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We present mid-infrared (MIR) spectral-timing measurements of the prototypical Galactic microquasar GRS 1915+105. The source was observed with the Mid-Infrared Instrument (MIRI) onboard JWST in June 2023 at a MIR luminosity L(MIR)~10^{36} erg/s exceeding past IR levels by about a factor of 10. By contrast, the X-ray flux is much fainter than the historical average, in the source's now-persistent 'obscured' state. The MIRI low-resolution spectrum shows a plethora of emission lines, the strongest of which are consistent with recombination in the hydrogen Pfund (Pf) series and higher. Low amplitude (~1%) but highly significant peak-to-peak photometric variability is found on timescales of ~1,000 s. The brightest Pf(6-5) emission line lags the continuum. Though difficult to constrain accurately, this lag is commensurate with light-travel timescales across the outer accretion disc or with expected recombination timescales inferred from emission line diagnostics. Using the emission line as a bolometric indicator suggests a moderate (~5-30% Eddington) intrinsic accretion rate. Multiwavelength monitoring shows that JWST caught the source close in-time to unprecedentedly bright MIR and radio long-term flaring. Assuming a thermal bremsstrahlung origin for the MIRI continuum suggests an unsustainably high mass-loss rate during this time unless the wind remains bound, though other possible origins cannot be ruled out. PAH features previously detected with Spitzer are now less clear in the MIRI data, arguing for possible destruction of dust in the interim. These results provide a preview of new parameter space for exploring MIR spectral-timing in XRBs and other variable cosmic sources on rapid timescales., Comment: Dedicated to the memory of our colleague, Tomaso Belloni. Submitted 2024 June 21; Comments welcome

The paper explores a plane symmetric cosmological model within the framework of the Lyra manifold, incorporating interactions among various fields. These fields include a charged perfect fluid, a mass-less scalar field, and an electromagnetic field. The study focuses on deriving relativistic field equations and exact solutions for this complex system. The relationships between the scalar field (\b{eta}) and the average scale factor (a(t)), as well as between the metric potentials, are assumed to solve the nonlinear field equations. Two specific expansion models are examined: 1) Exponential expansion and 2) Power law expansion. The research delves into the dynamic parameters behavior, observing changes in pressure, density, and cosmological parameters across different models. The findings indicate that while the Universe is expanding, the rate of expansion can vary among the different models. The investigation also involves kinematic parameters, such as jerk and snap parameters derived from the scale factor variation, and compares them to the {\Lambda}CDM model., Comment: 19 pages

Present work deals with the two fluid Bianchi Type-V cosmological models consisting of matter and radiating source in the $f(R, T)$ theory of gravity studied by Harko et al. (2011). In this paper, we developed a new idea about $f(R, T)$ gravity with the help of two fluids: one fluid is matter field modeling material content of the Universe and other fluid is radiation field modeling the CMB. We have determined the solution of the two fluid gravitational field equations with the systematic structure in $f(R, T)$ gravity. Here we have deliberated four types of universe such as dust universe, radiation universe, hard universe and Zeldovich universe and also extended our work to observe the big rip and big bang singularity. We have also tested the cosmological parameters.

We have explored cold dark matter and holographic dark energy cosmological models with big rip singularity. To obtain the solution of the field equation, we have supposed that scalar expansion $\theta$ is proportional to shear scalar $\sigma ^2 $ which leads to $p_1=(p_2) ^n $, where $A_1 $, $A_2$ are metric potentials and $ n$ is constant. Big bang and Big rip singularity are investigated and analyzed the state-finder parameter. The physical and geometrical parameters of the universe are explained.

In this current article, we introduce the quadruple Shehu transform and its inverse. We also introduce some properties of quadruple Shehu transform. The Convolution theorem and its proof are also discussed. Further, to solve homogeneous and nonhomogeneous partial differential equation we use this transform., Comment: 14 pages

ABSTRACT. The triple Shehu transform, a new generalisation of the triple Laplace transforms and triple Sumudu transform, has recently been introduced. The triple Shehu transform formulas for fractional Caputo operators were obtained in this study. The generalised integral transform was subsequently applied to solve fractional partial differential equations including the Caputo derivative., Comment: 14 pages

