Publications (129)
On the deep minimum state in the Seyfert galaxy MCG-6-30-15
C. S. Reynolds, J. Wilms, M. C. Begelman +2
(abridged) We present a detailed spectral analysis of the first observation of the Seyfert 1 galaxy MCG-6-30-15 by the European Photon Imaging Camera on board the XMM-Newton observ…
ROSAT Observations of BL Lacertae Objects
G. Lamer, H. Brunner, R. Staubert
We present soft X-ray spectra of 74 BL Lacertae objects observed with the PSPC detector on board of the ROSAT satellite. The sample contains all BL Lac objects detected during the…
RXTE Studies of Cyclotron Lines in Accreting Pulsars
W. A. Heindl, W. Coburn, D. E. Gruber +7
In this paper, we summarize the RXTE measurements of cyclotron resonance scattering features in 8 accreting pulsars. The wide bandpass and modest resolution of the RXTE instruments…
Probing stellar winds and accretion physics in high-mass X-ray binaries and ultra-luminous X-ray sources with LOFT
M. Orlandini, V. Doroshenko, L. Zampieri +28
This is a White Paper in support of the mission concept of the Large Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We discuss the potential of LOFT f…
GX 301-2 as seen by Integral
I. Kreykenbohm, K. Pottschmidt, P. Kretschmar +9
We present observations of the High Mass X-ray Binary GX 301-2 taken during the Galactic Plane Scan (GPS) with Integral following our RXTE observations (Kreykenbohm et al. 2004). T…
Variable precession of the neutron star in Her X-1
R. Staubert, D. Klochkov, K. Postnov +3
We present evidence for an identical behavior of the precession of the accretion disk and that of the neutron star (NS) in Her X-1, based on investigating the well established 35 d…
Outburst of GX 304-1 monitored with INTEGRAL: positive correlation between the cyclotron line energy and flux
D. Klochkov, V. Doroshenko, A. Santangelo +10
X-ray spectra of many accreting pulsars exhibit significant variations as a function of flux and thus of mass accretion rate. In some of these pulsars, the centroid energy of the c…
Does the neutron star in Her X-1 really show free precession?
R. Staubert, D. Klochkov, D. Vasco +4
The accreting X-ray pulsar Her X-1 shows two types of long-term variations, both with a period of 35 days: 1) A modulation of the flux with a ten day long Main-On and a 5 d long Sh…
Discovery of a Cyclotron Resonant Scattering Feature in the RXTE Spectrum of 4U 0352+309 (X Per)
W. Coburn, W. A. Heindl, D. E. Gruber +4
We have discovered a ~29 keV Cyclotron Resonant Scattering Feature (CRSF) in the X-Ray spectrum of 4U 0352+309 (X Per) using observations taken with the Rossi X-Ray Timing Explorer…
CGRO, Radio and Optical Observations of the Quasar NRAO 140
M. Maisack, R. Staubert, K. Otterbein +3
We report on Compton Gamma Ray Observatory (CGRO), radio and optical observations of the radio-loud, superluminal quasar NRAO 140. The source is not detected (at a significance of…
Hard X-ray observations of the X-ray pulsar A0535+26
V. Borkous, A. S. Kaniovsky, R. A. Sunyaev +4
We present the results of the observations of the giant bursts from the X-ray pu lsar A0535+26 made by HEXE onboard Mir-Kvant in April 1989, November 1993 and February 1994. The pu…
The INTEGRAL Science Data Centre (ISDC)
T. J. -L. Courvoisier, R. Walter, V. Beckmann +17
The INTEGRAL Science Data Centre (ISDC) provides the INTEGRAL data and means to analyse them to the scientific community. The ISDC runs a gamma ray burst alert system that provides…
Discovery of a Third Harmonic Cyclotron Resonance Scattering Feature in the X-ray Spectrum of 4U 0115+63
W. A. Heindl, W. Coburn, D. E. Gruber +5
