Detecting solar axions using Earth's magnetic field

We show that solar axion conversion to photons in the Earth's magnetosphere can produce an x-ray flux, with average energy \sim 4 keV, which is measurable on the dark side of the Earth. The smallness of the Earth's magnetic field is compensated by a large magnetized volume. For axion masses < 10^{-4} eV, a low-Earth-orbit x-ray detector with an effective area of 10^4 cm^2, pointed at the solar core, can probe the photon-axion coupling down to 10^{-11} GeV^{-1}, in one year. Thus, the sensitivity of this new approach will be an order of magnitude beyond current laboratory limits.Comment: 3 pages, 1 figure, typos corrected, references adde

SkyDOT (Sky Database for Objects in the Time Domain): A Virtual Observatory for Variability Studies at LANL

The mining of Virtual Observatories (VOs) is becoming a powerful new method for discovery in astronomy. Here we report on the development of SkyDOT (Sky Database for Objects in the Time domain), a new Virtual Observatory, which is dedicated to the study of sky variability. The site will confederate a number of massive variability surveys and enable exploration of the time domain in astronomy. We discuss the architecture of the database and the functionality of the user interface. An important aspect of SkyDOT is that it is continuously updated in near real time so that users can access new observations in a timely manner. The site will also utilize high level machine learning tools that will allow sophisticated mining of the archive. Another key feature is the real time data stream provided by RAPTOR (RAPid Telescopes for Optical Response), a new sky monitoring experiment under construction at Los Alamos National Laboratory (LANL).Comment: to appear in SPIE proceedings vol. 4846, 11 pages, 5 figure

MOXE: An X-ray all-sky monitor for Soviet Spectrum-X-Gamma Mission

A Monitoring Monitoring X-Ray Equipment (MOXE) is being developed for the Soviet Spectrum-X-Gamma Mission. MOXE is an X-ray all-sky monitor based on array of pinhole cameras, to be provided via a collaboration between Goddard Space Flight Center and Los Alamos National Laboratory. The objectives are to alert other observers on Spectrum-X-Gamma and other platforms of interesting transient activity, and to synoptically monitor the X-ray sky and study long-term changes in X-ray binaries. MOXE will be sensitive to sources as faint as 2 milliCrab (5 sigma) in 1 day, and cover the 2 to 20 KeV band

On the Correlated X-ray and Optical Evolution of SS Cygni

We have analyzed the variability and spectral evolution of the prototype dwarf nova system SS Cygni using RXTE data and AAVSO observations. A series of pointed RXTE/PCA observations allow us to trace the evolution of the X-ray spectrum of SS Cygni in unprecedented detail, while 6 years of optical AAVSO and RXTE/ASM light curves show long-term patterns. Employing a technique in which we stack the X-ray flux over multiple outbursts, phased according to the optical light curve, we investigate the outburst morphology. We find that the 3-12 keV X-ray flux is suppressed during optical outbursts, a behavior seen previously, but only in a handful of cycles. The several outbursts of SS Cygni observed with the more sensitive RXTE/PCA also show a depression of the X-rays during optical outburst. We quantify the time lags between the optical and X-ray outbursts, and the timescales of the X-ray recovery from outburst. The optical light curve of SS Cygni exhibits brief anomalous outbursts. During these events the hard X-rays and optical flux increase together. The long-term data suggest that the X-rays decline between outburst. Our results are in general agreement with modified disk instability models (DIM), which invoke a two-component accretion flow consisting of a cool optically thick accretion disk truncated at an inner radius, and a quasi-spherical hot corona-like flow extending to the surface of the white dwarf. We discuss our results in the framework of one such model, involving the evaporation of the inner part of the optically thick accretion disk, proposed by Meyer & Meyer-Hofmeister (1994).Comment: 24 pages, 8 figures, 2 tables, accepted for publication in Ap

High-resolution Elemental Mapping of the Lunar Surface

New instruments and missions are being proposed to study the lunar surface as a result of the resurgence of interest in returning to the Moon. One instrument recently proposed is similar in concept to the x-ray fluorescence detectors flown on Apollo, but utilizes fluorescence from the L- and M-shells rather than the K-shell. This soft X-Ray Flourescence Imager (XRFI) is discussed

XMM-Newton observations of the ultra-compact binary RX J1914+24

We present XMM–Newton observations of the 569-s-period system RX J1914+24 (V407 Vul). This period is believed to represent the binary orbital period making it an ultracompact binary system. By comparing the phase of the rise to maximum X-ray flux at various epochs (this includes observations made using ROSAT, ASCA and Chandra) we find that the system is spinning up at a rate of 3.17 ± 0.07 × 10−12 s s−1. We find that the spectra soften as the X-ray flux declines towards the off-phase of the 569-s period. Further, the spectra are best fitted by an absorbed blackbody component together with a broad emission feature around 0.59 keV. This emission feature is most prominent at the peak of the on-phase. We speculate on its origin

An Unusual X-ray Burst from the Globular Cluster M28

We report the discovery of an unusual X-ray burst from the direction of the Globular Cluster M28 using data acquired with the ASCA Observatory. The burst was recorded by all four ASCA telescopes and displays a fast (~ 70 ms) rise followed by an exponential decay (t = 7.5 s) and a steady afterglow which lasts between 800 - 3250 s. The image of the burst is consistent with an ASCA point source and is centered on quiescent X-ray emission from the core of M28. The burst temporal profile is similar to Type-I bursts emitted by accreting neutron stars of low mass X-ray binaries (LMXB). We argue that the burst arises from an LMXB that is located in the core of M28. The burst is unique in two ways: it is intrinsically sub-luminous, ~ 0.02 L_Edd and more importantly, originates from a source whose quiescent luminosity is fainter than that of the known cluster bursters by three orders of magnitude. We suggest that this burst is from a highly magnetized neutron star accreting at a low rate. These accreting systems may account for the mysterious low luminosity X-ray sources in globular clusters.Comment: 13 pages with 3 eps figures, LATEX, aastex, psfig. To appear in the Astrophysical Journal Letter