Artikel zu "X-ray binaries" INTEGRAL (Main) (i) (ii) (SGR) MIV X-Ray Pulsars MIV X-ray binaries
Ultra-Short Period Binaries (USP DDB) Supergiant transient X-ray binary stars X-ray Transients Compact Stellar X-ray Sources The rp process on neutron star surface (X-ray binaries) K1 GX 3+1 — unusual thermonuclear X-ray burst K2 Accreting X-ray Pulsars: Cyclotron Lines K3 4U 1907+09 K4	K5 V0332+53: Röntgen-Pulsar im Ausbruch K5a Binary X-ray Pulsar 4U0115+63 K6 X-ray binary IGR J17091-3624 Literatur

X-ray binaries

K1   GX 3+1 — unusual thermonuclear X-ray burst

GX 3+1 — unusual thermonuclear X-ray burst (duration 30 min)
	Authors: Jerome Chenevez, Maurizio Falanga, Soeren Brandt, Ruben Farinelli, Filippo Frontera, Andrea Goldwurm, Jean in 't Zand, Erik Kuulkers, Niels Lund
	Journal-ref: A&A (2006) [astro-ph/0512559 ]
	Title: Two-phase X-ray burst from GX 3+1 observed by INTEGRAL
Abstract: INTEGRAL detected on August 31, 2004, an unusual thermonuclear X-ray burst from the low-mass X-ray binary GX 3+1. Its duration was 30 min, which is between the normal burst durations for this source (<~10 s) and the superburst observed in 1998 (several hours). We see emission up to 30 keV energy during the first few seconds of the burst where the bolometric peak luminosity approaches the Eddington limit. This peculiar burst is characterized by two distinct phases: an initial short spike of ~6 s consistent with being similar to a normal type I X-ray burst, followed by a remarkable extended decay of cooling emission. We discuss three alternative schemes to explain its twofold nature: 1) unstable burning of a hydrogen/helium layer involving an unusually large amount of hydrogen, 2) pure helium ignition at an unusually large depth (unlikely in the present case), and 3) limited carbon burning at an unusually shallow depth triggered by unstable helium ignition. Though none of these provide a satisfactory description of this uncommon event, the former one seems the most probable.