We have discovered a third harmonic cyclotron resonance scattering feature (CRSF) in observations of the recent outburst of 4U 0115+63 with the Rossi X-ray Timing Explorer (RXTE).…
XMM-Newton Observations of the Be/X-ray transient A0538-66 in quiescence
P. Kretschmar, J. Wilms, R. Staubert +2
We present XMM-Newton observations of the recurrent Be/X-ray transient A0538-66, situated in the Large Magellanic Cloud, in the quiescent state. Despite a very low luminosity state…
RXTE monitoring of Centaurus A
S. Benlloch, R. E. Rothschild, J. Wilms +3
We report on the analysis from ~110 ks of X-ray observations of Centaurus A carried out with the Proportional Counter Array (PCA) and the High Energy X-ray Timing Experiment (HEXTE…
Pulse phase and precession phase resolved spectroscopy of Her X-1: studying a representative Main-On with RXTE
D. Vasco, R. Staubert, D. Klochkov +3
We performed a detailed pulse phase resolved spectroscopy of the accreting binary X-ray pulsar Her X-1 in the energy range 3.5-75 keV and have established pulse phase profiles for…
A fast X-ray timing capability on XEUS
D. Barret, G. Skinner, E. Kendziorra +6
Fast X-ray timing can be used to probe strong gravity fields around collapsed objects and constrain the equation of state of dense matter in neutron stars. These studies require ex…
Discovery of a Cyclotron Resonance Scattering Feature in the X-ray Spectrum of XTE J1946+274
W. A. Heindl, W. Coburn, D. E. Gruber +4
Observations of the transient accreting pulsar XTE J1946+274 made with the Rossi X-ray Timing Explorer during the course of the 1998 September-November outburst, reveal a cyclotron…
Cygnus X-1 from RXTE: Monitoring the short term variability
K. Pottschmidt, J. Wilms, R. Staubert +3
We present temporal and spectral results from monitoring Cygnus X-1 with the Rossi X-ray Timing Explorer (RXTE) in 1998 and 1999. We concentrate on the long term evolution of the h…
Quasi-Periodic Oscillation in Seyfert galaxies: Significance levels. The Case of Mrk 766
S. Benlloch, J. Wilms, R. Edelson +2
We discuss methods to compute significance levels for the existence of quasi-periodic oscillations (QPOs) in Active Galactic Nuclei (AGN) which take the red-noise character of the…
The Be/X-ray binary A0535+26 during its recent 2009/2010 outbursts
I. Caballero, K. Pottschmidt, A. Santangelo +20
The Be/X-ray binary A0535+26 showed a giant outburst in December 2009 that reached ~5.14 Crab in the 15-50 keV range. Unfortunately, due to Sun constraints it could not be observed…
Vertical wind structure in an X-ray binary revealed by a precessing accretion disk
P. Kosec, E. Kara, A. C. Fabian +11
The accretion of matter onto black holes and neutron stars often leads to the launching of outflows that can greatly affect the environments surrounding the compact object. In supe…
Pulse Phase Spectroscopy of A 0535+26 during its 1994 giant outburst observed with OSSE
M. Maisack, J. E. Grove, E. Kendziorra +3
We present pulse phase spectroscopy of A 0535+26 in the energy range 35-200 keV from OSSE observations of its giant outburst in 1994. We discuss the phase dependence of the continu…
Multiple Cyclotron Lines in the Spectrum of 4U 0115+63
W. A. Heindl, W. Coburn, D. E. Gruber +5
We report phase resolved spectroscopy of the transient accreting pulsar, 4U0115+63. For the first time, more than two cylotron resonance scattering features are detected in the spe…
The cyclotron line energy in Her X-1: stable after the decay
R. Staubert, L. Ducci, L. Ji +6
We summarize the results of a dedicated effort between 2012 and 2019 to follow the evolution of the cyclotron line in Her~X-1 through repeated NuSTAR observations. The previously o…
A model for cyclotron resonance scattering features
