Title : FiberPol-6D- Spectropolarimetric Integral Field mode for the SAAO 1.9 m Telescope using fibers

Abstract

Most optical spectropolarimeters built to date operate as long-slit or point-source instruments; they are inefficient for observations of extended objects such as galaxies and nebulae. 2D spectropolarimetry technique development is a major challenge in astronomical instrumentation. At the South African Astronomical Observatory (SAAO) FiberLab, we are developing a spectropolarimetry capable Integral Field front-end called FiberPol(-6D) for the existing SpUpNIC spectrograph on the SAAO 1.9 m telescope. SpUpNIC is a general purpose 2 arc-minute long-slit spectrograph with a grating suite covering the wavelength range from 350 to 1000 nm. FiberPol generates 6D observational data: x-y spatial dimensions, wavelength, and the three linear Stokes parameters I, q and u. Using a rotating half-wave plate and a Wollaston prism, FiberPol executes two-channel polarimetry, and each channel is fed to an array of 14 fibers, corresponding to a field of view of 10×20 arcseconds^2 sampled with 2.9 arcsecond diameter fiber cores. FiberPol aims to achieve a polarimetric accuracy of 0.1 % per spectral resolution bin. Further, it can also function as a non-polarimetric integral-field unit. The primary science goals include study of ISM of nearby galaxies to test the models of dust grain alignment and its dependence with the ambient magnetic field. The instrument design has been completed and it is currently being assembled and characterized in the lab. It is scheduled for on-sky commissioning in the second half of 2024. In this talk, I will present the scientific and technical goals of FiberPol, its overall design and initial results from the lab assembly and testing. FiberPol is a low cost technology demonstrator for 10m SALT and other large telescopes such as the 30m class telescopes. It can be modified and replicated for use on any existing spectrograph, especially on bigger telescopes.

Title : Multi-wavelength study of Blazars

Abstract

Blazars are a special subclass of active galactic nuclei, with relativistic jets pointing close to observers’ line of sight, making them the most luminous and rapidly variable extra-galactic sources in the universe. Their observed emissions are highly Doppler boosted and observable across the entire accessible electromagnetic spectrum (from radio to gamma-rays), with diverse variability timescales ranging from minutes to years. The observed emissions imply extreme physical conditions that are beyond replication by any current or future terrestrial laboratory. Almost every aspect, from jet formation, collimation to gamma-ray production in the jets, is poorly understood. However, over the past decade, the availability of long-term, high-cadence data in the multi-wavelength regime (i.e., optical, X-ray, and gamma-ray) has been helpful in addressing some aspects of these issues through study of i) multi-wavelength flux and spectral variability on diverse time scales, ii) physical origin of quasi periodic oscillations (QPOs) observed in the light curves, iii) multi-wavelength flux distribution of Blazars. In this talk, we will discuss our recent interesting results on the above topics related to Blazar emission properties.

Title : Effects of disorder on flat bands of some tight binding models.

Abstract

The effects of disorder on condensed matter systems where electrons move from one site to another by means of quantum mechanical diffusion described by tight binding models has garnered a lot of interest recently. In one dimension disorders almost always leads to localisation of electrons for lattices of reasonably big size. On the other hand, geometry of the lattice may lead to localisation of electrons at particular sites due to the onset of flat bands. In this talk we will discuss a system where both these localisation effects are present i.e. effects of different disorders on a system with flat bands and the net result of these effects.

Title : Minimal Z' for Radiative mechanism

Abstract

We discuss a mechanism in which the masses of the third, second, and first generation charged fermions are generated at tree level, 1-loop, and 2-loop levels, respectively. In this mechanism, loop-induced masses are obtained through fermionic self-energy corrections induced by heavy gauge bosons of a new single flavorful $U(1)_F$ symmetry, which have flavor-violating interactions with Standard Model fermions. Phenomenologically, the flavor-violating couplings $Q_{ij}$ are desired to have $|Q_{12}|<|Q_{23}|,|Q_{13}|$ because constraints from $K^0$-$\overline{K}^0$ mixing and $\mu$-$e$ conversion in nuclei, involving first and second family fermions, are more stringent than others. We establish a framework to achieve this condition and quantify the optimal flavor violations required to implement the radiative mass generation mechanism.

Title : Exploring scalar dark sector with Peceei-Quinn symmetry at the LHC.

Abstract

The Inert Higgs Doublet model (IDM), assisted by Peccei-Quinn (PQ) symmetry, offers a simple but natural framework of a dark sector that accommodates Weakly Interacting Massive Particle (WIMP) and axion as dark matter components. Spontaneous breaking of $U(1)_{PQ}$ symmetry, which was originally proposed as an elegant solution to the strong charge-parity (CP) problem, also ensures the stability of WIMP through a residual $\mathbb{Z}_2$ symmetry. Interestingly, additional fields necessitated by PQ symmetry further enrich the dark sector. These include a scalar field proprietor for axion DM and a vector-like quark (VLQ) that acts as a portal for the dark sector through Yukawa interactions. Moreover, this combination of the axion and WIMP components satisfies the observed DM relic density and reopens the phenomenologically exciting region of the IDM parameter space where the WIMP mass falls between 100 - 550 GeV. We investigate the model-independent pair production of VLQs exploring this region at the Large Hadron Collider (LHC), incorporating the effects of next-to-leading order (NLO) QCD corrections. After production, each VLQ decays into a top or bottom quark accompanied by an inert scalar, a consequence of the residual $\mathbb{Z}_2$ symmetry. Utilising relevant observables with a leptonic search channel and employing multivariate analysis, we demonstrate the ability of this analysis to exclude a significant portion of the parameter space with an integrated luminosity of 300 $\text{fb}^{-1}$.

Title : A Cauldron of Light: Mars as seen in ultraviolet

Abstract

Tremendous new insights into the Martian atmosphere have been achieved in recent years by two ultraviolet spectrographs built at LASP: the Imaging Ultraviolet Spectrograph (IUVS) aboard the Mars Atmospheric and Volatile EvolutioN (MAVEN) mission, and the Emirates Mars Ultraviolet Spectrometer (EMUS) aboard the Emirates Mars Mission (EMM). Both instruments have far exceeded their design goals in science return. This has been accomplished in part through opportunistic and innovative observations, not in the original concept of operations. large quantity of data and provided insights on present-day processes at Mars including dayglow, nightglow, aurora, meteor showers, clouds, and solar-planetary interactions. In this presentation, IÂ will highlight key results obtained by IUVS and EMUS, including (1) mapping of thermosphere composition, structure, and variability, including effects of the global dust storm ; (2) a surprisingly high level of auroral activity of three types; (3) characterizing the dynamics using nightglow. We will present an overview of these results and a discussion of their implications for understanding Mars's atmospheric dynamics and evolution.