scholarly journals Redshifted absorption lines from an isolated neutron star

2020 ◽  
Author(s):  
Sergio Campana
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Hydrogen Atmosphere ◽  
Oxygen Absorption ◽  
Spectral Features ◽  
Breeding Ground ◽  
X Ray ◽  
Cyclotron Absorption ◽  
Star Surface ◽  
Absorption Features

Abstract The solid crust constituting the outer layers of a hot neutron star is wrapped by an mm-to-cm thin atmosphere. Even if the atmosphere is so thin, it substantially affects the blackbody spectrum emitted by the surface, resulting in an overall hardening of the emitted spectrum. The composition of the atmosphere has so far remained elusive. Several narrow absorption features have been detected and interpreted as arising from proton (or electron) resonant cyclotron absorption in the neutron star magnetic field. Apart from these, for a Hydrogen atmosphere no spectral features are expected, whereas when it is polluted with metals, absorption features start appearing in soft X-ray spectra. Absorption edges and features have been possibly observed during thermonuclear explosions onto the neutron star surface. Isolated neutron stars represent a breeding ground where to look for absorption features, thanks to their simple X-ray spectra. Here we report on the detection of redshifted Nitrogen and Oxygen absorption features from the closest and brightest isolated neutron star. The lines are ~50 eV wide and their intensity is incompatible from originating in the interstellar path to the neutron star. Lines are redshifted by a common gravitational redshift of z_g=0.216±0.004.

The magnetic field of an isolated neutron star from X-ray cyclotron absorption lines

Nature ◽  
2003 ◽  
Vol 423 (6941) ◽  
pp. 725-727 ◽  
Author(s):  
G. F. Bignami ◽  
P. A. Caraveo ◽  
A. De Luca ◽  
S. Mereghetti
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Absorption Lines ◽  
X Ray ◽  
Cyclotron Absorption ◽  
The Magnetic Field

scholarly journals Determining the neutron star surface magnetic field strength of two Z sources

2012 ◽  
Vol 8 (S290) ◽  
pp. 203-204
Author(s):  
Guoqiang Ding ◽  
Chunping Huang ◽  
Yanan Wang
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Extreme Position ◽  
X Ray ◽  
Surface Magnetic Field ◽  
Axis Of Rotation ◽  
Star Surface ◽  
Z Sources

AbstractFrom the extreme position of disk motion, we infer the neutron star (NS) surface magnetic field strength (B0) of Z-source GX 17+2 and Cyg X-2. The inferred B0 of GX 17+2 and Cyg X-2 are ~(1–5)×108 G and ~(1–3)×108 G, respectively, which are not inferior to that of millisecond X-ray pulsars or atoll sources. It is likely that the NS magnetic axis of Z sources is parallel to the axis of rotation, which could result in the lack of pulsations in these sources.

scholarly journals Effect of Photon Rocket in X-ray Binaries

2000 ◽  
Vol 177 ◽  
pp. 653-654
Author(s):  
V. D. Pal’shin ◽  
A. I. Tsygan
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Gravitational Attraction ◽  
Dipolar Field ◽  
X Ray ◽  
The Galaxy ◽  
Star Surface ◽  
X Ray Binaries ◽  
The Magnetic Field

AbstractIt is shown that X-ray binaries can be accelerated by their own radiation. It is possible if the magnetic field of a neutron star in a binary differs from the dipolar field. Asymmetric X-ray emission generated due to accretion of matter onto a neutron star surface creates an accelerating force. Its magnitude can be comparable or even larger than gravitational attraction of the binary to the Galaxy.

scholarly journals MEASURING MAGNETIC FIELD OF NEUTRON STAR 4U 0115+63 WITH CYCLOTRON FEATURES

2013 ◽  
Vol 23 ◽  
pp. 161-164
Author(s):  
SU YAO ◽  
CHENGMIN ZHANG
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Relativistic Effect ◽  
Absorption Lines ◽  
Fundamental Feature ◽  
X Ray ◽  
Measuring Magnetic Field ◽  
Absorption Features ◽  
Main Region ◽  
Just Right

We analyze the 3-80 keV spectrum of X-ray pulsar 4U 0115+63 taken by Rossi X-ray Timing Explorer(RXTE) on April 22nd, 2008. Two absorption features at ~13.5 keV and ~20.5 keV are detected by using cyclotron scattering feature profiles to fit the spectrum, ignoring the inadequate photons of the analyzed data. The fundamental feature is just right between ~11 and ~16 keV. It seems implausible to interprete these absorption lines as cyclotron features because of their inharmonic behavior, even when relativistic effect has been taken into account. But it is possible that the main region where first harmonic line forms is slightly different from the fundamental one.

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 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 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.

scholarly journals Discovery of accretion-driven pulsations in the prolonged low X-ray luminosity state of the Be/X-ray transient GX 304–1

2018 ◽  
Vol 620 ◽  
pp. L13 ◽  
Author(s):  
A. Rouco Escorial ◽  
J. van den Eijnden ◽  
R. Wijnands
Keyword(s):  
Neutron Star ◽  
Stable State ◽  
Type I ◽  
X Ray ◽  
Monitoring Campaign ◽  
Spin Period ◽  
One Year ◽  
The Many ◽  
Low X ◽  
Star Surface

We present our Swift monitoring campaign of the slowly rotating neutron star Be/X-ray transient GX 304–1 (spin period of ∼275 s) when the source was not in outburst. We found that between its type I outbursts, the source recurrently exhibits a slowly decaying low-luminosity state (with luminosities of 1034 − 35 erg s−1). This behaviour is very similar to what has been observed for another slowly rotating system, GRO J1008–57. For that source, this low-luminosity state has been explained in terms of accretion from a non-ionised (“cold”) accretion disc. Because of the many similarities between the two systems, we suggest that GX 304–1 enters a similar accretion regime between its outbursts. The outburst activity of GX 304–1 ceased in 2016. Our continued monitoring campaign shows that the source is in a quasi-stable low-luminosity state (with luminosities a few factors lower than previously seen) for at least one year now. Using our NuSTAR observation in this state, we found pulsations at the spin period, demonstrating that the X-ray emission is due to accretion of matter onto the neutron star surface. If the accretion geometry during this quasi-stable state is the same as during the cold-disc state, then matter indeed reaches the surface (as predicted) during this later state. We discuss our results in the context of the cold-disc accretion model.

scholarly journals Einstein Observatory Limits on Neutron Star Surface Temperatures

1987 ◽  
Vol 125 ◽  
pp. 457-457
Author(s):  
F.R. Harnden
Keyword(s):  
Star Formation ◽  
Neutron Star ◽  
Neutron Stars ◽  
Supernova Remnants ◽  
Theoretical Models ◽  
X Ray ◽  
Star Models ◽  
Formation And Evolution ◽  
Star Surface ◽  
Einstein Observatory

For years the theoretical models of neutron star formation and evolution had remained largely unconstrained by observation. Following the Einstein X-ray Observatory surveys of supernova remnants and pulsars, however, strict temperature limits were placed on many putative neutron stars. The Einstein search for additional objects in the class of supernova remnants with embedded pulsars has increased the number of such objects by two. For the four objects in this class, the surface temperature limits (see Table 1) provide meaningful logically sound constraints on the neutron star models. For the future, however, still better X-ray observations are needed, both to increase the number of objects available for study and to refine the spatial and spectral capabilities of the X-ray measurements.

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