G. Schönherr, J. Wilms, P. Kretschmar +5
(abbreviated version of the abstract) We study the physics of cyclotron line formation in the high-energy spectra of accreting X-ray pulsars using Monte Carlo methods, assuming tha…
Her X-1: the positive cyclotron line energy / luminosity correlation
D. Vasco, D. Klochkov, R. Staubert
Studies of some bright, super-Eddington transient pulsars show a negative correlation between the energy of the cyclotron resonance scattering feature (CRSF) and the bolometric lum…
Simultaneous observations of the quasar 3C 273 with INTEGRAL, XMM-Newton and RXTE
T. J. -L. Courvoisier, V. Beckmann, G. Bourban +15
INTEGRAL has observed the bright quasar 3C 273 on 3 epochs in January 2003 as one of the first observations of the open programme. The observation on January 5 was simultaneous wit…
Magnetic Fields of Accreting X-Ray Pulsars with the Rossi X-Ray Timing Explorer
W. Coburn, W. A. Heindl, R. E. Rothschild +5
Using a consistent set of models, we parameterized the X-ray spectra of all accreting pulsars in the Rossi X-ray Timing Explorer database which exhibit Cyclotron Resonance Scatteri…
Accretion disk wind of Hercules X-1 during the Short High state
P. Kosec, E. Kara, A. C. Fabian +5
Hercules X-1 is a nearly edge-on X-ray binary with a warped, precessing accretion disk, which manifests through a 35-day cycle of alternating High and Low flux states. This disk pr…
The long stare at Hercules X-1 -- I. Emission lines from the outer disk, the magnetosphere boundary and the accretion curtain
P. Kosec, E. Kara, A. C. Fabian +11
Hercules X-1 is a nearly edge-on accreting X-ray pulsar with a warped accretion disk, precessing with a period of about 35 days. The disk precession allows for unique and changing…
A 0535+26 in outburst: magnetospheric instabilities and accretion geometry
I. Caballero, U. Kraus, K. Postnov +4
The Be/X-ray binary A 0535+26 showed a normal (type I) outburst in August/September 2005, which reached a maximum X-ray flux of 400mCrab in the 5-100keV range. The outburst was obs…
Temporal Evolution of X-ray Lags in Cygnus X-1
K. Pottschmidt, J. Wilms, M. A. Nowak +3
We present the long term evolution of the frequency-dependent X-ray time lags of the black hole candidate Cygnus X-1 as measured in 1996 and 1998 with the Rossi X-ray Timing Explor…
Pulse-to-pulse variability of bright accreting pulsars
D. Klochkov, A. Santangelo, R. Staubert +1
In addition to coherent pulsation, many accreting neutron stars exhibit flaring activity and strong aperiodic variability on time scales similar to or shorter than their pulsation…
The 1999 Hercules X-1 Anomalous Low State
W. Coburn, W. A. Heindl, J. Wilms +8
A failed main-on in the 35d cycle of Her X-1 was observed with the Rossi X-Ray Timing Explorer (RXTE) on 1999 April 26. Exceptions to the normal 35d cycle have been seen only twice…
A Suzaku View of Cyclotron Line Sources and Candidates
K. Pottschmidt, S. Suchy, E. Rivers +20
Seventeen accreting neutron star pulsars, mostly high mass X-ray binaries with half of them Be-type transients, are known to exhibit Cyclotron Resonance Scattering Features (CRSFs)…
Long Term Variability of Cyg X-1 I. X-ray spectral-temporal correlations in the hard state
K. Pottschmidt, J. Wilms, M. A. Nowak +6
We present the long term evolution of the timing properties of the black hole candidate Cygnus X-1 in the 0.002-128 Hz frequency range as monitored from 1998 to 2001 with the RXTE.…
The giant outburst of EXO 2030+375 II: Broadband spectroscopy and evolution
R. Ballhausen, P. Thalhammer, P. Pradhan +13
In 2021, the high-mass X-ray binary EXO 2030+375 underwent a giant X-ray outburst, the first since 2006, that reached a peak flux of (3-50\,keV). The go…
