W. Pietsch

Max Planck Institute for Extraterrestrial Physics, Arching, Bavaria, Germany

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Publications (570)989.49 Total impact

  • R. Sturm, W. Pietsch, J. Greiner, F. Haberl
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    ABSTRACT: Swift J004327.6+410452 was found as a ULX candidate in M31 (ATel #5743). We report on an on-axis Swift follow-up observation (ObsID 00033088001), performed on 2014-01-09 between 16:03 and 18:51 UT.
    12/2013;
  • R. Sturm, W. Pietsch, J. Greiner, F. Haberl
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    ABSTRACT: In recent monitoring observations of the M31 centre with the Swift satellite, we found an X-ray transient at RA=00:43:27.7 Dec=+41:04:53 (J2000, ePOS=3.6", 90% confidence), named Swift J004327.6+410452.
    12/2013;
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    ABSTRACT: [Abridged] Classical novae (CNe) represent the major class of supersoft X-ray sources (SSSs) in the central region of our neighbouring galaxy M31. We performed a dedicated monitoring of the M31 central region, aimed to detect SSS counterparts of CNe, with XMM-Newton and Chandra between Nov and Mar of the years 2009/10, 2010/11 and 2011/12. In total we detected 24 novae in X-rays. Seven of these sources were known from previous observations, including the M31 nova with the longest SSS phase, M31N~1996-08b, which was found to fade below our X-ray detection limit 13.8 yr after outburst. Of the new discoveries several novae exhibit significant variability in their short-term X-ray light curves with one object showing a suspected period of about 1.3 h. We studied the SSS state of the most recent outburst of a recurrent nova which had previously shown the shortest time ever observed between two outbursts (about 5 yr). The total number of M31 novae with X-ray counterpart was increased to 79 and we subjected this extended catalogue to detailed statistical studies. Four previously indicated correlations between optical and X-ray parameters could be confirmed and improved. We found indications that the multi-dimensional parameter space of nova properties might be dominated by a single physical parameter. We discuss evidence for a different X-ray behaviour of novae in the M31 bulge and disk. Exploration of the multi-wavelength parameter space of optical and X-ray measurements is shown to be a powerful tool for examining properties of extragalactic nova populations. While there are hints that the different stellar populations of M31 (bulge vs disk) produce dissimilar nova outbursts, there is also growing evidence that the overall behaviour of an average nova might be understood in surprisingly simple terms.
    12/2013;
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    ABSTRACT: We report optical spectroscopy and photometry of the recent M31 nova candidate M31N 2013-10h (= Swift J004304.9+411630 = TCP J00430483+4116306) discovered as Swift UVOT transient (ATel #5528). Koichi Nishiyama, Kurume and Fujio Kabashima, Miyaki (CBAT, 2013 10 31.4963) have confirmed the transient in the optical as 17.9 mag source in unfiltered CCD frames (on Oct. 29.571 UT they have reported only an upper limit).
    The Astronomer's Telegram. 11/2013;
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    ABSTRACT: In recent monitoring observations of the M31 centre with the Swift satellite, we find an X-ray transient at RA=00:42:57.0 Dec=+41:18:42 (J2000, ePOS=4.26", 90% confidence) that is likely associated with the X-ray binary candidate XMMM31 J004256.7+411843.
    The Astronomer's Telegram. 11/2013;
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    ABSTRACT: Aims: We present a detailed multi-wavelength study of four new supernova remnants (SNRs) in the Large Magellanic Cloud (LMC). The objects were identified as SNR candidates in X-ray observations performed during the survey of the LMC with XMM-Newton. Methods: Data obained with XMM-Newton are used to investigate the morphological and spectral features of the remnants in X-rays. We measure the plasma conditions, look for supernova (SN) ejecta emission, and constrain some of the SNR properties (e.g. age and ambient density). We supplement the X-ray data with optical, infrared, and radio-continuum archival observations, which allow us to understand the conditions resulting in the current appearance of the remnants. Based on the spatially-resolved star formation history (SFH) of the LMC together with the X-ray spectra, we attempt to type the supernovae that created the remnants. Results: We confirm all four objects as SNRs, to which we assign the names MCSNR J0508-6830, MCSNR J0511-6759, MCSNR J0514-6840, and MCSNR J0517-6759. In the first two remnants, an X-ray bright plasma is surrounded by very faint [S II] emission. The emission from the central plasma is dominated by Fe L-shell lines, and the derived iron abundance is greatly in excess of solar. This establishes their type Ia (i.e. thermonuclear) SN origin. They appear to be more evolved versions of other Magellanic Cloud iron-rich SNRs which are centrally-peaked in X-rays. From the two other remnants (MCSNR J0514-6840 and MCSNR J0517-6759), we do not see ejecta emission. At all wavelengths at which they are detected, the local environment plays a key role in their observational appearance. We present evidence that MCSNR J0517-6759 is close to and interacting with a molecular cloud, suggesting a massive progenitor.
