The X-ray pulsar A0535 + 26 - Pulse profile and its time variability in hard X-rays

1985 ◽  
Vol 298 ◽  
pp. 585 ◽  
Author(s):  
F. Frontera ◽  
D. dal Fiume ◽  
E. Morelli ◽  
G. Spada
Keyword(s):  
Time Variability ◽  
X Rays ◽  
Pulse Profile ◽  
X Ray

scholarly journals Wide-field Cameras for GRB Observations in X-rays and EUV

1995 ◽  
Vol 151 ◽  
pp. 431-434
Author(s):  
Eugene Moskalenko
Keyword(s):  
Time Scale ◽  
Field Of View ◽  
Time Variability ◽  
Wide Field ◽  
Main Task ◽  
X Rays ◽  
Interstellar Absorption ◽  
X Ray ◽  
Instrumental Approaches ◽  
Stationary Sources

Recent observations of the ASCA satellite resulted in the first identification of a GB source (Murakami et al. 1994). This success confirmed the importance of simultaneous observations in different wavelength bands for GB studies. Besides the ASCA results, there were several observations of GBs in X-ray band with the Ginga (Yoshida et al,.1989), V 78/1 (Laros et al. 1984) and other satellites. It became clear that GBs emit 4 - 8% of their energy in the 2 - 10 keV range. The main task now is to have an equipment which will be able to monitor the sky in X-rays in a mode similar to that of GRO observations, i.e. the telescope should have an all-sky field-of-view (FoV) and should work continuously.A telescope with these features but operating at soft X-ray energies may directly determine the GB distance scale, due to interstellar absorption of the photons with energies less than 2 keV, as was pointed out first by Schaefer (1993). Flaring sources similar to GBs in time scale may be found also in the EUV (hundreds of angstroms) with the help of very wide-field cameras. Of course each such device - in X-ray, soft X-ray and EUV bands - will discover many transient objects, flaring events, will study time variability of bright “stationary” sources etc. In this paper we describe several instrumental approaches in these fields.

scholarly journals Study of recent outburst in the Be/X-ray binary RX J0209.6−7427 with AstroSat: a new ultraluminous X-ray pulsar in the Magellanic Bridge?

2020 ◽  
Vol 495 (3) ◽  
pp. 2664-2672 ◽  
Author(s):  
Amar Deo Chandra ◽  
Jayashree Roy ◽  
P C Agrawal ◽  
Manojendu Choudhury
Keyword(s):  
Energy Band ◽  
Spectral Characteristics ◽  
Spectral Studies ◽  
X Rays ◽  
Energy Bands ◽  
Large Area ◽  
Pulse Profile ◽  
X Ray ◽  
Outburst Energy ◽  
Area X

ABSTRACT We present the timing and spectral studies of RX J0209.6–7427 during its rare 2019 outburst using observations with the Soft X-ray Telescope (SXT) and Large Area X-ray Proportional Counter (LAXPC) instruments on the AstroSat satellite. Pulsations having a periodicity of 9.29 s were detected for the first time by the NICER mission in the 0.2–10 keV energy band and, as reported here, by AstroSat over a broad energy band covering 0.3–80 keV. The pulsar exhibits a rapid spin-up during the outburst. Energy resolved folded pulse profiles are generated in several energy bands in 3–80 keV. To the best of our knowledge this is the first report of the timing and spectral characteristics of this Be binary pulsar in hard X-rays. There is suggestion of evolution of the pulse profile with energy. The energy spectrum of the pulsar is determined and from the best-fitting spectral values, the X-ray luminosity of RX J0209.6−7427 is inferred to be 1.6 × 1039 erg s−1. Our timing and spectral studies suggest that this source has features of an ultraluminous X-ray pulsar in the Magellanic Bridge. Details of the results are presented and discussed in terms of the current ideas.

scholarly journals Temporal and spatial variation of synchrotron X-ray stripes in Tycho’s supernova remnant

