3XMM J185246.6+003317: another low magnetic field magnetar

We study the outburst of the newly discovered X-ray transient 3XMMJ185246.6+003317, re-analyzing all available XMM-Newton observations of the source to perform a phase-coherent timing analysis, and derive updated values of the period and period derivative. We find the source rotating at P = 11.55871346(6) s (90% confidence level; at epoch MJD 54728.7) but no evidence for a period derivative in the seven months of outburst decay spanned by the observations. This translates to a 3σ upper limit for the period derivative of ˙ P <1.4×10−13 s s−1, which, assuming the classical magneto-dipolar braking model, gives a limit on the dipolar magnetic field of Bdip < 4.1×1013 G. The X-ray outburst and spectral characteristics of 3XMM J185246.6+003317 confirm its identification as a magnetar, but the magnetic field upper limit we derive defines it as the third “low-B” magnetar discovered in the past 3 yr, after SGR 0418+5729 and Swift J1822.3−1606. We have also obtained an upper limit to the quiescent luminosity (<4×1033 erg s−1), in line with the expectations for an old magnetar. The discovery of this new low field magnetar reaffirms the prediction of about one outburst per year from the hidden population of aged magnetars.

The X-ray outburst of the Galactic Centre magnetar SGR J1745−2900 during the first 1.5 year

In 2013 April a new magnetar, SGR 1745−2900, was discovered as it entered an outburst, at only 2.4 arcsec angular distance from the supermassive black hole at the centre of the Milky Way, Sagittarius A*. SGR 1745−2900 has a surface dipolar magnetic field of ∼2 × 1014 G, and it is the neutron star closest to a black hole ever observed. The new source was detected both in the radio and X-ray bands, with a peak X-ray luminosity LX ∼ 5 × 1035 erg s−1. Here we report on the long-term Chandra (25 observations) and XMM–Newton (eight observations) X-ray monitoring campaign of SGR 1745−2900 from the onset of the outburst in 2013 April until 2014 September. This unprecedented data set allows us to refine the timing properties of the source, as well as to study the outburst spectral evolution as a function of time and rotational phase. Our timing analysis confirms the increase in the spin period derivative by a factor of ∼2 around 2013 June, and reveals that a further increase occurred between 2013 October 30 and 2014 February 21. We find that the period derivative changed from 6.6 × 10−12 to 3.3 × 10−11 s s−1 in 1.5 yr. On the other hand, this magnetar shows a slow flux decay compared to other magnetars and a rather inefficient surface cooling. In particular, starquake-induced crustal cooling models alone have difficulty in explaining the high luminosity of the source for the first ∼200 d of its outburst, and additional heating of the star surface from currents flowing in a twisted magnetic bundle is probably playing an important role in the outburst evolution.

Twenty-year advanced DInSAR analysis of severe land subsidence: The Alto Guadalentín Basin (Spain) case study

A twenty-year period of severe land subsidence evolution in the Alto Guadalentín Basin (southeast Spain) is monitored using multi-sensor SAR images, processed by advanced differential interferometric synthetic aperture radar (DInSAR) techniques. The SAR images used in this study consist of four datasets acquired by ERS-1/2, ENVISAT, ALOS and COSMO-SkyMed satellites between 1992 and 2012. The integration of ground surface displacement maps retrieved for different time periods allows us to quantify up to 2.50 m of cumulated displacements that occurred between 1992 and 2012 in the Alto Guadalentín Basin. DInSAR results were locally compared with global positioning system (GPS) data available for two continuous stations located in the study area, demonstrating the high consistency of local vertical motion measurements between the two different surveying techniques. An average absolute error of 4.6 ± 4 mm for the ALOS data and of 4.8 ± 3.5 mm for the COSMO-SkyMed data confirmed the reliability of the analysis. The spatial analysis of DInSAR ground surface displacement reveals a direct correlation with the thickness of the compressible alluvial deposits. Detected ground subsidence in the past 20 years is most likely a consequence of a 100–200 m groundwater level drop that has persisted since the 1970s due to the overexploitation of the Alto Guadalentín aquifer system. The negative gradient of the pore pressure is responsible for the extremely slow consolidation of a very thick (> 100 m) layer of fine-grained silt and clay layers with low vertical hydraulic permeability (approximately 50 mm/h) wherein the maximum settlement has still not been reached.

Implantation of a diffractive trifocal intraocular lens: One-year follow-up

Purpose: To evaluate the visual, refractive, contrast-sensitivity, and aberrometric outcomes during a 1-year follow-up after implantation of a trifocal intraocular lens (IOL). Setting: Premium Clinic, Teplice, Czech Republic. Design: Prospective case series. Methods: This study included eyes of patients having cataract surgery with implantation of the trifocal IOL model AT Lisa tri 839MP. Distance, intermediate (66 and 80 cm), and near (33 and 40 cm) vision; contrast sensitivity; aberrometric outcomes; and the defocus curve were evaluated during a 12-month follow-up. The level of posterior capsule opacification (PCO) was also evaluated. Results: In 120 eyes (60 patients), 1 month postoperatively, an improvement was observed in all visual parameters (P ≤ .03) except corrected near and intermediate visual acuities (both P ≥ .05). From 1 month to 12 months postoperatively, small but statistically significant changes were observed in uncorrected and corrected distance and near visual acuities (all P ≤ .03) and in uncorrected intermediate visual acuity (P = .01). In the defocus curve, no significant differences were found between visual acuities corresponding to defocus levels of −1.0 diopter (D) and −2.0 D (P = .22). The level of ocular spherical aberration decreased statistically significantly at 6 months (P < .001). Ocular and internal higher-order aberrations increased minimally but significantly from 6 to 12 months postoperatively (P < .001). The mean 12-month PCO score was 0.32 ± 0.44 (SD). Four eyes (3.3%) required neodymium:YAG capsulotomy. Conclusion: The trifocal IOL provided complete and stable visual restoration after cataract surgery during a 12-month follow-up, with good levels of visual quality.