Multiple cyclotron line-forming regions in GX 301−2

We present two observations of the high-mass X-ray binary GX 301−2 with NuSTAR, taken at different orbital phases and different luminosities. We find that the continuum is well described by typical phenomenological models, like a very strongly absorbed NPEX model. However, for a statistically acceptable description of the hard X-ray spectrum we require two cyclotron resonant scattering features (CRSF), one at ∼35 keV and the other at ∼50 keV. Even though both features strongly overlap, the good resolution and sensitivity of NuSTAR allows us to disentangle them at ≥99.9% significance. This is the first time that two CRSFs have been seen in GX 301−2. We find that the CRSFs are very likely independently formed, as their energies are not harmonically related and, if the observed feature were due to a single line, the deviation from a Gaussian shape would be very large. We compare our results to archival Suzaku data and find that our model also provides a good fit to those data. We study the behavior of the continuum as well as the CRSF parameters as function of pulse phase in seven phase bins. We find that the energy of the 35 keV CRSF varies smoothly as a function of phase, between 30 and 38 keV. To explain this variation, we apply a simple model of the accretion column, taking into account the altitude of the line-forming region, the velocity of the in-falling material, and the resulting relativistic effects. We find that in this model the observed energy variation can be explained as being simply due to a variation of the projected velocity and beaming factor of the line-forming region towards us.

Download Full-text

The giant outburst of 4U 0115+634 in 2011 with Suzaku and RXTE

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935666 ◽

2020 ◽

Vol 634 ◽

pp. A99

Author(s):

Matthias Bissinger né Kühnel ◽

Ingo Kreykenbohm ◽

Carlo Ferrigno ◽

Katja Pottschmidt ◽

Diana M. Marcu-Cheatham ◽

...

Keyword(s):

Ad Hoc ◽

Resonant Scattering ◽

Emission Feature ◽

High Mass ◽

X Ray ◽

Cyclotron Absorption ◽

Cyclotron Emission ◽

Cyclotron Line ◽

First Time ◽

Rule Out

We present an analysis of X-ray spectra of the high-mass X-ray binary 4U 0115+634 as observed with Suzaku and RXTE in 2011 July, during the fading phase of a giant X-ray outburst. We used a continuum model consisting of an absorbed cutoff power law and an ad hoc Gaussian emission feature centered around 8.5 keV, which we attribute to cyclotron emission. Our results are consistent with a fundamental cyclotron absorption line centered at ∼10.2 keV for all observed flux ranges. At the same time we rule out significant influence of the 8.5 kev Gaussian on the parameters of the cyclotron resonant scattering feature, which are not consistent with the cyclotron line energies or the depths of previously reported flux-dependent descriptions. We also show that some continuum models can lead to artificial line-like residuals in the analyzed spectra, which are then misinterpreted as unphysically strong cyclotron lines. Specifically, our results do not support the existence of a previously claimed additional cyclotron feature at ∼15 keV. Apart from these features, we find for the first time evidence for a He-like Fe XXV emission line at ∼6.7 keV and weak H-like Fe XXVI emission close to ∼7.0 keV.

Download Full-text

Multi-wave Monitoring of the Gravitational Lensed Quasar Q0957+561

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312001238 ◽

2011 ◽

Vol 7 (S285) ◽

pp. 406-407

Author(s):

Vyacheslav N. Shalyapin ◽

Luis J. Goicoechea ◽

Rodrigo Gil-Merino

Keyword(s):

Correlation Analysis ◽

Cross Correlation ◽

Light Curves ◽

The Other ◽

Continuum Emission ◽

X Ray ◽

Cross Correlation Analysis ◽

First Time ◽

The Continuum

AbstractWe present X-ray (Chandra), ultraviolet (Swift/UVOT; U band) and optical-infrared (Liverpool Telescope; griz bands) continuum light curves of Q0957+561 observed in the first half of 2010. A cross-correlation analysis of the light curves shows that the U-band fluctuation leads the other variations at higher and lower energies. The study constrains the geometry of the continuum emission regions in a distant radio-loud AGN for the first time. We note that our work opens a new window in echo-mapping of high-z AGNs with the use of lensed quasars, since the variability of some of the images of a given multiply-imaged quasar can be predicted in advance, provided there is a modest optical follow-up of the system.

