F. Haberl

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

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Publications (477)1044.53 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: On MJD 56590-1 (2013 Oct 25-26) observations of the Magellanic Clouds by the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) observatory discovered a previously-unreported bright, flaring X-ray source. This source was initially given the identification IGR J00569-7226. Subsequent multi-wavelength observations identified the system as new Be/X-ray binary system in the Small Magellanic Cloud. Follow-up X-ray observations by Swift and XMM-Newton revealed an X-ray pulse period of 5.05s and that the system underwent regular occulation/eclipse behaviour every 17d. This is the first reported eclipsing Be/X-ray binary system in the SMC, and only the second such system known to date. Furthermore, the nature of the occultation makes it possible to use the neutron star to X-ray the circumstellar disk, thereby, for the first time, revealing direct observational evidence for its size and clumpy structure. Swift timing measurements allowed for the binary solution to be calculated from the Doppler shifted X-ray pulsations. This solution suggests this is a low eccentricity binary relative to others measured in the SMC. Finally it is interesting to note that the mass determined from this dynamical method for the Be star (approx 13 solar masses) is significantly different from that inferred from the spectroscopic classification of B0.2Ve (approx 16 solar masses) - an effect that has been noted for some other high mass X-ray binary (HMXB) systems.
    12/2014;
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    ABSTRACT: Aims: We present a study of the superbubble (SB) 30 Dor C and the newly identified MCSNR J0536-6913 in the LMC. Methods: All available XMM-Newton data (exposure times of 420 ks EPIC-pn, 556 ks EPIC-MOS1, 614 ks EPIC-MOS2) were used to characterise the thermal X-ray emission in the region. An analysis of the non-thermal X-rays is also presented and discussed in the context of emission mechanisms previously suggested in the literature. These data are supplemented by X-ray data from Chandra, optical data from the MCELS, and radio data from ATCA and MOST. Results: The brightest thermal emission was found to be associated with a new supernova remnant, MCSNR J0536-6913. X-ray spectral analysis of MCSNR J0536-6913 suggested an ejecta-dominated remnant with lines of O, Ne, Mg, and Si, and a total 0.3-10 keV luminosity of ~8E+34 erg/s. Based on derived ejecta abundance ratios, we determined the mass of the stellar progenitor to be either ~18 M_sun or as high as >40 M_sun, though the spectral fits were subject to assumptions (e.g., uniform temperature and well-mixed ejecta). The thermal emission from the SB exhibited enrichment by alpha-process elements, evidence for a recent core-collapse SNR interaction with the SB shell. We detected non-thermal X-ray emission throughout 30 Dor C, with the brightest regions being highly correlated with the H-alpha and radio shells. We created a non-thermal spectral energy distribution for the north-eastern shell of 30 Dor C which was best-fit with an exponentially cut-off synchrotron model. Conclusions: Thermal X-ray emission from 30 Dor C is very complex, consisting of a large scale SB emission at the eastern shell wall with the brightest emission due to MCSNR J0536-6913. The fact that the non-thermal spectral energy distribution of the SB shell was observed to roll-off is further evidence that the non-thermal X-rays from 30 Dor C are synchrotron in origin.
    09/2014;
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    ABSTRACT: We identify a new candidate for a Be/X-ray binary in the XMM-Newton slew survey and archival Swift observations that is located in the transition region of the Wing of the Small Magellanic Cloud and the Magellanic Bridge. We investigated and classified this source with follow-up XMM-Newton and optical observations. We model the X-ray spectra and search for periodicities and variability in the X-ray observations and the OGLE I-band light curve. The optical counterpart has been classified spectroscopically, with data obtained at the SAAO 1.9 m telescope, and photometrically, with data obtained using GROND at the MPG 2.2 m telescope. The X-ray spectrum is typical of a high-mass X-ray binary with an accreting neutron star. We detect X-ray pulsations, which reveal a neutron-star spin period of P = (264.516+-0.014) s. The source likely shows a persistent X-ray luminosity of a few 10^35 erg/s and in addition type-I outbursts that indicate an orbital period of ~146 d. A periodicity of 0.867 d, found in the optical light curve, can be explained by non-radial pulsations of the Be star. We identify the optical counterpart and classify it as a B1-2II-IVe star. This confirms SXP 265 as a new Be/X-ray binary pulsar originating in the tidal structure between the Magellanic Clouds.
