◽  
Bidzina Z. Kapanadze
Keyword(s):  
Time Scales ◽  
Significant Variation ◽  
Optical Variability ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lac ◽  
Long Time

AbstractWe present optical R band photometry of nine X-ray selected BL Lac objects: 1ES 0229+200, 1ES 0323+022, 1ES 502+675, 1ES 0647+250, 1ES 0806+524, 1ES0927+500, 1ES 1028+511, 1ES 1959+650, 1ES2344+514.Variability on long time scales within one magnitude in R band was found for all of the observed objects, except 1ES 0229+200 and 1ES0927+500. Largest variation was detected for 1ES 0502+675 and equals to 1.07 mag. Only few objects show statistically significant variation on intra-day scale.

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