scholarly journals Discovery of 105 Hz coherent pulsations in the ultracompact binary IGR J16597–3704

2018 ◽  
Vol 610 ◽  
pp. L2 ◽  
Author(s):  
A. Sanna ◽  
A. Bahramian ◽  
E. Bozzo ◽  
C. Heinke ◽  
D. Altamirano ◽  
...  
Keyword(s):  
Neutron Star ◽  
Energy Spectrum ◽  
Binary System ◽  
Broad Band ◽  
Major Axis ◽  
Semi Major Axis ◽  
Band Energy ◽  
X Ray ◽  
Neutron Star Mass ◽  
Photon Index

We report the discovery of X-ray pulsations at 105.2 Hz (9.5 ms) from the transient X-ray binary IGR J16597–3704 using NuSTAR and Swift. The source was discovered by INTEGRAL in the globular cluster NGC 6256 at a distance of 9.1 kpc. The X-ray pulsations show a clear Doppler modulation that implies an orbital period of ~46 min and a projected semi-major axis of ~5 lt-ms, which makes IGR J16597–3704 an ultracompact X-ray binary system. We estimated a minimum companion mass of 6.5 × 10−10 M⊙, assuming a neutron star mass of 1.4 M⊙, and an inclination angle of <75° (suggested by the absence of eclipses or dips in its light curve). The broad-band energy spectrum of the source is well described by a disk blackbody component (kT ~ 1.4 keV) plus a comptonised power-law with photon index ~2.3 and an electron temperature of ~30 keV. Radio pulsations from the source were unsuccessfully searched for with the Parkes Observatory.

scholarly journals Properties of the transient X-ray pulsar Swift J1816.7–1613 and its optical companion

2019 ◽  
Vol 622 ◽  
pp. A198 ◽  
Author(s):  
Armin Nabizadeh ◽  
Sergey S. Tsygankov ◽  
Dmitrij I. Karasev ◽  
Juhani Mönkkönen ◽  
Alexander A. Lutovinov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Energy Spectrum ◽  
Timing Analysis ◽  
Broad Band ◽  
Type I ◽  
Quiescent State ◽  
Band Energy ◽  
X Ray ◽  
Cyclotron Absorption

We present results of investigation of the poorly studied X-ray pulsar Swift J1816.7–1613 during its transition from the type I outburst to the quiescent state. Our studies are based on the data obtained from X-ray observatories Swift, NuSTAR, and Chandra alongside with the latest IR data from UKIDSS/GPS and Spitzer/GLIMPSE surveys. The aim of the work is to determine the parameters of the system, namely the strength of the neutron star magnetic field and the distance to the source, which are required for the interpretation of the source behaviour in the framework of physically motivated models. No cyclotron absorption line was detected in the broad-band energy spectrum. However, the timing analysis hints at the typical for the X-ray pulsars magnetic field from a few ×1011 to a few ×1012 G. We also estimated the type of the IR-companion as a B0-2e star located at a distance of 7–13 kpc.

scholarly journals NuSTAR and NICER reveal IGR J17591–2342 as a new accreting millisecond X-ray pulsar

2018 ◽  
Vol 617 ◽  
pp. L8 ◽  
Author(s):  
A. Sanna ◽  
C. Ferrigno ◽  
P. S. Ray ◽  
L. Ducci ◽  
G. K. Jaisawal ◽  
...  
Keyword(s):  
Neutron Star ◽  
Broad Band ◽  
Major Axis ◽  
Black Body ◽  
Mass Function ◽  
Emission Region ◽  
Semi Major Axis ◽  
Telescope Array ◽  
X Ray ◽  
Direct Emission

We report the discovery by the Nuclear Spectroscopic Telescope Array (NuSTAR) and the Neutron Star Interior Composition Explorer (NICER) of the accreting millisecond X-ray pulsar IGR J17591–2342. Coherent X-ray pulsations around 527.4 Hz (1.9 ms) with a clear Doppler modulation were detected. This implies an orbital period of ∼8.8 h and a projected semi-major axis of ∼1.23 lt-s. With the binary mass function, we estimate a minimum companion mass of 0.42 M⊙, obtained assuming a neutron star mass of 1.4 M⊙ and an inclination angle lower than 60°, as suggested by the absence of eclipses or dips in the light curve of the source. The broad-band energy spectrum, obtained by combining NuSTAR, swift and INTEGRAL observations, is dominated by Comptonisation of soft thermal seed photons with a temperature of ∼0.7 keV by electrons heated to 21 keV. We also detect black-body-like thermal direct emission that is compatible with an emission region of a few kilometers and a temperature compatible with the seed source of Comptonisation. A weak Gaussian line centred on the iron Kα complex can be interpreted as a signature of disc reflection. A similar spectrum characterises the NICER spectra, which was measured when the outburst faded.