    Monthly Notices of the Royal Astronomical Society 08/2014; 444(4):3571-3580. · 4.90 Impact Factor
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    ABSTRACT: We observed RX J0520.5-6932 in the X-rays and studied the optical light curve of its counterpart to verify it as a Be/X-ray binary. We performed an XMM-Newton anticipated target of opportunity observation in January 2013 during an X-ray outburst of the source in order to search for pulsations and derive its spectral properties. We monitored the source with Swift to follow the evolution of the outburst and to look for further outbursts to verify the regular pattern seen in the optical light curve with a period of ~24.4 d. The XMM-Newton EPIC light curves show coherent X-ray pulsations with a period of 8.035331(15) s (1 sigma). The X-ray spectrum can be modelled by an absorbed power law with photon index of ~0.8, an additional black-body component with temperature of ~0.25 keV and an Fe K line. Phase-resolved X-ray spectroscopy reveals that the spectrum varies with pulse phase. We confirm the identification of the optical counterpart within the error circle of XMM-Newton at an angular distance of ~0.8 arcsec, which is an O9Ve star with known Halpha emission. By analyzing the combined data from three OGLE phases we derived an optical period of 24.43 d.The X-ray pulsations and long-term variability, as well as the properties of the optical counterpart, confirm that RX J0520.5-6932 is a Be/X-ray binary pulsar in the Large Magellanic Cloud. Based on the X-ray monitoring of the source we conclude that the event in January 2013 was a moderately bright type-I X-ray outburst, with a peak luminosity of 1.79e36 erg/s.
    Astronomy and Astrophysics 07/2014; 567. · 5.08 Impact Factor
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    ABSTRACT: We present new optical spectroscopy of 20 candidate counterparts of 17 X-ray sources in the direction of the M31 disc. By comparing the X-ray catalogue from the XMM-Newton survey of M31 with star catalogues from the Local Group Galaxy Survey, we chose counterpart candidates based on optical colour and X-ray hardness. We have discovered 17 counterpart candidates with spectra containing stellar features. Eight of these are early-type stars of O or B type in M31, with hard X-ray spectra, making them good HMXB candidates. Three of these eight exhibit emission lines, which we consider to be the strongest HMXB candidates. In addition, our spectra reveal two likely Galactic cataclysmic variables, one foreground M star, two probable LMXBs related to M31 globular clusters, one emission line region with an embedded Wolf-Rayet star, and one newly-discovered supernova remnant. Finally, two of the sources have stellar spectra with no features indicative of association with an X-ray source.
    Monthly Notices of the Royal Astronomical Society 06/2014; · 4.90 Impact Factor
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    ABSTRACT: We present new Australia Telescope Compact Array (ATCA) radio-continuum and XMM-Newton/Chandra X-ray Observatory (CXO) observations of the unusual supernova remnant HFPK 334 in the Small Magellanic Cloud (SMC). The remnant follows a shell type morphology in the radio-continuum and has a size of $\sim$20~pc at the SMC distance. The X-ray morphology is similar, however, we detect a prominent point source close to the center of the SNR exhibiting a spectrum with a best fit powerlaw with a photon index of $\Gamma = 2.7 \pm 0.5$. This central point source is most likely a background object and cannot be directly associated with the remnant. The high temperature, nonequilibrium conditions in the diffuse region suggest that this gas has been recently shocked and point toward a younger SNR with an age of $\lesssim 1800$ years. With an average radio spectral index of $\alpha=-0.59\pm0.09$ we find that an equipartition magnetic field for the remnant is $\sim$90~$\mu$G, a value typical of younger SNRs in low-density environments. Also, we report detection of scattered radio polarisation across the remnant at 20~cm, with a peak fractional polarisation level of 25$\pm$5\%.
