Aims. IKT 16 is an X-ray and radio-faint supernova remnant (SNR) in the Small Magellanic Cloud (SMC). A detailed X-ray study of this SNR with XMM-Newton confirmed the presence of a hard X-ray source ...near its centre, indicating the detection of the first composite SNR in the SMC. With a dedicated Chandra observation we aim to resolve the point source and confirm its nature. We also acquire new ATCA observations of the source at 2.1 GHz with improved flux density estimates and resolution. Methods. We perform detailed spatial and spectral analysis of the source. With the highest resolution X-ray and radio image of the centre of the SNR available today, we resolve the source and confirm its pulsar wind nebula (PWN) nature. Further, we constrain the geometrical parameters of the PWN and perform spectral analysis for the point source and the PWN separately. We also test for the radial variations of the PWN spectrum and its possible east west asymmetry. Results. The X-ray source at the centre of IKT 16 can be resolved into a symmetrical elongated feature centring a point source, the putative pulsar. Spatial modelling indicates an extent of 5.2′′ of the feature with its axis inclined at 82° east from north, aligned with a larger radio feature consisting of two lobes almost symmetrical about the X-ray source. The picture is consistent with a PWN which has not yet collided with the reverse shock. The point source is about three times brighter than the PWN and has a hard spectrum of spectral index 1.1 compared to a value 2.2 for the PWN. This points to the presence of a pulsar dominated by non-thermal emission. The expected Ė is ~1037 erg s-1 and spin period <100 ms. However, the presence of a compact nebula unresolved by Chandra at the distance of the SMC cannot completely be ruled out.
We investigate the nature of CXOU\,J005440.5-374320 ( a peculiar bright ($ and soft X-ray transient in the spiral galaxy NGC\,300 with a six-hour periodic flux modulation that was detected in a 2014 ...observation. Subsequent observations with and as well as a large observational campaign of NGC\,300 and its sources performed with the Swift Neil Gehrels Observatory showed that this source exhibits recurrent flaring activity: four other outbursts were detected across sim 8 years of monitoring. Using data from the archive and from the and catalogues, we determined that the source is likely associated with a bright blue optical/ultraviolet counterpart. This prompted us to perform follow-up observations with the Southern African Large Telescope in December 2019. With the multi-wavelength information at hand, we discuss several possibilities for the nature of Although none is able to account for the full range of the observed peculiar features, we found that the two most promising scenarios are a stellar-mass compact object in a binary system with a Wolf--Rayet star companion, or the recurrent tidal stripping of a stellar object trapped in a system with an intermediate-mass (sim 1000\,M$_ black hole.
ABSTRACT The detection of the first gravitational wave (GW) transient GW150914 prompted an extensive campaign of follow-up observations at all wavelengths. Although no dedicated XMM-Newton ...observations have been performed, the satellite passed through the GW150914 error region during normal operations. Here we report the analysis of the data taken during these satellite slews performed two hours and two weeks after the GW event. Our data cover 1.1 and 4.8 deg2 of the final GW localization region. No X-ray counterpart to GW150914 is found down to a sensitivity of 6 × 10−13 erg cm−2 s−1 in the 0.2-2 keV band. Nevertheless, these observations show the great potential of XMM-Newton slew observations for searching for the electromagnetic counterparts of GW events. A series of adjacent slews performed in response to a GW trigger would take 1.5 days to cover most of the typical GW credible region. We discuss this scenario and its prospects for detecting the X-ray counterpart of future GW detections.
White dwarfs typically have masses in a narrow range centered at about 0.6 solar mass (Mmiddle dot in circle). Only a few ultramassive white dwarfs (mass > 1.2 Mmiddle dot in circle) are known. Those ...in binary systems are of particular interest, because a small amount of accreted mass could drive them above the Chandrasekhar limit, beyond which they become gravitationally unstable. Using data from the x-ray multimirror mission (XMM)-Newton satellite, we show that the x-ray pulsator RX J0648.0-4418 is a white dwarf with mass > 1.2 Mmiddle dot in circle, based on dynamical measurements only. This ultramassive white dwarf in a post-common envelope binary with a hot subdwarf can reach the Chandrasekhar limit, and possibly explode as a type Ia supernova, when its helium-rich companion will transfer mass at an increased rate through Roche lobe overflow.
We report on the quiescent state of the soft gamma repeater SGR 0501+4516 observed by XMM-Newton on 2009 August 30. The source exhibits an absorbed flux ∼75 times lower than that measured at the peak ...of the 2008 outburst, and a rather soft spectrum, with the same value of the blackbody temperature observed with ROSAT back in 1992. This new observation is put into the context of all existing X-ray data since its discovery in 2008 August, allowing us to complete the study of the timing and spectral evolution of the source from outburst until its quiescent state. The set of deep XMM-Newton observations performed during the few years time-scale of its outburst allows us to monitor the spectral characteristics of this magnetar as a function of its rotational period, and their evolution along these years. After the first ∼10 d, the initially hot and bright surface spot progressively cooled down during the decay. We discuss the behaviour of this magnetar in the context of its simulated secular evolution, inferring a plausible dipolar field at birth of 3 × 1014 G, and a current (magnetothermal) age of ∼10 kyr.
