ALBERT

Description: We report on the discovery of a new member of the magnetar class, SGR J1935+2154, and on its timing and spectral properties measured by an extensive observational campaign carried out between 2014 July and 2015 March with Chandra and XMM–Newton (11 pointings). We discovered the spin period of SGR J1935+2154 through the detection of coherent pulsations at a period of about 3.24 s. The magnetar is slowing down at a rate of $\dot{P} = 1.43(1)\times 10^{-11}$  s s –1 and with a decreasing trend due to a negative $\ddot{P}$ of –3.5(7) x 10 –19  s s –2 . This implies a surface dipolar magnetic field strength of ~2.2 x 10 14  G, a characteristic age of about 3.6 kyr and a spin-down luminosity L sd ~1.7 x 10 34  erg s –1 . The source spectrum is well modelled by a blackbody with temperature of about 500 eV plus a power-law component with photon index of about 2. The source showed a moderate long-term variability, with a flux decay of about 25 per cent during the first four months since its discovery, and a re-brightening of the same amount during the second four months. The X-ray data were also used to study the source environment. In particular, we discovered a diffuse emission extending on spatial scales from about 1 arcsec up to at least 1 arcmin around SGR J1935+2154 both in Chandra and XMM–Newton data. This component is constant in flux (at least within uncertainties) and its spectrum is well modelled by a power-law spectrum steeper than that of the pulsar. Though a scattering halo origin seems to be more probable we cannot exclude that part, or all, of the diffuse emission is due to a pulsar wind nebula.

Description: At the end of March 2015 the onboard software configuration of the AGILE satellite was modified in order to disable the veto signal of the anticoincidence shield for the minicalorimeter instrument. The motivation for such a change was the understanding that the dead time induced by the anticoincidence prevented the detection of a large fraction of Terrestrial Gamma-Ray Flashes (TGFs). The configuration change was highly successful resulting in an increase of one order of magnitude in TGF detection rate. As expected, the largest fraction of the new events has short duration (〈 100 μ s), and part of them has simultaneous association with lightning sferics detected by the World Wide Lightning Location Network (WWLLN). The new configuration provides the largest TGF detection rate surface density (TGFs / km 2 / year) to date, opening prospects for improved correlation studies with lightning and atmospheric parameters on short spatial and temporal scales along the equatorial region.

Description: The AGILE satellite detects Terrestrial Gamma-ray Flashes (TGFs) in the 0.35–100 MeV energy range using its Mini-Calorimeter (MCAL) instrument with an average detection rate of 10 TGFs/month. Thanks to its Low Earth Orbit with only 2.5 degree of inclination, AGILE guarantees an unprecedented exposure above the equator, where both lightning activity and TGF detection peak. Here we report the comparison between the AGILE TGFs detected between March 2009 and February 2010 and full climatology lightning worldwide distribution based on satellite optical observations from LIS (Lightning Imaging Sensor) and OTD (Optical Transient Detector) instruments. This approach is complementary to the one-to-one TGF/lightning correlations by ground-based sferics measurements. Based on mono and bi-dimensional Kolmogorov-Smirnov tests, we show that the AGILE TGFs and time-averaged global lightning in the equatorial area are not drawn from the same distribution. However, we find significant regional differences in the degree of correlation as well as in the TGF/lightning ratio. In the case of south east Asia we find a 87% probability for the TGF and lightning being samples of the same distribution. This result supports the idea that the physical conditions at play in TGF generation can have strong geographical and climatological modulation. Based on the assumption that the observed range of TGF/flash ratio holds at all latitudes we can estimate a global rate of $\dot{N}$ $\simeq$ 220 ÷ 570 TGFs per day. The observed TGF/flash geographical modulation as well as the TGF global rate estimate are in agreement with previous observations.

