A re-analysis of Gliese 667C HARPS precision radial velocity data was carried out with a Bayesian multi-planet Kepler periodogram (from 0 to 7 planets) based on a fusion Markov chain Monte Carlo algorithm. The most probable number of signals detected is six with a Bayesian false alarm probability of 0.012. The residuals were shown to be consistent with white noise. The six signals detected include two previously reported with periods of 7.198 (b) and 28.14 (c) days, plus additional periods of 30.82, 38.82, 53.22, and 91.3 days. The existence of these Keplerian-like signals suggest the possibility of additional planets in the habitable zone of Gl 667C although some of the signals could be artifacts arising from the sampling or stellar surface activity. N-body orbital integrations are being undertaken to determine which of these signals are consistent with a stable planetary system. Preliminary results demonstrate that four of the signals, with periods of 7.2, 28.1, 38.8, & 91 d, are consistent with a stable 4 planet system on time scales of 107 yr. The M sin i values are ~5.5, 4.4, 1.9, and 4.7 M⊕, respectively.

The clumping of massive star winds is an established paradigm, which is confirmed by multiple lines of evidence and is supported by stellar wind theory. We use the results from time-dependent hydrodynamical models of the instability in the line-driven wind of a massive supergiant star to derive the time-dependent accretion rate on to a compact object in the Bondi-Hoyle-Lyttleton approximation. The strong density and velocity fluctuations in the wind result in strong variability of the synthetic X-ray light curves. Photoionization of inhomogeneous winds is different from the photoinization of smooth winds. The degree of ionization is affected by the wind clumping. The wind clumping must also be taken into account when comparing the observed and model spectra of the photoionized stellar wind.

Magnetic helicity was found important in understanding solar activities such as flares and coronal mass ejections (CME). Berger and field (1984) derived an expression for helicity flux dHm/dt, that can be applied to an individual solar active region (AR) occupying an area S of the photosphere, (1)

\begin{linenomath} dH_{m}/dt=-2\int_{s}[(\mathbf{A_{p}}\cdot \mathbf{V})\mathbf{B}-(\mathbf{A_{p}} \cdot \mathbf{B})\mathbf{V}] dS, \eqno{(1)} \end{linenomath}

(2)

\begin{linenomath} dH/dt=-\int2(\textbf{A}_{p}\cdot \textbf{V}_{LCT})B_{n}dS, \eqno{(2)} \end{linenomath}

With the cylindrical equal area (CEA) projection data from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO), we reconstructed the three-dimensional (3D) magnetic fields in the corona, using a non-linear force-free field (NLFFF) extrapolation method every 12 minutes during five days, to calculate the squashing degree factor Q in the volume. The results show that this AR has an hyperbolic flux tube (HFT) configuration, a typical topology of quadrupole, which is stable even during the two large flares (M6.6 and X2.2 class flares).

We report on Chandra observations of the black widow pulsar, PSR B1957+20. Evidence for a binary-phase dependence of the X-ray emission from the pulsar is found with a deep observation. The binary-phase resolved spectral analysis reveals non-thermal X-ray emission of PSR B1957+20, confirming the results of previous studies. This suggests that the X-rays are mostly due to intra-binary shock emission which is strongest when the pulsar wind interacts with the ablated material from the companion star. The geometry of the peak emission is determined in our study. The marginal softening of the spectrum of the non-thermal X-ray tail may indicate that particles injected at the termination shock is dominated by synchrotron cooling.

Our analysis of a VLBA 12-hour synthesis observations of the OH masers in W49N has provided detailed high angular-resolution images of the maser sources, at 1612, 1665 and 1667 MHz. The images, of several dozens of spots, reveal anisotropic scatter broadening; with typical sizes of a few tens of milli-arc-seconds and axial ratios between 1.5 to 3. The image position angles oriented perpendicular to the galactic plane are interpreted in terms of elongation of electron-density irregularities parallel to the galactic plane, due to a similarly aligned local magnetic field. However, we find the apparent angular sizes on the average a factor of 2.5 less than those reported by Desai et al., indicating significantly less scattering than inferred earlier. The average position angle of the scattered broadened images is also seen to deviate significantly (by about 10 degrees) from that implied by the magnetic field in the Galactic plane. More intriguingly, for a few Zeeman pairs in our set, we find significant differences in the scatter broadened images for the two hands of polarization, even when apparent velocity separation is less than 0.1 km/s. Here we present the details of our observations and analysis, and discuss the interesting implications of our results for the intervening anisotropic magneto-ionic medium, as well as a comparison with the expectations based on earlier work.