2020 ◽  
Vol 72 (5) ◽  
Author(s):  
Masamune Matsuda ◽  
Takaaki Tanaka ◽  
Hiroyuki Uchida ◽  
Yuki Amano ◽  
Takeshi Go Tsuru
Keyword(s):  
Surface Brightness ◽  
Supernova Remnant ◽  
Time Variability ◽  
X Rays ◽  
Temporal And Spatial Variation ◽  
Proton Acceleration ◽  
X Ray ◽  
Temporal And Spatial ◽  
Imaging And Spectroscopy ◽  
The Magnetic Field

Abstract The synchrotron X-ray “stripes” discovered in Tycho’s supernova remnant (SNR) have been attracting attention as they may be evidence for proton acceleration up to PeV. We analyzed Chandra data taken in 2003, 2007, 2009, and 2015 for imaging and spectroscopy of the stripes in the southwestern region of the SNR. Comparing images obtained at different epochs, we find that time variability of synchrotron X-rays is not limited to two structures previously reported but is more common in the region. Spectral analysis of nine bright stripes reveals not only their time variabilities but also a strong anti-correlation between the surface brightness and photon indices. The spectra of the nine stripes have photon indices of Γ = 2.1–2.6 and are significantly harder than those of the outer rim of the SNR in the same region with Γ = 2.7–2.9. Based on these findings, we indicate that the magnetic field is substantially amplified, and suggest that particle acceleration through a stochastic process may be at work in the stripes.

scholarly journals Broadband X-ray observations of four gamma-ray narrow-line Seyfert 1 galaxies

2019 ◽  
Vol 632 ◽  
pp. A120 ◽  
Author(s):  
M. Berton ◽  
V. Braito ◽  
S. Mathur ◽  
L. Foschini ◽  
E. Piconcelli ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Gamma Ray ◽  
High Energy ◽  
Time Variability ◽  
X Rays ◽  
Narrow Line ◽  
X Ray ◽  
Relativistic Jet ◽  
Line Region ◽  
Spectrum Radio

Narrow-line Seyfert 1 galaxies (NLS1s) is one of the few classes of active galactic nuclei harboring powerful relativistic jets and detected in γ-rays. NLS1s are well-known X-ray sources. While in non-jetted sources the origin of this X-ray emission may be a hot corona surrounding the accretion disk, in jetted objects, especially beamed ones, the contribution of corona and relativistic jet is difficult to disentangle without a proper sampling of the hard X-ray emission. For this reason, we observed with NuSTAR the first four NLS1s detected at high energy γ-rays. These data, along with XMM-Newton and Swift/XRT observations, confirmed that X-rays originate both in the jet and in the accretion disk corona. Time variability in hard X-rays furthermore suggests that, as observed in flat-spectrum radio quasars, the dissipation region during flares could change its position from source to source, and it can be located both inside and outside the broad-line region. We find that jetted NLS1s, and other blazars as well, seem not to follow the classical fundamental plane of black hole (BH) activity, which therefore should be used as a BH mass estimator in blazars with extreme care only. Our results strengthen the idea according to which γ-NLS1s are smaller and younger version of flat-spectrum radio quasars, in which both a Seyfert and a blazar component co-exist.

scholarly journals Detection of X-ray flares from AX J1714.1−3912, the unidentified source near RX J1713.7−3946

2018 ◽  
Vol 612 ◽  
pp. A32 ◽  
Author(s):  
Marco Miceli ◽  
Aya Bamba
Keyword(s):  
Supernova Remnants ◽  
Time Variability ◽  
X Rays ◽  
Energy Bands ◽  
X Ray ◽  
Nonthermal Emission ◽  
Photon Index ◽  
Unidentified Source