Present paper deals with flat Friedmann - Robertson - Walker (FRW) model with two - fluid source in fractal cosmology. In this model one fluid represents matter content of the universe and another fluid is radiation field modeling the cosmic microwave background. To get the deterministic model, we have used the relation between pressure and density for matter through the gamma law equation of state $p_{m} = (\gamma-1)\, \rho_{m}, \,\, 1\leq \gamma\leq2$ . The solutions of fractal field equations are obtained in terms of Kummer's confluent hypergeometric function of the first kind. Some physical parameters of the models are obtained and discussed their behavior with the help of graphs in detail., Comment: 25 pages, 16 figures

In the present paper an attempt has been made to study the flat fractal Friedmann - Robertson - Walker model filled with domain walls. We have obtained the fractal equation of deceleration parameter and tension of the domain wall. It is observed that, while domain walls exist at early times, they disappear at late time. Finally, some physical parameters of the model are discussed using graphs., Comment: 17 pages 18 figures, International journal of Modern Physics A

This article contains a new discussion for the generalized fractional Cauchy-type problem involving Hilfer-Katugampola-type fractional derivative. We study an existence and continuation of its solution. Firstly, we establish a new theorems of local existence. Then, we deduce a continuation theorems for a general fractional differential equations. By applying continuation theorems deduced in this article, we present several global existence results. Moreover, the examples are given to illustrate our main results., Comment: 19 pages

This paper contain a new discussion for the type of generalized nonlinear Caputo fractional $q$-difference equations with $m$-point boundary value problem and Riemann-Stieltjes integral $\tilde{\alpha}[x]:=\int_{0}^{1}~x(t)d\Lambda(t).$ By applying the fixed point theorem in cones, we investigate an existence of a unique positive solution depends on $\lambda>0.$ We present some useful properties related to the Green's function for $m-$point boundary value problem., Comment: 11 pages

In this article, we presented some properties of the Katugampola fractional integrals and derivatives. Also we studied the fractional calculus properties involving Katugampola Fractional integrals and derivatives of generalized $k-$Wright function $_{n}\Phi_{m}^{k}(z).$\\[2mm]

In this paper we have studied Kaluza-Klein string cosmological model within the framework of f(R; T) theory of gravity, where R is the Ricci scalar and T is the trace of the stress energy momentum tensor. We have obtained the solution of the corresponding field equations by using a time varying deceleration parameter. We also discussed various physical and dynamical properties of the model. The variation of different cosmological parameters are shown graphically for specific values of the parameters of the model., Comment: Accepted for publication in New Astronomy, May 2018

In this paper, we consider the Cauchy-type problem (1.1) involving Hilfer-Hadamard-type fractional derivative for a nonlinear fractional differential equation. We prove an equivalence between the Cauchy-type problem (1.1) and Volterra integral equation(VIE), existence, and uniqueness. We present a slight generalization for the Gronwall inequality which was used in studying the continuous dependence of a solution for the Cauchy-type problem (1.2)., Comment: 18 pages

In this paper, we used some theorems of fixed point for studying the results of existence and uniqueness for Hilfer-Hadamard-Type fractional differential equations, \[_{H}D^{\alpha,\beta}x(t)+f(t,x(t))=0, \hbox{ on the interval } J:=(1,e]\] with nonlinear boundary value problems \[x(1+\epsilon)=\sum_{i=1}^{n-2}\nu_{i}x(\zeta_{i}), \quad\quad\quad~_{H}D^{1,1}x(e) = \sum_{i=1}^{n-2} \sigma_i~_{H} D^{1,1}x(\zeta_{i})\], Comment: 17 pages. arXiv admin note: text overlap with arXiv:1801.10400

In this paper, we used some theorems of fixed point for studying the results of Existence and Uniqueness For Hilfer-Hadamard-Type Fractional Differential Equations, \[_{H}D^{\alpha,\beta}x(t)+f(t,x(t))=0, ~~~~~~ on~~the~~ interval~~ J:=(1,e]\] with Boundary Value Problems \[x(1+\epsilon)=0,~~~~~~~~~~_{H}D^{1,1}x(e)=\nu~_{H}D^{1,1}x(\zeta)\], Comment: 13 pages

Large Area X-ray Propositional Counter (LAXPC) instrument on AstroSat is aimed at providing high time resolution X-ray observations in 3 to 80 keV energy band with moderate energy resolution. To achieve large collecting area, a cluster of three co-aligned identical LAXPC detectors, is used to realize an effective area in access of about 6000 cm2 at 15 keV. The large detection volume of the LAXPC detectors, filled with xenon gas at about 2 atmosphere pressure, results in detection efficiency greater than 50%, above 30 keV. In this article, we present salient features of the LAXPC detectors, their testing and characterization in the laboratory prior to launch and calibration in the orbit. Some preliminary results on timing and spectral characteristics of a few X-ray binaries and other type of sources, are briefly discussed to demonstrate that the LAXPC instrument is performing as planned in the orbit., Comment: 11 pages, 15 Figures, Accepted for publication in Journal of Astronomy and Astrophysics

