The emission of steady compact jets observed in the hard spectral state of X-ray binaries is likely to be powered by internal shocks caused by fluctuations of the outflow velocity. The dynamics of the internal shocks and the resulting spectral energy distribution (SED) of the jet is very sensitive to the shape of the Power Spectral Density (PSD) of the fluctuations of the jet Lorentz factor. It turns out that Lorentz factor fluctuations injected at the base of the jet with a flicker noise power spectrum (i.e. P(f) ∝1/f) naturally produce the canonical flat SED observed from radio to IR band in X-ray binary systems in the hard state. This model also predicts a strong, wavelength dependent, variability that resembles the observed one. In particular, strong sub-second variability is predicted in the infrared and optical bands. The assumed fluctuations of the jet Lorentz factor are likely to be triggered by the variability of the accretion flow which is best traced by the X-ray emission. In the case of GX339-4 for which high quality and simultaneous multi-wavelength data are available, we performed simulations assuming that the fluctuation of the jet Lorentz factor have the same PSD as the observed X-ray PSD. The synthetic SED calculated under this assumption provides a remarkable match to the observed radio to IR SED. In this case the model also produces strong mid-infrared spectral variability that is comparable to that reported in this source.

We investigate the systematics of the properties of highly relativistic jets at multiple frequencies, including Fermi, and MOJAVE data. We test the hypothesis that the blazar divide constitutes a dichotomy. We also explore possible measures of the Doppler factor for these highly Doppler-beamed active galactic nuclei.

We observed the inner filament of NGC 5128 (Centaurus A) with the Hubble Space Telescope Wide Field Camera 3 (WFC3), using the F225W, F657N and F814W filters. We find a young stellar population near the south-west tip of the filament. We constrain the ages of these stars to 1-3 Myrs. No further recent star formation is found along the filament.

We propose an updated explanation for the origin of the inner filament. It has been suggested Sutherland et al.1993 that radio jets can shock the surrounding gas, giving rise to the observed optical line emission. We argue that such shocks can naturally arise due to a weak cocoon-driven bow shock (rather than from the radio jet directly) propagating through the diffuse interstellar medium. We suggest such a shock has overrun a molecular cloud, triggering star formation in the dense molecular core. The outer, more diffuse parts of the cloud are then ablated and shock heated, giving rise to the observed optical line and X-ray emission.

We report the current results on a comprehensive scan of the near-Earth asteroid catalog for evidence of the Yarkovsky effect in the orbital motion of these bodies. While most objects do not have sufficient observational data to reveal such slight acceleration, we do identify 42 asteroids with a “valid” detection of the Yarkovsky effect, i.e., those with a signal at least 3 times greater than the formal uncertainty and a value compatible with the Yarkovsky mechanism.

We also identify a special category of non-detection, which we refer to as “weak signal,” where the objects are of a size that would permit a clear detection if the Yarkovsky effect is maximized, and yet the orbit is clearly incompatible with such accelerations. The implication is that the Yarkovsky effect is reduced in these cases, presumably due to mid-range obliquity, but possibly also due to size, bulk density, thermal inertia, albedo, or spin rate markedly different from assumptions.

Finally, there are a number of asteroids showing a significant signal for nongravitational acceleration, and yet with a magnitude too great to be attributed to the Yarkovsky effect. We term these “spurious detections” because most are due to erroneous optical astrometry, often involving a single isolated night from precovery observations. Some cases may be due to other nongravitational accelerations, such as outgassing, mass loss, or micro-meteoroid flux.

Here we address the importance of frequency cross-redistribution on the scattering polarization of the O i line at 130.2 nm. We compute the polarized profiles of this line with ordinary partial frequency redistribution and cross-redistribution using a two-dimensional radiative transfer code.

We numerically investigate the thermally unstable accretion discs around spinning black holes with different spins. We adopted an additional evolutionary viscosity equation to replace the standard alpha-prescription based on the results of two MHD simulations. We find an interesting oscillation when accretion switches to slim disc mode. The oscillation arises from the sonic point of accretion flow and propagates outwards. We mimic the bolometric light-curve and find a series of harmonics on its power spectrum. The frequency ratio of those harmonics is a regular integer series. The lowest frequency of the harmonics is identical to the prediction of trapped p-mode in QPO theory.

We revisit recent claims of significant mirror-parity in CMB data from WMAP and Planck with a careful analysis using statistical estimators in both harmonic and pixel spaces. While the data indeed show significant signs of odd mirror-parity under some circumstances, the broad study shows that the results are not in significant tension with ΛCDM.

