scholarly journals PSR B0656+14: the unified outlook from the infrared to X-rays

2021 ◽  
Vol 502 (2) ◽  
pp. 2005-2022
Author(s):  
S Zharikov ◽  
D Zyuzin ◽  
Yu Shibanov ◽  
A Kirichenko ◽  
R E Mennickent ◽  
...  
Keyword(s):  
Neutron Star ◽  
Absorption Line ◽  
Optical Spectrum ◽  
Near Infrared ◽  
Thermal Emission ◽  
Model Parameters ◽  
X Rays ◽  
Polar Cap ◽  
X Ray ◽  
Star Surface

ABSTRACT We report detection of PSR B0656+14 with the Gran Telescopio Canarias in narrow optical F657, F754, F802, and F902 and near-infrared JHKs bands. The pulsar detection in the Ks band extends its spectrum to 2.2 $\mu$m and confirms its flux increase towards the infrared. We also present a thorough analysis of the optical spectrum obtained by us with the VLT. For a consistency check, we revised the pulsar near-infrared and narrow-band photometry obtained with the HST. We find no narrow spectral lines in the optical spectrum. We compile available near-infrared-optical-UV and archival 0.3–20 keV X-ray data and perform a self-consistent analysis of the rotation phase-integrated spectrum of the pulsar using unified spectral models. The spectrum is best fitted by the four-component model including two blackbodies, describing the thermal emission from the neutron star surface and its hot polar cap, the broken power law, originating from the pulsar magnetosphere, and an absorption line near ∼0.5 keV detected previously. The fit provides better constraints on the model parameters than using only a single spectral domain. The derived surface temperature is $T_{NS}^{\infty } = 7.9(3)\times 10^5$ K. The intrinsic radius (7.8–9.9 km) of the emitting region is smaller than a typical neutron star radius (13 km) and suggests a non-uniform temperature distribution over the star surface. In contrast, the derived radius of the hot polar cap is about twice as large as the ‘canonical’ one. The spectrum of the non-thermal emission steepens from the optical to X-rays and has a break near 0.1 keV. The X-ray data suggest the presence of another absorption line near 0.3 keV.

scholarly journals XMM–Newton observations of a gamma-ray pulsar J0633+0632: pulsations, cooling and large-scale emission

2020 ◽  
Vol 493 (2) ◽  
pp. 1874-1887 ◽  
Author(s):  
A Danilenko ◽  
A Karpova ◽  
D Ofengeim ◽  
Yu Shibanov ◽  
D Zyuzin
Keyword(s):  
Neutron Star ◽  
Large Scale ◽  
Gamma Ray ◽  
Thermal Emission ◽  
Absorption Feature ◽  
Model Parameters ◽  
Pulse Profile ◽  
X Ray ◽  
Polar Caps ◽  
Star Surface

ABSTRACT We report results of XMM–Newton observations of a γ-ray pulsar J0633+0632 and its wind nebula. We reveal, for the first time, pulsations of the pulsar X-ray emission with a single sinusoidal pulse profile and a pulsed fraction of 23 ± 6 per cent in the 0.3–2 keV band. We confirm previous Chandra findings that the pulsar X-ray spectrum consists of thermal and non-thermal components. However, we do not find the absorption feature that was previously detected at about 0.8 keV. Thanks to the greater sensitivity of XMM–Newton, we get stronger constraints on spectral model parameters compared to previous studies. The thermal component can be equally well described by either blackbody or neutron star atmosphere models, implying that this emission is coming from either hot pulsar polar caps with a temperature of about 120 eV or from the colder bulk of the neutron star surface with a temperature of about 50 eV. In the latter case, the pulsar appears to be one of the coolest among other neutron stars of similar ages with estimated surface temperatures. We discuss cooling scenarios relevant to this neutron star. Using an interstellar absorption–distance relation, we also constrain the distance to the pulsar to the range of 0.7–2 kpc. Besides the pulsar and its compact nebula, we detect regions of weak large-scale diffuse non-thermal emission in the pulsar field and discuss their possible nature.

