The intriguing existence of ‘True’-Seyfert 2s has opened a debate on the validity of the unified model of active galactic nuclei (AGN). These objects, also called ‘Naked’-AGN, seem to lack a broad line region. In some cases, their X-ray emission is unabsorbed, typical of Seyfert 1 galaxies, indicating a clear view toward the nucleus, but no broad lines are seen in the optical. In ‘True’-Seyfert 2s with higher column densities, observations of polarized light have failed to reveal the hidden broad emission. We performed high-resolution near-infrared integral-field observations of two ‘True’-Seyfert 2 candidates: IRAS 01072+4954 and NGC 7496. We found that the AGN in these sources might power very faint and narrow broad emission lines (FWHMbroad < 1500km s−1). Here, we discuss the properties of the broad components estimated from published X-ray and/or optical measurements and present their near-infrared candidate identification. Both galaxies host intermediate-mass black holes, with masses ~ 105−106 M⊙. Our results favor the unified model in the cases of high accretion rates, and stress the necessity of a multiwavelength approach to unveil the nature of ‘Naked’-AGN.

The discovery of the two giant γ-ray lobes (Fermi bubbles) in the Galactic center (see Dobler et al. 2010 and Su et al. 2010) was one of the most impressive events of the last few years in astrophysics. However, some indications on giant structures in the Galactic center (GC) were observed several years before by WMAP in the radio frequency range between 23 and 33 MHz (Finkbeiner 2004), and by ROSAT in hard X-rays (Bland-Hawthorn & Cohen 2003). Recent observations performed by the Planck Collaboration (Ade et al. 2012) found also lobes in the microwave range which spatially coincided the Fermi bubbles that indicated on the common origin of these phenomena.

Stellar radial velocity is estimated by using template fitting and Markov Chain Monte Carlo(MCMC) methods. This method works on the LAMOST stellar spectra. The MCMC simulation generates a probability distribution of the RV. The RV error can also computed from distribution.

To test recent suggestions that the infrared emission of low-luminosity AGN arises in a truncated thin accretion disk, we compare recent, high-resolution IR data with published SED model fits that include emission from the truncated disk. We also fit the data with clumpy torus and optically thin dust shell models. These comparisons suggest that dust can better account for the IR emission of the objects in question than can the truncated disk. That optically thin models give a good fit to the data may support a scenario in which the torus of the AGN unified model does not persist in low accretion rate AGN.

Cool supergiants offer a good opportunity to study the interplay of magnetic fields and stellar evolution. We present the results of spectropolarimetric study of the cool supergiants and classical Cepheids η Aql and ζ Gem.

We present a time-series Doppler imaging study of the K-subgiant component in the RS CVn-type binary system IL Hya (Porb=12.905 d). From re-processing the unique long-term spectroscopic dataset of 70 days taken in 1996/97, we perform a thorough cross-correlation analysis to derive surface differential rotation. As a result we get solar-type differential rotation with a shear value α of 0.05, in agreement with preliminary suggestions from previous attempts. A possible surface pattern of meridional circulation is also detected.

We present the new, second spectroscopic telescope of Poznań Astronomical Observatory. The telescope allows automatic simultaneous spectroscopic and photometric observations and is scheduled to begin operation from Arizona in autumn 2013. Together with the telescope located in Borowiec, Poland, it will constitute a perfect instrument for nearly continuous spectroscopic observations of variable stars. With both instruments operational, the Global Astrophysical Telescope System will be established.

Galaxies, which often contain ionised gas, sometimes also exhibit a so-called low-ionisation nuclear emission line region (LINER). For 30 years, this was attributed to a central mass-accreting supermassive black hole (more commonly known as active galactic nucleus or AGN) of low luminosity, making LINER galaxies the largest AGN sub-population, which dominate in numbers over higher AGN-luminosity Seyfert galaxies and quasars. This, however, poses a serious problem. While the inferred energy balance is plausible, many LINERs clearly do not contain any other independent signatures of an AGN. Using integral field spectroscopic data from the CALIFA survey, we compare the observed radial surface brightness profiles with what is expected from illumination by an AGN. For 48 galaxies with LINER-like emission we show, that the radial emission-line surface brightness profiles are inconsistent with ionisation by a central point-source and hence cannot be due to an AGN alone. The most probable explanation for the excess LINER-like emission is ionisation by evolved stars during the short but very hot and energetic phase known as post-AGB. This leads us to an entirely new interpretation. Post-AGB stars are ubiquitous and their ionising effect should be potentially observable in every galaxy with gas present and with stars older than ~1 Gyr, unless a stronger radiation field from young hot stars or an AGN outshines them. This means, that galaxies with LINER-like emission are not a class defined by a property but rather by the absence of a property. It also explains why LINER emission is observed mostly in massive galaxies with old stars and little star formation.

The definition of γ Dor stars as a new class of variable stars by Kaye et al. (1999) was based on a number of criteria, including the failure to detect any emission in the Ca II H & K lines in these stars (Kaye & Strassmeier 1998; KS98). Over the last 30 years, efforts continue to look for the blue edge of chromospheric activity. As a part of this effort, we put γ Dor stars to the test to see if magnetic fields play a non-trivial role in their variability.

Thermonuclear explosions from helium double-detonation sub-Chandrasekhar mass model have been considered as an alternative way for the production of type Ia supernovae (SNe Ia). In this work, we systematically studied the helium double-detonation model, in which a carbon–oxygen white dwarf (CO WD) accumulates a helium layer from a non-degenerate helium star.

