Soft X-ray characterisation of the long term properties of Supergiant Fast X-ray Transients

We perform the first high-sensitivity soft X-ray long-term monitoring with Swift/XRT of three relatively unexplored Supergiant Fast X-ray Transients (SFXTs), IGR J08408-4503, IGR J16328-4726, and IGR J16465-4507, whose hard X-ray duty cycles are the lowest measured among the SFXT sample, and compare their properties with those of the prototypical SFXTs. The behaviour of J08408 and J16328 resembles that of other SFXTs, and it is characterized by a relatively high inactivity duty cycle (IDC) and pronounced dynamic range (DR) in the X-ray luminosity. Like the SFXT prototypes, J08408 shows two distinct populations of flares, the first one associated with the brightest outbursts ($L_{\rm X}\gtrsim 10^{35-36}$ erg s$^{-1}$), the second one comprising less bright events with $L_{\rm X}\lesssim$10$^{35}$ erg s$^{-1}$. This double-peaked distribution seems to be a ubiquitous feature of the extreme SFXTs. The lower DR of J16328 suggests it is an intermediate SFXT. We find J16465 is characterized by IDC$\sim$5% and DR$\sim$40, reminiscent of classical supergiant HMXBs. The duty cycles measured with XRT are found to be comparable with those reported previously by BAT and INTEGRAL, when the higher limiting sensitivities of these instruments are taken into account and sufficiently long observational campaigns are available. We prove that no clear correlation exists between the duty cycles of the SFXTs and their orbital periods, which makes it difficult to interpret the SFXT peculiar variability by only using arguments related to the properties of supergiant star winds. Our findings favour the idea that a correct interpretation of the SFXT phenomenology requires a mechanism to strongly reduce the mass accretion rate onto the compact object during most of its orbit around the companion, as proposed in a number of theoretical works. [Abridged]Comment: Accepted for publication in Astronomy and Astrophysics. 18 pages, 8 figures, 8 table

The magnetospheric radius of an inclined rotator in the magnetically threaded disk model

The estimate of the magnetospheric radius in a disk-fed neutron star X-ray binary is a long standing problem in high energy Astrophysics. We review the magnetospheric radius calculations in the so-called magnetically threaded disk model, comparing the simplified approach originally proposed by Ghosh & Lamb (1979) with the revised version proposed by Wang (1987), Wang (1995), and Wang (1997). We show that for a given set of fixed parameters (assuming also a comparable screening factor of the neutron star magnetic field by the currents induced on the disk surface) the revised magnetically threaded disk model predicts a magnetospheric radius that is significantly smaller than that derived from the Ghosh & Lamb (1979) treatment. For a fixed value of the neutron star magnetic field and a wide range of mass accretion rates, the inclusion of a large inclination angle between the neutron star rotation and magnetic field axes ($\chi$$\gtrsim$60 deg) leads to a further decrease of the magnetospheric radius. To illustrate the relevance of these calculations, we consider, as an example, the case of the transitional pulsars. During the so-called "high mode" of their sub-luminous accretion disk state, these sources have shown X-ray pulsations interpreted as due to accretion at an unprecedented low luminosity level compared to other neutron stars in X-ray binaries. In the context of the magnetic threaded disk model, we show that accretion at luminosities of $\sim$10$^{33}$ erg s$^{-1}$ (and thus accretion-driven X-ray pulsations) can be more easily explained when the prescription of the magnetospheric radius provided by Wang (1997) is used. This avoids the need of invoking very strong propeller outflows in the transitional pulsars, as proposed in other literature works.Comment: Accepted for publication in A&

The Atmospheric Monitoring System of the JEM-EUSO Space Mission

An Atmospheric Monitoring System (AMS) is a mandatory and key device of a space-based mission which aims to detect Ultra-High Energy Cosmic Rays (UHECR) and Extremely-High Energy Cosmic Rays (EHECR) from Space. JEM-EUSO has a dedicated atmospheric monitoring system that plays a fundamental role in our understanding of the atmospheric conditions in the Field of View (FoV) of the telescope. Our AMS consists of a very challenging space infrared camera and a LIDAR device, that are being fully designed with space qualification to fulfil the scientific requirements of this space mission. The AMS will provide information of the cloud cover in the FoV of JEM-EUSO, as well as measurements of the cloud top altitudes with an accuracy of 500 m and the optical depth profile of the atmosphere transmittance in the direction of each air shower with an accuracy of 0.15 degree and a resolution of 500 m. This will ensure that the energy of the primary UHECR and the depth of maximum development of the EAS ( Extensive Air Shower) are measured with an accuracy better than 30\% primary energy and 120 $g/cm^2$ depth of maximum development for EAS occurring either in clear sky or with the EAS depth of maximum development above optically thick cloud layers. Moreover a very novel radiometric retrieval technique considering the LIDAR shots as calibration points, that seems to be the most promising retrieval algorithm is under development to infer the Cloud Top Height (CTH) of all kind of clouds, thick and thin clouds in the FoV of the JEM-EUSO space telescope