scholarly journals Modelling decretion discs in Be/X-ray binaries

2019 ◽  
Author(s):  
R O Brown ◽  
M J Coe ◽  
W C G Ho ◽  
A T Okazaki
Keyword(s):  
Neutron Star ◽  
Orbital Period ◽  
Major Axis ◽  
High Mass ◽  
Model Parameters ◽  
Be Stars ◽  
Semi Major Axis ◽  
X Ray ◽  
Smoothed Particle ◽  
X Ray Binaries

Abstract As the largest population of high mass X-ray binaries, Be/X-ray binaries provide an excellent laboratory to investigate the extreme physics of neutron stars. It is generally accepted that Be stars possess a circumstellar disc, providing an additional source of accretion to the stellar winds present around young hot stars. Interaction between the neutron star and the disc is often the dominant accretion mechanism. A large amount of work has gone into modelling the properties of these circumstellar discs, allowing for the explanation of a number of observable phenomena. In this paper, smoothed particle hydroynamics simulations are performed whilst varying the model parameters (orbital period, eccentricity, the mass ejection rate of the Be star and the viscosity and orientation of the disc). The relationships between the model parameters and the disc’s characteristics (base gas density, the accretion rate of the neutron star and the disc’s size) are presented. The observational evidence for a dependency of the size of the Be star’s circumstellar disc on the orbital period (and semi-major axis) is supported by the simulations.

scholarly journals Unveiling the Multi-wavelength Phenomenology of Anomalous X-ray Pulsars

2004 ◽  
Vol 218 ◽  
pp. 247-250 ◽  
Author(s):  
GianLuca Israel ◽  
Luigi Stella ◽  
Stefano Covino ◽  
Sergio Campana ◽  
Lorella Angelini ◽  
...  
Keyword(s):  
Energy Spectrum ◽  
Broad Band ◽  
Archival Data ◽  
X Rays ◽  
Spectral Variability ◽  
Band Energy ◽  
X Ray ◽  
Pulse Phase ◽  
Multi Wavelength ◽  
Ir Bands

During 2002–2003 the number of IR-identified counterparts to the Anomalous X-ray Pulsars (AXPs) has grown to four (4U 0142+61, IE 2259+586, IE 1048.1−5937 and RXS J170849−400910) out of the six objects (plus two candidates) known in this class. More importantly, some new common characteristics have been identified, such as IR variability, IR flattening in the broad-band energy spectrum, X-ray spectral variability as a function of pulse phase (which are not predicted by the magnetar model), and X-ray bursts (which cannot be explained in terms of standard accretion models). We present the results obtained from an extensive multi-wavelength observational campaign carried out with the NTT and CFHT for the optical/IR bands, and XMM and Chandra (plus BeppoSAX archival data) in X-rays. Based on these results and those reported in the literature, the IR-to-X-ray emission of AXPs is compared.

scholarly journals XMM-Newton detection of the 2.1 ms coherent pulsations from IGR J17379–3747

2018 ◽  
Vol 616 ◽  
pp. L17 ◽  
Author(s):  
A. Sanna ◽  
E. Bozzo ◽  
A. Papitto ◽  
A. Riggio ◽  
C. Ferrigno ◽  
...  
Keyword(s):  
Inclination Angle ◽  
Major Axis ◽  
Black Body ◽  
Orbital Evolution ◽  
Semi Major Axis ◽  
Companion Star ◽  
X Ray ◽  
Orbital Parameters ◽  
Photon Index ◽  
Soft Disk

We report the detection of X-ray pulsations at 2.1 ms from the known X-ray burster IGR J17379–3747 using XMM-Newton. The coherent signal shows a clear Doppler modulation from which we estimate an orbital period of ~1.9 h and a projected semi-major axis of ~8 lt-ms. Taking into account the lack of eclipses (inclination angle of <75°) and assuming a neutron star mass of 1.4 M⊙, we have estimated a minimum companion star of ~0.06 M⊙. Considerations on the probability distribution of the binary inclination angle make the hypothesis of a main-sequence companion star less likely. On the other hand, the close correspondence with the orbital parameters of the accreting millisecond pulsar SAX J1808.4–3658 suggests the presence of a bloated brown dwarf. The energy spectrum of the source is well described by a soft disk black-body component (kT ~ 0.45 keV) plus a Comptonisation spectrum with photon index ~1.9. No sign of emission lines or reflection components are significantly detected. Finally, combining the source ephemerides estimated from the observed outbursts, we obtained a first constraint on the long-term orbital evolution of the order of Ṗorb = (−2.5 ± 2.3) × 10−12 s s−1.

