Time-resolved spectroscopy of the rapidly oscillating Ap star KIC 10195926

We report an analysis of high time resolution spectra of the chemically peculiar Ap star KIC 10195926 obtained with the Subaru telescope. We find that the star has low overabundances of rare earth elements compared with other rapidly oscillating Ap stars. We found only upper limits for pulsations from spectral lines of rare earth and other chemical elements. Pulsation was found only for the narrow core of the Hα line with an amplitude of 171 ± 41ms−1 and with the frequency corresponding to photometric frequency obtained from Kepler observations

A 3D study of the photosphere of HD 99563 - I. Pulsation analysis

We have used high-speed spectroscopy of the rapidly oscillating Ap (roAp) star HD 99563 to study the pulsation amplitude and phase behaviour of elements in its stratified atmosphere over one 2.91-d rotation cycle. We identify spectral features related to patches in the surface distribution of chemical elements and study the pulsation amplitudes and phases as the patches move across the stellar disc. The variations are consistent with a distorted non-radial dipole pulsation mode. We measure a 1.6 km s−1 rotational variation in the mean radial velocities of Hα and argue that this is the first observation of Hα abundance spots caused by He settling through suppression of convection by the magnetic field on an oblique rotator, in support of a prime theory for the excitation mechanism of roAp star pulsation. We demonstrate that HD 99563 is the second roAp star to show aspect dependence of blue-to-red running wave line profile variations in Nd iii spots

The first evidence for multiple pulsation axes: a new roAp star in the Kepler field, KIC 10195926

We have discovered a new rapidly oscillating Ap star among the Kepler Mission target stars, KIC 10195926. This star shows two pulsation modes with periods that are amongst the longest known for roAp stars at 17.1 min and 18.1 min, indicating that the star is near the terminal age main sequence. The principal pulsation mode is an oblique dipole mode that shows a rotationally split frequency septuplet that provides information on the geometry of the mode. The secondary mode also appears to be a dipole mode with a rotationally split triplet, but we are able to show within the improved oblique pulsator model that these two modes cannot have the same axis of pulsation. This is the first time for any pulsating star that evidence has been found for separate pulsation axes for different modes. The two modes are separated in frequency by 55 microHz, which we model as the large separation. The star is an alpha^2 CVn spotted magnetic variable that shows a complex rotational light variation with a period of Prot = 5.68459 d. For the first time for any spotted magnetic star of the upper main sequence, we find clear evidence of light variation with a period of twice the rotation period; i.e. a subharmonic frequency of $\nu_{\rm rot}/2$. We propose that this and other subharmonics are the first observed manifestation of torsional modes in an roAp star. From high resolution spectra we determine Teff = 7400 K, log g = 3.6 and v sin i = 21 km/s. We have found a magnetic pulsation model with fundamental parameters close to these values that reproduces the rotational variations of the two obliquely pulsating modes with different pulsation axes. The star shows overabundances of the rare earth elements, but these are not as extreme as most other roAp stars. The spectrum is variable with rotation, indicating surface abundance patches.Comment: 17 pages; 16 figures; MNRA

Dissipation in Quasi One-Dimensional Superconducting Single-Crystal Sn Nanowires

Electrical transport measurements were made on single-crystal Sn nanowires to understand the intrinsic dissipation mechanisms of a one-dimensional superconductor. While the resistance of wires of diameter larger than 70 nm drops precipitately to zero at Tc near 3.7 K, a residual resistive tail extending down to low temperature is found for wires with diameters of 20 and 40 nm. As a function of temperature, the logarithm of the residual resistance appears as two linear sections, one within a few tenths of a degree below Tc and the other extending down to at least 0.47 K, the minimum temperature of the measurements. The residual resistance is found to be ohmic at all temperatures below Tc of Sn. These findings are suggestive of a thermally activated phase slip process near Tc and quantum fluctuation-induced phase slip process in the low temperature regime. When the excitation current exceeds a critical value, the voltage-current (V-I) curves show a series of discrete steps in approaching the normal state. These steps cannot be fully understood with the classical Skocpol-Beasley-Tinkham phase slip center model (PSC), but can be qualitatively accounted for partly by the PSC model modified by Michotte et al.Comment: 7 pages, 5 figures. To be appeared on Physical Review B 71, 200

Stochastic B\"acklund transformations

How does one introduce randomness into a classical dynamical system in order to produce something which is related to the `corresponding' quantum system? We consider this question from a probabilistic point of view, in the context of some integrable Hamiltonian systems