K2   Accreting X-ray Pulsars: Cyclotron Lines

Accreting X-ray Pulsars — Cyclotron Lines
	Authors: W.A. Heindl, R.E. Rothschild, W. Coburn, R. Staubert, J. Wilms, I. Kreykenbohm, P. Kretschmar
	Journal-ref: "X-Ray Timing 2003: Rossi and Beyond", eds. P. Kaaret, F.K. Lamb, & J.H. Swank (Melville, NY: AIP) (2004) [astro-ph/0403197 ]
	Title: Timing and Spectroscopy of Accreting X-ray Pulsars: the State of Cyclotron Line Studies
Abstract: A great deal of emphasis on timing in the RXTE era has been on pushing toward higher and higher frequency phenomena, particularly kHz QPOs. However, the large areas of the RXTE pointed instruments provide another capability which is key for the understanding of accreting X-ray pulsars -- the ability to accumulate high quality spectra in a limited observing time. For the accreting X-ray pulsars, with their relatively modest spin frequencies, this translates into an ability to study broad band spectra as a function of pulse phase. This is a critical tool, as pulsar spectra are strong functions of the geometry of the "accretion mound" and the observers' viewing angle to the ~10^12 G magnetic field. In particular, the appearance of "cyclotron lines" is sensitively dependent on the viewing geometry, which must change with the rotation of the star. These spectral features, seen in only a handful of objects, are quite important, as they give us our only direct measure of neutron star magnetic fields. Furthermore, they carry a great deal of information as to the geometry and physical conditions in the accretion mound. In this paper, we review the status of cyclotron line studies with the RXTE. We present an overview of phase-averaged results and give examples of observations which illustrate the power of phase-resolved spectroscopy. INTRODUCTION Image credit: FIGURE 1. Schematic diagram of the “accretion mound” showing the line-forming region as a discrete layer covering the continuum production zone. Table 1.2. Energies of Cyclotron Lines in Accretion-Powered Pulsars Source P E H 4U 0115+63 3.61 12 Yes 4U 1907+09 438 18 Yes 4U 1538-52 530 20 Yes Vela X-1 283 25 Yes V 0332+53 4.37 27 Cep X-4 66.2 28 Cen X-3 4.82 28.5 4U 0352+309 835 29 E J1946+274 15.8 36 MX 0656-072 160. 36 4U 1626-67 7.66 37 GX 301-2 681 37 Her X-1 1.24 41 A 0535+26 105 50 P: Spin Period (s), E: Energy (keV), H: Harmonics Cyclotron lines, or more precisely “cyclotron resonance scattering features” (CRSFs) are formed at or near the neutron star magnetic polar cap where electron motions perpendicular to the field are quantized in Landau orbits. This gives rise to increased magnetic Compton scattering opacity at the (harmonically spaced) Landau energies resulting in absorption-line-like features in the emergent spectra. Owing to the ~ 1012 G field strength, the Landau transitions have energies in the hard X-ray band: En,s = (n + ½ + s)Ecyc, where n is the principle quantum number, s = ±½ is the electron spin, and Ecyc = eB/me = 11.6 B12 keV. Thus, the cyclotron line energy gives a direct measure of the magnetic field in the scattering region. General Relativity: line redshift Of course, the observed line energy will be redshifted in the strong gravitational field of the neutron star such that B12 = (1+z) Eobs 11.6keV, where B12 is the field strength in 1012 G and z is the redshift in the scattering region. Special Relativity: Ecyc = E(Bcrit) In addition, when relativistic effects are considered the line spacing is no longer expected to be harmonic: where q is viewing angle with respect to the magnetic field and Bcrit = m2c3/e = 4.4×1013G. For magnetic fields in the 1012 G range, these shifts are <~ 10%. These considerations lay down the basic theoretical principles for cyclotron line formation.

K3   4U 1907+09

4U 1907+09 — P = 441 s — torque reversal — Cyclotron Lines at 19 & 40 keV
	Authors: S. Fritz, I. Kreykenbohm, J. Wilms, R. Staubert, F. Bayazit, K. Pottschmidt, J. Rodriguez, A. Santangelo
	Journal-ref: (2006) [astro-ph/0608518 ]
	Title: A torque reversal of 4U 1907+09
Image credit: Fritz et al. Fig. 1. Upper Panel: Rossi X-ray Timing Explorer All Sky Monitor (ASM) 2–12 keV light curve of 4U1907+09 folded on the orbital period of 8.3753 days. Lower Panel: Same for the IBIS 20–40 keV light curve. Abstract: We present an analysis of the accreting X-ray pulsar system 4U 1907+09 based on INTEGRAL data. The main focus of this analysis is a study of the timing behavior of this source. In addition we also show an analysis of the 5-90 keV spectrum. The data were extracted using the official INTEGRAL software OSA 5.1. Timing analysis was performed using epoch folding and pulsar pulse phasing. We have measured 12 individual pulse periods for the years 2003 to 2005. We confirm earlier RXTE results that during 2003 the spin down became slower and show furthermore that after this phase 4U 1907+09 started to spin up with dP/dt = -0.158 s/yr in 2004. The similarity of the pulse period histories of 4U 1907+09 and 4U 1626-26 suggests that accretion onto an oblique rotator, as recently proposed by Perna et al., is a possible explanation for this change. 1. Introduction The wind-accreting High Mass X-ray Binary system 4U1907+09 (Giacconi et al. 1971) consists of a neutron star in an eccentric (e = 0.28) 8.3753 d orbit around its companion, which has been identified optically with a highly reddened mV = 16.37mag star. Using interstellar atomic lines of Na I and KI, Cox et al. (2005) set a lower limit of 5 kpc for the distance. According to this value a lower limit of the X-ray luminosity above 1 keV is given by LX = 2 × 1036 erg s-1. Cox et al. (2005) also confirm earlier suggestions that the stellar companion is a O8–O9 Ia supergiant with an effective temperature of 30500K, a radius of 26R, a luminosity of 5 105 L, and a mass loss rate of 7× 10-6M yr-1. Note that the presence of X-ray flaring seen twice per neutron star orbit (Fig. 1) had led some authors to the suggestion of a Be star companion, however, this classification would require a distance of < 1.5 kpc, which is in contradiction to the significant interstellar extinction measured in optical observations. Image credit: Fritz et al.    Fig. 6. Close up of the periods found in this work. Between MJD52643 (May 2003) to MJD53131 (April 2004) the derived pulse periods show a spin down of the source with P'pulse = +0.026 s yr-1. After MJD53131 the accretion torque changes sign and 4U1907+09 spins up with P'pulse = -0.158 s yr-1. The line indicates the linear fit to the periods as described in the text. After almost 20 years of constant spin down at a rate of P'pulse = +0.225 s yr-1, with the available data being consistent with P'' = 0 s-1, in 2002 and 2003 first indications for a decrease in the magnitude of spin down were detected. The new INTEGRAL data show a torque reversal from ~MJD53131 onwards, with the source now exhibiting a spin up with a rate of P'pulse = -0.158 s yr-1. So far, the INTEGRAL results appear to be consistent with P'' = 0 s-1 (the 1s upper limit for P'' during the spin up is -4 × 10-5 s-1 yr-2).