scholarly journals Effects of Compton scattering on the neutron star radius constraints in rotation-powered millisecond pulsars

2019 ◽  
Vol 627 ◽  
pp. A39 ◽  
Author(s):  
Tuomo Salmi ◽  
Valery F. Suleimanov ◽  
Juri Poutanen
Keyword(s):  
Angular Distribution ◽  
Neutron Star ◽  
Energy Spectrum ◽  
Compton Scattering ◽  
Electron Scattering ◽  
Exact Formulation ◽  
Millisecond Pulsars ◽  
X Ray ◽  
Synthetic Phase ◽  
Neutron Star Radius

The aim of this work is to study the possible effects and biases on the radius constraints for rotation-powered millisecond pulsars when using Thomson approximation to describe electron scattering in the atmosphere models, instead of using exact formulation for Compton scattering. We compare the differences between the two models in the energy spectrum and angular distribution of the emitted radiation. We also analyse a self-generated, synthetic, phase-resolved energy spectrum, based on Compton atmosphere and the most X-ray luminous, rotation-powered millisecond pulsars observed by the Neutron star Interior Composition ExploreR (NICER). We derive constraints for the neutron star parameters using both the Compton and Thomson models. The results show that the method works by reproducing the correct parameters with the Compton model. However, biases are found in both the size and the temperature of the emitting hotspot, when using the Thomson model. The constraints on the radius are still not significantly changed, and therefore the Thomson model seems to be adequate if we are interested only in the radius measurements using NICER.

New insight into the origin of the GeV flare in the binary system PSR B1259-63/LS 2883 from the 2017 periastron passage

2020 ◽  
Vol 497 (1) ◽  
pp. 648-655
Author(s):  
M Chernyakova ◽  
D Malyshev ◽  
S Mc Keague ◽  
B van Soelen ◽  
J P Marais ◽  
...  
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Energy Release ◽  
Broad Band ◽  
Strong Shock ◽  
Optical Observations ◽  
X Rays ◽  
X Ray ◽  
Inverse Compton ◽  
Pulsar Wind

ABSTRACT PSR B1259-63 is a gamma-ray binary system hosting a radio pulsar orbiting around an O9.5Ve star, LS 2883, with a period of ∼3.4 yr. The interaction of the pulsar wind with the LS 2883 outflow leads to unpulsed broad-band emission in the radio, X-rays, GeV, and TeV domains. While the radio, X-ray, and TeV light curves show rather similar behaviour, the GeV light curve appears very different with a huge outburst about a month after a periastron. The energy release during this outburst seems to significantly exceed the spin-down luminosity of the pulsar and both the GeV light curve and the energy release vary from one orbit to the next. In this paper, we present for the first time the results of optical observations of the system in 2017, and also reanalyse the available X-ray and GeV data. We present a new model in which the GeV data are explained as a combination of the bremsstrahlung and inverse Compton emission from the unshocked and weakly shocked electrons of the pulsar wind. The X-ray and TeV emission is produced by synchrotron and inverse Compton emission of energetic electrons accelerated on a strong shock arising due to stellar/pulsar winds collision. The brightness of the GeV flare is explained in our model as a beaming effect of the energy released in a cone oriented, during the time of the flare, in the direction of the observer.

scholarly journals Broad-band study of high-synchrotron-peaked BL Lac object 1ES 1218+304

2020 ◽  
Vol 496 (4) ◽  
pp. 5518-5527
Author(s):  
N Sahakyan
Keyword(s):  
Energy Distribution ◽  
Electron Energy ◽  
Power Law ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Energy Distributions ◽  
X Ray ◽  
Bl Lac ◽  
Photon Index ◽  
Γ Ray