scholarly journals Middle aged γ-ray pulsar J1957+5033 in X-rays: pulsations, thermal emission and nebula

2020 ◽  
Author(s):  
D A Zyuzin ◽  
A V Karpova ◽  
Y A Shibanov ◽  
A Y Potekhin ◽  
V F Suleimanov
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Power Law ◽  
Thermal Emission ◽  
Single Pulse ◽  
X Rays ◽  
Middle Aged ◽  
X Ray ◽  
Photon Index ◽  
Γ Ray

Abstract We analyze new XMM-Newton and archival Chandra observations of the middle-aged γ-ray radio-quiet pulsar J1957+5033. We detect, for the first time, X-ray pulsations with the pulsar spin period of the point-like source coinciding by position with the pulsar. This confirms the pulsar nature of the source. In the 0.15–0.5 keV band, there is a single pulse per period and the pulsed fraction is ≈18 ± 6 per cent. In this band, the pulsar spectrum is dominated by a thermal emission component that likely comes from the entire surface of the neutron star, while at higher energies (≳ 0.7 keV) it is described by a power law with the photon index Γ ≈ 1.6. We construct new hydrogen atmosphere models for neutron stars with dipole magnetic fields and non-uniform surface temperature distributions with relatively low effective temperatures. We use them in the spectral analysis and derive the pulsar average effective temperature of ≈(2 − 3) × 105 K. This makes J1957+5033 the coldest among all known thermally emitting neutron stars with ages below 1 Myr. Using the interstellar extinction–distance relation, we constrain the distance to the pulsar in the range of 0.1–1 kpc. We compare the obtained X-ray thermal luminosity with those for other neutron stars and various neutron star cooling models and set some constraints on latter. We observe a faint trail-like feature, elongated ∼8 arcmin from J1957+5033. Its spectrum can be described by a power law with a photon index Γ = 1.9 ± 0.5 suggesting that it is likely a pulsar wind nebula powered by J1957+5033.

scholarly journals NICER Study of Pulsed Thermal X-Rays from Calvera: A Neutron Star Born in the Galactic Halo?

2021 ◽  
Vol 922 (2) ◽  
pp. 253
Author(s):  
S. Mereghetti ◽  
M. Rigoselli ◽  
R. Taverna ◽  
L. Baldeschi ◽  
S. Crestan ◽  
...  
Keyword(s):  
Neutron Star ◽  
Galactic Halo ◽  
Galactic Disk ◽  
Good Description ◽  
Hydrogen Atmosphere ◽  
Galactic Latitude ◽  
X Rays ◽  
X Ray ◽  
Polar Caps ◽  
Star Surface

Abstract Calvera (1RXS J141256.0+792204) is an isolated neutron star detected only through its thermal X-ray emission. Its location at high Galactic latitude (b = +37°) is unusual if Calvera is a relatively young pulsar, as suggested by its spin period (59 ms) and period derivative (3.2 × 10−15 s s−1). Using the Neutron Star Interior Composition Explorer, we obtained a phase-connected timing solution spanning four years, which allowed us to measure the second derivative of the frequency ν ̈ = − 2.5 × 10 − 23 Hz s−2 and to reveal timing noise consistent with that of normal radio pulsars. A magnetized hydrogen atmosphere model, covering the entire star surface, provides a good description of the phase-resolved spectra and energy-dependent pulsed fraction. However, we found that a temperature map more anisotropic than that produced by a dipole field is required, with a hotter zone concentrated toward the poles. By adding two small polar caps, we found that the surface effective temperature and that of the caps are ∼0.1 and ∼0.36 keV, respectively. The inferred distance is ∼3.3 kpc. We confirmed the presence of an absorption line at 0.7 keV associated with the emission from the whole star surface, difficult to interpret as a cyclotron feature and more likely originating from atomic transitions. We searched for pulsed γ-ray emission by folding seven years of Fermi-LAT data using the X-ray ephemeris, but no evidence for pulsations was found. Our results favor the hypothesis that Calvera is a normal rotation-powered pulsar, with the only peculiarity of being born at a large height above the Galactic disk.