    Astronomy and Astrophysics 10/2013; · 5.08 Impact Factor
  • R. Sturm, F. Haberl, W. Pietsch, J. Greiner
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    ABSTRACT: We report the discovery of a UV-transient (Swift J004304.9+411630) in a monitoring observation (ObsID 00032702034) of the central region of the Andromeda Galaxy (M 31) with the Ultra-Violet/Optical Telescope (UVOT) on board the Swift satellite. The transient is visible in the last two exposures, but not in the first two exposures, thus constraining the appearance between 2013-10-30.07 UT and 2013-10-30.28 UT.
    The Astronomer's Telegram. 10/2013;
  • åp. 10/2013; 558:A101.
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    ABSTRACT: We observed the newly discovered X-ray source Swift J053041.9-665426 in the X-ray and optical regime to confirm its proposed nature as a high mass X-ray binary. We obtained XMM-Newton and Swift X-ray data, along with optical observations with the ESO Faint Object Spectrograph, to investigate the spectral and temporal characteristics of Swift J053041.9-665426. The XMM-Newton data show coherent X-ray pulsations with a period of 28.77521(10) s (1 sigma). The X-ray spectrum can be modelled by an absorbed power law with photon index within the range 0.76 to 0.87. The addition of a black body component increases the quality of the fit but also leads to strong dependences of the photon index, black-body temperature and absorption column density. We identified the only optical counterpart within the error circle of XMM-Newton at an angular distance of ~0.8 arcsec, which is 2MASS J05304215-6654303. We performed optical spectroscopy from which we classify the companion as a B0-1.5Ve star. The X-ray pulsations and long-term variability, as well as the properties of the optical counterpart, confirm that Swift J053041.9-665426 is a new Be/X-ray binary pulsar in the Large Magellanic Cloud.
    Astronomy and Astrophysics 09/2013; · 5.08 Impact Factor
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    ABSTRACT: We report the discovery of a UV-transient (Swift J00431492+4119130) in a monitoring observation of the central region of the Andromeda Galaxy (M 31) with the Ultra-violet/Optical Telescope (UVOT) on board the Swift satellite (ObsID 00035336120, starting 2013-09-11.01 UT). The source is located at RA 00h 43m 14.93s, Dec +41d 19' 13.0" (J2000, ePos=0.5", 90% confidence level). Light curve information for filters uvw1 (central wavelength: 260 nm) and uvm2 (225 nm) is given in the table below (Vega system, 1σ statistical uncertainties).
    The Astronomer's Telegram. 09/2013;
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    ABSTRACT: The XMM-Newton survey of the Small Magellanic Cloud (SMC) revealed 3053 X-ray sources with the majority expected to be active galactic nuclei (AGN) behind the SMC. However, the high stellar density in this field often does not allow assigning unique optical counterparts and hinders source classification. On the other hand, the association of X-ray point sources with radio emission can be used to select background AGN with high confidence, and to constrain other object classes like pulsar wind nebula. To classify X-ray and radio sources, we use clear correlations of X-ray sources found in the XMM-Newton survey with radio-continuum sources detected with ATCA and MOST. Deep radio-continuum images were searched for correlations with X-ray sources of the XMM-Newton SMC-survey point-source catalogue as well as galaxy clusters seen with extended X-ray emission. Eighty eight discrete radio sources were found in common with the X-ray point-source catalogue in addition to six correlations with extended X-ray sources. One source is identified as a Galactic star and eight as galaxies. Eight radio sources likely originate in AGN that are associated with clusters of galaxies seen in X-rays. One source is a PWN candidate. We obtain 43 new candidates for background sources located behind the SMC. A total of 24 X-ray sources show jet-like radio structures.
    08/2013;
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    ABSTRACT: Local-Group galaxies provide access to samples of X-ray source populations of whole galaxies. The XMM-Newton survey of the Small Magellanic Cloud (SMC) completely covers the bar and eastern wing with a 5.6 deg^2 area in the (0.2-12.0) keV band. To characterise the X-ray sources in the SMC field, we created a catalogue of point sources and sources with moderate extent. Sources with high extent (>40") have been presented in a companion paper. We searched for point sources in the EPIC images using sliding-box and maximum-likelihood techniques and classified the sources using hardness ratios, X-ray variability, and their multi-wavelength properties. The catalogue comprises 3053 unique X-ray sources with a median position uncertainty of 1.3" down to a flux limit for point sources of ~10^-14 erg cm^-2 s^-1 in the (0.2-4.5) keV band, corresponding to 5x10^33 erg s^-1 for sources in the SMC. We discuss statistical properties, like the spatial distribution, X-ray colour diagrams, luminosity functions, and time variability. We identified 49 SMC high-mass X-ray binaries (HMXB), four super-soft X-ray sources (SSS), 34 foreground stars, and 72 active galactic nuclei (AGN) behind the SMC. In addition, we found candidates for SMC HMXBs (45) and faint SSSs (8) as well as AGN (2092) and galaxy clusters (13). We present the most up-to-date catalogue of the X-ray source population in the SMC field. In particular, the known population of X-ray binaries is greatly increased. We find that the bright-end slope of the luminosity function of Be/X-ray binaries significantly deviates from the expected universal high-mass X-ray binary luminosity function.