Download Full-text

X-ray variability of the HMXB Cen X-3: evidence for inhomogeneous accretion flows.

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3953 ◽

2020 ◽

Author(s):

G Sanjurjo-Ferrín ◽

J M Torrejón ◽

K Postnov ◽

L Oskinova ◽

J J Rodes-Roca ◽

...

Keyword(s):

Equivalent Width ◽

Compact Star ◽

Timing Analysis ◽

Roche Lobe ◽

The Other ◽

Emission Lines ◽

High Mass ◽

X Ray ◽

Accretion Flows ◽

Inner Radius

Abstract Cen X-3 is a compact high mass X-ray binary likely powered by Roche lobe overflow. We present a phase-resolved X-ray spectral and timing analysis of two pointed XMM-Newton observations. The first one took place during a normal state of the source, when it has a luminosity LX ∼ 1036 erg s−1. This observation covered orbital phases φ = 0.00 − 0.37, i.e. the egress from the eclipse. The egress lightcurve is highly structured, showing distinctive intervals. We argue that different intervals correspond to the emergence of different emitting structures. The lightcurve analysis enables us to estimate the size of such structures around the compact star, the most conspicuous of which has a size ∼0.3R*, of the order of the Roche lobe radius. During the egress, the equivalent width of Fe emission lines, from highly ionized species, decreases as the X-ray continuum grows. On the other hand, the equivalent width of the Fe Kα line, from near neutral Fe, strengthens. This line is likely formed due to the X-ray illumination of the accretion stream. The second observation was taken when the source was 10 times X-ray brighter and covered the orbital phases φ = 0.36 − 0.80. The X-ray lightcurve in the high state shows dips. These dips are not caused by absorption but can be due to instabilities in the accretion stream. The typical dip duration, of about 1000 s, is much longer than the timescale attributed to the accretion of the clumpy stellar wind of the massive donor star, but is similar to the viscous timescale at the inner radius of the accretion disk.

Download Full-text

Water maser and radio continuum emission towards IRAS 23139+5939

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307012896 ◽

2007 ◽

Vol 3 (S242) ◽

pp. 180-181

Author(s):

M. A. Trinidad ◽

S. Curiel ◽

J. M. Torrelles ◽

L. F. Rodríguez ◽

V. Migenes ◽

...

Keyword(s):

Flux Density ◽

Line Emission ◽

The Other ◽

Radio Continuum ◽

High Mass ◽

Continuum Emission ◽

Maser Line ◽

Water Masers ◽

Water Maser ◽

The Continuum

AbstractWe present simultaneous observations of continuum (3.5 and 1.3cm) and water maser line emission (1.3cm) carried out with the VLA-A toward the high-mass object IRAS 23139+5939. We detected two radio continuum sources at 3.5cm separated by 0”5 (~2400 AU), I23139 and I23139S. Based on the observed continuum flux density and the spectral index, we suggest that I23139 is a thermal radio jet associated with a high-mass YSO. On the other hand, based on the spatio-kinematical distribution of the water masers, together with the continuum emission information, we speculate that I23139S is also a jet source powering some of the masers detected in the region.

Download Full-text

X-ray Spectroscopy of the Ultra-soft Transient 4U1543-47

International Astronomical Union Colloquium ◽

10.1017/s0252921100012355 ◽

1990 ◽

Vol 115 ◽

pp. 205-208

Author(s):

H. van der Woerd ◽

N.E. White ◽

S.M. Kahn

Keyword(s):