scholarly journals X-rays from the mode-switching PSR B0943+10

2017 ◽  
Vol 13 (S337) ◽  
pp. 62-65 ◽  
Author(s):  
S. Mereghetti ◽  
L. Kuiper ◽  
A. Tiengo ◽  
J. Hessels ◽  
W. Hermsen ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Thermal Emission ◽  
Mode Switching ◽  
X Rays ◽  
Radio Telescopes ◽  
Polar Cap ◽  
Radio Observations ◽  
X Ray ◽  
First Time

AbstractNew simultaneous X-ray and radio observations of the archetypal mode-switching pulsar PSR B0943+10 have been carried out with XMM-Newton and the LOFAR, LWA and Arecibo radio telescopes in November 2014. They allowed us to better constrain the X-ray spectral and variability properties of this pulsar and to detect, for the first time, the X-ray pulsations also during the X-ray-fainter mode. The combined timing and spectral analysis indicates that unpulsed non-thermal emission, likely of magnetospheric origin, and pulsed thermal emission from a small polar cap are present during both radio modes and vary in a correlated way.

scholarly journals Joint radio and X-ray modelling of PSR J1136+1551

2019 ◽  
Vol 491 (1) ◽  
pp. 80-91 ◽  
Author(s):  
J Pétri ◽  
D Mitra
Keyword(s):  
Magnetic Dipole ◽  
Thermal Emission ◽  
Essential Feature ◽  
Radio Pulse ◽  
Time Lag ◽  
Polar Cap ◽  
Pulse Profile ◽  
X Ray ◽  
Surface Magnetic Field ◽  
Star Surface

ABSTRACT Multiwavelength observations of pulsar emission properties are powerful means to constrain their magnetospheric activity and magnetic topology. Usually a star centred magnetic dipole model is invoked to explain the main characteristics of this radiation. However, in some particular pulsars where observational constraints exist, such simplified models are unable to predict salient features of their multiwavelength emission. This paper aims to carefully model the radio and X-ray emission of PSR J1136+1551 with an off-centred magnetic dipole to reconcile both wavelength measurements. We simultaneously fit the radio pulse profile with its polarization and the thermal X-ray emission from the polar cap hotspots of PSR J1136+1551. We are able to pin down the parameters of the non-dipolar geometry (which we have assumed to be an offset dipole) and the viewing angle, meanwhile accounting for the time lag between X-ray and radio emission. Our model fits the data if the off-centred magnetic dipole lies about 20 per cent below the neutron star surface. We also expect very asymmetric polar cap shapes and sizes, implying non-antipodal and non-identical thermal emission from the hotspots. We conclude that a non-dipolar surface magnetic field is an essential feature to explain the multiwavelength aspects of PSR J1136+1551 and other similar pulsars.

scholarly journals Discovery of X-ray pulsations in the Be/X-ray binary IGR J06074+2205

2018 ◽  
Vol 613 ◽  
pp. A52 ◽  
Author(s):  
P. Reig ◽  
A. Zezas
Keyword(s):  
Neutron Star ◽  
Model Fitting ◽  
High Energy ◽  
X Rays ◽  
Energy Bands ◽  
X Ray ◽  
Be Star ◽  
Best Fitting ◽  
Open Question ◽  
Star Surface