Distances to Accreting X-ray pulsars: impact of the Gaia DR2
S. Treuz, V. Doroshenko, A. Santangelo +1
A well constrained estimate of the distance remains one of the main factors to properly interpret the observations of accreting X-ray pulsars. Since these objects are typically wel…
The 35-day cycle in Her X-1 as observational appearance of freely precessing neutron star and forcedly precessing accretion disk
N. A. Ketsaris, M. Kuster, K. A. Postnov +4
A careful analysis of X-ray light curves and pulse profiles of Her X-1 obtained over more than 20 years strongly evidences for free precession of a magnetized neutron star with rot…
Finding a 24-day orbital period for the X-ray binary 1A 1118-616
R. Staubert, K. Pottschmidt, V. Doroshenko +4
We report the first determination of the binary period and orbital ephemeris of the Be X-ray binary containing the pulsar 1A 1118-616 (35 years after the discovery of the source).…
GRO J1008-57: an (almost) predictable transient X-ray binary
M. Kühnel, S. Müller, I. Kreykenbohm +13
A study of archival RXTE, Swift, and Suzaku pointed observations of the transient high mass X-ray binary GRO J1008-57 is presented. A new orbital ephemeris based on pulse arrival t…
Pulse-amplitude-resolved spectroscopy of bright accreting pulsars: indication of two accretion regimes
D. Klochkov, R. Staubert, A. Santangelo +2
Context: In addition to coherent pulsation, many accreting neutron stars exhibit flaring activity and strong aperiodic variability on time scales comparable to or shorter than thei…
Modeling of 35-day superorbital cycle of and light curves of IMXB HZ Her/Her X-1
D. A. Kolesnikov, N. I. Shakura, K. A. Postnov +13
The X-ray binary Her X-1 consists of an accreting neutron star and the optical component HZ Her. The 35-day X-ray superorbital variability of this system is known since its discove…
Two ~35 day clocks in Her X-1: evidence for neutron star free precession
R. Staubert, D. Klochkov, K. Postnov +3
We present evidence for the existence of two ~35 day clocks in the Her X-1/HZ Her binary system. ~35 day modulations are observed 1) in the Turn-On cycles with two on- and two off-…
X-ray Timing Analysis of Six Pulsars Using ESA's XMM-Newton Observatory
A. Martin-Carrillo, M. Kirsch, E. Kendziorra +1
We present results of a timing analysis of various isolated pulsars using ESA's \emph{XMM-Newton} observatory. Isolated pulsars are useful for calibration purposes because of their…
INTEGRAL observation of hard X-ray variability of the TeV binary LS5039 / RX J1826.2-1450
A. D. Hoffmann, D. Klochkov, A. Santangelo +4
LS 5039/RX J1826.2-1450 is one of the few High Mass X-ray binary systems from which radio and high energy TeV emission has been observed. Moreover, variability of the TeV emission…
Observation of V0332+53 over the 2004/2005 outburst with Integral
I. Kreykenbohm, N. Mowlavi, K. Pottschmidt +8
We present the spectral and temporal analysis of the 2004/2005 outburst of the transient X-ray pulsar V0332+53 as observed with Integral. After the discovery of the third cyclotron…
Inversion of the decay of the cyclotron line energy in Her X-1
R. Staubert, D. Klochkov, F. Fürst +3
Recent observations of Her X-1 with NuSTAR and INTEGRAL in 2016 have provided evidence that the 20-year decay of the cyclotron line energy found between 1996 and 2015 has ended and…
Analyzing short-term X-ray variability of Cygnus X-1 with Linear State Space Models
K. Pottschmidt, M. Koenig, J. Wilms +1
Cyg X-1 exhibits irregular X-ray variability on all measured timescales. The usually applied shot noise models describe the typical short-term behavior of this source by superposit…
