AR_final file_2018-19

has also been showing strong X-ray flaring activity at various epochs. They have studied the X-ray variability of 1ES 1959+650 using the simultaneous observations with SXT and LAXPC in October 2017 when the source was in a flaring cycle, and have investigated the evolution of X-ray spectral properties during the observation of the source using the method of time-resolved spectroscopy. They observed a weak anti-correlation between the photon index and X-ray flux of the source at zero time lag. However, the preliminary results suggest a stronger positive correlation between the parameters with a time delay of about 40 ks. Disc-jet connection in the NLS1/Blazar 1H 0323+342 The launching of jets in astrophysical systems with black hole mass ranging over nearly 10 orders of magnitude is not yet a well-understood phe- nomenon. The accretion disc, which is present in all systems with jets, is thought to play a major role in determining the launching and properties of the jet. Radio-loud AGN (RL-AGN) are associated with strongly collimated jets, the origin of which re- mains unclear. The radio-loud narrow line Seyfert 1 galaxies (RL-NLS1s) are a special class of RL-AGN that show similar properties to that of NLS1s in the optical and X-ray bands. They are characterised by low black hole mass, high accretion rate, and relativistic jet emission. Gulab C. Dewangan, Ranjeev Misra, Abhishek Paswan , Biny Sebas- tian, Preeti Kharb, Ritesh Ghosh, Ninan Sajeeth Philip have worked on the gamma-ray detected RL- NLS1/NLS1-blazar 1H 0323+342. The highly vari- able emissions from disc/corona component and rel- ativistic jet make the source ideal to investigate the disc-jet connection. Using the simultaneous ra- dio, infrared, optical, UV and X-ray data from the coordinated observations from Astrosat, HCT and GMRT they could study the disc-jet coupling in the source by investigating the correlated variabil- ity properties associated with accretion flow, line emission regions and jet emission. Stars, Interstellar Medium and Planetary Studies Modelling of mid-infrared polariza- tion in dust around young stars Recently, crystalline silicates (SiC) have been de- tected in circumstellar envelops of several young pre-main sequence stars. Ranjan Gupta and col- laborators have probed the presence of SiC in the dust around protoplanetary disks in a sample of young stars. The only detection of SiC has been in a young star SVS13 based on studies of MIR polar- ization in its disc/envelop. They have modelled the linear polarization of composite dust grains in the mid-infrared (MIR: 813 µm ) using silicates as the host with various inclusions of SiC and graphites using the Discrete Dipole Approximation (DDA) and the Effective Medium Approximation (EMA) T-Matrix methods. The results are compared with polarimetric observations made in the protoplane- tary disks surrounding two Herbig Be stars and one T-Tauri star with the 10 µm silicate feature using CanariCam mounted over the Gran Telescopio Ca- narias (GTC). This model has the host spheroid made up of sil- icates with inclusions of either silicon carbide (SiC) or graphite (Gr) at a time. The sites external to the grain are assumed to be vacuum, and internal sites are given to the silicate host. They have used oblate (axial ratio AR > 1) spheroids since interstellar ex- tinction curves produced using models with grains in the form of oblate spheroids have been seen to show best fits with observed data. They used a dust grain size, a min = 0 . 1 µm to a max = 0 . 5 µm , where a represents the radius of a sphere such that its vol- ume is equal to that of the dust grain spheroid and used three different fractions by volume, f = 0.1 (10%), 0.2 (20%) and 0.3 (30%) for SiC, graphite as well as porous grain inclusions (in compliance with the findings of other workers). As seen in Figures (16), (17), and (18), all the three objects in this sample of study: MWC 1080A, MWC 297 and HL Tau, show polarization in ab- sorption, but only the MWC 1080A polarization seems to have been caused due to SiC mixed with ( 83 )