The gas and dust rich disks around young stars are the formation sites of planets. Observations of molecular trace species have great potential as probes of the disk structures and volatile compositions that together regulate planet formation. The disk around young star TW Hya has become a template for disk molecular studies due to a combination of proximity, a simple face-on geometry and richness in volatiles. It is unclear, however, how typical the chemistry of the TW disk is. In this proceeding, we review lessons learnt from exploring the TW Hya disk chemistry, focusing on the CO snowline, and on deuterium fractionation chemistry. We compare these results with new ALMA observations toward more distant, younger disks. We find that while all disks have some chemical structures in common, there are also substantial differences between the disks, which may be due to different initial conditions, structural or chemical evolutionary stages, or a combination of all three.

We study the stellar content of three galactic bulges with the high resolution gratings (R=7000) of the WiFeS integral field unit in order to better understand their formation and evolution. In all cases we find that at least 50% of the stellar mass already existed 12 Gyrs ago, more than currently predicted by simulations. A younger component (age between ∼1 to ∼8 Gyrs) is also prominent and its present day distribution seems to be much more affected by morphological structures, especially bars, than the older one. This in-depth analysis supports the notion of increasing complexity in bulges which cannot be achieved by mergers alone, but requires a non-negligible contribution from secular evolution.

One of the methods for diagnosing vector magnetic fields in solar prominences is the so called “inversion” of observed polarized spectral lines. This inversion usually assumes a fairly simple generative model and in this contribution we aim to study the possible systematic errors that are introduced by this assumption. On two-dimensional toy model of a prominence, we first demonstrate importance of multidimensional radiative transfer and horizontal inhomogeneities. These are able to induce a significant level of polarization in Stokes U, without the need for the magnetic field. We then compute emergent Stokes spectrum from a prominence which is pervaded by the vector magnetic field and use a simple, one-dimensional model to interpret these synthetic observations. We find that inferred values for the magnetic field vector generally differ from the original ones. Most importantly, the magnetic field might seem more inclined than it really is.

The current use of Type Ia supernova (SN Ia) as standard candles is to measure the dark energy equation-of-state to better than 10%. However, we still lack a clear understanding of their progenitor systems. We analyze the host galaxies of type Ia Supernova (SN Ia) discovered by the ESSENCE survey using UV and optical data, as studying the environments of SN Ia is a great way to understand the progenitors. We developed a new method for determining the SED and rest-frame magnitudes of the host galaxies and we use empirical relations to derive stellar mass and star-formation rate (SFR) measurements of the host galaxies. We find a high rate of UV emission in our passive galaxies, suggesting current star-formation in these galaxies.

We present the estimates of the black hole spins of five quasars. The peaks of the spectra of the accretion discs surrounding massive black holes in quasars are in the far-UV or soft X-ray band, which are usually not observed. However, in the disc corona model, the soft photons from the disc are Comptonized to high energy in the hot corona, and the hard X-ray spectra (luminosity and spectral shape) contain the information of the incident spectra from the disc. The values of black hole spin parameter a are inferred from the spectral fitting, which spread over a large range, ~ −0.94 to 0.998.

Due to the close distance to the Sun, solar radiation pressure (SRP) plays an important role in the dynamics of satellites around near-Earth asteroids (NEAs). In this paper, we focus on the equilibrium points of a satellite orbiting around an asteroid in presence of SRP in the asteroid rotating frame. The asteroid is modelled as a uniformly rotating triaxial ellipsoid. When SRP comes into play, the equilibrium points transformed into periodic orbits termed as``dynamical substitutes". We obtain the analytical approximate solutions of the dynamical substitutes from the linearised equations of motion. The analytical solutions are then used as initial guesses and are numerically corrected to compute the accurate orbits of the dynamical substitutes. The stability of the dynamical substitutes is analysed and the stability maps are obtained by varying parameters of the ellipsoid model as well as the magnitude of SRP.

The Cold Spot is an anomalously cold region in the Cosmic Microwave Background (Vielva et al. 2004), either caused by a structure in the line of sight or could be of primordial origin. We search for a supervoid aligned with the Cold Spot region, filling the gap in redshift at z<0.3 which has never been explored in details. We find a large projected under density in the recently constructed WISE-2MASS catalogue, whose median redshift is z ≃ 0.14, with an angular size of 30 degrees. We show that a spherically symmetric Lemaitre-Tolman-Bondi (LTB) void model can simultaneously fit the δgal/b=δ2D≃ −0.12 underdensity in the WISE-2MASS catalogue, and the Cold Spot as observed by both the WMAP and Planck satellites. Such an LTB supervoid gives a plausible explanation of the Cold Spot anomaly, and is preferred over the null hypothesis or a texture model.

The SAGES Legacy Unifying Galaxies and GlobularS (SLUGGS) survey probes the outskirts of early-type galaxies (ETGs). SLUGGS uses the DEIMOS spectrograph on Keck to simultaneously obtain globular cluster and spatially resolved galaxy spectra. The galaxy spectra allow for the reconstruction of kinematic maps out to ∼3 effective radii (Re), while globular clusters (GCs) push the galactocentric limit out to ∼8–10Re. Stellar population parameters (abundances) can also be recovered. This provides a unique dataset for exploring the outer gradients (abundance and/or kinematic transition). We briefly present recent and salient results of the SLUGGS survey so far.

