Be X-RAY TRANSIENT 4U 0115+63 IN 2008 OUTBURST

2013 ◽  
Vol 23 ◽  
pp. 208-212
Author(s):  
JUN LI ◽  
WEI WANG ◽  
YONGHENG ZHAO
Keyword(s):  
Spectral Analysis ◽  
Neutron Star ◽  
Theoretical Work ◽  
Apsidal Motion ◽  
Line Energy ◽  
X Ray ◽  
Spin Period ◽  
Cyclotron Absorption ◽  
Photon Index ◽  
Fundamental Line

We present both timing and spectral analysis of the outburst of 4U 0115+63 in 2008 with INTEGRAL and RXTE observations. We have determined the spin period of the neutron star at ~ 3.61422 ± 0.00011 s, and a spin up rate during the outburst of Ṗ = (-2.66 ± 1.81) × 10-6s d-1, the angle of periapsis ω = 49.6° ± 0.68° in 2008 and its variation (apsidal motion) [Formula: see text] when comparing with previous measured values. During the outburst, four cyclotron absorption lines were detected (fundamental line at 10–15 keV; 2nd harmonic at 22 keV; 3rd at ~ 34 keV, 4th at ~ 42 keV), the fifth harmonic around 54 keV was also hinted in our data. The fundamental absorption line energy varies during the outburst: around 15 keV during the rising phase, and transiting to ~ 10 keV during the peak of the outburst, and further coming back to ~ 15 keV during the decreasing phase. The photon index shows the correlation with the fundamental line energy: the source becomes harder around the peak of the outburst and softer in both rising and decreasing phases. This correlation and transition processes during the outburst need further studies in both observations and theoretical work.

scholarly journals Magnetar X-ray emission mechanisms

2012 ◽  
Vol 8 (S291) ◽  
pp. 160-160
Author(s):  
Silvia Zane
Keyword(s):  
Spectral Analysis ◽  
Physical Interpretation ◽  
Spectral Properties ◽  
Gamma Ray ◽  
X Ray ◽  
Spectral Components ◽  
Self Consistent ◽  
Photon Index ◽  
Index 2 ◽  
Surface Fields

AbstractSoft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are peculiar X-ray sources which are believed to be magnetars: ultra-magnetized neutron stars which emission is dominated by surface fields (often in excess of 1E14 G, i.e. well above the QED threshold).Spectral analysis is an important tool in magnetar astrophysics since it can provide key information on the emission mechanisms. The first attempts at modelling the persistent (i.e. outside bursts) soft X-ray (¡10 keV) spectra of AXPs proved that a model consisting of a blackbody (kT 0.3-0.6 keV) plus a power-law (photon index 2-4) could successfully reproduce the observed emission. Moreover, INTEGRAL observations have shown that, while in quiescence, magnetars emit substantial persistent radiation also at higher energies, up to a few hundreds of keV. However, a convincing physical interpretation of the various spectral components is still missing.In this talk I will focus on the interpretation of magnetar spectral properties during quiescence. I will summarise the present status of the art and the currents attempts to model the broadband persistent emission of magnetars (from IR to hard Xrays) within a self consistent, physical scenario.

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 NGC 300 ULX1: A test case for accretion torque theory

2018 ◽  
Vol 620 ◽  
pp. L12 ◽  
Author(s):  
G. Vasilopoulos ◽  
F. Haberl ◽  
S. Carpano ◽  
C. Maitra
Keyword(s):  
Neutron Star ◽  
Test Case ◽  
X Ray ◽  
Spin Period ◽  
Spin Evolution ◽  
Spin Reversal ◽  
Eddington Limit

NGC 300 ULX1 is a newly identified ultra-luminous X-ray pulsar. The system is associated with the supernova impostor SN 2010da that was later classified as a possible supergiant Be X-ray binary. In this work we report on the spin period evolution of the neutron star based on all the currently available X-ray observations of the system. We argue that the X-ray luminosity of the system has remained almost constant since 2010, at a level above ten times the Eddington limit. Moreover, we find evidence that the spin period of the neutron star evolved from ∼126 s down to ∼18 s within a period of about 4 years. We explain this unprecedented spin evolution in terms of the standard accretion torque theory. An intriguing consequence for NGC 300 ULX1 is that a neutron star spin reversal should have occurred a few years after the SN 2010da event.

scholarly journals An X-ray and optical study of the outbursting behaviour of the SMC Be X-ray binary SXP 91.1

2019 ◽  
Vol 489 (1) ◽  
pp. 993-999 ◽  
Author(s):  
I M Monageng ◽  
M J Coe ◽  
J A Kennea ◽  
L J Townsend ◽  
D A H Buckley ◽  
...  
Keyword(s):  
Neutron Star ◽  
Gravitational Lensing ◽  
Optical Data ◽  
Type I ◽  
X Ray ◽  
Spin Period ◽  
Average Spin ◽  
Period Derivative ◽  
Inclination Angles ◽  
Using Data