    05/2014;
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    ABSTRACT: We present a detailed study of new Australia Telescope Compact Array (ATCA) and XMM-Newton observations of LHA 120-N 70 (hereafter N 70), a spherically shaped object in the Large Magellanic Cloud (LMC) classified as a superbubble (SB). Both archival and new observations were used to produce high quality radio-continuum, X-ray and optical images. The radio spectral index of N 70 is estimated to be $\alpha=-0.12\pm 0.06$ indicating that while a supernova or supernovae have occurred in the region at some time in the distant past, N70 is not the remnant of a single specific supernova. N70 exhibits limited polarisation with a maximum fractional polarisation of 9% in a small area of the north west limb. We estimate the size of N 70 to have a diameter of 104 pc ($\pm 1$ pc). The morphology of N 70 in X-rays closely follows that in radio and optical, with most X-ray emission confined within the bright shell seen at longer wavelengths. Purely thermal models adequately fit the soft X-ray spectrum which lacks harder emission (above 1 keV). We also examine the pressure output of N 70 where the values for the hot (PX) and warm (PHii) phase are consistent with other studied Hii regions. However, the dust-processed radiation pressure (PIR) is significantly smaller than in any other object studied in Lopez et al. (2013). N70 is a very complex region that is likely to have had multiple factors contributing to both the origin and evolution of the entire region.
    The Astronomical Journal 04/2014; 147(6). · 4.97 Impact Factor
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    ABSTRACT: The group of thermally emitting isolated neutron stars (INSs) known as the ``Magnificent Seven'' (M7) is unique among the various neutron star populations. Crustal heating by means of magnetic field decay and an evolutionary link with magnetars may explain why these objects rotate slower and have higher thermal luminosities and magnetic field intensities than standard pulsars of similar age. The third brightest INS, RX J1605.3+3249, is the only object amidst the seven still lacking a detected periodicity. We observed the source with the XMM-Newton Observatory for 60 ks aiming at unveiling the neutron star rotation rate and investigating its spectrum in detail. A periodic signal at P=3.387864(16) s, likely the neutron star spin period, is detected at the 4-sigma confidence level. The coherent combination of the new data with a past XMM-Newton EPIC-pn observation of the source constrains the pulsar spin-down rate at the 2-sigma confidence level, implying a dipolar magnetic field of B~7.4e13 G. If confirmed, RX J1605.3+3249 would be the neutron star with the highest dipolar field amongst the M7. The spectrum of the source shows evidence for a cool blackbody component, as well as for the presence of two broad absorption features. Furthermore, high-resolution spectroscopy with the RGS cameras confirms the presence of the narrow absorption feature at energy 0.57 keV in the co-added spectrum of the source, also seen in other thermally emitting isolated neutron stars. Phase-resolved spectroscopy, as well as a dedicated observing campaign aimed at determining a timing solution, will give invaluable constraints on the neutron star geometry and will allow one to confirm the high value of spin down, which would place the source closer to a magnetar than any other M7 INS.
    Astronomy and Astrophysics 01/2014; 563. · 5.08 Impact Factor
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    ABSTRACT: We present a detailed radio, X-ray and optical study of a newly discovered Large Magellanic Cloud (LMC) supernova remnant (SNR) which we denote MCSNR J0508-6902. Observations from the Australian Telescope Compact Array (ATCA) and the $\textit{XMM-Newton}$ X-ray observatory are complemented by deep H$\alpha$ images and Anglo Australian Telescope AAOmega spectroscopic data to study the SNR shell and its shock-ionisation. Archival data at other wavelengths are also examined. The remnant follows a filled-in shell type morphology in the radio-continuum and has a size of $\sim$74 pc $\times$ 57 pc at the LMC distance. The X-ray emission exhibits a faint soft shell morphology with Fe-rich gas in its interior $-$ indicative of a Type Ia origin. The remnant appears to be mostly dissipated at higher radio-continuum frequencies leaving only the south-eastern limb fully detectable while in the optical it is the western side of the SNR shell that is clearly detected. The best-fit temperature to the shell X-ray emission ($kT = 0.41^{+0.05}_{-0.06}$ keV) is consistent with other large LMC SNRs. We determined an O/Fe ratio of $<21$ and an Fe mass of 0.5-1.8$~M_{\odot}$ in the interior of the remnant, both of which are consistent with the Type Ia scenario. We find an equipartition magnetic field for the remnant of $\sim$28 $\mu$G, a value typical of older SNRs and consistent with other analyses which also infer an older remnant.
    01/2014; 439(1).
