Complex Lagrangian embeddings of moduli spaces of vector bundles

By means of a Fourier-Mukai transform we embed moduli spaces of stable bundles on an algebraic curve C as isotropic subvarieties of moduli spaces of mu-stable bundles on the Jacobian variety J(C). When g(C)=2 this provides new examples of special Lagrangian submanifolds.Comment: 9 pages, no figures, to appear in Diff. Geom. App

IGR J14257-6117, a magnetic accreting white dwarf with a very strong X-ray orbital modulation

IGR J14257-6117 is an unclassified source in the hard X-ray catalogues. Optical follow-ups suggest it could be a Cataclysmic Variable of the magnetic type. We present the first high S/N X-ray observation performed by \XMM\ at 0.3--10 keV, complemented with 10--80 keV coverage by \Swift/BAT, aimed at revealing the source nature. We detected for the first time a fast periodic variability at 509.5\,s and a longer periodic variability at 4.05\,h, ascribed to the white dwarf (WD) spin and binary orbital periods, respectively. These unambiguously identify IGR J14257-6117 as a magnetic CV of the Intermediate Polar (IP) type. The energy resolved light curves at both periods reveal amplitudes decreasing with increasing energy, with the orbital modulation reaching $\sim100\%$ in the softest band. The energy spectrum shows optically thin thermal emission with an excess at the iron complex, absorbed by two dense media (${\rm N_{H}\sim10^{22-23}\,cm^{-2}}$), partially covering the X-ray source. These are likely localised in the magnetically confined accretion flow above the WD surface and at the disc rim, producing the energy dependent spin and orbital variabilities, respectively. IGR J14257-6117, joins the group of strongest orbitally modulated IPs now counting four systems. Drawing similarities with low-mass X-ray binaries displaying orbital dips, these IPs should be seen at large orbital inclinations allowing azimuthally extended absorbing material fixed in the binary frame to intercept the line of sight. For IGR J14257-6117, we estimate ($50^o\,\lesssim\,i\,\lesssim\,70^o$). Whether also the mass accretion rate plays a role in the large orbital modulations in IPs cannot be established with the present data.Comment: Accepted for publication on MNRAS. 9 pages, 6 table, 5 figure

A new measurement of thermal conductivity of amorphous ice and its implications for the thermal evolution of comets

Very slowly deposited amorphous ice has a thermal conductivity about four orders of magnitude or more smaller than hitherto estimated. Using the exceedingly low value of the thermal conductivity of comets deduced from the properties of amorphous ice leads to the expectation that internal heating of comets is negligible below the outer several tens of centimeters

Swift J0525.6+2416 and IGR J04571+4527: two new hard X-ray selected magnetic cataclysmic variables identified with XMM-Newton

IGR J04571+4527 and Swift J0525.6+2416 are two hard X-ray sources detected in the Swift/BAT and INTEGRAL/IBIS surveys. They were proposed to be magnetic cataclysmic variables of the Intermediate Polar (IP) type, based on optical spectroscopy. IGR J04571+4527 also showed a 1218 s optical periodicity, suggestive of the rotational period of a white dwarf, further pointing towards an IP classification. We here present detailed X-ray (0.3-10 keV) timing and spectral analysis performed with XMM-Newton, complemented with hard X-ray coverage (15-70 keV) from Swift/BAT. These are the first high signal to noise observations in the soft X-ray domain for both sources, allowing us to identify the white dwarf X-ray spin period of Swift J0525.6+2416 (226.28 s), and IGR J04571+4527 (1222.6 s). A model consisting of multi-temperature optically thin emission with complex absorption adequately fits the broad-band spectrum of both sources. We estimate a white dwarf mass of about 1.1 and 1.0 solar masses for IGR J04571+4527 and Swift J0525.6+2416, respectively. The above characteristics allow us to unambiguously classify both sources as IPs, confirming the high incidence of this subclass among hard X-ray emitting Cataclysmic Variables.Comment: 8 pages, 4 figures, 3 tables. Accepted for publication in MNRA

A Fourier transform for sheaves on Lagrangian families of real tori

We systematically develop a transform of the Fourier-Mukai type for sheaves on symplectic manifolds $X$ of any dimension fibred in Lagrangian tori. One obtains a bijective correspondence between unitary local systems supported on Lagrangian submanifolds of $X$ and holomorphic vector bundles with compatible unitary connections supported on complex submanifolds of the relative Jacobian of $X$ (suitable conditions being verified on both sides).Comment: Latex, 30 pages (in a4wide format), no figures. v2: Minor expository changes, typos corrected. v3: Final version to appear in two parts in J. Geom. Phy

Broad-band characteristics of seven new hard X-ray selected cataclysmic variables

Indexación: Web of Science; Scopus.We present timing and spectral analysis of a sample of seven hard X-ray selected cataclysmic variable candidates based on simultaneous X-ray and optical observations collected with XMM–Newton, complemented with Swift/BAT and INTEGRAL /IBIS hard X-ray data and ground-based optical photometry. For six sources, X-ray pulsations are detected for the first time in the range of ∼296–6098 s, identifying them as members of the magnetic class. Swift J0927.7−6945, Swift J0958.0−4208, Swift J1701.3−4304, Swift J2113.5+5422 and possibly PBC J0801.2−4625 are intermediate polars (IPs), while Swift J0706.8+0325 is a short (1.7 h) orbital period polar, the 11th hard X-ray-selected identified so far. X-ray orbital modulation is also observed in Swift J0927.7−6945 (5.2 h) and Swift J2113.5+5422 (4.1 h). Swift J1701.3−4304 is discovered as the longest orbital period (12.8 h) deep eclipsing IP. The spectra of the magnetic systems reveal optically thin multitemperature emission between 0.2 and 60 keV. Energy-dependent spin pulses and the orbital modulation in Swift J0927.7−6945 and Swift J2113.5+5422 are due to intervening local high-density absorbing material (NH ∼ 1022 − 23 cm−2). In Swift J0958.0−4208 and Swift J1701.3−4304, a soft X-ray blackbody (kT ∼ 50 and ∼80 eV) is detected, adding them to the growing group of ‘soft’ IPs. White dwarf masses are determined in the range of ∼0.58–1.18 M, indicating massive accreting primaries in five of them. Most sources accrete at rates lower than the expected secular value for their orbital period. Formerly proposed as a long-period (9.4 h) nova-like CV, Swift J0746.3−1608 shows peculiar spectrum and light curves suggesting either an atypical low-luminosity CV or a low-mass X-ray binary.https://academic.oup.com/mnras/article/470/4/4815/390658

Discovery of a new pulsating X-ray source with a 1549.1-s period, AX J183220-0840

A new pulsating X-ray source, AX J183220-0840, with a 1549.1-s period was discovered at R.A.= 18h32m20s and Dec.=-8d40'30'' (J2000, uncertainty=0.6degree) during an ASCA observation on the Galactic plane. The source was observed two times, in 1997 and in 1999. A phase-averaged X-ray flux of 1.1E-11 ergs cm-2 s-1 and pulsation period of 1549.1+/-0.4 s were consistently obtained from these two observations. The X-ray spectrum was represented by a flat absorbed power-law with a photon-index of =~0.8 and an absorption column density of =~1.3E22 cm-2. Also, a signature of iron K-shell line emission with a centroid of 6.7 keV and an equivalent width of approximately 450 eV was detected. From the pulsation period and the iron-line feature, AX J183220-0840 is likely to be a magnetic white dwarf binary with a complexly absorbed thermal spectrum with a temperature of about 10 keV.Comment: 13 pages, 4 figures, accepted for publication in ApJ Letter