Conveners
Neutron Stars: Session 1
- Manoneeta Chakraborty (IIT Indore)
Neutron Stars: Session 2
- Sudip Bhattacharyya (TIFR, India)
An understanding of spin frequency evolution of neutron stars I the low-mass X-ray binary (LMXB) phase is essential to explain the observed spin distribution of millisecond pulsars (MSPs), and to probe the stellar and binary physics, including the possibility of continuous gravitational wave emission. I will discuss the crucial effects of transient accretion on the spin evolution of neutron...
With the advent of the time-domain astronomy brilliant transients have been discovered near the centers of the galaxies. Photometric and Spectroscopic follow-ups of these objects by transient surveys like ePESSTO, ZTF, ASASSN have shown that spectral evolutions of these objects are different from that of supernovae, and their temporal evolutions can be explained to some extent as a...
SMC X-2 is one of the high-mass X-ray binary (HMXB) pulsar in the Small Magellanic Cloud (SMC). After a long interval of 15 years, the source was observed in its third outburst in September 2015. The source reached a very high X-ray luminosity of ~5 × 10^38 erg s-1 at the peak of the outburst. The luminosity of the source slowly decayed over the course of a month. We will present results from...
LMC X-4 is a highly luminous and eclipsing high-mass X-ray binary pulsar which is known to exhibit variations in X-ray flux over a wide range of time scales. The Large Area X-ray Proportional Counter (LAXPC) and Soft X-ray Telescope (SXT) instruments onboard the AstroSat observed the source in August 2016. The source was found to emit an X-ray luminosity of $\sim 2 \times 10^{38}$ erg...
In Low Mass X-ray Binary (LMXB) sources, during the active accretion from the secondary star, the accumulated fuel (a mixture of Hydrogen and Helium) undergoes hydrostatic compression as more matter keeps piling up. When temperature and density conditions reach ignition levels (typically within a few hours to days), the entire fuel layer on the NS surface burns rapidly, leading to a...
In the past decades, several neutron stars (NSs), particularly pulsars, with mass $M>2M_\odot$ have been observed. On the other hand, the existence of massive white dwarfs (WDs), even violating Chandrasekhar mass-limit, was inferred from the peak luminosities of type Ia supernovae. Hence, there is a generic question of the origin of massive compact objects. Here we explore the existence of...
In May 2022, MAXI made the discovery of the millisecond pulsar MAXI J1816–195. The unstable burning of accreted material on the surface of neutron stars results in thermonuclear (Type-I) bursts. During the 2022 outburst, MAXI J1816–195 generated a number of thermonuclear bursts. An exponential decay function and a sharp linear rise are used to model the burst profiles. The faster decay of the...
Intense X-ray bursts (type-I bursts) originating from unstable thermonuclear conflagration, are observed from the surface of neutron star low-mass X-ray binaries (LMXBs) and they offer a promising tool to constrain the equation of state of the supra-nuclear matter at the neutron star core and to probe gravity in strong regime near the compact object. Recent observations show the burst spectra...
GX 9+1, an atoll type neutron star low-mass X-ray binary (NS-LMXB), was observed by the Soft X-ray Telescope and the Large Area X-ray Proportional Counters on-board AstroSat during May 2 - 4, 2019. The hardness-intensity-diagram (HID) of the source showed it to be in the soft spectral state during the observation. Flux-resolved spectra of the source could be adequately modelled with an...
Low mass X-ray binaries hosting weakly magnetized neutron stars (NS-LMXB) are classified as atoll sources and Z sources, based on their correlated spectral and temporal variability properties. Some atoll sources have been reported to exhibit type I X-ray bursts, characterized by a Fast Rise Exponential Decay (FRED) profile. One such atoll source is GX 3+1, which was first discovered in 1964....
PSR J0026-1955 was recently independently discovered by the Murchison Widefield Array (MWA) and was quickly found to show both subpulse drifting and nulling. We have observed this pulsar with the upgraded Giant Metrewave Radio Telescope (uGMRT), covering a frequency range of 300-500 MHz. Our analysis shows that the pulsar exhibits two distinct subpulse drifting modes, with various evolutionary...
In the presence of strong magnetic fields, such as in the accretion columns of Neutron Stars, the electrons get quantized into circular orbits, and Cyclotron Resonant Scattering Feature (CRSF) is observed as absorption features in the X-ray spectrum as photons scatter off these electrons at the resonant energies. CRSF or cyclotron lines are the best diagnostic tools that we have to probe the...
Be/X-ray binaries represent the largest population of high
mass X-ray binaries (HMXBs) consist of a Be star and mainly a neutron star as a compact object. In this talk, I will discuss the results obtained from the X-ray studies of the Be/X-ray binary 1A 0535+262 during the 2020 October giant X-ray outburst using AstroSat. The pulsar was detected at a pulsation period of ∼103.55 s in the...