CAIRNS: The Cluster And Infall Region Nearby Survey I. Redshifts and Mass Profiles

The CAIRNS (Cluster And Infall Region Nearby Survey) project is a spectroscopic survey of the infall regions surrounding eight nearby, rich, X-ray luminous clusters of galaxies. We collect 15665 redshifts (3471 new or remeasured) within \sim 5-10 Mpc of the centers of the clusters, making it the largest study of the infall regions of clusters. We determine cluster membership and the mass profiles of the clusters based on the phase space distribution of the galaxies. All of the clusters display decreasing velocity dispersion profiles. The mass profiles are fit well by functional forms based on numerical simulations but exclude an isothermal sphere. Specifically, NFW and Hernquist models provide good descriptions of cluster mass profiles to their turnaround radii. Our sample shows that the predicted infall pattern is ubiquitous in rich, X-ray luminous clusters over a large mass range. The caustic mass estimates are in excellent agreement with independent X-ray estimates at small radii and with virial estimates at intermediate radii. The mean ratio of the caustic mass to the X-ray mass is 1.03\pm0.11 and the mean ratio of the caustic mass to the virial mass (when corrected for the surface pressure term) is 0.93\pm0.07. We further demonstrate that the caustic technique provides reasonable mass estimates even in merging clusters.Comment: 54 pages, 18 figures, to appear in The Astronomical Journa

Class I methanol masers in low-mass star formation regions

Four Class I maser sources were detected at 44, 84, and 95 GHz toward chemically rich outflows in the regions of low-mass star formation NGC 1333I4A, NGC 1333I2A, HH25, and L1157. One more maser was found at 36 GHz toward a similar outflow, NGC 2023. Flux densities of the newly detected masers are no more than 18 Jy, being much lower than those of strong masers in regions of high-mass star formation. The brightness temperatures of the strongest peaks in NGC 1333I4A, HH25, and L1157 at 44 GHz are higher than 2000 K, whereas that of the peak in NGC 1333I2A is only 176 K. However, rotational diagram analysis showed that the latter source is also a maser. The main properties of the newly detected masers are similar to those of Class I methanol masers in regions of massive star formation. The former masers are likely to be an extension of the latter maser population toward low luminosities of both the masers and the corresponding YSOs.Comment: 5 pages, 1 figure, Proc. IAU Symp. 287 "Cosmic Masers: from OH to H0". LSR velocities of the HH25 masers, which are presented in Table 1, are correcte

The detection of Class I methanol masers towards regions of low-mass star formation

Six young bipolar outflows in regions of low-to-intermediate-mass star formation were observed in the 7_0-6_1A+, 8_0-7_1A+, and 5_{-1}-4_0E methanol lines at 44, 95, and 84 GHz, respectively. Narrow features were detected towards NGC 1333IRAS4A, HH 25MMS, and L1157 B1. Flux densities of the detected lines are no higher than 11 Jy, which is much lower than the flux densities of strong maser lines in regions of high-mass star formation. Analysis shows that most likely the narrow features are masers.Comment: 12 pages, 6 figures, to be published in Astronomy Report

Excited Hydroxyl Outflow in the High-Mass Star-Forming Region G34.26+0.15

G34.26+0.15 is a region of high-mass star formation that contains a broad range of young stellar objects in different stages of evolution, including a hot molecular core, hyper-compact HII regions and a prototypical cometary ultra-compact HII region. Previous high-sensitivity single dish observations by our group resulted in the detection of broad 6035 MHz OH absorption in this region; the line showed a significant blue-shifted asymmetry indicative of molecular gas expansion. We present high-sensitivity Karl G. Jansky Very Large Array (VLA) observations of the 6035 MHz OH line conducted to image the absorption and investigate its origin with respect to the different star formation sites in the region. In addition, we report detection of 6030 MHz OH absorption with the VLA and further observations of 4.7 GHz and 6.0 GHz OH lines obtained with the Arecibo Telescope. The 6030 MHz OH line shows a very similar absorption profile as the 6035 MHz OH line. We found that the 6035 MHz OH line absorption region is spatially unresolved at $\sim 2$" scales, and it is coincident with one of the bright ionized cores of the cometary HII region that shows broad radio recombination line emission. We discuss a scenario where the OH absorption is tracing the remnants of a pole-on molecular outflow that is being ionized inside-out by the ultra-compact HII region.Comment: 19 pages, 6 figures. Accepted for publication in The Astrophysical Journa