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    ABSTRACT: INTEGRAL observations of the Small Magellanic Cloud on 11 January 2014 detected a bright X-ray source in the Wing of the SMC which we identify as IGR J01217-7257. The best position determined from JEM-X is 01 21 40.6, -72 57 21.9 with an uncertainty of 1.5 arcmins. The IBIS flux was 0.92 +/- 0.16 counts/s. Near the centre of this error circle is a 14th magnitude star identified in OGLE IV as SMC732.03.3540 (position 01 21 40.6, -72 57 31).
    12/2013;
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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: We report on the evolution of the current X-ray outburst of the LMC Be/X-ray binary pulsar RX J0520.5-6932 (see ATel #5673) from our Swift/XRT monitoring. Since the start of the outburst (2013 Dec 28) the luminosity of the source has continued to rise to a maximum of 1.91×1038erg s-1 (0.3-10 keV band), which is close to or at the Eddington limit for a neutron star.
    12/2013;
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    ABSTRACT: INTEGRAL observations of the SMC on 11 January 2014 confirm a very bright X-ray detection of the source RX J0059.2-7138 = SXP2.76. Krimm et al (ATel #5756) report detecting the source with Swift/BAT 16 days earlier on 26 Dec 2013. The INTEGRAL JEM-X source position is fully consistent with the position of SXP2.76, but we note no sign of any brightening of the proposed optical counterpart to SXP2.76 in the OGLE IV data in the last month or so.
    12/2013;
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    ABSTRACT: A series of observations performed with Swift/XRT (Target ID 33042) in the SMC detected a variable X-ray source within the field of view. The source appeared in observations performed on and after 2014 Jan 06, while it remained undetected in the period 2013 Dec 13 - 24. The XRT J2000 position is RA = 01:07:45.00, DEC = -72:27:40.9, (90% error radius of 4.0"). This position matches [MCS2008] 206, detected with Chandra on 2006 Feb 10.
    12/2013;
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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;
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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: A combination of Swift/XRT and XMM-Newton observations over the last 30 days has detected a modulation in the X-ray flux at a period of 5.05s in the newly discovered Small Magellanic Cloud source IGR J00569-7226 (Coe et al ATel #5547, Kennea ATel #5553). This probable spin period, combined with the proposed orbital period of 17d (Schmidtke et al ATel #5557, Coe et al ATel #5631) puts this system on the edge of the Corbet diagram for Be/X-ray binary systems.
    The Astronomer's Telegram. 12/2013;
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    ABSTRACT: RX J0520.5-6932 is a recently confirmed Be/X-ray binary system in the LMC (see ATel #4748).
    The Astronomer's Telegram. 12/2013;
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    ABSTRACT: A combination of Swift/XRT and INTEGRAL observations over the last 30 days has detected a modulation in the X-ray flux at a period around 17d in the newly discovered Small Magellanic Cloud source IGR J00569-7226 (Coe et al ATel #5547, Kennea #5553). Such a period was reported by Schmitdke et al (ATel #5557) based upon the first year of OGLE II observations of the optical counterpart. On-going INTEGRAL & XMM observations of this object suggest this source is still undergoing a Type II outburst typical of Be/X-ray binary systems.
    The Astronomer's Telegram. 12/2013;
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    ABSTRACT: A series of observations performed with Swift/XRT (Target ID 33042) in the SMC detected a relatively bright X-ray source at the edge of the field of view. The source is consistent with XMMU J010429.4-723136. It is classified as a high-mass X-ray binary (HMXB) candidate in the XMM-Newton point-source catalogue of the SMC (Sturm et al.
    The Astronomer's Telegram. 12/2013;

Publication Stats

3k Citations
1,044.53 Total Impact Points

Institutions

  • 1994–2014
    • Max Planck Institute for Extraterrestrial Physics
      Arching, Bavaria, Germany
  • 2008
    • Milton Keynes College
      Milton Keynes, England, United Kingdom
  • 2005
    • University of Crete
      Retimo, Crete, Greece
  • 2000
    • Max Planck Institute of Physics
      München, Bavaria, Germany
    • University of Western Sydney
      Penrith, New South Wales, Australia
  • 1988–1989
    • Massachusetts Institute of Technology
      • Department of Physics
      Cambridge, Massachusetts, United States