Context. Molecular clouds are predicted to emit nonthermal X-rays when they are close to particle-accelerating supernova remnants (SNRs), and the hard X-ray source AX J1714.1−3912, near the SNR RX J1713.7−3946, has long been considered a candidate for diffuse nonthermal emission associated with cosmic rays diffusing from the remnant to a closeby molecular cloud. Aim. We aim at ascertaining the nature of this source by analyzing two dedicated X-ray observations performed with Suzaku and Chandra. Methods. We extracted images from the data in various energy bands, spectra, and light curves and studied the long-term evolution of the X-ray emission on the basis of the ~4.5 yr time separation between the two observations. Results. We found that there is no diffuse emission associated with AX J1714.1−3912, which is instead the point-like source CXOU J171343.9−391205. We discovered rapid time variability (timescale ~ 103 s), together with a high intrinsic absorption and a hard nonthermal spectrum (power law with photon index Γ ~ 1.4). We also found that the X-ray flux of the source drops down by 1–2 orders of magnitude on a timescale of a few years. Conclusions. Our results suggest a possible association between AX J1714.1−3912 and a previously unknown supergiant fast X-ray transient, although further follow-up observations are necessary to prove this association definitively.

scholarly journals Inner Disk Structure of Dwarf Novae in the Light of X-Ray Observations

2015 ◽  
Vol 2 (1) ◽  
pp. 116-122 ◽  
Author(s):  
S. Balman
Keyword(s):  
White Dwarf ◽  
Spectral Characteristics ◽  
Time Variability ◽  
Time Lags ◽  
X Rays ◽  
Dwarf Novae ◽  
Disk Radius ◽  
X Ray ◽  
Disk Structure ◽  
Band Limited

Diversity of the X-ray observations of dwarf nova are still not fully understood. I review the X-ray spectral characteristics of dwarf novae during the quiescence in general explained by cooling flow models and the outburst spectra that show hard X-ray emission dominantly with few sources that reveal soft X-ray/EUV blackbody emission. The nature of aperiodic time variability of brightness of dwarf novae shows band limited noise, which can be adequately described in the framework of the model of propagating fluctuations. The frequency of the break (1-6 mHz) indicates inner disk truncation of the optically thick disk with a range of radii (3.0-10.0)×109 cm. The RXTE and optical (RTT150) data of SS Cyg in outburst and quiescence reveal that the inner disk radius moves towards the white dwarf and receeds as the outburst declines to quiescence. A preliminary analysis of SU UMa indicates a similar behaviour. In addition, I find that the outburst spectra of WZ Sge shows two component spectrum of only hard X-ray emission, one of which may be fitted with a power law suggesting thermal Comptonization occuring in the system. Cross-correlations between the simultaneous UV and X-ray light curves (XMM −Newton) of five DNe in quiescence show time lags in the X-rays of 96-181 sec consistent with travel time of matter from a truncated inner disk to the white dwarf surface. All this suggests that dwarf novae and other plausible nonmagnetic systems have truncated accretion disks indicating that the disks may be partially evaporated and the accretion may occur through hot (coronal) flows in the disk.

scholarly journals The Remarkable Spin-down and Ultrafast Outflows of the Highly Pulsed Supersoft Source of Nova Herculis 2021

2021 ◽  
Vol 922 (2) ◽  
pp. L42
Author(s):  
Jeremy J. Drake ◽  
Jan-Uwe Ness ◽  
Kim L. Page ◽  
G. J. M. Luna ◽  
Andrew P. Beardmore ◽  
...  
Keyword(s):  
White Dwarf ◽  
Emission Lines ◽  
Optical Observations ◽  
High Mass ◽  
X Rays ◽  
Pulse Profile ◽  
X Ray ◽  
Classical Nova ◽  
First Time ◽  
The Magnetic Field