Emission Line ◽

Compact Object ◽

Relativistic Effects ◽

Emission Feature ◽

Continuum Emission ◽

X Ray ◽

Black Hole Candidate ◽

Transmission Grating ◽

Cool Plasma ◽

The Continuum

AbstractThe X-ray transient 4U1543-47 was observed in 1983 by the EXOSAT observatory near the maximum of an outburst. The X-ray spectrum was measured using a gas scintillation proportional counter (GSPC) and a transmission grating spectrometer (TGS). Two emission line features are resolved. A broad (FWHM ~2.7 keV) line at 5.9 keV is detected in the GSPC, which we interprete as a redshifted and broadened iron Kα line. The Une broadening and redshift may arise from either Compton scattering in a cool plasma with small optical depth (τ ≈ 5), or from Doppler and relativistic effects in the vicinity of a compact object. The spectrum below 2 keV, obtained with the TGS, shows evidence for a broad emission line feature at 0.74 keV, which may be an iron L-transition complex. However, we find that such an emission feature could be an artifact caused by an anomalously low interstellar absorption by neutral Oxygen. The continuum emission is extremely soft and is well described by an unsaturated Comptonized spectrum from a very cool plasma (kT = 0.84 keV) with large scattering depth (τ ≈ 27). The continuum spectrum is strikingly similar to that of black hole candidate LMC X-3.

Download Full-text

The Nature of the Compact Object in the Hard X-Ray Source 4U2206+54

International Astronomical Union Colloquium ◽

10.1017/s0252921100152546 ◽

2004 ◽

Vol 194 ◽

pp. 208-208

Author(s):

J. M. Torrejón ◽

I. Kreykenbohni ◽

A. Orr ◽

L. Titarchuk ◽

I. Negueruela

Keyword(s):

Neutron Star ◽

Accretion Disk ◽

Compact Object ◽

High Energy ◽

Energy Data ◽

X Ray ◽

Hot Plasma ◽

Cyclotron Line ◽

First Time

We present an analysis of archival RXTE and BeppoSAX data of the X-ray source 4U2206+54. For the first time, high energy data (≥ 30 keV) is analyzed. The data is well described by comptonization models in which seed photons with temperatures between 1.1 keV arid 1.5 keV are comptonized by a hot plasma at 50 keV thereby producing a hard tail which extends up to 100 keV. From luminosity arguments it is shown that the area of the soft photons source must be small (r ≈ 1 km) and that the presence of an accretion disk in this system is unlikely. Here we report on the possible existence of a cyclotron line around 30 keV . The presence of a neutron star in the system is strongly favored by the available data.

Download Full-text

Cyclotron lines in highly magnetized neutron stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834479 ◽

2019 ◽

Vol 622 ◽

pp. A61 ◽

Cited By ~ 34

Author(s):

R. Staubert ◽

J. Trümper ◽

E. Kendziorra ◽

D. Klochkov ◽

K. Postnov ◽

...

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Neutron Stars ◽

Direct Measurement ◽

Resonant Scattering ◽

Electron Cyclotron ◽

X Ray ◽

Cyclotron Line ◽

The Magnetic Field ◽

Proton Cyclotron

Cyclotron lines, also called cyclotron resonant scattering features are spectral features, generally appearing in absorption, in the X-ray spectra of objects containing highly magnetized neutron stars, allowing the direct measurement of the magnetic field strength in these objects. Cyclotron features are thought to be due to resonant scattering of photons by electrons in the strong magnetic fields. The main content of this contribution focusses on electron cyclotron lines as found in accreting X-ray binary pulsars (XRBP) with magnetic fields on the order of several 1012Gauss. Also, possible proton cyclotron lines from single neutron stars with even stronger magnetic fields are briefly discussed. With regard to electron cyclotron lines, we present an updated list of XRBPs that show evidence of such absorption lines. The first such line was discovered in a 1976 balloon observation of the accreting binary pulsar Hercules X-1, it is considered to be the first direct measurement of the magnetic field of a neutron star. As of today (end 2018), we list 35 XRBPs showing evidence of one ore more electron cyclotron absorption line(s). A few have been measured only once and must be confirmed (several more objects are listed as candidates). In addition to the Tables of objects, we summarize the evidence of variability of the cyclotron line as a function of various parameters (especially pulse phase, luminosity and time), and add a discussion of the different observed phenomena and associated attempts of theoretical modeling. We also discuss our understanding of the underlying physics of accretion onto highly magnetized neutron stars. For proton cyclotron lines, we present tables with seven neutron stars and discuss their nature and the physics in these objects.