ABSTRACT In this paper we report on the optical and X-ray behaviour of the Be X-ray binary, SXP 91.1, during a recent type I outburst. We monitored the outburst using the Neil Gehrels Swift Observatory. These data were supported by optical data from the Southern African Large Telescope and the Optical Gravitational Lensing Experiment (OGLE) to show the circumstellar disc activity. Matter from this disc accretes on to the neutron star, giving rise to the X-ray outburst as seen in the synchronous evolution of the optical and X-ray light curves. Using data taken with OGLE we show that the circumstellar disc has exhibited stable behaviour over two decades. A positive correlation is seen between the colour and magnitude from the OGLE and massive compact halo object observations, which indicates that the disc is orientated at relatively low-inclination angles. From the OGLE and Swift data, we demonstrate that the system has shown relative phase offsets that have persisted for many years. The spin period derivative is seen to be at maximum spin-up at phases when the mass accretion rate is at maximum. We show that the neutron star in SXP 91.1 is an unusual member of its class in the sense that it has had a consistent spin period derivative over many years, with the average spin-up rate being one of the highest for known Small Magellanic Cloud pulsars. The most recent measurements of the spin-up rate reveal higher values than the global trend, which is attributed to the recent mass accretion event leading to the current outburst.

scholarly journals Early neutron star evolution in high-mass X-ray binaries

2020 ◽  
Vol 494 (1) ◽  
pp. 44-49 ◽  
Author(s):  
Wynn C G Ho ◽  
M J P Wijngaarden ◽  
Nils Andersson ◽  
Thomas M Tauris ◽  
F Haberl
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Thermal Emission ◽  
Equilibrium Phase ◽  
High Mass ◽  
X Ray ◽  
Spin Period ◽  
Long Duration ◽  
X Ray Binaries ◽  
The Magnetic Field

ABSTRACT The application of standard accretion theory to observations of X-ray binaries provides valuable insights into neutron star (NS) properties, such as their spin period and magnetic field. However, most studies concentrate on relatively old systems, where the NS is in its late propeller, accretor, or nearly spin equilibrium phase. Here, we use an analytic model from standard accretion theory to illustrate the evolution of high-mass X-ray binaries (HMXBs) early in their life. We show that a young NS is unlikely to be an accretor because of the long duration of ejector and propeller phases. We apply the model to the recently discovered ∼4000 yr old HMXB XMMU J051342.6−672412 and find that the system’s NS, with a tentative spin period of 4.4 s, cannot be in the accretor phase and has a magnetic field B > a few × 1013 G, which is comparable to the magnetic field of many older HMXBs and is much higher than the spin equilibrium inferred value of a few × 1011 G. The observed X-ray luminosity could be the result of thermal emission from a young cooling magnetic NS or a small amount of accretion that can occur in the propeller phase.

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

PULSAR DISTRIBUTIONS IN THE MAGNETIC AND SPIN PERIOD DIAGRAM

2013 ◽  
Vol 23 ◽  
pp. 165-169
Author(s):  
CHENGMIN ZHANG ◽  
YUANYUE PAN ◽  
ALI TAANI
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Stellar Evolution ◽  
Distribution Characteristics ◽  
Radio Pulsars ◽  
X Ray ◽  
Spin Period

The various types of pulsars are classified in the magnetic and spin period (B-P) diagram, by which one can recognize their properties there. We also investigate the relation of radio pulsars and X-ray neutron stars, and their distribution characteristics, implying their evolution links. B-P diagram is divided by the special lines, e.g. spin-up line and "death line", which indicate the evolution information of pulsars. Like Hertzsprung-Russell (H-R) diagram of showing the stellar evolution or "lives of stars", we try to develop B-P diagram as a function of representing the evolution track of neutron star.

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 Orbital and superorbital periods in ULX pulsars, disc-fed HMXBs, Be/X-ray binaries, and double-periodic variables

2020 ◽  
Vol 495 (1) ◽  
pp. L139-L143
Author(s):  
L J Townsend ◽  
P A Charles
Keyword(s):  
Neutron Star ◽  
Orbital Period ◽  
Binary Systems ◽  
High Mass ◽  
Early Type ◽  
Present Evidence ◽  
X Ray ◽  
Spin Period ◽  
Simple Linear Relationship ◽  
X Ray Binaries

ABSTRACT We present evidence for a simple linear relationship between the orbital period and superorbital period in ultra-luminous X-ray (ULX) pulsars, akin to what is seen in the population of disc-fed neutron star supergiant X-ray binary and Be/X-ray binary systems. We argue that the most likely cause of this relationship is the modulation of precessing hotspots or density waves in an accretion or circumstellar disc by the binary motion of the system, implying a physical link between ULX pulsars and high-mass X-ray binary (HMXB) pulsars. This hypothesis is supported by recent studies of Galactic and Magellanic Cloud HMXBs accreting at super-Eddington rates, and the position of ULX pulsars on the spin period–orbital period diagram of HMXBs. An interesting secondary relationship discovered in this work is the apparent connection between disc-fed HMXBs, ULXs, and a seemingly unrelated group of early-type binaries showing so-called double-periodic variability. We suggest that these systems are good candidates to be the direct progenitors of Be/X-ray binaries.

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