K4  

K5  V0332+53: Röntgen-Pulsar im Ausbruch

Image credit: INTEGRAL / Kreykenbohm et al. Lightcurve of V0332+53 (P = 4.37492 s).

X-ray Binary V0332+53 (EXO 0331+530) — P = 4.37 s
	Authors: I. Kreykenbohm, N. Mowlavi, N. Produit, S. Soldi, R. Walter, P. Dubath, P. Lubinski, M. Tuerler, W. Coburn, A. Santangelo, R. E. Rothschild, R. Staubert
	Journal-ref: A&A 433 (2005) L45 [astro-ph/0503028 ]
	Title: INTEGRAL observations of V0332+53 in outburst
Abstract: We present the analysis of a 100ksec Integral(3-100kev) observation of the transient X-ray pulsar V0332+53 in outburst. The source is pulsating at P = 4.3751 ± 0.0002s with a clear double pulse from 6 kev to 60 kev. The average flux was ~550 mCrab between 20 kev and 60 kev. We modeled the broad band continuum from 5 kev to 100 kev with a power-law modified by an exponential cut off. We observe three cyclotron lines: the fundamental line at 24.9±0.1 kev, the first harmonic at 50.5±0.1 kev as well as the second harmonic at 71.7±0.8 kev, thus confirming the discovery of the harmonic lines by Coburn et al. (2005) in RXTE data.

The High-Mass X-ray Binary V0332+53 (EXO 0331+530), currently undergoing a dramatic outburst, was a Target of Opportunity for an INTEGRAL observation on 6-10 January 2005.

The source was observed as soon as allowed by visibility constraints on 6 January in staring mode and then in the hexagonal dithering mode for a total of about 110 ksec.

[12-JAN-2005] The outbursts of V0332+53
The V0332+53 system is composed of a Be star and a pulsar with a pulsation period of 4.4 sec detected with EXOSAT by Stella et al. (1985, ApJ 288, L45).
The source was first detected with Vela 5B during an outburst in 1973 (Terrell & Priedhorsky, 1984, ApJ 285, L15).
A second outburst occured in 1983 and was observed with EXOSAT.
A third outburst was detected by the Ginga satellite in 1989 and Quasi-Periodic Oscillations (QPOs) have been detected at a frequency of about 0.05 Hz (Takeshima et al., 1994, ApJ 436, 871).
The current outburst reaches a flux of about 1 Crab in the X-rays (3-10 keV). The V0332+53 flux increased steadily between the end of November 2004 and New Year 2005 as can be seen on the RXTE All Sky Monitor (ASM) light curve provided by the Massachusetts Institute of Technology (MIT).

R. Walter (ISDC, Geneva) The image above shows the IBIS/ISGRI mosaic image of the field around V0332+53 (EXO 0331+530) in this TOO observation.