Download Full-text

Localisation of intracellular calcium in the neutrophil through the selective precipitation with the antimonate ion

Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie ◽

10.4102/satnt.v20i1.243 ◽

2001 ◽

Vol 20 (1) ◽

pp. 4-8

Author(s):

A. M. Koorts ◽

A. N. Hall ◽

M. Viljoen Viljoen

Keyword(s):

Intracellular Calcium ◽

The Other ◽

Precipitation Reaction ◽

Sodium Ions ◽

Selective Precipitation ◽

X Ray ◽

Transmission Electron ◽

Microscopy Method ◽

Electron Microscopy Method ◽

First Time

The antimonate ion was used for the first time in 1962 by Komnick for the precipitation of intracellular sodium ions. The antimonate ion can, however, also precipitate other cations and can be employed in subcellular calcium localisation studies. The greatest difficulty encountered with such subcellular calcium localisation studies is the selectivity of the antimonate ion for calcium in the presence of the other intracellular cations. Various x-ray analyses and chelation studies have shown that the antimonate precipitation reaction can be specific for calcium under appropriate conditions. A transmission electron microscopy method for the selective localisation of intracellular calcium in the neutrophil with the antimonate ion is discussed. It is indicated that the antimonate ion can specifically precipitate calcium in the presence of the other intracellular cations.

Download Full-text

LMC X–4: Different Types of Long-Term Variability

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318002442 ◽

2017 ◽

Vol 14 (S339) ◽

pp. 146-146

Author(s):

S. Molkov

Keyword(s):

Binary Systems ◽

Noise Model ◽

High Mass ◽

Time Interval ◽

Spin Torque ◽

X Ray ◽

Spin Period ◽

Different Types ◽

First Time

AbstractThis talk presented a summary of our study of different types of long-term variability in the high-mass X-ray binary LMC X-4, by taking advantage of more than 43 years of measurements in the X-ray domain. In particular, we investigated the 30-day cycle of modulation of the X-ray emission from the source (super-orbital or precessional variability), and refined the orbital period and its first derivative. We showed that the precession period in the time-interval 1991–2015 is near its equilibrium value of Psup = 30.370 days, while the observed historical changes in the phase of this variability can be interpreted in terms of the ‘red noise’ model. We obtained an analytical law from which the precession phase can be determined to within 5% throughout the entire time-interval under consideration. Our analysis revealed for the first time that the source is displaying near-periodic variations of its spin period, on a time-scale of roughly 6.8 years, thus making LMC X-4 one of the (few) known binary systems that show remarkable long-term spin–torque reversals.

Download Full-text

New measurements of the cyclotron line energy in Cen X-3

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3477 ◽

2020 ◽

Vol 500 (3) ◽

pp. 3454-3461

Author(s):

Gunjan Tomar ◽

Pragati Pradhan ◽

Biswajit Paul

Keyword(s):

Broad Band ◽

Resonant Scattering ◽

High Energy ◽

Emission Lines ◽

Power Law Model ◽

Pulse Profile ◽

Line Energy ◽

X Ray ◽

Cyclotron Absorption ◽

Cyclotron Line

ABSTRACT We report results from the analysis of data from two observations of the accreting binary X-ray pulsar Cen X-3 carried out with the broad-band X-ray observatories Suzaku and NuSTAR. The pulse profile is dominated by a broad single peak and show some energy dependence with two additional weak pulse peaks at energies below 15 and 25 keV, respectively. The broad-band X-ray spectrum for 0.8–60.0 keV for Suzaku and 3.0–60.0 keV for NuSTAR is fitted well with high-energy cut-off power-law model along with soft-excess, multiple iron emission lines and a cyclotron absorption. The cyclotron line energy is found to be $30.29^{+0.68}_{-0.61}$ and $29.22^{+0.28}_{-0.27}$ keV, respectively, in the Suzaku and NuSTAR spectra. We make a comparison of these two measurements with four previous measurements of Cyclotron Resonant Scattering Feature (CRSF) in Cen X-3 obtained with Ginga, BeppoSAX, and RXTE. We find no evidence for a dependence of the CRSF on luminosity. Except for one CRSF measurement with BeppoSAX , the remaining measurements are consistent with a CRSF energy in the range of 29.5–30.0 keV over a luminosity range of 1.1–5.4 × 1037 erg s−1 different from several other sources that show considerable CRSF variation in the same luminosity range.

Download Full-text