We present the results of the spectropolarimetric study of the classical Cepheid η Aql in 2002, 2004, 2010, and 2012. The longitudinal magnetic field of η Aql was found to be variable with the pulsation cycle of 7.176726 day. The amplitude, phase, and mean value of the field vary from year to year presumably due to stellar rotation or dynamo mechanisms.

For 30 years, cyclical wind variability in OB stars has puzzled the astronomical community. Phenomenological models involving co-rotating bright spots provide a potential explanation for the observed variations, but the underlying physics remains unknown. We present recent results from hydrodynamical simulations constraining bright spot properties and compare them to what can be inferred from space-based photometry. We also explore the possibility that these spots are caused by magnetic fields and discuss the detectability of such fields.

In addition to boasting the highest density of baryonic matter in our galaxy, the center of the Milky Way is also believed to contain an extremely high density of dark matter particles. While dark matter is expected to be gravitationally subdominant to baryons near the Galactic center, many models allow for the annihilation of dark matter into standard model particles, a phenomenon which could be a significant source of high energy radiation in the Galactic center region. In fact, standard models of the dark matter density distribution and annihilation spectrum predict that dark matter at the Galactic center would (1) produce the brightest flux from dark matter annihilation of any region in the sky, and (2) contribute a significant portion of the total γ-ray luminosity observed within several degrees of the Galactic center by the Fermi/LAT. This makes the effort to understand and differentiate the morphologies and spectral features of dark matter and astrophysical γ-ray emission at the Galactic center potentially rewarding. Here, I will summarize the recent developments in indirect searches for dark matter annihilation at the Galactic center, and discuss several of the difficulties in producing accurate models of the high energy astrophysical emission. Finally, I will comment on current efforts to produce multi-wavelength models which better constrain or indicate a dark matter signal at the Galactic center.

We present preliminary results of the variability survey in the field of the globular cluster NGC 4833. We observed all 34 variable stars known in the cluster. In addition, we have found two new SX Phoenicis stars, one new RR Lyrae star, twelve new eclipsing systems mostly of the W Ursae Majoris type, nine new variable red giants, and ten new field-stars showing irregular variations. Properties of RR Lyrae stars indicate that NGC 4833 is an Oosterhoff's type II globular cluster.

Using 192 composite spectra stacked from subsamples of individual SDSS quasar spectra binned in spectral index, αλ, and logarithm of monochromatic luminosity at 1450 Å, log l1450, and modelling separate spectral ranges with superposition of emission lines it was found that: there is a dependence of emission line equivalent width (EW) on αλ (correlation or anti-correlation) for some lines, mostly for those lines for which the Baldwin effect is detected, while for the lines for which the Baldwin effect is not observed any αλ-dependence was found.

The MiMeS project demonstrated that a small fraction of massive stars (around 7%) presents large-scale, stable, generally dipolar magnetic fields at their surface. These fields that do not present any evident correlations with stellar mass or rotation are supposed to be fossil remnants of the initial phases of stellar evolution. They result from the relaxation to MHD equilibrium states, during the formation of stable radiation zones, of initial fields resulting from a previous convective phase. In this work, we present new theoretical results, where we generalize previous studies by taking rotation into account. The properties of relaxed fossil fields are compared to those obtained when rotation is ignored. Consequences for magnetic fields in the radiative envelope of rotating early-type stars and their stability are finally discussed.

Employing Fermi/LAT γ-ray observations, several independent groups have found excess extended γ-ray emission at the Galactic center (GC). Both, annihilating dark matter (DM) or a population of ~ 103 unresolved millisecond pulsars (MSPs) are regarded as well motivated possible explanations. However, there is significant uncertainties in the diffuse Galactic background at the GC. We have performed a revaluation of these two models for the extended γ-ray source at the GC by accounting for the systematic uncertainties of the Galactic diffuse emission model. We also marginalize over point source and diffuse background parameters in the region of interest. We show that the excess emission is significantly more extended than a point source. We find that the DM (or pulsar population) signal is larger than the systematic errors and therefore proceed to determine the sectors of parameter space that provide an acceptable fit to the data. We found that a population of several thousand MSPs with parameters consistent with the average spectral shape of Fermi/LAT measured MSPs was able to fit the GC excess emission. For DM, we found that a pure τ+τ− annihilation channel is not a good fit to the data. But a mixture of τ+τ− and bb with a 〈σ v〉 of order the thermal relic value and a DM mass of around 20 to 60 GeV provides an adequate fit.

We present a new Doppler imaging study for the Li-rich single K-giant DI Psc. Surface temperature maps are reconstructed for two subsequent rotation cycles. From the time evolution of the spot distribution antisolar-type differential rotation pattern is revealed. We show marks of non-uniform Li-abundance as well. The possible connection between the current evolutionary phase of the star and its magnetic activity is briefly discussed.

The single-degenerate (SD) model is currently a favourable progenitor scenario for the production of type Ia supernovae (SNe Ia). The companion in the SD model would survive after the SN explosion. In this work, we obtained the velocity distribution of the surviving companion stars from different SD scenarios in the Galaxy, which can be verified by future observations.

It is shown that the diagnostics from an observed circularly polarized line in a rapidly rotating star are directly interpretable, not in terms of the observed Stokes V profiles, but in terms of its antiderivative with respect to wavelength (in velocity units if preferred). This also leads to a new mean-field diagnostic that is just as easily obtained as the standard “center of gravity” approach, and is less susceptible to cancellation if the line-of-sight field changes sign over the face of the star.