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Journal Club


"Hidden Broad Line Regions in Seyfert 2 Galaxies"

Swayamtrupta Panda (CAMK/CFT, Warsaw)

based on Pu Du et. al ApJL (2017)


"Pulse Profiles: A tool to probe into the accretion geometry of Accretion Powered X-ray pulsars"

Aru Beri (University of Southampton)

In the case of high magnetic field neutron star binary systems (1012 -1013 Gauss), stellar magnetic field plays an important role in channelling of matter onto the surface of a neutron star. Physics of boundary layer (magnetosphere) is quite complicated. The pulse profiles of accretion powered pulsars and its dependence on energy, luminosity and time provide clues about the accretion geometry of the emission region, beaming pattern, reprocessing etc. In this talk, I will discuss the pulse profiles of two unique pulsars, 4U 1626-67 and LMC X-4. Using all the available data of the accretion powered X-ray pulsar 4U 1626–67 over the last 40 years since its discovery, we have established a clear link between the accretion torque and its pulse profile. I will also discuss an interesting feature known as dips in the pulse profiles. In particular, I will show results from a very detailed pulse profile evolution study of an X-ray pulsar LMC X–4. LMC X-4 is one of the very few sources that show strong X-ray flares. Using the long observations of LMC X-4 that contain both flares and persistent emission we have estimated the timescales required for the formation of accretion stream that caused dip in the pulse profiles of LMC X–4, after the accretion region and the beaming etc is disturbed during flares in this system.


"A 3D map of Galactic dust"

Gregory Green (Stanford U.)

Dust is a critical foreground for many areas of astronomy, extinguishing and reddening sources in the ultraviolet, optical and near-infrared regions of the spectrum, and contaminating our view of the cosmic microwave background in the far-infrared. Dust also traces the interstellar medium, and is therefore itself an interesting probe of Milky Way structure. Maps of interstellar dust therefore find wide application in astronomy. Up until recently, most such maps have been two-dimensional in nature, tracing the column density of dust with angle on the sky. However, in order to correct observations of sources embedded in the Milky Way, or to study dust clouds within the Galaxy, a three-dimensional map that traces dust density with distance is desirable. I present a three-dimensional map of interstellar dust reddening, covering the northernmost three-quarters of the sky out to a distance of several kiloparsecs, based on optical and near-infrared stellar photometry from Pan-STARRS 1 and 2MASS. The map is probabilistic, yielding the uncertainty in dust reddening along each line of sight. It has an angular resolution ranging from 3.4' to 13.7', and a distance resolution of ~25%. The map reveals detailed structure within the Milky Way, from filaments to large cloud complexes. Out of the plane of the Galaxy, where we c an see through the entire dust column, we find good agreement with previous two-dimensional dust maps. In the plane of the Galaxy, our map gives distances to dust clouds which are consistent with known literature distances. In order to extend the map further into the Southern Hemisphere, I have completed an optical/near-infrared survey of the Galactic plane south of a declination of -30 degrees, using the Dark Energy Camera on the 4m Blanco telescope on Cerro Tololo. In the near future, the addition of Gaia parallaxes and spectrophotometry will help us to refine the distances in our map.


" Constraining Superfluidity in Dense Matter from the Cooling of Isolated Neutron Stars"

Vadym Khomenko (CAMK, Warsaw)

based on Beloin et al. arXiv:1612.04289