Context. IGR J06074+2205 is a poorly studied X-ray source with a Be star companion. It has been proposed to belong to the group of Be/X-ray binaries (BeXBs). In BeXBs, accretion onto the neutron star occurs via the transfer of material from the Be star’s circumstellar disk. Thus, in the absence of the disk, no X-ray should be detected. Aims. The main goal of this work is to study the quiescent X-ray emission of IGR J06074+2205 during a disk-loss episode. Methods. We obtained light curves at different energy bands and a spectrum covering the energy range 0.4–12 keV. We used Fourier analysis to study the aperiodic variability and epoch folding methods to study the periodic variability. Model fitting to the energy spectrum allowed us to identify the possible physical processes that generated the X-rays. Results. We show that at the time of the XMM-Newton observation, the decretion disk around the Be star had vanished. Still, accretion appears as the source of energy that powers the high-energy radiation in IGR J06074+2205. We report the discovery of X-ray pulsations with a pulse period of 373.2 s and a pulse fraction of ~50%. The 0.4–12 keV spectrum is well described by an absorbed power law and blackbody components with the best fitting parameters: NH = (6.2 ± 0.5) × 1021 cm−2, kTbb = 1.16 ± 0.03 keV, and Γ = 1.5 ± 0.1. The absorbed X-ray luminosity is LX = 1.4 × 1034 erg s−1 assuming a distance of 4.5 kpc. Conclusions. The detection of X-ray pulsations confirms the nature of IGR J06074+2205 as a BeXB. We discuss various scenarios to explain the quiescent X-ray emission of this pulsar. We rule out cooling of the neutron star surface and magnetospheric emission and conclude that accretion is the most likely scenario. The origin of the accreted material remains an open question.

scholarly journals Extreme Ultraviolet Emission from Neutron Stars

1996 ◽  
Vol 152 ◽  
pp. 437-442 ◽  
Author(s):  
R.S. Foster ◽  
J. Edelstein ◽  
S. Bowyer
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Power Law ◽  
Extreme Ultraviolet ◽  
Millisecond Pulsar ◽  
Polar Cap ◽  
X Ray ◽  
Euv Emission ◽  
Standard Neutron ◽  
Star Surface

We summarize the detections of extreme ultraviolet (EUV) emission from neutron stars. Three firm detections have been made of spin-powered pulsars: the aged millisecond pulsar PSR J0437−4715, the middle-aged X-ray pulsar Geminga, and the radio pulsar PSR B0656+14. These observations allow us to evaluate both power-law and thermal-law emission models as the source of the EUV flux. For the case of PSR B0656+14 the lack of flux modulation with pulse period argues that the EUV radiation originates from the cooling neutron star surface rather than from a hot polar cap. If the emission is from a thermalized neutron star surface, then limits can be placed on the surface temperature. For the case of Geminga we can explain the observed EUV flux using thermal models that are consistent with standard neutron cooling scenarios. We also have a weak indication that the EUV emission from Geminga is pulsed in a manner consistent with the lowest energy channel observed with Rosat. For the case of the millisecond pulsar PSR J0437−4715 standard neutron star cooling models require surface re-heating. We compare different heating models to the data on this object. We rule out re-heating by crust-core friction, and find that models for the accretion from the interstellar medium, accretion from the white dwarf companion and a particle-wind nebula do not account for the EUV luminosity. Models of pulsar re-heating by magnetic monopole catalysis of nucleon decay are used to establish new limits to the flux of monopoles in the Galaxy. A single power-law source with properties derived from X-ray data cannot explain the EUV flux from PSR J0437−4715. The strongest model for explaining the EUV emission consists of a large ~ 3 km2 polar cap heated from particle production in the pulsar magnetic field. We consider the prospects for detecting other neutron stars in the extreme ultraviolet.

scholarly journals UV and X-ray observations of the neutron star LMXB EXO 0748–676 in its quiescent state

2020 ◽  
Vol 501 (1) ◽  
pp. 1453-1462
Author(s):  
A S Parikh ◽  
N Degenaar ◽  
J V Hernández Santisteban ◽  
R Wijnands ◽  
I Psaradaki ◽  
...  
Keyword(s):  
Neutron Star ◽  
Thermal Emission ◽  
Hubble Space Telescope ◽  
Dense Matter ◽  
Continuum Emission ◽  
Quiescent State ◽  
X Ray ◽  
Low Level ◽  
Low Mass ◽  
Different Origins

