R. Sturm

The XMM-Newton serendipitous survey - VII. The third XMM-Newton serendipitous source catalogue

© ESO, 2016.Context. Thanks to the large collecting area (3 × ∼1500 cm2 at 1.5 keV) and wide field of view (30′ across in full field mode) of the X-ray cameras on board the European Space Agency X-ray observatory XMM-Newton, each individual pointing can result in the detection of up to several hundred X-ray sources, most of which are newly discovered objects. Since XMM-Newton has now been in orbit for more than 15 yr, hundreds of thousands of sources have been detected. Aims. Recently, many improvements in the XMM-Newton data reduction algorithms have been made. These include enhanced source characterisation and reduced spurious source detections, refined astrometric precision of sources, greater net sensitivity for source detection, and the extraction of spectra and time series for fainter sources, both with better signal-to-noise. Thanks to these enhancements, the quality of the catalogue products has been much improved over earlier catalogues. Furthermore, almost 50% more observations are in the public domain compared to 2XMMi-DR3, allowing the XMM-Newton Survey Science Centre to produce a much larger and better quality X-ray source catalogue. Methods. The XMM-Newton Survey Science Centre has developed a pipeline to reduce the XMM-Newton data automatically. Using the latest version of this pipeline, along with better calibration, a new version of the catalogue has been produced, using XMM-Newton X-ray observations made public on or before 2013 December 31. Manual screening of all of the X-ray detections ensures the highest data quality. This catalogue is known as 3XMM. Results. In the latest release of the 3XMM catalogue, 3XMM-DR5, there are 565 962 X-ray detections comprising 396 910 unique X-ray sources. Spectra and lightcurves are provided for the 133 000 brightest sources. For all detections, the positions on the sky, a measure of the quality of the detection, and an evaluation of the X-ray variability is provided, along with the fluxes and count rates in 7 X-ray energy bands, the total 0.2-12 keV band counts, and four hardness ratios. With the aim of identifying the detections, a cross correlation with 228 catalogues of sources detected in all wavebands is also provided for each X-ray detection. Conclusions. 3XMM-DR5 is the largest X-ray source catalogue ever produced. Thanks to the large array of data products associated with each detection and each source, it is an excellent resource for finding new and extreme objects.

The XMM-Newton survey of the Small Magellanic Cloud ,,

Context. Although numerous archival XMM-Newton observations existed towards the Small Magellanic Cloud (SMC) before 2009, only a fraction of the whole galaxy had been covered. Aims. Between May 2009 and March 2010, we carried out an XMM-Newton survey of the SMC, to ensure a complete coverage of both its bar and wing. Thirty-three observations of 30 different fields with a total exposure of about one Ms filled the previously missing parts. Methods. We systematically processed all available SMC data from the European Photon Imaging Camera. After rejecting observations with very high background, we included 53 archival and the 33 survey observations. We produced images in five different energy bands. We applied astrometric boresight corrections using secure identifications of X-ray sources and combined all the images to produce a mosaic covering the main body of the SMC. Results. We present an overview of the XMM-Newton observations, describe their analysis, and summarise our first results, which will be presented in detail in follow-up papers. Here, we mainly focus on extended X-ray sources, such as supernova remnants (SNRs) and clusters of galaxies, that are seen in our X-ray images. Conclusions. Our XMM-Newton survey represents the deepest complete survey of the SMC in the 0.15−12.0 keV X-ray band. We propose three new SNRs that have low surface brightnesses of a few 10 −14 erg cm −2 s −1 arcmin −2 and large extents. In addition, several known remnants appear larger than previously measured at either X-rays or other wavelengths extending the size distribution of SMC SNRs to larger values.

SXP 1062, a young Be X-ray binary pulsar with long spin period - Implications for the neutron star birth spin

Context. The Small Magellanic Cloud (SMC) is ideally suited to investigating the recent star formation history from X-ray source population studies. It harbours a large number of Be/X-ray binaries (Be stars with an accreting neutron star as companion), and the supernova remnants can be easily resolved with imaging X-ray instruments. Aims. We search for new supernova remnants in the SMC and in particular for composite remnants with a central X-ray source. Methods. We study the morphology of newly found candidate supernova remnants using radio, optical and X-ray images and investigate their X-ray spectra. Results. Here we report on the discovery of the new supernova remnant around the recently discovered Be/X-ray binary pulsar CXO J012745.97−733256.5 = SXP 1062 in radio and X-ray images. The Be/X-ray binary system is found near the centre of the supernova remnant, which is located at the outer edge of the eastern wing of the SMC. The remnant is oxygen-rich, indicating that it developed from a type Ib event. From XMM-Newton observations we find that the neutron star with a spin period of 1062 s (the second longest known in the SMC) shows a very high average spin-down rate of 0.26 s per day over the observing period of 18 days. Conclusions. From the currently accepted models, our estimated age of around 10 000−25 000 years for the supernova remnant is not long enough to spin down the neutron star from a few 10 ms to its current value. Assuming an upper limit of 25 000 years for the age of the neutron star and the extreme case that the neutron star was spun down by the accretion torque that we have measured during the XMM-Newton observations since its birth, a lower limit of 0.5 s for the birth spin period is inferred. For more realistic, smaller long-term average accretion torques our results suggest that the neutron star was born with a correspondingly longer spin period. This implies that neutron stars in Be/X-ray binaries with long spin periods can be much younger than currently anticipated.