    Astronomy and Astrophysics 07/2013; · 5.08 Impact Factor
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    ABSTRACT: The XMM-Newton survey of the Small Magellanic Cloud (SMC) yields a complete coverage of the bar and eastern wing in the 0.2-12.0keV band. This catalogue comprises 3053 unique X-ray point sources and sources with moderate extent that have been reduced from 5236 individual detections found in observations between April 2000 and April 2010. Sources have a median position uncertainty of 1.3" (1σ) and limiting fluxes down to ~1*10-14erg/s/cm2 in the 0.2-4.5keV band, corresponding to 5*1033erg/s for sources in the SMC. Sources have been classified using hardness ratios, X-ray variability, and their multi-wavelength properties. In addition to the main-field (5.58deg2) available outer fields have been included in the catalogue, yielding a total field area of 6.32deg2. X-ray sources with high extent (>40", e.g. supernova remnants and galaxy cluster) have been presented by Haberl et al. (2012, Cat. J/A+A/545/A128) (2 data files).
    VizieR Online Data Catalog. 07/2013;
  • L. Ducci, M. Sasaki, F. Haberl, W. Pietsch
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    ABSTRACT: Aims: We present the results obtained from the analysis of three XMM-Newton observations of M 83. The aims of the paper are studying the X-ray source populations in M 83 and calculating the X-ray luminosity functions of X-ray binaries for different regions of the galaxy. Methods: We detected 189 sources in the XMM-Newton field of view in the energy range of 0.2-12 keV. We constrained their nature by means of spectral analysis, hardness ratios, studies of the X-ray variability, and cross-correlations with catalogues in X-ray, optical, infrared, and radio wavelengths. Results: We identified and classified 12 background objects, five foreground stars, two X-ray binaries, one supernova remnant candidate, one super-soft source candidate and one ultra-luminous X-ray source. Among these sources, we classified for the first time three active galactic nuclei (AGN) candidates. We derived X-ray luminosity functions of the X-ray sources in M 83 in the 2-10 keV energy range, within and outside the D25 ellipse, correcting the total X-ray luminosity function for incompleteness and subtracting the AGN contribution. The X-ray luminosity function inside the D25 ellipse is consistent with that previously observed by Chandra. The Kolmogorov-Smirnov test shows that the X-ray luminosity function of the outer disc and the AGN luminosity distribution are uncorrelated with a probability of ~99.3%. We also found that the X-ray sources detected outside the D25 ellipse and the uniform spatial distribution of AGNs are spatially uncorrelated with a significance of 99.5%. We interpret these results as an indication that part of the observed X-ray sources are X-ray binaries in the outer disc of M 83. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.Appendix A is available in electronic form at http://www.aanda.orgAppendix B is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/553/A7
    Astronomy and Astrophysics 05/2013; · 5.08 Impact Factor
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    ABSTRACT: For all Chandra HRC-I observations a source catalogue was created and the energy flux of each source in each observation was derived. Fluxes were calculated assuming a generic power law spectrum and Galactic foreground absorption for each source. (5 data files).
    VizieR Online Data Catalog. 05/2013;
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    ABSTRACT: [Abridged] The central field of the Andromeda galaxy (M 31) has been monitored, using the Chandra HRC-I detector (about 0.1-10 keV energy range) from 2006 to 2012 with the main aim to detect X-rays from optical novae. We present a systematic analysis of all X-ray sources found in the 41 nova monitoring observations, along with 23 M 31 central field HRC-I observations available from the Chandra data archive starting in December 1999. Based on these observations, we studied the X-ray long-term variability of the source population and especially of X-ray binaries in M 31. We created a catalogue of sources, detected in the 64 available observations, which add up to a total exposure of about 1 Ms. We present a point-source catalogue, containing 318 X-ray sources with detailed long-term variability information, 28 of which are published for the first time. The spatial and temporal resolution of the catalogue allows us to classify 115 X-ray binary candidates showing high X-ray variability or even outbursts in addition to 14 globular cluster X-ray binary candidates showing no significant variability. The analysis may suggest, that outburst sources are less frequent in globular clusters than in the field of M 31. We detected 7 supernova remnants, one of which is a new candidate and in addition resolved the first X-rays from a known radio supernova remnant. Besides 33 known optical nova/X-ray source correlations, we also discovered one previously unknown super-soft X-ray outburst and several new nova candidates. The catalogue contains a large sample of detailed long-term X-ray light curves in the M 31 central field, which helps to understand the X-ray population of our neighbouring spiral galaxy M 31.