I. Kreykenbohm (ISDC & IAAT) INTEGRAL spectra of V0332+53 in outburst. The raw count rate spectrum of IBIS/ISGRI (white) and SPI (red) (above) shows wiggles which are the clear signature of cyclotron lines.

I. Kreykenbohm (ISDC & IAAT) This is confirmed by applying a simple continuum model composed of a power-law with a high energy cut-off to the combined ISGRI (red), SPI (green) and JEM-X (white) spectrum (on the right).

A preliminary analysis of the INTEGRAL data at the ISDC produced a high signal to noise very steep spectrum featuring 3 cyclotron lines (Soldi et al., 2005). This is one of the best cyclotron line spectrum ever obtained and confirms the lines discovered with RXTE by Coburn et al. (2005). This makes V0332+53 the only accreting pulsar other than 4U0115+63 to exhibit more than two cyclotron lines:
a pair of features with energies (26.34±0.03)keV and (49.1±0.2)keV and another line-like feature at (74±2)keV.

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	Authors: N. Mowlavi, I. Kreykenbohm, S. E. Shaw, K. Pottschmidt, J. Wilms, J. Rodriguez, N. Produit, S. Soldi, S. Larsson, P. Dubath
	Journal-ref: (2006) [astro-ph/0512414 ]
	Title: INTEGRAL observation of the high-mass X-ray transient V0332+53 during the 2005 outburst decline
Abstract: The decline of the high mass X-ray transient V0332+53 during the Dec. 2004 to Feb. 2005 outburst is analysed from the data recorded by INTEGRAL. The flux is shown to decrease exponentially until 2005 Feb. 10, with a decay time scale of ~30 days above 20 keV and ~20 days at lower energies, and to decrease linearly thereafter. The energy spectrum is well modelled throughout the decay by a power law with a folding energy of ~7.5 keV, and with two cyclotron absorption features. The folding energy does not vary significantly over the decay, but the spectrum becomes harder with time. Most importantly, we show that the parameters describing the fundamental cyclotron line around 27 keV do vary with time: its energy and depth increase (by about 17% for the energy in ~6 weeks), while its width decreases. These changes of the cyclotron line parameters are interpreted as resulting from a change in the extent of the cyclotron scattering region. Two quasi-periodic oscillations are also observed at various times during the observations, one at 0.05 Hz and another one near the pulsation frequency around 0.23 Hz. INTRODUCTION

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	Authors: Shu Zhang, Diego F. Torres, JinLu Qu
	Journal-ref: A&A (2006) [astro-ph/0605351 ]
	Title: A quasi periodic signal with ultra low frequency discovered in V0332+53?
Abstract: We have analyzed International Gamma-Ray Astrophysics Laboratory (INTEGRAL) data corresponding to observations of the high mass X-ray binary (HMXB) V0332+53 during its huge outburst occurred in 2004-2005, and found that the source may have a quasi periodic signal with ultra low frequency of roughly 4-5 × 10-5 Hz in the energy band 20-40 keV. This feature is revealed through a series of consistent analysis of imaging and fitting the energy spectrum for each science window (SCW), and shows up in the corresponding light curves. The analysis of the power spectrum provides a hint of a power peak located around 4 × 10-5 Hz. Although the signal is weak (at 2 sigma level) and suffers from the uncertainties residing in the data, it is consistent with the previous analyses. INTRODUCTION Outbursts of HMXB V0332+53 were observed four times in the hard X-rays since its discovery. With these detections, V0332+53 was identified as a high mass X-ray binary system, consisting of an early-type star BQ Cam (Honeycutt and Schlegel 1985) and a neutron star. The distance to the source was estimated to be 2.2-5.8 kpc (Corbet et al. 1986). A cyclotron absorption component at 28.5 keV suggested that the magnetic field could be as high as 2.5×1012 G on the surface of the neutron star. The most recent outburst was detected by the All-Sky Monitor (ASM) of the Rossi X-ray Timing Explorer (RXTE) in November 2004. Apart from the feature of 0.05 Hz quasi-periodic oscillation (QPO) reported in Takeshima et al. (1994), an additional QPO feature was discovered from the Proportional Counter Array (PCA) data of RXTE to ride on the spin frequency (Qu et al. 2005). The orbital parameters were updated and refined by Zhang et al. (2005). Multiple cyclotron lines of ~ 25 keV, 50 keV and 72 keV were found in RXTE (Pottschmidt et al. 2005) and INTEGRAL (Kreykenbohm et al. 2005), respectively, by using the observational data when the source was around its flux maximum during the outburst. We report in this letter the likely discovery of a new quasi periodic signal with an ultra low frequency, by using the INTEGRAL data when the outburst was decaying. References Corbert R. H. D., Charles P. A., van der Klis, M. 1986, A&A, 162, 117 Honeycutt, R. K. & Schlegel, E.M. 1985, PASP, 97, 300 Kreykenbohm I., Mowlavi N., Produit N.;, et al., 2005, A&A, 433, L45 Makishima K., Ohashi, T., Kawai, N., et al. 1990, PASJ, 42, 295 Mowlavi N., Kreykenbohm I., Shaw S.E., et al., 2006, A&A, in press Pottschmidt K., Kreykenbohm I., Wilms J., et al., 2005, ApJ, 634, L97 Takeshima T., Dotani T., Mitsuda K., et al. 1994, ApJ, 436, 871 Zhang S., Qu J.L., Song L.M. and Torres D.F., 2005, ApJ, 630, L65

