The outburst decay of the low magnetic field magnetar SGR 0418+5729

We report on the long-term X-ray monitoring of the outburst decay of the low magnetic field magnetar SGR 0418+5729 using all the available X-ray data obtained with RXTE, Swift, Chandra, and XMM-Newton observations from the discovery of the source in 2009 June up to 2012 August. The timing analysis allowed us to obtain the first measurement of the period derivative of SGR 0418+5729: ˙ P = 4(1) × 10−15 s s−1, significant at a ∼3.5σ confidence level. This leads to a surface dipolar magnetic field of Bdip 6 × 1012 G. This measurement confirms SGR 0418+5729 as the lowest magnetic field magnetar. Following the flux and spectral evolution from the beginning of the outburst up to ∼1200 days, we observe a gradual cooling of the tiny hot spot responsible for the X-ray emission, from a temperature of ∼0.9 to 0.3 keV. Simultaneously, the X-ray flux decreased by about three orders of magnitude: from about 1.4 × 10−11 to 1.2 × 10−14 erg s−1 cm−2. Deep radio, millimeter, optical, and gamma-ray observations did not detect the source counterpart, implying stringent limits on its multi-band emission, as well as constraints on the presence of a fossil disk. By modeling the magneto-thermal secular evolution of SGR 0418+5729, we infer a realistic age of ∼550 kyr, and a dipolar magnetic field at birth of ∼1014 G. The outburst characteristics suggest the presence of a thin twisted bundle with a small heated spot at its base. The bundle untwisted in the first few months following the outburst, while the hot spot decreases in temperature and size. We estimate the outburst rate of low magnetic field magnetars to be about one per year per galaxy, and we briefly discuss the consequences of such a result in several other astrophysical contexts.

The action cam phenomenon: a new trend in audiovisual production

When the GoPro camera was first put on the market in 2004, it brought about a new generation of ultracompact cameras designed to be attached to the user’s body, and which came to be known as action cams. Their principal characteristics were their tiny size, their high-quality images and a wide-angle, fixed-focal-length lens. This combination has made it much simpler to get spectacular subjective shots with considerable depth of field. The users of this technology now form a whole generation of citizen-filmmakers who produce thousands of videos every day in a novel realistic style dominated by first-person narrative. Their work is principally shared via video platforms like YouTube and Vimeo, which provide instant feedback in the form of millions of views. In this paper we analize the common features of the action cam recording style and we state these videos will bring about a redefinition of the realist visual style. Furthermore, we propose to relate the success of the action cam phenomenon with the cognitive concept of embodiment and argue that the viewer’s mirror neurons copy the real sensations and enable the viewer to experience, virtually and in safety, the same emotions felt by the person actually taking part in the action.

Fortification and Frontier: The Project Drawn up by Juan Martín Zermeño for Puebla de Sanabria in 1766

Following the death of engineer General Jorge Próspero de Verboom in 1744 and after a few years of transition in the management of Spanish fortifications, Juan Martín Zermeño took on the role, initially with a temporary mandate, but then definitively during a second period that ran from 1766 until his death in 1772. He began this second period with a certain amount of concern because of what had taken place during the last period of conflict. The Seven Years War (1756–1763) which had brought Spain into conflict with Portugal and England in the Caribbean had also lead to conflict episodes along the Spanish–Portuguese border. Zermeño’s efforts as a planner and general engineer gave priority to the northern part of the Spanish–Portuguese border. After studying the territory and the existing fortifications on both sides of the border, Zermeño drew up three important projects in 1766. The outposts that needed to be reinforced were located, from north to south, at Puebla de Sanabria, Zamora and Ciudad Rodrigo, which is where he is believed to have come from. This latter township already had a modern installation built immediately after the war of the Spanish Succession and reinforced with the Fort of La Concepción. However, Zamora and Puebla de Sanabria had some obsolete fortifications that needed modernising. Since the middle of the 15th century Puebla de Sanabria had had a modern castle with rounded turrets, that of the counts of benavente. During the 16th and 17th centuries it had also been equipped with a walled enclosure with small bastions. During the war of the Spanish Succession the Portuguese had enlarged the enclosure and had erected a tentative offshoot to the west. In order to draw up the ambitious Puebla de Sanabria project Zermeño had the aid of some previous reports and projects, such as those by the count of robelin in 1722, the one by Antonio de Gaver in 1752, and Pedro Moreau’s report dated June 1755. This study includes a technical analysis of Zermeño’s project and its strategic position within the system of fortifications along the Spanish–Portuguese border.