Insight-HXMT firm detection of the highest energy fundamental cyclotron resonance scattering feature in the spectrum of GRO J1008-57
M. Y. Ge, L. Ji, S. N. Zhang +118
We report on the observation of the accreting pulsar GRO J1008-57 performed by Insight-HXMT at the peak of the source's 2017 outburst. Pulsations are detected with a spin period of…
Monitoring the Short-Term Variability of Cyg X-1: Spectra and Timing
K. Pottschmidt, J. Wilms, R. Staubert +4
We present first results from the spectral and temporal analysis of an RXTE monitoring campaign of the black hole candidate Cygnus X-1 in 1999. The timing properties of this hard s…
Quasi-periodic flares in EXO 2030+375 observed with INTEGRAL
D. Klochkov, C. Ferrigno, A. Santangelo +5
Context: Episodic flaring activity is a common feature of X-ray pulsars in HMXBs. In some Be/X-ray binaries flares were observed in quiescence or prior to outbursts. EXO 2030+375 i…
Probing the outer edge of an accretion disk: A Her X-1 turn-on observed with RXTE
M. Kuster, J. Wilms, R. Staubert +4
We present the analysis of Rossi X-ray Timing Explorer (RXTE) observations of the turn-on phase of a 35 day cycle of the X-ray binary Her X-1. During the early phases of the turn-o…
Confirmation of Two Cyclotron Lines in Vela X-1
I. Kreykenbohm, W. Coburn, J. Wilms +4
We present pulse phase-resolved X-ray spectra of the high mass X-ray binary Vela X-1 using the Rossi X-ray Timing Explorer. We observed Vela X-1 in 1998 and 2000 with a total obser…
Future X-ray timing missions
D. Barret, M. van der Klis, G. K. Skinner +2
Thanks to the Rossi X-ray Timing Explorer (RXTE), it is now widely recognized that fast X-ray timing can be used to probe strong gravity fields around collapsed objects and constra…
Episodic Random Accretion and the Cosmological Evolution of Supermassive Black Hole Spins
J. -M. Wang, C. Hu, Y. -R. Li +7
The growth of supermassive black holes (BHs) located at the centers of their host galaxies comes mainly from accretion of gas, but how to fuel them remains an outstanding unsolved…
SRGA J124404.1-632232/SRGU J124403.8-632231: a new X-ray pulsar discovered in the all-sky survey by SRG
V. Doroshenko, R. Staubert, C. Maitra +12
Ongoing all-sky surveys by the the eROSITA and the Mikhail Pavlinsky ART-XC telescopes on-board the Spectrum Roentgen Gamma (SRG) mission have already revealed over a million of X-…
Peculiar outburst of A 0535+26 observed with INTEGRAL, RXTE and Suzaku
I. Caballero, K. Pottschmidt, L. Barragan +17
A normal outburst of the Be/X-ray binary system A0535+26 has taken place in August 2009. It is the fourth in a series of normal outbursts that have occured around the periastron pa…
Continued decay in the cyclotron line energy in Hercules X-1
R. Staubert, D. Klochkov, V. Vybornov +2
The centroid energy Ecyc of the cyclotron line in the spectrum of the binary X-ray pulsar Her X-1 had been found to decrease with time on a time scale of a few tens of years - surp…
The broad iron Kalpha line of Cygnus X-1 as seen by XMM-Newton in the EPIC-pn modified timing mode
R. Duro, T. Dauser, J. Wilms +7
We present the analysis of the broadened, flourescent iron Kalpha line in simultaneous XMM-Newton and RXTE data from the black hole Cygnus X-1. The XMM-Newton data were taken in a…
RXTE Observations of Cygnus X-1: Broad-Band Spectra and High-Resolution Timing
K. Pottschmidt, J. Wilms, M. A. Nowak +3
We present results from a 20 ksec RXTE observation of the black hole candidate Cyg X-1. We apply self-consistent accretion disk corona models to these hard state data and show that…
A double-peaked outburst of A 0535+26 observed with INTEGRAL, RXTE, and Suzaku