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	Authors: S. S. Tsygankov, A. A. Lutovinov, E. M. Churazov, R. A. Sunyaev
	Journal-ref: (2006) [astro-ph/0511237 ]
	Title: V0332+53 in the outburst of 2004—2005: luminosity dependence of the cyclotron line and pulse profile
Abstract: We present results of observations of the transient X-ray pulsar V0332+53 performed during a very powerful outburst in Dec, 2004 — Feb, 2005 with the INTEGRAL and RXTE observatories in a wide (3-100 keV) energy band. A cyclotron resonance scattering line at an energy of ~26 keV has been detected in the source spectrum together with its two higher harmonics at ~50 and ~73 keV, respectively. We show that the energy of the line is not constant but linearly changes with the source luminosity. Strong pulse profile variations, especially near the cyclotron line, are revealed for different levels of the source intensity. We discuss the obtained results in terms of the theoretical models of X-ray pulsars. DISCUSSION The transient X-ray pulsar V0332+53 demonstrates powerful outbursts in which its intensity exceeds 1 Crab. The source is a member of a high mass X-ray binary system with a companion star (BQ Cam) that belongs to the class of Be stars. According to current ideas such objects represent quick rotating stars with a dense, but radially slow, stellar wind. This wind forms the so-called equatorial disc around the star, the size and the presence of the disc are not permanent. Most X-ray sources in binary systems with Be stars are transients demonstrating outbursting activity. This is presumably connected with the evolution of the normal star. Matter from the equatorial disc is captured and an accretion disc around the relativistic object is formed. The system V0332+53/BQ Cam is an obvious example of the picture described above.

K5a   Binary X-ray Pulsar 4U0115+63

Binary X-ray Pulsar 4U0115+63 — Luminosity-Dependent Cyclotron Resonance
	Authors: Motoki Nakajima, Tatehiro Mihara, Kazuo Makishima, Hisako Niko
	Journal-ref: Astrophysical Journal (2006) [astro-ph/0601491 ]
	Title: A Further Study of the Luminosity-Dependent Cyclotron Resonance Energies of the Binary X-ray Pulsar 4U0115+63 with RXTE
Abstract: The present paper reports on the RXTE observations of the binary X-ray pulsar 4U0115+63, covering an outburst in 1999 March-April with 44 pointings. The 3-30 keV PCA spectra and the 15-50 keV HEXTE spectra were analyzed jointly for the cyclotron resonance features. When the 3-50 keV luminosity at an assumed distance of 7 kpc was in the range (5-13)x1037 erg s-1, harmonic double cyclotron features were observed in absorption at ~11 and ~22 keV, as was measured previously during typical outbursts. As the luminosity decreased below ~ 5x1037 erg s-1, the second resonance disappeared, and the fundamental resonance energy gradually increased, up to ~ 16 keV at 0.16x1037 erg s-1. These results reconfirm the report by Mihara et al. (2004) using Ginga, who observed a single absorption at ~ 16 keV in a minor (~ 1037 erg s-1) outburst of this object. The luminosity-dependent cyclotron resonance energy may be understood as a result of a decrease in the accretion column height, in response to a decrease in the mass accretion rate.

