Narrow-line Seyfert 1 (NLS1) galaxies, as active galactic nuclei with low-mass black holes and high accretion rates, are important targets when addressing questions related to black hole growth and accretion physics. We have studied the correlations among the optical emission-line and continuum properties of a sample of NLS1 galaxies, in comparison with a sample of broad-line Seyfert 1 galaxies. We have shown that the density of the narrow-line region is a key component of Eigenvector 1 space. Density turned out to be as important as the Eddington ratio L/LEdd. This result therefore establishes a close link between central engine and host properties, and places new constraints on host - black hole co-evolution.

An anti-correlation between the optical brightness and the strength of the Hα emission was observed from two Be/X-ray binaries, A0535+26 and MXB 0656-072: when the optical brightness showed a decrease, the intensity of the Hα emission displayed an obvious increase. This anti-correlation is interpreted as the result of the mass ejection from the Be star. After the mass ejection event, a cavity or low-density region will be developing in the inner parter of the circumstellar disk. The X-ray outbursts of the Be/X-ray binaries might be connected with the mass ejections from the Be star.

Here we present results on the effects of dust on the derived Sérsic index of disks and bulges. This is part of a larger study (see Pastrav et al. 2012a, Pastrav et al. 2012b) that quantifies the dust effects on all photometric parameters, including scale-lengths, axis-ratios, central surface brightness and effective radii of individual and decomposed (from B/D decomposition) disks and bulges. The effects of dust are derived for both broadband and narrow line (Balmer lines) images. The changes in the derived photometric parameters from their intrinsic values (as seen in the absence of dust) were obtained by fitting simulated images of disks and bulges produced using radiative transfer calculations and the model of Popescu et al. (2011). This study follows on the analysis of Möllenhoff et al. (2006), who quantified the effects of dust on the photometry of old stellar disks seen at low and intermediate inclination. We extend the study to disks at all inclinations and we investigate the changes in the photometry of young stellar disks and bulges. For the individual components, in the majority of cases: 1) the dust lowers the Sérsic index from its intrinsic value; 2) the Sérsic index decreases as the inclination and the B band central face-on dust opacity, τBf, increase. For the decomposed disks and bulges, dust slightly increases the Sérsic index as compared with the one derived on individual components (e.g. Fig. 1); this effect is stronger for higher values of the inclination, τBf and B/D.

The response of a debris disc to a planetary perturber is the result of the complex interplay between gravitational effects, grain collisions and stellar radiation pressure (Stark & Kuchner (2009). We investigate to what extent this response can depart from the pure gravitational case when including grain collisional production and radiation pressure. We use the DyCoSS code (Thébault (2012), designed to study the coupled effect of collisions and dynamics for systems at steady state with one perturbing body. We focus on two outcomes: the 2D surface density profile of the disc+planet system, and the way the Particle Size Distribution (PSD) is spatially segregated within the disc. We consider two set-ups: 1) a narrow ring with an exterior “shepherding” planet, and 2) an extended disc in which a planet is embedded. For each case, the planet mass and orbit are explored as free parameters, and an unperturbed “no-planet” case is also considered. Another parameter is the disc's collisional activity, as parameterized by its optical depth τ.

On 2011 July 14, a transient X-ray source, Swift J1822.3–1606, was detected by Swift BAT via its burst activities. It was subsequently identified as a new magnetar upon the detection of a pulse period of 8.4 s. Using follow-up RXTE, Swift, and Chandra observations, we have determined a spin-down rate of Ṗ ~ 3 × 10−13, implying a dipole magnetic field of ~ 5 × 1013 G, second lowest among known magnetars, although our timing solution is contaminated by timing noise. The post-outburst flux evolution is well modelled by surface cooling resulting from heat injection in the outer crust, although we cannot rule out other models. We measure an absorption column density similar to that of the open cluster M17 at 10′ away, arguing for a comparable distance of ~1.6 kpc. If confirmed, this could be the nearest known magnetar.

We present a short Chandra observation that confirms a previous unidentified extended X-ray source, G308.3-1.4, as a new supernova remnant (SNR) in the Milky Way. Apart from identifying its SNR nature, a bright X-ray point source has also been discovered at the geometrical center. Its X-ray spectral properties are similar to those of a particular class of neutron star known as central compact objects (CCOs). On the other hand, the optical properties of this counterpart suggests it to be a late-type star. Together with the interesting ~ 1.4 hours X-ray periodicity found by Chandra, this system can possibly provide the first direct evidence of a compact binary survived in a supernova explosion.