Fanaroff-Riley I radiogalaxies have been observed in TeV gamma-rays during the last decades. The origin of the emission processes related with this energy band is still under debate. Here we consider the case of the two closest Fanaroff-Riley I objects: Centaurus A and M87. Their entire broadband spectral energy distributions and variability fluxes show evidences that leptonic models are not sufficient to explain their fluxes above 100 GeV. Indeed, both objects have been imaged by LAT instrument aboard of Fermi telescope with measured spectra well connected with one-zone leptonic models. However, to explain the TeV spectra obtained with campaigns by H.E.S.S., for Centaurus A, and by VERITAS, MAGIC and H.E.S.S. for M87, different emission processes must be introduced. In this work we introduce hadronic scenarios to describe the TeV gamma-ray fluxes observed and to obtain the expected neutrino counterparts for each considered TeV campaign. With the obtained neutrino spectra we calculate, through Monte Carlo simulations, the expected neutrino event rate in a hypothetical Km3 neutrino telescope and we compare the results with what has been observed by IceCube experiment up to now.

Young stars are surrounded by copious amounts of circumstellar material. Its composition, in particular its gas-to-dust ratio, is an important parameter. However, measuring this ratio is challenging, because gas mass estimates are often model dependent. X-ray absorption is sensitive to the gas along the line-of-sight while optical/near-IR extinction depends on the dust. Therefore, the absorber's gas-to-dust ratio is directly given by the ratio between X-ray and optical/near-IR extinction. We present three systems where we used X-ray and optical/near-IR data to constrain the gas-to-dust ratio of circumstellar material; from a dust rich debris disk to gaseous protoplanetary disks.

We present continuous, monochromatic star formation rate (SFR) indicators over the mid-infrared wavelength range of 6–70 μm. We use a sample of 58 star forming galaxies (SFGs) in the Spitzer-SDSS-GALEX Spectroscopic Survey (SSGSS) at z<0.2, for which there is a rich suite of multi-wavelength photometry and spectroscopy from the ultraviolet through to the infrared. The data from the Spitzer infrared spectrograph (IRS) of these galaxies, which spans 5–40 μm, is anchored to their photometric counterparts. The spectral region between 40-70 μm is interpolated using dust model fits to the IRS spectrum anchored by Spitzer 70 and 160 μm photometry. Since there are no sharp spectral features in this region, we expect these interpolations to be robust. This spectral range is calibrated as a SFR diagnostic using several reference SFR indicators to mitigate potential bias. Our band-specific continuous SFR indicators are found to be consistent with monochromatic calibrations in the local universe, as derived from Spitzer, WISE, and Herschel photometry. Additionally, in the era of the James Webb Space Telescope this will become a flexible tool, applicable to any SFG up to z∼3.

We summarise the recent progress in understanding the formation and evolution of globular clusters (GCs) in the context of galaxy formation and evolution. It is discussed that an end-to-end model for GC formation and evolution should capture four different phases: (1) star and cluster formation in the high-pressure interstellar medium of high-redshift galaxies, (2) cluster disruption by tidal shocks in the gas-rich host galaxy disc, (3) cluster migration into the galaxy halo, and (4) the final evaporation-dominated evolution of GCs until the present day. Previous models have mainly focussed on phase 4. We present and discuss a simple model that includes each of these four steps – its key difference with respect to previous work is the simultaneous addition of the high-redshift formation and early evolution of young GCs, as well as their migration into galaxy haloes. The new model provides an excellent match to the observed GC mass spectrum and specific frequency, as well as the relations of GCs to the host dark matter halo mass and supermassive black hole mass. These results show (1) that the properties of present-day GCs are reproduced by assuming that they are the natural outcome of regular high-redshift star formation (i.e. they form according to same physical processes that govern massive cluster formation in the local Universe), and (2) that models only including GC evaporation strongly underestimate their integrated mass loss over a Hubble time.

The Minor Planet Center receives up to several million astrometric observations of minor planets and comets each month. Given the volume of observations, the sheer number of known objects against which to possibly match, the shortness of the time interval over which each object was likely observed, and the uncertainties in the positions, and occasionally possible errors in times, reported, a number of data processing challenges present themselves. These include: Identifying observations of objects reported as new with already known objects; linking together sets of observations from different nights which may belong to the same object; determining if a set of observations has been assigned to the wrong object; determining if an object with a very short arc is possibly a Near-Earth object; prioritizing newly discovered objects in order of need of follow up; and, efficiently matching one or more observations with known objects.