ACCESS TO SERVICES FOR THE HOMELESS

poster abstractMy project is based on research done in the anthropology and geography departments by myself, Dr. Zimmerman and Courtney Singleton pertaining to homeless encampments in Indianapolis. This poster presentation illustrates locations of selected encampments and their access to service providers. Geographic information system (GIS) technologies were used to conduct a network analysis that visually shows access to services and quantifies travel time and network distance to selected service locations. The analysis presented is based on data collected by my colleagues from subjects in one specific camp describing preferred travel routes, distances traveled and services needed- prescription medication for example. I plan to apply this analytical method to other encampments to create a model of hypothetical routes based upon tow paths, walking trails and street networks

Swift monitoring of the new accreting millisecond X-ray pulsar IGRJ17511-3057 in outburst

A new accreting millisecond X-ray pulsar, IGR J17511-3057, was discovered in outburst on 2009 September 12 during the INTEGRAL Galactic bulge monitoring programme. To study the evolution of the source X-ray flux and spectral properties during the outburst, we requested a Swift monitoring of IGRJ17511-3057. In this paper we report on the results of the first two weeks of monitoring the source. The persistent emission of IGR J17511-3057 during the outburst is modeled well with an absorbed blackbody (kT~0.9 keV) and a power-law component (photon index~1-2), similar to what has been observed from other previously known millisecond pulsars. Swift also detected three type-I Xray bursts from this source. By assuming that the peak luminosity of these bursts is equal to the Eddington value for a pure helium type-I X-ray burst, we derived an upper limit to the source distance of ~10 kpc. The theoretical, expected recurrence time of the bursts according to the helium burst hypothesis is 0.2-0.9 days, in agreement with the observations.Comment: Accepted for publication in A&A Letters. V2: corrected some typos and added one referenc

XMM-Newton observations of IGRJ18410-0535: The ingestion of a clump by a supergiant fast X-ray transient

IGRJ18410-0535 is a supergiant fast X-ray transients. This subclass of supergiant X-ray binaries typically undergoes few- hour-long outbursts reaching luminosities of 10^(36)-10^(37) erg/s, the occurrence of which has been ascribed to the combined effect of the intense magnetic field and rotation of the compact object hosted in them and/or the presence of dense structures ("clumps") in the wind of their supergiant companion. IGR J18410-0535 was observed for 45 ks by XMM-Newton as part of a program designed to study the quiescent emission of supergiant fast X-ray transients and clarify the origin of their peculiar X-ray variability. We carried out an in-depth spectral and timing analysis of these XMM-Newton data. IGR J18410-0535 underwent a bright X-ray flare that started about 5 ks after the beginning of the observation and lasted for \sim15 ks. Thanks to the capabilities of the instruments on-board XMM-Newton, the whole event could be followed in great detail. The results of our analysis provide strong convincing evidence that the flare was produced by the accretion of matter from a massive clump onto the compact object hosted in this system. By assuming that the clump is spherical and moves at the same velocity as the homogeneous stellar wind, we estimate a mass and radius of Mcl \simeq1.4\times10^(22) g and Rcl \simeq8\times10^(11) cm. These are in qualitative agreement with values expected from theoretical calculations. We found no evidence of pulsations at \sim4.7 s after investigating coherent modulations in the range 3.5 ms-100 s. A reanalysis of the archival ASCA and Swift data of IGR J18410-0535, for which these pulsations were previously detected, revealed that they were likely to be due to a statistical fluctuation and an instrumental effect, respectively.Comment: Accepted for publication on A&A. V2: Inserted correct version of Fig.1

Longevity risk and economic growth in sub-populations: evidence from Italy

Forecasting mortality is still a big challenge for Governments that are interested in reliable projections for defining their economic policy at local and national level. The accuracy of mortality forecasting is considered an important issue for longevity risk management. In the literature, many authors have analyzed the long-run relationship between mortality evolution and socioeconomic variables, such as economic growth, unemployment rate or educational level. This paper investigates the existence of a link between mortality and real gross domestic product per capita (GDPPC) over time in the Italian regions. Empirical evidence shows the presence of a relationship between mortality and the level of real GDPPC (and not its trend). Therefore, we propose a multi-population model including the level of real GDPPC and we compare it with the Boonen–Li model (Boonen and Li in Demography 54:1921–1946, 2017). The validity of the model is tested in the out-of-sample forecasting experiment

XMM-Newton and Swift observations of XTE J1743-363

XTEJ1743-363 is a poorly known hard X-ray transient, that displays short and intense flares similar to those observed from Supergiant Fast X-ray Transients. The probable optical counterpart shows spectral properties similar to those of an M8 III giant, thus suggesting that XTEJ1743-363 belongs to the class of the Symbiotic X-ray Binaries. In this paper we report on the first dedicated monitoring campaign of the source in the soft X-ray range with XMM-Newton and Swift/XRT. T hese observations confirmed the association of XTEJ1743-363 with the previously suggested M8 III giant and the classification of the source as a member of the Symbiotic X-ray binaries. In the soft X-ray domain, XTEJ1743-363 displays a high absorption (~6x10^22 cm^-2 ) and variability on time scales of hundreds to few thousand seconds, typical of wind accreting systems. A relatively faint flare (peak X-ray flux 3x10^-11 erg/cm^2/s) lasting ~4 ks is recorded during the XMM-Newton observation and interpreted in terms of the wind accretion scenario.Comment: Accepted for publication on A&