A new super-soft X-ray source in the Small Magellanic Cloud: Discovery of the first Be/white dwarf system in the SMC?

Context. The Small Magellanic Cloud (SMC) hosts a large number of Be/X-ray binaries, however no Be/white dwarf system is known so far, although population synthesis calculations predict that they might be more frequent than Be/neutron star systems. Aims. XMMU J010147.5-715550 was found as a new faint super-soft X-ray source (SSS) with a likely Be star optical counterpart. We investigate the nature of this system and search for further high-absorbed candidates in the SMC. Methods. We analysed the XMM-Newton X-ray spectrum and light curve, optical photometry, and the I-band OGLE III light curve. Results. The X-ray spectrum is well represented by black-body and white dwarf atmosphere models with highly model-dependent temperature between 20 and 100 eV. The likely optical counterpart AzV 281 showed low near infrared emission during X-ray activity, followed by a brightening in the I-band afterwards. We find further candidates for high-absorbed SSSs with a blue star as counterpart. Conclusions. We discuss XMMU J010147.5-715550 as the first candidate for a Be/white dwarf binary system in the SMC.

X-ray source variability study of the M 31 central field using Chandra HRC-I

[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.

Multi-frequency study of supernova remnants in the Large Magellanic Cloud - confirmation of the supernova remnant status of DEM L205

Context. The Large Magellanic Cloud (LMC) is an ideal target for the study of an unbiased and complete sample of supernova remnants (SNRs). We started an X-ray survey of the LMC with XMM-Newton, which, in combination with observations at other wavelengths, will allow us to discover and study remnants that are either even fainter or more evolved (or both) than previously known. Aims. We present new X-ray and radio data of the LMC SNR candidate DEM L205, obtained by XMM-Newton and ATCA, along with archival optical and infrared observations. Methods. We use data at various wavelengths to study this object and its complex neighbourhood, in particular in the context of the star formation activity, past and present, around the source. We analyse the X-ray spectrum to derive some remnant’s properties, such as age and explosion energy. Results. Supernova remnant features are detected at all observed wavelengths : soft and extended X-ray emission is observed, arising from a thermal plasma with a temperature kT between 0.2 keV and 0.3 keV. Optical line emission is characterised by an enhanced [S ii]-to-Hα ratio and a shell-like morphology, correlating with the X-ray emission. The source is not or only tentatively detected at near-infrared wavelengths (shorter than 10 μm), but there is a detection of arc-like emission at mid and far-infrared wavelengths (24 and 70 μm) that can be unambiguously associated with the remnant. We suggest that thermal emission from dust heated by stellar radiation and shock waves is the main contributor to the infrared emission. Finally, an extended and faint non-thermal radio emission correlates with the remnant at other wavelengths and we find a radio spectral index between −0.7 and −0.9, within the range for SNRs. The size of the remnant is∼79 × 64 pc and we estimate a dynamical age of about 35 000 years. Conclusions. We definitely confirm DEM L205 as a new SNR. This object ranks amongst the largest remnants known in the LMC. The numerous massive stars and the recent outburst in star formation around the source strongly suggest that a core-collapse supernova is the progenitor of this remnant.

Highly absorbed X-ray binaries in the Small Magellanic Cloud

Many of the high mass X-ray binaries (HMXRBs) discovered in recent years in our Galaxy are characterized by a high absorption, most likely intrinsic to the system, that can impede their detection at the softest X-ray energies. Exploiting the good coverage obtained with sensitive XMM-Newtonobservations, we have undertaken a search for highly absorbed X-ray sources in the Small Magellanic Cloud (SMC), which is known to contain a large number of HMXRBs. After a systematic analysis of 62 XMM-NewtonSMC observations, we obtained a sample of 30 sources with evidence of an equivalent hydrogen column density larger than 3×10 23 cm 2 . Five of these sources are clearly identified as HMXRBs, four being previously known (including three X-ray pulsars) and one, XMMU J005605.8-720012, being reported here for the first time. For the latter, we present optical spectroscopy confirming the asso ciation with a Be star in the SMC. The other sources in our sample have optical counterparts fainter than magnitude ∼16 in the V band, and many have possible NIR counterparts consistent with highly reddened early-type stars in the SMC. While their number is broadly consistent with the expected population of background highly absorbed active galactic nuclei, a few of them could be HMXRBs in which an early-type companion is severely reddened by local material.