We present some results obtained by high resolution spectroscopic observations for symbiotic stars EG And, AG Dra, and BX Mon in recent years which were performed with 1.8-m reflector and echelle spectrograph BOES at Bohyunsan Optical Astronomy Observatory, Youngcheon, South Korea. The variations of Hα emission line during a night and the variations of H Balmer lines and He I emission lines among several analyzed lines over months and years are shown and discussed.

Using N-body simulations with planet-disk interactions, we present a mechanism capable of forming compact systems of hot super Earths such as Kepler 11. Recent studies show that outward migration is common in the inner parts of radiative disks. However we show that two processes naturally tip the balance in favor of inward migration. First the corotation torque is too weak to generate outward migration for planetary embryos less massive than 4M⊕. Second, system of multiple embryos generate sustained non-zero eccentricities that damp the corotation torque and again favor inward migration. Migration and accretion of planetary embryos in realistic disks naturally produce super Earths in resonant chains near the disk inner edge. Their compact configuration is similar to the observed systems.

Dust is a crucial component of galaxies in modifying the observed properties of galaxies. Previous studies have suggested that dust reddening in star-forming galaxies is correlated with star formation rate (SFR), luminosity, gas-phase metallicity (Z), stellar mass (M*) and inclination. In this work we investigate the fundamental relations between dust reddening and physical properties of galaxies, and obtain a well-defined empirical recipe for dust reddening. The empirical formulae can be incorporated into semi-analytical models of galaxy formation and evolution to estimate the dust reddening and facilitate comparison with observations.

The mass-semimajor axis diagram for exoplanets is populated by at least three distinct planetary populations: hot Jupiters at small orbital radii, more massive Jovian planets gathered at about 1 AU, and a rapidly growing population of SuperEarths at short periods. Our work shows that low mass and rapidly migrating planetary cores get trapped at disk inhomogeneities, where strong density or thermal gradients exist (namely dead zone boundaries, ice lines, and disk heating transition regions). Planet growth and movement occur at rates dictated by planetary accretion, and the slow radial inward motion of the traps due to falling disk accretion rates during disk evolution. By combining the theory of traps in evolving disks with standard ideas about how protoplanets accrete, we develop evolutionary tracks of how planets evolve in the mass- semimajor axis diagram. Our models account for the planetary “pile-up” at 1AU, the origin of SuperEarths and hot Jupiters, and the relative scarcity of Jovian planets at large distances.

The LOw Frequency ARray – LOFAR – is a new radio interferometer designed with emphasis on flexible digital hardware instead of mechanical solutions. The array elements, so-called stations, are located in the Netherlands and in neighbouring countries. The design of LOFAR allows independent use of its international stations, which, coupled with a dedicated backend, makes them very powerful telescopes in their own right. This backend is called the Advanced Radio Transient Event Monitor and Identification System (ARTEMIS). It is a combined software/hardware solution for both targeted observations and real-time searches for millisecond radio transients which uses Graphical Processing Unit (GPU) technology to remove interstellar dispersion and detect millisecond radio bursts from astronomical sources in real-time.

We study the multiwavelength properties of an optically selected sample of Low Ionization Nuclear Emission-line Regions (LINERs), in an attempt to determine the accretion mechanism powering their central engine. We show how their X-ray spectral characteristics, and their spectral energy distribution compare to luminous AGN, and briefly discuss their connection to their less massive counter-parts galactic black-hole X-ray binaries.

Supernovae play an integral role in the feedback of processed material back into the interstellar medium (ISM) of galaxies and are responsible for most of the chemical enrichment of the universe. The rate of supernovae can also reveal the star formation histories. In a sample of 11 nearby galaxies observed with SINFONI, a strong linear correlation between [FeII]1.26 luminosity and Starburst 99-derived supernova rate is found on a pixel-pixel basis. In the very nearby archetypal starburst galaxy NGC 253, the excitation of molecular gas is a subject of debate. Using the correlation between [FeII] and supernova rate, we can determine if supernovae can account for the excitation of the bright observed near-infrared H2 emission.