I. Caballero, K. Pottschmidt, D. M. Marcu +18
The Be/X-ray binary A 0535+26 showed a normal (type I) outburst in August 2009. It is the fourth in a series of normal outbursts associated with the periastron, but is unusual by p…
RXTE observations of the 1A 1118-61 in an outburst, and the discovery of a cyclotron line
V. Doroshenko, S. Suchy, A. Santangelo +5
We present the analysis of RXTE monitoring data obtained during the January 2009 outburst of the hard X-ray transient 1A 1118-61. Using these observations the broadband (3.5-120 ke…
The multiwavelength variability of 3C 273
S. Soldi, M. Türler, S. Paltani +11
We present an update of 3C 273's database hosted by the ISDC, completed with data from radio to gamma-ray observations over the last 10 years. We use this large data set to study t…
INTEGRAL observations of the variability of OAO 1657-415
J. Barnstedt, R. Staubert, A. Santangelo +7
The Galactic Plane Scan (GPS) was one of the core observation programmes of the INTEGRAL satellite. The highly variable accreting pulsar OAO 1657-415 was frequently observed within…
Monitoring of pulse period in Her X-1 with Swift/BAT: evidence of mass ejection
D. Klochkov, R. Staubert, K. Postnov +2
Monitoring of pulse period variations in accreting binary pulsars is an important tool to study the interaction between the magnetosphere of the neutron star and the accretion disk…
INTEGRAL and Swift observations of EXO 2030+375 during a giant outburst
D. Klochkov, D. Horns, A. Santangelo +11
Aims: We investigate the X-ray spectral and timing properties of the high mass X-ray binary EXO 2030+375 observed during its June-September 2006 giant (type II) outburst. Methods:…
Long Term Variability of Cyg X-1, II. The rms-Flux Relation
T. Gleissner, J. Wilms, K. Pottschmidt +3
We study the long term evolution of the relationship between the root mean square (rms) variability and flux (the ``rms-flux relation'') for the black hole Cygnus X-1 as monitored…
Discovery of a flux-related change of the cyclotron line energy in Her X-1
R. Staubert, N. I. Shakura, K. Postnov +5
We present the results of ten years of repeated measurements of the Cyclotron Resonance Scattering Feature (CRSF) in the spectrum of the binary X-ray pulsar Her X-1 and report the…
The XMM-Newton view of the Crab
M. G. F. Kirsch, G. Schoenherr, E. Kendziorra +7
We discuss the current X-ray view of the Crab Nebula and Pulsar, summarising our analysis of observations of the source with the EPIC-pn camera on board the XMM-Newton observatory.…
Study of the cyclotron feature in MXB 0656-072
V. A. McBride, J. Wilms, M. J. Coe +7
We have monitored a Type II outburst of the Be/X-ray binary MXB 0656-072 in a series of pointed RXTE observations during October through December 2003. The source spectrum shows a…
Constraining the Number Density of the Accretion Disk Wind in Hercules X-1 Using its Ionization Response to X-ray Pulsations
P. Kosec, D. Rogantini, E. Kara +6
X-ray binaries are known to launch powerful accretion disk winds that can have significant impact on the binary systems and their surroundings. To quantify the impact and determine…
OSSE Observations of the Radio Quiet Quasar PG 1416-129
R. Staubert, M. Maisack
We report the detection of the bright radio quiet quasar PG 1416-129 by the OSSE instrument on the Compton Gamma Ray Observatory (CGRO). This object had the hardest spectral index…
Short term X-ray rms variability of Cyg X-1
T. Gleissner, J. Wilms, K. Pottschmidt +3
A linear dependence of the amplitude of broadband noise variability on flux for GBHC and AGN has been recently shown by Uttley & McHardy (2001). We present the long term evolution…