    Astronomy and Astrophysics 04/2013; · 5.08 Impact Factor
  • R. Sturm, F. Haberl, W. Pietsch, A. Udalski
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    ABSTRACT: Aims: To confirm faint Be/X-ray binary candidates from the XMM-Newton survey of the Small Magellanic Cloud, we searched for X-ray outbursts in archival ROSAT observations. We found that RX J0123.4-7321 was much brighter when detected with ROSAT than seen 16 years later by XMM-Newton. Methods: We analysed the ROSAT observations and the OGLE I-band light curve of the optical counterpart to investigate the nature of the system. Results: High long-term variability in the X-ray flux of a factor of ~150 was found between the ROSAT and XMM-Newton detections, indicating strong outburst activity during the ROSAT observations. The I-band light curve reveals long-term variability and regular outbursts with a period of (119.9 ± 2.5) days, indicating the orbital period of the binary system. Conclusions: The large X-ray flux variations and the properties of the optical counterpart confirm RX J0123.4-7321 as a new Be/X-ray binary in the wing of the Small Magellanic Cloud.
    Astronomy and Astrophysics 03/2013; · 5.08 Impact Factor
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    ABSTRACT: We report the discovery of LXP169, a new high-mass X-ray binary (XRB) in the LMC. The optical counterpart has been identified and appears to exhibit an eclipsing light curve. We performed follow-up observations to clarify the eclipsing nature of the system. Energy spectra and time series were extracted from two XMM-Newton observations to search for pulsations, characterise the spectrum, and measure spectral and timing changes. Long-term X-ray variability was studied using archival ROSAT data. The XMM positions were used to identify the optical counterpart. We obtained UV to NIR photometry to characterise the companion, along with its 4000 d long I-band light curve. We observed LXP169 with Swift at two predicted eclipse times. We found a spin period of 168.8 s that did not change between two XMM observations. The X-ray spectrum, well characterised by a power law, was harder when the source was brighter. The X-ray flux of LXP169 is found to be variable by a factor of at least 10. The counterpart is highly variable on short and long timescales, and its photometry is that of an early-type star with a NIR excess. This classifies the source as a BeXRB pulsar. We observed a transit in the UV, thereby confirming that the companion star itself is eclipsed. We give an ephemeris for the transit of MJD 56203.877 + N*24.329. We propose and discuss the scenario where the matter captured from the companion's equatorial disc creates an extended region of high density around the neutron star (NS), which partially eclipses the companion as the NS transits in front of it. This is most likely the first time the compact object in an XRB is observed to eclipse its companion star. LXP169 would be the first eclipsing BeXRB, and a wealth of important information might be gained from additional observations, such as a measure of the possible Be disc/orbital plane misalignment, or the mass of the NS.
    Astronomy and Astrophysics 02/2013; · 5.08 Impact Factor
  • W. Pietsch, F. Hofmann
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    ABSTRACT: We confirm an optical nova candidate, designated PNV J00424629+4113517 by the optical discoverers K. Nishiyama and F. Kabashima (Miyaki-Argenteus Observatory, Japan), as a bright source on three Swift UVOT UVW2 filter prediscovery images (central wavelength 192.8 nm, FWHM 65.7 nm) with about 815 s exposure (ObsID 00032702015) starting on 2013 Feb. 22.070, 22.137, and 22.204 UT with brightness increasing from magnitude 16.88± 0.05, 16.70± 0.05, to 16.41± 0.04, respectively.
    The Astronomer's Telegram. 02/2013;

Publication Stats

3k Citations
989.49 Total Impact Points

Institutions

  • 1970–2013
    • Max Planck Institute for Extraterrestrial Physics
      Arching, Bavaria, Germany
  • 2008
    • University of Washington Seattle
      Seattle, Washington, United States
  • 2005
    • University of Crete
      Retimo, Crete, Greece
  • 2000
    • University of Western Sydney
      Penrith, New South Wales, Australia
  • 1991–1997
    • University of Birmingham
      Birmingham, England, United Kingdom
    • CSU Mentor
      Long Beach, California, United States
  • 1992–1994
    • Space Research Institute
      Moskva, Moscow, Russia
  • 1975–1994
    • University of Tuebingen
      • Institute for Astronomy and Astrophysics
      Tübingen, Baden-Wuerttemberg, Germany
  • 1986–1993
    • Massachusetts Institute of Technology
      • Department of Physics
      Cambridge, MA, United States