We present evidence for chaotic dynamics in pulsar spin-down rates originally measured by Lyne et al. (2010). Using techniques that allow us to re-sample the original measurements without losing structural information, we have searched for evidence for a strange attractor in the time series of frequency derivative for each pulsar. Our measurements of correlation dimension and Lyapunov exponent show, particularly in the case of PSR B1828-11, that the underlying behavior appears to be driven by a strange attractor with approximately three governing nonlinear equations.

The bottom magnetic fields of neutron stars (NSs) in LMXBs are found to be proportionally related to their accretion rate, i.e. Z (Atoll) source with Eddington (less Eddington) rate is associated with a stronger value of about B ~109 G (B ~108 G). We discuss the relation between the jet formation of NS and its bottom magnetic field strength, and pointed out that the accretion powered millisecond pulsar will not exclude the jet production, furthermore the appearance of kHz QPOs may be also coexistence with the jets. The observer's viewing angle to the NS rotating axis may be a significant factor for observing the jet, pulsar or kHz QPO.

We investigate the distribution of encounter velocities and impact angles describing collisions in the habitable zone of the early planetary system. Here we present a catalogue of collision characteristics for a particular mass ratio of the colliding bodies and seven different planetesimal masses ranging from a tenth of Ceres' mass to 10 times the mass of the Moon. We show that there are virtually no collisions with impact speeds lower than the surface escape velocity and a similar velocity-impact angle distribution for different planetesimal masses if velocities are normalized using the escape velocity. An additional perturbing Jupiter-like object distorts the collision velocity and impact picture in the sense that grazing impacts at higher velocities are promoted if the perturber's orbit is close to the habitable zone whereas a more distant perturber has more the effect of a mere widening of the velocity dispersion.

We combine 12CO J = 3 − 2 for 155 nearby galaxies, obtained as part of the James Clerk Maxwell Telescope (JCMT) Nearby Galaxies Legacy Survey (NGLS), with star formation rates derived from Hα luminosities to probe the relation between warm, dense gas and star formation. These data are compared with ancillary data from the literature, including infrared (IR) and 1.4 GHz radio continuum luminosities and Hi masses. We find a good correlation between CO J = 3 − 2 luminosities and Hα-derived star formation rates (SFRs), which is in agreement with previous studies. Several groups of galaxies show a peculiar behaviour in the SFR(Hα) − LCOJ = 3 − 2 plot, which disappears when using IR data. We analyse these regions and propose several hypotheses to explain this behaviour, including group interactions and very recent (≲20 Myr) bursts of star formation only traced by Hα emission. While atomic hydrogen is hardly related with SFR, molecular and total gas (Hi + H2) show similar correlations with Hα luminosities. No correlation is found between CO J = 3−2 luminosity and metallicity, although galaxies with low metallicity are more likely to not be detected. We discuss that CO J = 3 − 2 does not seem to be a significantly better tracer of the star-forming gas, but its independence from metallicity may be used to constrain the conversion factor between CO and H2.

Star formation is evolving very fast in the second half of the Universe, and it is as yet unclear whether this is due to evolving gas content, or evolving star formation efficiency (SFE). We have carried out a survey of ultra-luminous galaxies (ULIRG) between z = 0.2 and 1, to check the gas fraction in this domain of redshift which is still poorly known. Our survey with the IRAM-30m detected 33 galaxies out of 69, and we derive a significant evolution of both the gas fraction and SFE of ULIRGs over the whole period, and in particular a turning point around z = 0.35. The result is sensitive to the CO-to-H2 conversion factor adopted, and both gas fraction and SFE have comparable evolution, when we adopt the low starburst conversion factor of α = 0.8 M⊙ (K km s−1 pc2)−1. Adopting a higher α will increase the role of the gas fraction. Using α = 0.8, the SFE and the gas fraction for z∼0.2-1.0 ULIRGs are found to be significantly higher, by a factor 3, than for local ULIRGs, and are comparable to high redshift ones. We compare this evolution to the expected cosmic H2 abundance and the cosmic star formation history.

Preferred frame effects (PFEs) are predicted by a number of alternative gravity theories which include vector or additional tensor fields, besides the canonical metric tensor. In the framework of parametrized post-Newtonian (PPN) formalism, we investigate PFEs in the orbital dynamics of binary pulsars, characterized by the two strong-field PPN parameters, and . In the limit of a small orbital eccentricity, and contributions decouple. By utilizing recent radio timing results and optical observations of PSRs J1012+5307 and J1738+0333, we obtained the best limits of and in the strong-field regime. The constraint on also surpasses its counterpart in the weak-field regime.