ABSTRACT The origin of the multiwavelength emission from the high-synchrotron-peaked BL Lac 1ES 1218+304 is studied using the data from SwiftUVOT/XRT, NuSTAR, and Fermi-LAT. A detailed temporal and spectral analysis of the data observed during 2008–2020 in the  γ-ray (&gt;100 MeV), X-ray (0.3–70 keV), and optical/UV bands is performed. The γ-ray spectrum is hard with a photon index of 1.71 ± 0.02 above 100 MeV. The SwiftUVOT/XRT data show a flux increase in the UV/optical and X-ray bands; the highest 0.3–3 keV X-ray flux was (1.13 ± 0.02) × 10−10 erg cm−2 s−1. In the 0.3–10 keV range, the averaged X-ray photon index is &gt;2.0 which softens to 2.56 ± 0.028 in the 3–50 keV band. However, in some periods, the X-ray photon index became extremely hard (&lt;1.8), indicating that the peak of the synchrotron component was above 1 keV, and so 1ES 1218+304 behaved like an extreme synchrotron BL Lac. The hardest X-ray photon index of 1ES 1218+304 was 1.60 ± 0.05 on MJD 58489. The time-averaged multiwavelength spectral energy distribution is modelled within a one-zone synchrotron self-Compton leptonic model using a broken power law and power law with an exponential cutoff electron energy distributions. The data are well explained when the electron energy distribution is $E_{\rm e}^{-2.1}$ extending up to γbr/cut ≃ (1.7 − 4.3) × 105, and the magnetic field is weak (B ∼ 1.5 × 10−2 G). By solving the kinetic equation for electron evolution in the emitting region, the obtained electron energy distributions are discussed considering particle injection, cooling, and escape.

scholarly journals Prolonged sub-luminous state of the new transitional pulsar candidate CXOU J110926.4−650224

2019 ◽  
Vol 622 ◽  
pp. A211 ◽  
Author(s):  
Francesco Coti Zelati ◽  
Alessandro Papitto ◽  
Domitilla de Martino ◽  
David A. H. Buckley ◽  
Alida Odendaal ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Broad Band ◽  
Optical Emission ◽  
Bimodal Distribution ◽  
X Ray ◽  
The Past ◽  
Upper Limits ◽  
Photon Index ◽  
Multi Wavelength ◽  
Absorbed Power

We report on a multi-wavelength study of the unclassified X-ray source CXOU J110926.4−650224 (J1109). We identified the optical counterpart as a blue star with a magnitude of ∼20.1 (3300–10500 Å). The optical emission was variable on timescales from hundreds to thousands of seconds. The spectrum showed prominent emission lines with variable profiles at different epochs. Simultaneous XMM-Newton and NuSTAR observations revealed a bimodal distribution of the X-ray count rates on timescales as short as tens of seconds, as well as sporadic flaring activity. The average broad-band (0.3–79 keV) spectrum was adequately described by an absorbed power law model with photon index of Γ = 1.63  ±  0.01 (at 1σ c.l.), and the X-ray luminosity was (2.16  ±  0.04)  ×  1034 erg s−1 for a distance of 4 kpc. Based on observations with different instruments, the X-ray luminosity has remained relatively steady over the past ∼15 years. J1109 is spatially associated with the gamma-ray source FL8Y J1109.8−6500, which was detected with Fermi at an average luminosity of (1.5  ±  0.2)  ×  1034 erg s−1 (assuming the distance of J1109) over the 0.1–300 GeV energy band between 2008 and 2016. The source was undetected during ATCA radio observations that were simultaneous with NuSTAR, down to a 3σ flux upper limit of 18 μJy beam−1 (at 7.25 GHz). We show that the phenomenological properties of J1109 point to a binary transitional pulsar candidate currently in a sub-luminous accretion disk state, and that the upper limits derived for the radio emission are consistent with the expected radio luminosity for accreting neutron stars at similar X-ray luminosities.

scholarly journals Luminosity Correlation of the X-ray Selected Radio-Loud AGNs

1999 ◽  
Vol 194 ◽  
pp. 306-310
Author(s):  
Q. Yuan ◽  
J. Wu ◽  
K. Huang
Keyword(s):  
Active Galactic Nuclei ◽  
Broad Band ◽  
Galactic Nuclei ◽  
Radio Galaxies ◽  
Spectral Indices ◽  
Strong Correlations ◽  
Band Energy ◽  
X Ray ◽  
Sky Survey ◽  
Bl Lacs

This paper presents a test of the luminosity correlation of the X-ray selected radio-loud Active Galactic Nuclei (AGNs), based on a large sample constructed by combining our cross-identification of southern sky sources with the radio-loud sources in the northern hemisphere given by Brinkmann et al. (1995). All sources were detected both by the ROSAT All-Sky Survey and the radio surveys at 4.85 GHz. The broad band energy distribution confirms the presence of strong correlations between luminosities in the radio, optical, and X-ray bands which differ for quasars, seyferts, BL Lacs, and radio galaxies. The tight correlations between spectral indices αox and monochromatic luminosities at 5500 Å and 4.85 GHz are also shown.

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