Description: Super-massive black holes in active galaxies can accelerate particles to relativistic energies, producing jets with associated gamma-ray emission. Galactic 'microquasars', which are binary systems consisting of a neutron star or stellar-mass black hole accreting gas from a companion star, also produce relativistic jets, generally together with radio flares. Apart from an isolated event detected in Cygnus X-1, there has hitherto been no systematic evidence for the acceleration of particles to gigaelectronvolt or higher energies in a microquasar, with the consequence that we are as yet unsure about the mechanism of jet energization. Here we report four gamma-ray flares with energies above 100 MeV from the microquasar Cygnus X-3 (an exceptional X-ray binary that sporadically produces radio jets). There is a clear pattern of temporal correlations between the gamma-ray flares and transitional spectral states of the radio-frequency and X-ray emission. Particle acceleration occurred a few days before radio-jet ejections for two of the four flares, meaning that the process of jet formation implies the production of very energetic particles. In Cygnus X-3, particle energies during the flares can be thousands of times higher than during quiescent states.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tavani, M -- Bulgarelli, A -- Piano, G -- Sabatini, S -- Striani, E -- Evangelista, Y -- Trois, A -- Pooley, G -- Trushkin, S -- Nizhelskij, N A -- McCollough, M -- Koljonen, K I I -- Pucella, G -- Giuliani, A -- Chen, A W -- Costa, E -- Vittorini, V -- Trifoglio, M -- Gianotti, F -- Argan, A -- Barbiellini, G -- Caraveo, P -- Cattaneo, P W -- Cocco, V -- Contessi, T -- D'Ammando, F -- Del Monte, E -- De Paris, G -- Di Cocco, G -- Di Persio, G -- Donnarumma, I -- Feroci, M -- Ferrari, A -- Fuschino, F -- Galli, M -- Labanti, C -- Lapshov, I -- Lazzarotto, F -- Lipari, P -- Longo, F -- Mattaini, E -- Marisaldi, M -- Mastropietro, M -- Mauri, A -- Mereghetti, S -- Morelli, E -- Morselli, A -- Pacciani, L -- Pellizzoni, A -- Perotti, F -- Picozza, P -- Pilia, M -- Prest, M -- Rapisarda, M -- Rappoldi, A -- Rossi, E -- Rubini, A -- Scalise, E -- Soffitta, P -- Vallazza, E -- Vercellone, S -- Zambra, A -- Zanello, D -- Pittori, C -- Verrecchia, F -- Giommi, P -- Colafrancesco, S -- Santolamazza, P -- Antonelli, A -- Salotti, L -- England -- Nature. 2009 Dec 3;462(7273):620-3. doi: 10.1038/nature08578. Epub 2009 Nov 22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉INAF-IASF Roma, Via del Fosso del Cavaliere 100, I-00133 Roma, Italy. pi.agile@iasf-roma.inaf.it〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19935645" target="_blank"〉PubMed〈/a〉

Description: Observations with the Newton X-ray Multimirror Mission satellite show a strong periodic modulation at 6.67 +/- 0.03 hours of the x-ray source at the center of the 2000-year-old supernova remnant RCW 103. No fast pulsations are visible. If genetically tied to the supernova remnant, the source could either be an x-ray binary, composed of a compact object and a low-mass star in an eccentric orbit, or an isolated neutron star. In the latter case, the combination of its age and period would indicate that it is a peculiar magnetar, dramatically slowed down, possibly by a supernova debris disc. Both scenarios require nonstandard assumptions about the formation and evolution of compact objects in supernova explosions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉De Luca, A -- Caraveo, P A -- Mereghetti, S -- Tiengo, A -- Bignami, G F -- New York, N.Y. -- Science. 2006 Aug 11;313(5788):814-7. Epub 2006 Jul 6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Istituto Nazionale d'Astrofisica-Istituto di Astrofisica Spaziale e Fisica Cosmica, Via Bassini 15, I-20133 Milano, Italy. deluca@iasf-milano.inaf.it〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16825535" target="_blank"〉PubMed〈/a〉

Description: Soft gamma repeaters (SGRs) and anomalous x-ray pulsars form a rapidly increasing group of x-ray sources exhibiting sporadic emission of short bursts. They are believed to be magnetars, that is, neutron stars powered by extreme magnetic fields, B ~ 10(14) to 10(15) gauss. We report on a soft gamma repeater with low magnetic field, SGR 0418+5729, recently detected after it emitted bursts similar to those of magnetars. X-ray observations show that its dipolar magnetic field cannot be greater than 7.5 x 10(12) gauss, well in the range of ordinary radio pulsars, implying that a high surface dipolar magnetic field is not necessarily required for magnetar-like activity. The magnetar population may thus include objects with a wider range of B-field strengths, ages, and evolutionary stages than observed so far.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rea, N -- Esposito, P -- Turolla, R -- Israel, G L -- Zane, S -- Stella, L -- Mereghetti, S -- Tiengo, A -- Gotz, D -- Gogus, E -- Kouveliotou, C -- New York, N.Y. -- Science. 2010 Nov 12;330(6006):944-6. doi: 10.1126/science.1196088. Epub 2010 Oct 14.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut de Ciencies de l'Espai, Consejo Superior de Investigaciones Cientificas, Institut d'Estudis Espacials de Catalunya, Facultat de Ciencies, Campus UAB, Torre C5-parell, 2a planta, 08193 Bellaterra (Barcelona), Spain. rea@ieec.uab.es〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20947727" target="_blank"〉PubMed〈/a〉