We study the temporal and spatial evolution of magnetic field parameters, and multi-wavelength observations of the AR 11226 and AR 11261, observed during 02-09 June 2011 and 31 July to 06 August 2011 respectively, to probe the origin of the associated solar energetic particles (SEPs). The magnetic-field toplogy of both ARs shows complex magnetic structure of β and βγ configuration. The X-ray observations by GOES and RHESSI reveal that the AR 11226 as well as AR 11261 has been most turbulent to produce flares accompanying CMEs and SEPs. We restrict our study of magnetic field evolution of ARs to helio-longitudes E20-W70. The AR 11226 produced 28 flares (⩾ GOES C-class) and 8 CMEs as well as 5 SEPs. On the other hand, the AR 11261 produced 29 flares (⩾ GOES C class), 8 CMEs as well as 5 SEPs. We study the temporal evolution of magnetic field parameters viz. gradient, shear, rotation to probe the origin of the energy release in the flare and associated CME and SEP. We do not find convincing relationship in view of predicting SEPs.

Examining both optical and optical-infrared color distributions of the globular cluster (GC) systems in large elliptical galaxies is the key to study how non-linearities in the color-metallicity relations of their GC systems are linked to bimodal optical color distributions. In order to do this for the core of the Coma cluster of galaxies (Abell 1656), centered on the giant elliptical galaxy NGC 4874, we have combined F160W (H160) near-infrared (NIR) imaging data acquired with the Wide Field Camera 3 IR Channel (WFC3/IR), installed on Hubble Space Telescope (HST) in 2009, with F475W (g475) and F814W (I814) optical imaging data from the HST Advanced Camera for Surveys (ACS). Since optical-NIR color distributions of extragalactic GC systems reflect the underlying features of the metallicity distributions, we have probed not only optical g475–I814 and optical-NIR I814–H160 color distributions but also the color-color relation for this GC system. The features of these color distributions have been quantitatively analyzed using the Gaussian Mixture Modeling code. We find that brighter GCs have a much redder mean color than fainter ones. The optical color distribution of the GC system in the Coma cluster core shows the typical bimodality, while the evidence for bimodality is significantly weaker in the optical-NIR color distribution.

In recent years several multi-body, circumbinary planets have been proposed to orbit short-period eclipsing binaries. In light of the recent discoveries based on the Kepler data, the existence of such systems seems plausible. However, performing a detailed dynamical analysis reveals that the majority of the proposed planetary systems follow highly unstable orbits. In order to solve the origin of this problem, we have started to model synthetic light-travel time signals of stable planetary systems. In particular, we aim to study the response of the model in various circumstances (e.g red/white noise level, various sampling frequencies, in-homogeneous data sets, baseline dependency.) This work will significantly increase the confidence with which model work is carried out for future systems and help towards an understaning when models break down (e.g resulting in unstable systems).

We present results of our world-wide observing campaign which was dedicated to one of the most active dwarf novae, IX Draconis. We investigated photometric behaviour of the system to derive its basic parameters. This study is important in the context of our understanding of the accretion process of IX Draconis, as well as other active cataclysmic variables, especially those from the still poorly studied type of ER UMa stars.

We present the analysis of a large solar near-relativistic (>50 keV) electron event observed by the Wind spacecraft on 1998 April 20. In-situ data show variations of the local magnetic field direction accompanied by changes in the topology of the observed electron pitch-angle distributions. These suggest changes in the magnetic flux tubes scanned by Wind. Using simulations of the interplanetary particle transport, we model the early rising phase of the electron event, from 10:30 to 11:00 UT, and infer the propagation conditions and the injection history of the first arriving 50–82 keV solar electrons. The results reveal a prompt (≤1 min) release in coincidence with the soft X-ray and type III radio bursts, suggesting that the first arriving electrons were flare-accelerated.

We present a summary of the physical and chemical properties we have obtained for the molecular gas found in galaxies, an essential triggering ingredient to any star formation (SF) process. In particular, we focus our studies on the molecular gas phases as traced by CO, HCO+ and CS line emissions, in a sample of galaxies including starbursts -SBs-, irregulars galaxies, low-metallicity sources, normal spirals, mergers, Early Type Galaxies (ETGs), galaxies with an Active Galactic Nucleus (AGN), with Cosmic Ray Dominated Regions (CRDRs) and with Photo-Dominated Regions (PDRs). Our studies mix theoretical developments (i.e. computational models) with the acquisition of large observational datatsets (at both low and high spatial resolution) that we then compare in order to better determine the conditions under which some SF activity is starting and/or is maintained.

