Discovery of an Unusual High State in the Long-Term Light Curve of AM Herculis

The magnetic cataclysmic variable archetype AM Herculis is known to display high and low photometric states, in which it switches from Roche lobe-overflow accretion (high) to wind accretion (low). The origin of this behavior is still unknown (although it is believed to be linked to the presence of starspots located near the L1 point on the secondary star), as are the specifics of duration and frequency of the two states. During the recent (2007) transition from an exceptionally long period of persistent low state behavior back to the high state, AM Her entered a short (~2 month) intermediate state, in which its brightness remained at ~0.5 mag fainter than the normal high-state level. Within the recorded history of AM Her, this was the first time the system displayed such behavior. Using data from the American Association of Variable Star Observers, we compare the characteristics of this faint high state to the subsequent normal high state, and a prior "failed high state," in which the system briefly reached a brightness level near that of the normal high state before rapidly returning to the low state. The distribution of magnitude values attained during each state, along with the shapes of the orbital light curve in each state, support a scenario in which the specific configuration of the accretion flow between the secondary star and the white dwarf must be rapidly established at the end of a low state, even before the mass transfer rate has reached the normal high-state level

Verwirklichung einer vollkommenen Glücksmöglichkeit/A perfect bliss-potential realized: “Wunsch, Indianer zu werden” im Lichte des Dao Kafkas übersetzend gelesen/Transreading “Wish, to Become Indian” in light of Kafka’s Dao

Walking an unexplored path, Huiwen Helen Zhang contextualizes Kafka's pithy and cryptic parable, “Wish, to Become Indian” in his transplantation of Daoist philosophy—an astonishing cross-cultural enigma that Zhang terms “Kafka's Dao”—and parses it through a micro-level approach that Zhang terms “transreading.” Contextualizing “Wish, to Become Indian” in Kafka's dialogue with ancient Chinese philosophers such as Laozi, Liezi, and Zhuangzi enables the reader to comprehend a series of otherwise incomprehensible puzzles. Zhang's scrutiny of Kafka's Dao shows how, through creative writing, Kafka not only penetrates esoteric Daoist classics, but also furthers their spirit in a way that transcends Richard Wilhelm, the pioneer European Sinologist. Transreading “Wish, to Become Indian” illuminates nuances that otherwise might have been overlooked. Wordplay, punctuational oddity, syntactic complexity, lyric density, and the curiously interlaced tenses and cases are all part of the idiosyncratic delivery of Kafka's message. Integrating the four activities of transreading—lento reading demanded and enhanced by cultural hermeneutics, creative writing required and inspired by poetic translation—unravels Kafka's riddle as a historical-cultural phenomenon.publishedVersio

Observations of V592 Cas -— an Outflow at Optical Wavelengths

We present new red optical spectra of V592 Cas aimed at exploring the properties of the outflow of this system in a spectral region where the underlying white dwarf and the accretion disk do not contribute significantly to the observed absorption components of the Hα and He I line profiles. We use the Hα emission line to study the wind, which appears as pronounced blueshifted P Cygni absorption troughs whose low velocity end contaminates the blue side of the emission line profile. The wind appears to be episodic in nature, with multiple events reaching velocities of 5000 km s^–1 in Hα. Similar (but weaker) wind signatures appear in the He I 5876 Å line but are absent in He I 6678 Å. Our data suggest that during wind episodes the wind is phase dependent and is visible for half of the orbit of the system. Considering that V592 Cas is viewed almost face-on, the symmetry axis of the outflow cannot be orthogonal to the disk and/or the outflow must have some other inherent asymmetry in outflow geometry. A possible origin of the wind is in a disk hotspot, either at the initial impact point of the accretion stream on the disk edge or as a result of disk overflow (similar to SW Sextantis stars). Simultaneous optical photometry during one night of our spectroscopic observations indicate that there is no clear relationship between the optical brightness variations and the strength of the outflow in this system

Orbit-resolved photometry and echelle spectroscopy of the cataclysmic variable ST LMi during a 2007 high state

We present high-resolution echelle spectra and contemporaneous photometry of the polar ST LMi during a high state in 2007 March. Emission lines at Hα, He I λ5876, and He I λ7065 show similar line profiles over orbital phase and have narrow and broad components. These profile changes with phase are very similar to those reported in earlier high-state studies of ST LMi. The radial velocity curves from double Gaussian fits to the line profiles are interpreted as two crossing curves, neither of which is coincident with the orbital motion of the secondary star. We attribute one component to infall motions near the white dwarf and the other to a gas streaming along magnetic field lines connecting the two stars

What’s Cool About Hot Stars? Cataclysmic Variables in the Mid-Infrared

We review recent results from mid-infrared observations of cataclysmic variables with the Spitzer Space Telescope. In general, these observations have revealed mid-infrared excesses, above the level expected from the stellar and accretion components, in numerous systems. This excess can be modeled as originating from circumstellar and/or circumbinary dust. We present an overview of spectral energy distributions spanning the ultraviolet to the mid-infrared, as well as mid-infrared light curves, of disk-accreting and magnetic cataclysmic variables. Physically realistic models constructed to reproduce these data indicate that the mid-infrared luminosity of many cataclysmic variables is dominated by emission from warm (T < 2000 K) dust. The presence and characteristics of dust in cataclysmic variables has potentially important implications for the secular evolution scenario for interacting binary stars

Apparent multiple Delta m^2_32 in muon anti-neutrino and muon neutrino survival oscillations from non-standard interaction matter effect

Neutrinos propagating through matter may participate in forward coherent neutral-current-like scattering arising from non-standard interactions as well as from the Mikheyev-Smirnov-Wolfenstein matter potential $V_e$. We show that at fixed long baselines through matter of constant density, the non-standard interaction potential $\epsilon_{\mu\tau} V_e$ can contribute an additional term to the oscillation phase whose sign differs for \anumu versus \numu propagation in matter. Its presence can cause different apparent $\Delta m^2$ to be erroneously inferred on the basis of oscillations in vacuum, with values lying above (for \anumu) or below (for \numu) the actual $\Delta m^2_{32}$ for the case where $\epsilon_{\mu\tau}$ is predominantly real-valued and of sign opposite to $\Delta m_{32}^2$. An NSI scenario invoking only $\Re(\epsilon_{\mu\tau})$ is shown to be capable of accounting for a disparity recently reported between oscillation survival for \anumu and \numu fluxes measured at $735~\mathrm{km}$ by the MINOS experiment. Implications for mantle traversal by atmospheric neutrinos are examined. The NSI matter potential with non-maximal mixing could evade conventional atmospheric neutrino analyses which do not distinguish \numu from \anumu on an event-by-event basis.Comment: 7 pages, 5 figures. Accepted for publication in Physical Review

"Dark Matter" in Accretion Disks

Using Spitzer Space Telescope photometric observations of the eclipsing, interacting binary WZ Sge, we have discovered that the accretion disk is far more complex than previously believed. Our 4.5 and 8 micron time series observations reveal that the well known gaseous accretion disk is surrounded by an asymmetric disk of dusty material with a radius approximately 15 times larger than the gaseous disk. This dust ring contains only a small amount of mass and is completely invisible at optical and near-IR wavelengths, hence consisting of "dark matter". We have produced a model dust ring using 1 micron spherical particles with a density of 3 g/cm$^3$ and with a temperature profile ranging from 700-1500K. Our discovery about the accretion disk structure and the presence of a larger, outer dust ring have great relevance for accretion disks in general, including those in other interacting binary systems, pre-main sequence stars, and active galaxies.Comment: 34 pages, 8 figures (3 in color). Accepted to Ap