We report here on the outburst onset and evolution of the new soft gamma-ray repeater SGR 0501+4516. We monitored the new SGR with XMM–Newton starting on 2008 August 23, 1 day after the source became ...burst active, and continuing with four more observations in the following month, with the last one on 2008 September 30. Combining the data with the Swift X-ray telescope (Swift–XRT) and Suzaku data, we modelled the outburst decay over a 3-month period, and we found that the source flux decreased exponentially with a time-scale of tc= 23.8 d. In the first XMM–Newton observation, a large number of short X-ray bursts were observed, the rate of which decayed drastically in the following observations. We found large changes in the spectral and timing behaviour of the source during the first month of the outburst decay, with softening emission as the flux decayed, and the non-thermal soft X-ray spectral component fading faster than the thermal one. Almost simultaneously to our second and fourth XMM–Newton observations (on 2008 August 29 and September 2), we observed the source in the hard X-ray range with INTEGRAL, which clearly detected the source up to ∼100 keV in the first pointing, while giving only upper limits during the second pointing, discovering a variable hard X-ray component fading in less than 10 days after the bursting activation. We performed a phase-coherent X-ray timing analysis over about 160 days starting with the burst activation and found evidence of a strong second derivative period component . Thanks to the phase connection, we were able to study the phase-resolved spectral evolution of SGR 0501+4516 in great detail. We also report on the ROSAT quiescent source data, taken back in 1992 when the source exhibits a flux ∼80 times lower than that measured during the outburst, and a rather soft, thermal spectrum.
Abstract
We report on the results of the XMM–Newton observation of IGR J01572−7259 during its most recent outburst in 2016 May, the first since 2008. The source reached a flux f ∼ 10−10 erg cm−2 s−1, ...which allowed us to perform a detailed analysis of its timing and spectral properties. We obtained a pulse period Pspin = 11.58208(2) s. The pulse profile is double peaked and strongly energy dependent, as the second peak is prominent only at low energies and the pulsed fraction increases with energy. The main spectral component is a power-law model, but at low energies, we also detected a soft thermal component, which can be described with either a blackbody or a hot plasma model. Both the EPIC and RGS spectra show several emission lines, which can be identified with the transition lines of ionized N, O, Ne, and Fe and cannot be described with a thermal emission model. The phase-resolved spectral analysis showed that the flux of both the soft excess and the emission lines vary with the pulse phase: the soft excess disappears in the first pulse and becomes significant only in the second, where also the Fe line is stronger. This variability is difficult to explain with emission from a hot plasma, while the reprocessing of the primary X-ray emission at the inner edge of the accretion disc provides a reliable scenario. On the other hand, the narrow emission lines can be due to the presence of photoionized matter around the accreting source.
ABSTRACT
The wealth of detections of millisecond pulsars (MSPs) in γ-rays by Fermi has spurred searches for these objects among the several unidentified γ-ray sources. Interesting targets are a ...sub-class of binary MSPs, dubbed ‘black widows’ (BWs) and ‘redbacks’ (RBs), which are in orbit with low-mass non-degenerate companions fully or partially ablated by irradiation from the MSP wind. These systems can be easily missed in radio pulsar surveys owing to the eclipse of the radio signal by the intra-binary plasma from the ablated companion star photosphere, making them better targets for multiwavelength observations. We used optical and X-ray data from public data bases to carry out a systematic investigation of all the unidentified γ-ray sources from the Fermi Large Area Telescope Third Source Catalog, which have been pre-selected as likely MSP candidates according to a machine-learning technique analysis. We tested our procedure by recovering known binary BW/RB identifications and searched for new ones, finding two possible candidates. At the same time, we investigated previously proposed BW/RB identifications and we ruled out one of them based upon the updated γ-ray source coordinates.
Aim: The aim of this study was to compare the efficacy and safety of a basal‐bolus insulin regimen comprising either insulin detemir or neural protamine hagedorn (NPH) insulin in combination with ...mealtime insulin aspart in patients with type 2 diabetes.
Methods: This was a 26‐week, multinational, open‐label, parallel group trial with 505 patients with type 2 diabetes (mean age, 60.4 ± 8.6 years; mean BMI, 30.4 ± 5.3 kg/m2; mean HbA1c, 7.9 ± 1.3%). Patients, randomized 2 : 1 to insulin detemir or NPH insulin, received basal insulin either once or twice daily according to their pretrial insulin treatment and insulin aspart at mealtimes.
Results: After 26 weeks of treatment, significant reductions in HbA1c were observed for insulin detemir (0.2%‐points, p = 0.004) and NPH insulin (0.4%‐points; p = 0.0001); HbA1c levels were comparable at study end (insulin detemir, 7.6%; NPH insulin, 7.5%). The number of basal insulin injections administered per day had no effect on HbA1c levels (p = 0.50). Nine‐point self‐measured blood glucose (SMBG) profiles were similar for the two treatment groups (p = 0.58), as were reductions in fasting plasma glucose (FPG) (insulin detemir, 0.5 mmol/l; NPH insulin, 0.6 mmol/l). At study end, FPG concentrations were similar for the two treatment groups (p = 0.66). By contrast, within‐subject day‐to‐day variation in fasting SMBG was significantly lower with insulin detemir (p = 0.021). Moreover, patients receiving insulin detemir gained significantly less body weight than those who were administered NPH insulin (1.0 and 1.8 kg, respectively, p = 0.017). The frequency of adverse events and the risk of hypoglycaemia were comparable for the two treatment groups.
Conclusions: Patients with type 2 diabetes, treated for 26 weeks with insulin detemir plus insulin aspart at mealtimes, experienced comparable glycaemic control but significantly lower within‐subject variability and less weight gain compared to patients treated with NPH insulin and insulin aspart. Insulin detemir was well tolerated and had a similar safety profile to NPH insulin.
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