We are investigating if the orbital geometry of exoplanets affects the activity of their host star by studying a sample of planetary systems known to contain massive planets on short period, highly elliptical orbits. While recent studies in the optical, UV, and X-Ray have shown enhanced chromospheric activity for stars hosting exoplanets with orbital semi-major axes less than 0.1 AU (Krejcova 2012, Shkolnik 2013, Kashyap 2008, Poppenhaeger 2010), it is not yet clear whether this activity is driven by magnetic or tidal interactions. We are probing the dependence of star-planet interactions (SPI) on the orbital geometry of the planetary systems by analyzing chromospheric lines (such as Ca II H & K) for variability phased with the exoplanet's orbit. We have obtained high resolution spectra of several systems with the McDonald 2.1-m Sandiford echelle spectrograph, ARCES on the APO 3.5-m, and for HIRES on Keck I from the Keck Observatory Archive. We describe our methodology and review how our results will use orbital geometry to deduce how planets may affect the activity of their host stars.

We investigate 10 M-class flares observed by the SOXS mission to study the influence of the solar flare plasma cooling on the Neupert effect. We study the temporal evolution of 1s cadence X-ray emission in 7-10 keV and 10-30 keV representing the SXR and HXR emission respectively. We model the cooling as a function of time by the ratio of time-derivative of SXR with the HXR flux. We report that the ratio is exponentially decaying in rise phase of the flare, which, however, saturates after the impulsive phase. We estimate the cooling time scale in the rise phase for the flares and found to be varying between 39 and 525 s.

186 binary pulsars are shown in the magnetic field versus spin period (B-P) diagram, and their relations to the millisecond pulsars can be clearly seen. We declaim a minimum accretion rate for the millisecond pulsar formation both from the observation and theory. If the accretion rate is lower than the minimum accretion rate, the pulsar in binary system will not become a millisecond pulsar after the evolution.

The Atacama Large Millimeter/submillimeter Array (ALMA)‡, and the Jansky Very Large Array (JVLA) have recently begun probing the Universe. Both provide the largest collecting area available at locations on a high dry site, endowing them with unparalleled potential for sensitive spectral line observations. Over the next few years, these telescopes will be joined by other telescopes to provide advances in maser science, including NOEMA and the LMT. Other instruments of note for maser science which may commence construction include the North American Array, the CCAT, and an enlarged worldwide VLB network outfitted to operate into the millimeter wavelength regime.

Sudden Galactic Cosmic Ray (GCR) intensity decreases are related to the passage of Interplanetary Coronal Mass Ejections (ICMEs). These phenomena are also known as Forbush Decreases (FDs). The deepest FDs are associated with the passage of Magnetic Clouds (MCs). In this preliminary study we select “non-interacting” MCs associated with FDs observed from ground Neutron Monitors in the period 1996-2009, with the aim of reducing the complexity and the number of parameters involved in the GCR-MC interactions. We introduce a method to determine properties of the “ejecta component” of the FD. We analyze properties of the ejecta component in combination with properties of MCs. From the resulting selection of events, we find that those FDs containing ejecta components show stronger correlations with MC parameters than our total sample of events.

The Herschel/HIFI absorption spectroscopy surveys reveal the unexpected molecular richness of the Galactic diffuse ISM, even in gas of very low average H2 molecular fraction. In particular, two hydrides, CH+ and SH+ with highly endoergic formation routes have abundances that challenge models of UV-driven chemistry. The intermittent dissipation of turbulence appears as a plausible additional source of energy for the diffuse ISM chemistry. We present recent results of the so-called models of Turbulent Dissipation Regions (TDR). The abundances of many of the molecules observed in the diffuse ISM, including CO that is used as a tracer of the molecular cloud mass, may be understood in the framework of the TDR models.

Using the data of the ATNF pulsar catalog we study the relation connected the real age t of young neutron stars (NS) and their spin-down age τ. We suppose that this relation is independent from both initial period of the NS and its initial surface magnetic field, and that the laws of the surface magnetic field decay are similar for all NSs in the Milky Way. We further assume that the birth-rate of pulsars was constant during at least last 200 million years. With these assumptions we were able to restore the history of the magnetic field decay for the galactic NSs. We reconstruct the universal function f(t) = B(t)/B0, where B0 is the initial magnetic field and B(t) is the magnetic field of NS at the age t. The function f(t) can be fitted by a power law with power index α = −1.17.

Based on the South Galactic Cap U-band Sky Survey (SCUSS) and SDSS observations, we adopted the star-count method to analyze the stellar distribution in different directions of the Galaxy. We find that the scale height of the disk may be variable with the observed direction, which cannot simply be attributed to statistical errors. The main reason can be possibly attributed to the disk (mainly the thick disk) being flared, with a scale height increasing with radius. The axis ratio of the Galactic halo is in the range 0.4-0.6. This finding supports Galactic models with a flattened inner halo, partly formed through a merger early in the Galaxy's history.