Luminosity dependence of the cyclotron line energy in 1A 0535+262 observed by Insight-HXMT during 2020 giant outburst
L. D. Kong, S. Zhang, L. Ji +11
We report on a detailed spectral analysis of the transient X-ray pulsar 1A~0535+262, which underwent the brightest giant outburst ever recorded for this source from November to Dec…
The relative and absolute timing accuracy of the EPIC-pn camera on XMM-Newton, from X-ray pulsations of the Crab and other pulsars
A. Martin-Carrillo, M. G. F. Kirsch, I. Caballero +13
Reliable timing calibration is essential for the accurate comparison of XMM-Newton light curves with those from other observatories, to ultimately use them to derive precise physic…
Formation of phase lags at the cyclotron energies in the pulse profiles of magnetized, accreting neutron stars
G. Schönherr, F. -W. Schwarm, S. Falkner +13
Context: Accretion-powered X-ray pulsars show highly energy-dependent and complex pulse-profile morphologies. Significant deviations from the average pulse profile can appear, in p…
2003--2005 INTEGRAL and XMM-Newton observations of 3C 273
M. Chernyakova, A. Neronov, T. J. -L. Courvoisier +9
The aim of this paper is to study the evolution of the broadband spectrum of one of the brightest and nearest quasars 3C 273. We analyze the data obtained during quasi-simultaneous…
The pre-outburst flare of the A 0535+26 August/September 2005 outburst
I. Caballero, A. Santangelo, P. Kretschmar +11
We study the spectral and temporal behavior of the High Mass X-ray Binary A 0535+26 during a `pre-outburst flare' which took place ~5 d before the peak of a normal (type I) outburs…
Short-Term Radio-X-ray Correlations of Cygnus X-1
T. Gleissner, J. Wilms, G. G. Pooley +6
We analyze simultaneous radio-X-ray data of Cygnus X-1 from the Ryle telescope (RT) and RXTE over more than 4 a. We show that apparent correlations on short time scales in the ligh…
The giant outburst of EXO 2030+375 I: Spectral and pulse profile evolution
P. Thalhammer, R. Ballhausen, E. Sokolova-Lapa +12
The Be X-ray binary EXO 2030+375 went through its third recorded giant outburst from June 2021 to early 2022. We present the results of both spectral and timing analysis based on N…
Constant cyclotron line energy in Hercules X-1 -- Joint Insight-HXMT and NuSTAR observations
G. C. Xiao, L. Ji, R. Staubert +108
The long-term evolution of the centroid energy of the CRSF in Her X-1 is still a mystery. We report a new measurement from a campaign between {\sl Insight}-HXMT and {\sl NuSTAR} pe…
Spectral Formation in Accreting X-Ray Pulsars: Bimodal Variation of the Cyclotron Energy with Luminosity
P. A. Becker, D. Klochkov, G. Schonherr +7
Accretion-powered X-ray pulsars exhibit significant variability of the Cyclotron Resonance Scattering Feature (CRSF) centroid energy on pulse-to-pulse timescales, and also on much…
Properties of the X-ray pulsar GX 301-2 in hard X-rays
V. Borkus, A. Kaniovsky, R. Sunyaev +5
In 1993-1994 a series of observations of the X-ray pulsar GX 301-2 by HEXE onboard Mir-Kvant was made. A period of pulsations was measured (it varied between 675 and 678 s) and pul…
INTEGRAL observations of V0332+53 in outburst
I. Kreykenbohm, N. Mowlavi, N. Produit +9
We present the analysis of a 100ksec Integral(3-100kev) observation of the transient X-ray pulsar V0332+53 inoutburst. The source is pulsating at P=4.3751+/-0.0002s with a clear do…
Giant outburst of EXO 2030+375: pulse-phase resolved analysis of INTEGRAL data
D. Klochkov, A. Santangelo, R. Staubert +1
In June-September 2006 the Be/X-ray binary EXO 2030+375 experienced the second giant outburst since its discovery. The source was shown to have a complicated pulse-averaged X-ray s…