Description: We report the X-ray Multimirror Mission-Newton European Photon Imaging Camera observation of two elongated parallel x-ray tails trailing the pulsar Geminga. They are aligned with the object's supersonic motion, extend for approximately 2', and have a nonthermal spectrum produced by electron-synchrotron emission in the bow shock between the pulsar wind and the surrounding medium. Electron lifetime against synchrotron cooling matches the source transit time over the x-ray features' length. Such an x-ray detection of a pulsar bow shock (with no Halpha emission) allows us to gauge the pulsar electron injection energy and the shock magnetic field while constraining the angle of Geminga's motion and the local matter density.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Caraveo, P A -- Bignami, G F -- DeLuca, A -- Mereghetti, S -- Pellizzoni, A -- Mignani, R -- Tur, A -- Becker, W -- New York, N.Y. -- Science. 2003 Sep 5;301(5638):1345-7. Epub 2003 Jul 24.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Istituto di Astrofisica Spaziale e Fisica Cosmica-Consiglio Nazionale della Richerche, Via Bassini, 15-20133 Milano, Italy. pat@mi.iasf.cnr.it〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12881574" target="_blank"〉PubMed〈/a〉

Description: Isolated neutron stars are seen in x-rays through their nonthermal and/or surface thermal emissions. X-ray Multimirror Mission-Newton observations of the Geminga pulsar show a 43-electron volt spectrum from the whole neutron star surface, as well as a power-law component above 2 kiloelectron volts. In addition, we have detected a hot (170 electron volts) thermal emission from an approximately 60-meter-radius spot on the pulsar's surface. Such a thermal emission, only visible at selected phase intervals, may be coming from polar hot spot(s), long thought to exist as a result of heating from magnetospheric accelerated particles. It may provide the missing link between the x-ray and gamma-ray emission of the pulsar.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Caraveo, P A -- De Luca, A -- Mereghetti, S -- Pellizzoni, A -- Bignami, G F -- New York, N.Y. -- Science. 2004 Jul 16;305(5682):376-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Istituto di Astrofisica Spaziale e Fisica Cosmica, Consiglio Nazionale delle Ricerche, Via Bassini, 15-20133 Milano, Italy. pat@mi.iasf.cnr.it〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15256666" target="_blank"〉PubMed〈/a〉

Description: Soft-gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are slowly rotating, isolated neutron stars that sporadically undergo episodes of long-term flux enhancement (outbursts) generally accompanied by the emission of short bursts of hard X-rays. This behaviour can be understood in the magnetar model, according to which these sources are mainly powered by their own magnetic energy. This is supported by the fact that the magnetic fields inferred from several observed properties of SGRs and AXPs are greater than-or at the high end of the range of-those of radio pulsars. In the peculiar case of SGR 0418+5729, a weak dipole magnetic moment is derived from its timing parameters, whereas a strong field has been proposed to reside in the stellar interior and in multipole components on the surface. Here we show that the X-ray spectrum of SGR 0418+5729 has an absorption line, the properties of which depend strongly on the star's rotational phase. This line is interpreted as a proton cyclotron feature and its energy implies a magnetic field ranging from 2 x 10(14) gauss to more than 10(15) gauss.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tiengo, Andrea -- Esposito, Paolo -- Mereghetti, Sandro -- Turolla, Roberto -- Nobili, Luciano -- Gastaldello, Fabio -- Gotz, Diego -- Israel, Gian Luca -- Rea, Nanda -- Stella, Luigi -- Zane, Silvia -- Bignami, Giovanni F -- England -- Nature. 2013 Aug 15;500(7462):312-4. doi: 10.1038/nature12386.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Istituto Universitario di Studi Superiori, piazza della Vittoria 15, I-27100 Pavia, Italy. andrea.tiengo@iusspavia.it〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23955229" target="_blank"〉PubMed〈/a〉

Description: White dwarfs typically have masses in a narrow range centered at about 0.6 solar mass (M(o)). Only a few ultramassive white dwarfs (mass 〉 1.2 M(o)) 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 M(o), 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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mereghetti, S -- Tiengo, A -- Esposito, P -- La Palombara, N -- Israel, G L -- Stella, L -- New York, N.Y. -- Science. 2009 Sep 4;325(5945):1222-3. doi: 10.1126/science.1176252.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Istituto Nazionale di Astrofisica-Istituto di Astrofisica Spaziale e Fisica cosmica di Milano, via E. Bassini 15, 20133 Milano, Italy. sandro@iasf-milano.inaf.it〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19729650" target="_blank"〉PubMed〈/a〉