Abstract Nova Her 2021 (V1674 Her), which erupted on 2021 June 12, reached naked-eye brightness and has been detected from radio to γ-rays. An extremely fast optical decline of 2 magnitudes in 1.2 days and strong Ne lines imply a high-mass white dwarf. The optical pre-outburst detection of a 501.42 s oscillation suggests a magnetic white dwarf. This is the first time that an oscillation of this magnitude has been detected in a classical nova prior to outburst. We report X-ray outburst observations from Swift and Chandra that uniquely show (1) a very strong modulation of supersoft X-rays at a different period from reported optical periods, (2) strong pulse profile variations and the possible presence of period variations of the order of 0.1–0.3 s, and (3) rich grating spectra that vary with modulation phase and show P Cygni–type emission lines with two dominant blueshifted absorption components at ∼3000 and 9000 km s−1 indicating expansion velocities up to 11,000 km s−1. X-ray oscillations most likely arise from inhomogeneous photospheric emission related to the magnetic field. Period differences between reported pre- and post-outburst optical observations, if not due to other period drift mechanisms, suggest a large ejected mass for such a fast nova, in the range 2 × 10−5–2 × 10−4 M ⊙. A difference between the period found in the Chandra data and a reported contemporaneous post-outburst optical period, as well as the presence of period drifts, could be due to weakly nonrigid photospheric rotation.

scholarly journals Revisiting the spectral and timing properties of 4U 1909+07 with NuSTAR and Astrosat

2020 ◽  
Vol 498 (4) ◽  
pp. 4830-4838 ◽  
Author(s):  
Gaurava K Jaisawal ◽  
Sachindra Naik ◽  
Wynn C G Ho ◽  
Neeraj Kumari ◽  
Prahlad Epili ◽  
...  
Keyword(s):  
Broad Band ◽  
High Energy ◽  
High Mass ◽  
X Rays ◽  
Pulse Profile ◽  
X Ray ◽  
Beam Geometry ◽  
Cyclotron Absorption ◽  
Using Data ◽  
Wind Distribution

ABSTRACT We present the results obtained from the analysis of high-mass X-ray binary pulsar 4U 1909+07 using NuSTAR and Astrosat observations in July 2015 and 2017, respectively. X-ray pulsations at ≈604 s are clearly detected in our study. Based on the long-term spin-frequency evolution, the source is found to spun-up in the last 17 yr. We observed a strongly energy-dependent pulse profile that evolved from a complex broad structure in soft X-rays into a profile with a narrow emission peak followed by a plateau in energy ranges above 20 keV. This behaviour ensured a positive correlation between the energy and pulse fraction. The pulse profile morphology and its energy evolution are almost similar during both the observations, suggesting a persistent emission geometry of the pulsar over time. The broad-band energy spectrum of the pulsar is approximated by an absorbed high-energy exponential cut-off power-law model with iron emission lines. In contrast to the previous report, we found no statistical evidence for the presence of cyclotron absorption features in the X-ray spectra. We performed phase-resolved spectroscopy using data from the NuSTAR observation. Our results showed a clear signature of absorbing material at certain pulse phases of the pulsar. These findings are discussed in terms of stellar wind distribution and its effect on the beam geometry of this wind-fed accreting neutron star. We also reviewed the subsonic quasi-spherical accretion theory and its implication on the magnetic field of 4U 1909+07 depending on the global spin-up rate.

scholarly journals Optical Observations of Pulsars

1996 ◽  
Vol 160 ◽  
pp. 299-300
Author(s):  
Christian Gouiffes ◽  
Hakki Ögelman
Keyword(s):  
Single Channel ◽  
Photon Counting ◽  
Optical Observations ◽  
Crab Pulsar ◽  
X Rays ◽  
Pulse Profile ◽  
Standard Analysis ◽  
Counting System ◽  
X Ray ◽  
Index 2

In the course of a programme to study optical pulsars, we have observed at different occasions PSR0540-69, the 50 msec pulsar in the LMC. Like the Crab pulsar, it has been detected at X-rays, optical and radio and its braking index (∼2) determined. In this communication we report some results obtained on this pulsar, in particular the presence of narrow features in the pulse profile and compare it with a nearly simultaneous X-ray observation.The observations were carried out at the 3.6m telescope at La. Silla observatory, Chile. The instrument consisted on a single channel photometer coupled with a. photomultiplier (GaAs photocathode). The sampling frequency was 10 kHz and the output of the photon counting system was recorded sequentially on magnetic tape. A set of filters and diaphragms were available. A standard analysis was then performed. After corrections to the solar system barycenter, the data were analyzed and the best period determined using thetest (Buccheri et al, 1983).

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