Pulse Period History and Phase Resolved Spectra of 1A 0535+262
I. Caballero, P. Kretschmar, A. Santangelo +3
The Be/X-ray binary 1A 0535+262 was discovered in 1975 during a giant outburst. Afterwards it has shown periods of quiescence (flux below 10 mCrab), normal outbursts (10 mCrab-1Cra…
Evolution of spectral parameters during a pre-eclipse dip of Her X-1
B. Stelzer, J. Wilms, R. Staubert +2
We report on a pre-eclipse dip of the X-ray binary Her X-1 observed by the Rossi X-ray Timing Explorer (RXTE) in July 1996. We present the evolution of the spectral parameters in t…
RXTE Observations of LMC X-1 and LMC X-3
J. Wilms, M. A. Nowak, J. B. Dove +4
Of all known persistent stellar-mass black hole candidates, only LMC X-1 and LMC X-3 consistently show spectra that are dominated by a soft, thermal component. We present results f…
Vela X-1 as seen by RXTE
I. Kreykenbohm, P. Kretschmar, J. Wilms +5
We present results from four observations of the accreting X-ray pulsar Vela X-1 with RXTE in 1996 February. The light curves show strong pulse to pulse variations, while the avera…
The appearance of magnetospheric instability in flaring activity at the onset of X-ray outbursts in A0535+26
K. Postnov, R. Staubert, A. Santangelo +3
We argue that X-ray flaring variability observed in the transient X-ray pulsar A 0535+26 is due to low-mode magnetospheric instability. This instability develops at the onset of ac…
Cyclotron lines in highly magnetized neutron stars
R. Staubert, J. Trümper, E. Kendziorra +10
Cyclotron lines, also called cyclotron resonant scattering features (CRSF) are spectral features, generally appearing in absorption, in the X-ray spectra of objects containing high…
INTEGRAL broadband spectroscopy of Vela X-1
P. Kretschmar, R. Staubert, I. Kreykenbohm +11
The wind-accreting X-ray binary pulsar and cyclotron line source Vela X-1 has been observed extensively during INTEGRAL Core Program observations of the Vela region in June-July an…
Observation of the Anomalous X-Ray Pulsar 4U 0142+61
E. Goehler, J. Wilms, R. Staubert
We present results of an observation of the anomalous X-ray pulsar 4U 0142+61 with the EPIC cameras on XMM-Newton performed on 2003 January 24. The pulse phase averaged spectrum ca…
Timing and Spectroscopy of Accreting X-ray Pulsars: the State of Cyclotron Line Studies
W. A. Heindl, R. E. Rothschild, W. Coburn +4
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 poi…
Highly structured wind in Vela X-1
I. Kreykenbohm, J. Wilms, P. Kretschmar +6
We present an in-depth analysis of the spectral and temporal behavior of a long almost uninterrupted INTEGRAL observation of Vela X-1 in Nov/Dec 2003. In addition to an already hig…
Analyzing X-ray variability by State Space Models
M. König, J. Timmer, R. Staubert
In recent years, autoregressive models have had a profound impact on the description of astronomical time series as the observation of a stochastic process. These methods have adva…
A Her X-1 Turn-On: Using the pulse profile to probe the outer edge of an accretion disk
M. Kuster, J. Wilms, R. Staubert +5
The X-ray binary pulsar Her X-1 shows a wide variety of long and short term variabilities in the X-ray light curve. The 35 d variability of the source is interpreted as the influen…
Observational evidence for a changing tilt of the accretion disk with respect to the orbital plane in Her X-1 over its 35 day cycle
D. Klochkov, N. Shakura, K. Postnov +3
Analysis and interpretation of the Her X-1 X-ray light curve obtained with the ASM onbord RXTE over the period 1996 February to 2004 September is presented. We report that the feat…