POLIX Onboard XPoSat Initiates Scientific Observations.

The Indian X-ray Polarimeter (POLIX) has initiated its scientific observations as part of India’s X-ray polarimetry mission XPoSat. During the period from January 15-18, 2024, POLIX conducted observations leading to the generation of a pulse profile of the Crab pulsar. This pulsating star, located near the center of the Crab Nebula, exhibits a rapid rotation, spinning about its axis approximately 30 times per second. The data obtained from these observations contributes to the understanding of the unique characteristics of the Crab pulsar and enhances our knowledge of celestial phenomena.

The presented plot showcases the temporal distribution of X-rays scattered by the Beryllium scatterer within POLIX, originating from the Crab pulsar. This unique visualization, unprecedented in this energy range, highlights a time window crucial for analyzing X-rays emitted solely by the pulsar. The X-axis denotes the time span for two pulses, totaling approximately 67 milliseconds. Additionally, the plot includes timing details of non-pulsed emission components from the Pulsar Wind Nebula enveloping the pulsar.This temporal framework aids in isolating X-rays emitted by the pulsar, excluding those from the wind nebula. Notably, the polarization of X-rays from the source becomes detectable as the degree of asymmetry in the scattering process within the instrument correlates with the polarization of the incoming X-rays.

The activation of the POLIX payload occurred in two stages, completed by January 10, 2024, followed by initial scan observations focused on the Crab pulsar, the designated primary target. The collected data from January 15-18, 2024, underwent thorough review, confirming alignment with expectations.

This marks a significant milestone for POLIX, underscoring its operational prowess and readiness for investigating a range of celestial phenomena, including pulsars, black holes, and other astronomical sources. As the sole payload providing data in this energy band, POLIX is poised to deliver unique insights, contributing to a deeper understanding of the physical processes associated with Astronomical X-ray sources. Developed by the X-ray Astronomy Laboratory at Raman Research Institute, Bengaluru, POLIX stands as an indigenous creation with support from the Indian industry, showcasing a collaborative effort in advancing space exploration capabilities.