IKT 16: a composite supernova remnant in the Small Magellanic Cloud

Aims. IKT 16 is an X-ray and radio-faint supernova remnant (SNR) in the Small Magellanic Cloud (SMC). A previous X-ray study of this SNR found a hard X-ray source near its centre. Using all available archival and proprietary XMM-Newtondata, alongside new multi-frequency radio-continuum surveys and optical observations at Hand forbidden (SII) and (OIII) lines, we aim to constrain the properties of the SNR and discover the nature of the hard source within. Methods. We combine XMM-Newtondatasets to produce the highest quality X-ray image of IKT 16 to date. We use this, in combina- tion with radio and optical images, to conduct a multi-wavelength morphological analysis of the remnant. We extract separate spectra from the SNR and the bright source near its centre, and conduct spectral fitting of both regions. Results. We find IKT 16 to have a radius of 37 �3 pc, with the bright source located 8�2 pc from the centre. This is the largest known SNR in the SMC. The large size of the remnant suggests it is likely in the Sedov-adiabatic phase of evolution. Using a Sedov model to fit the SNR spectrum, we find an electron temperature k T of 1: 03�0: 12 keV and an age of�14700 yr. The absorption found requires the remnant to be located deep within the SMC. The bright source is fit with a power law with index = 1: 58�0: 07, and is associated with diffuse radio emission extending towards the centre of the SNR. We argue that this source is likely to be the neutron star remnant of the supernova explosion, and infer its trans verse kick velocity to be 580�100 km s −1 . The X-ray and radio properties

The XMM–Newton survey of the Small Magellanic Cloud: XMMU J005011.2−730026 = SXP 214, a Be/X-ray binary pulsar★

In the course of the XMM―Newton survey of the Small Magellanic Cloud, a region to the east of the emission nebula N19 was observed in 2009 November. To search for new candidates for high-mass X-ray binaries, the EPIC-pn and EPIC-MOS data of the detected point sources were investigated and their spectral and temporal characteristics identified. A new transient (XMMU J005011.2-730026 = SXP 214) with a pulse period of 214.05 s was discovered; the source had a hard X-ray spectrum with a power-law index of ~0.65. The accurate X-ray source location permits the identification of the X-ray source with an ~15th magnitude Be star, thereby confirming this system as a new Be/X-ray binary.

The XMM-Newton survey of the Small Magellanic Cloud: discovery of the 11.866 s Be/X-ray binary pulsar XMMU J004814.0-732204(SXP11.87)

Warsaw University Observatory, Aleje Ujazdowskie 4, 00-478 Warsaw, PolandReceived 21 September 2010 / Accepted 6 November 2010ABSTRACTAims.One of the goals of the XMM-Newton survey of the Small Magellanic Cloud is the study of the Be/X-ray binary population.During one of our first survey observations a bright new trans ient − XMMUJ004814.0-732204− was discovered.Methods.We present the analysis of the EPIC X-ray data together with optical observations, to investigate the spectral and temporalcharacteristics of XMMUJ004814.0-732204.Results.We found coherent X-ray pulsations in the EPIC data with a period of (11.86642 ± 0.00017) s. The X-ray spectrum can bemodelled by an absorbed power-law with indication for a softexcess. Depending on the modelling of the soft X-ray spectrum, thephoton index ranges between 0.53 and 0.66. We identify the optical counterpart as a B = 14.9mag star which was monitored duringthe MACHO and OGLE-III projects. The optical light curves show regular outbursts by ∼0.5 mag in B and R and up to 0.9 mag in Iwhich repeat with a time scale of about 1000 days. The OGLE-III optical colours of the star are consistent with an early B spectraltype. An optical spectrum obtained at the 1.9m telescope of the South African Astronomical Observatory in December 2009 showsHα emission with an equivalent width of 3.5 ± 0.6A.Conclusions.The X-ray spectrum and the detection of pulsations suggest that XMMUJ004814.0-732204 is a new high mass X-raybinary pulsar in the SMC. The long term variability and the Hα emission line in the spectrum of the optical counterpart identify it asa Be/X-ray binary system.Key words. galaxies: individual: Small Magellanic Cloud – galaxies: stellar content – stars: emission-line, Be – stars: neutron –X-rays: binaries