ABSTRACT The accretion behaviour in low-mass X-ray binaries (LMXBs) at low luminosities, especially at <1034 erg s−1, is not well known. This is an important regime to study to obtain a complete understanding of the accretion process in LMXBs, and to determine if systems that host neutron stars with accretion-heated crusts can be used probe the physics of dense matter (which requires their quiescent thermal emission to be uncontaminated by residual accretion). Here, we examine ultraviolet (UV) and X-ray data obtained when EXO 0748–676, a crust-cooling source, was in quiescence. Our Hubble Space Telescope spectroscopy observations do not detect the far-UV continuum emission, but do reveal one strong emission line, C iv. The line is relatively broad (≳3500 km s−1), which could indicate that it results from an outflow such as a pulsar wind. By studying several epochs of X-ray and near-UV data obtained with XMM–Newton, we find no clear indication that the emission in the two wavebands is connected. Moreover, the luminosity ratio of LX/LUV ≳ 100 is much higher than that observed from neutron star LMXBs that exhibit low-level accretion in quiescence. Taken together, this suggests that the UV and X-ray emission of EXO 0748–676 may have different origins, and that thermal emission from crust-cooling of the neutron star, rather than ongoing low-level accretion, may be dominating the observed quiescent X-ray flux evolution of this LMXB.

scholarly journals 1/4 Ke V Diffuse Background and the Local Interstellar Medium

1989 ◽  
Vol 120 ◽  
pp. 536-536
Author(s):  
S.L. Snowden
Keyword(s):  
Interstellar Medium ◽  
Filling Factor ◽  
Thermal Emission ◽  
Mean Free Path ◽  
Physical Parameters ◽  
X Rays ◽  
Local Interstellar Medium ◽  
X Ray ◽  
Diffuse Background ◽  
X Ray Background

The 1/4 keV diffuse X-ray background (SXRB) is discussed in relation to the local interstellar medium (LISM). The most likely source for these soft X-rays is thermal emission from a hot diffuse plasma. The existence of a non-zero flux from all directions and the short ISM mean free path of these X-rays (1020HI cm-2), coupled with ISM pressure constraints, imply that the plasma has a local component and that it must, at least locally (nearest hundred parsecs), have a large filling factor. Our understanding of the geometry and physical parameters of the LISM is therefore directly tied to our understanding of the SXRB.

scholarly journals An Emission Line in the Hard X-Ray Spectrum of Hercules X-1: Quantized Cyclotron Emission from the Neutron Star

1977 ◽  
Vol 43 ◽  
pp. 34-34
Author(s):  
W. Pietsch ◽  
C. Reppin ◽  
R. Staubert ◽  
J. Truemper ◽  
W. Voges ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Field Strength ◽  
Second Harmonic ◽  
Narrow Line ◽  
Electron Cyclotron Emission ◽  
Polar Cap ◽  
Astrophysical Application ◽  
X Ray ◽  
Cyclotron Emission

A four hour balloon observation of HERC X-l during the 'On-state' in the 35 day cycle was performed on May 3rd, 1976. The 1.24 second pulsations show a pulsed fraction of 58 ± 8% in the 18-31 KeV interval. A pulsed flux (1.24 sec) was discovered in the 31-88 KeV interval with a pulsed fraction of 51 ± 14%. The spectrum of the pulsed flux can be represented up to 50 KeV by an exponential distribution with KT approximately 8 KeV. At approximately 58 KeV a strong and narrow line feature occurs which we interpret as electron cyclotron emission (ΔN = 1 Landau transition) from the polar cap plasma of the rotating neutron star. The corresponding magnetic field strength is approximately 5 x 1012 Gauss, neglecting gravitational red shift. There is evidence for a second harmonic at approximately 110 KeV (ΔN = 2 ).The astrophysical application of this discovery will be discussed in some detail.

Sign in / Sign up

Export Citation Format

Share Document