K6   X-ray binary IGR J17091-3624

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	Authors: : F. Capitanio, A. Bazzano, P. Ubertini, A. A. Zdziarski, A. J. Bird, G. De Cesare, A. J. Dean, J. B. Stephen, A. Tarana
	Journal-ref: Astrophysical Journal (2006) [astro-ph/0601503 ]
	Title: Spectral states of the X-ray binary IGR J17091-3624 observed by INTEGRAL and RXTE
Abstract: IGR J17091-3624 was discovered in 2003 April by INTEGRAL/IBIS during its Galactic Centre Deep Exposure programme. The source was initially detectable only in the 40--100 keV range, but after two days was also detected in the 15-40 keV range. Its flux had by then increased to 40 mCrab and 25 mCrab in the 15-40 keV and 40-100 keV bands respectively. RXTE observed the source simultaneously on 2003 April 20, with an effective exposure of 2 ksec. We report here the spectral and temporal evolution of the source, which shows a transition between the hard and soft states. We analyse in detail the RXTE/INTEGRAL Comptonised spectrum of the hard state as well as the JEM-X detection of a blackbody component during the source softening. Even though the source spectral behaviour and time variability show a similarity with the outburst of the black-hole candidate IGR J17464-3213 (= H1743-322), observed by INTEGRAL in 2003, the nature of its compact object (BH vs. NS) remains controversial.

GRB 030406 —
	Authors: Marcinkowski, R.; Denis, M.; Bulik, T.; Goldoni, P.; Laurent, Ph.; Rau, A.
	Journal-ref: A&A 452 (2006) 113 [astro-ph/0604433 ]
	Title: GRB 030406 - an extremely hard burst outside of the INTEGRAL field of view
Abstract: Image credit: ESA This artist's impression provides a schematic of how the imager on-board ESA's Integral satellite (IBIS) can reconstruct images of powerful events like gamma-ray bursts (GRB) using the radiation that passes through the side of Integral’s imaging telescope. Using the IBIS Compton mode, the INTEGRAL satellite is able to detect and localize bright and hard GRBs, which happen outside of the nominal INTEGRAL field of view. We have developed a method of analyzing such INTEGRAL data to obtain the burst location and spectra. We present the results for the case of GRB 030406. The burst is localized with the Compton events, and the location is consistent with the previous Interplanetary Network position. A spectral analysis is possible by detailed modeling of the detector response for such a far off-axis source with an offset of 36.9 °. The average spectrum of the burst is extremely hard: the photon index above 400 keV is -1.7, with no evidence of a break up to 1.1 MeV at a 90% confidence level. INTRODUCTION [16 June 2006] Integral sees a GRB out of the corner of its eye. Thanks to a clever piece of design and a sophisticated piece of analysis by European astronomers, ESA's gamma ray observatory can make images of gamma-ray bursts even if the spacecraft itself is pointing somewhere completely different. Thanks to a clever piece of design and a sophisticated piece of analysis by European astronomers, Integral - ESA’s orbiting gamma ray observatory - can now make images of the most powerful gamma-ray bursts even if the spacecraft itself is pointing somewhere completely different. When GRB 030406 exploded unexpectedly in early April this year, Integral was observing another part of the Universe, about 74 times the diameter of the full Moon away. Nevertheless Dr Radoslaw Marcinkowski, Space Research Center, Warsaw, Poland, and colleagues have reconstructed an image of the event using the radiation that passed through the side of Integral’s imaging telescope. Marcinkowski had heard of Integral registering a solar flare in this way even though the satellite wasn’t pointing at the Sun. He thought that if it worked with solar flares, it must work with the most powerful GRBs. On 6 April 2003, his hunch was proved correct, Integral provided an accurate location for GRB 030406 even though it was not looking in the burst’s direction.

Literatur zu ""
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H. Heintzmann

( Eintrag vom 1.3.2006)

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