Tilted two fluids cosmological models with variable G and {\Lambda} In General Relativity are presented. Here one fluid is matter field modelling material content of the universe and another fluid is radiation field modelling the cosmic microwave background (CMB). The tiltedness is also considered .To get the deterministic model, we have assumed a supplementary condition where s and n are constants. We have also discussed the behaviours of some physical parameters., Comment: 13 pages

In the present paper an attempt has been made to study the spatially homogeneous and isotropic FRW model and axially symmetric spacetime in f(R) theory of gravity. We have obtained the solutions of the field equations in vacuum. To find the solutions of axially symmetric space-time we have assumed the relation between scale factor and scalar field and also we considered that scalar expansion ({\theta}) in the model is proportional to shear scalar ({\sigma}). The physical behavior for both models have been discussed by using physical parameters. The function of Ricci scalar is investigated for these models. Key words: f(R) theory of gravity, FRW universe, Axially symmetric space-time., Comment: Under review in Iranian Journal of Science and Technology

We present the calibration and background model for the Large Area X-ray Proportional Counter (LAXPC) detectors on-board AstroSat. LAXPC instrument has three nominally identical detectors to achieve large collecting area. These detectors are independent of each other and in the event analysis mode, they record the arrival time and energy of each photon that is detected. The detectors have a time-resolution of 10 $\mu$s and a dead-time of about 42 $\mu$s. This makes LAXPC ideal for timing studies. The energy resolution and peak channel to energy mapping were obtained from calibration on ground using radioactive sources coupled with GEANT4 simulations of the detectors. The response matrix was further refined from observations of the Crab X-ray source after launch. At around 20 keV the energy resolution of detector is about 10--15\%, while the combined effective area of the 3 detectors is about 6000 cm$^2$., Comment: Accepted for publication in ApJS

We studied plane symmetric cosmological model in the presence of quark and strange quark matter with the help of f(R,T) theory. To decipher solutions of Plane symmetric space-time, we used power law relation between scale factor and deceleration parameter. We considered the special law of variation of Hubble's parameter proposed by Berman (Nuovo Cimento B 74, 182, 1983) which yields constant deceleration parameter. We also discussed the physical behavior of the solutions by using some physical parameters., Comment: Accepted for publication in Journal of Astrophysics and Astronomy, August 2016

ASTROSAT is India's first satellite fully devoted to astronomical observations covering a wide spectral band from optical to hard X-rays by a complement of 4 co-aligned instruments and a Scanning Sky X-ray Monitor. One of the instruments is Large Area X-ray Proportional Counter with 3 identical detectors. In order to assess the performance of this instrument, a balloon experiment with two prototype Large Area X-ray Proportional Counters (LAXPC) was carried out on 2008 April 14. The design of these LAXPCs was similar to those on the ASTROSAT except that their field of view (FOV) was 3$^{\circ}$ $\times$ 3$^{\circ}$ versus FOV of 1$^{\circ}$ $\times$ 1$^{\circ}$ for the LAXPCs on the ASTROSAT. The LAXPCs are aimed at the timing and spectral studies of X-ray sources in 3-80 keV region. In the balloon experiment, the LAXPC, associated electronics and support systems were mounted on an oriented platform which could be pre-programmed to track any source in the sky. A brief description of the LAXPC design, laboratory tests, calibration and the detector characteristics is presented here. The details of the experiment and background counting rates of the 2 LAXPCs at the float altitude of about 41 km are presented in different energy bands. The bright black hole X-ray binary Cygnus X-1 (Cyg X-1) was observed in the experiment for $\sim$ 3 hours. Details of Cyg X-1 observations, count rates measured from it in different energy intervals and the intensity variations of Cyg X-1 detected during the observations are presented and briefly discussed., Comment: 23 pages, 14 figures in Experimental Astronomy Astrophysical Instrumentation and Methods August 2016,Vol 42, ISSN 0922-6435

The main purpose of the present paper is to investigate LRS Bianchi type I metric in the presence of perfect fluid and dark energy. In order to obtain a deterministic solution of the field equations we have assumed that, the two sources of the perfect fluid and dark energy interact minimally with separate conservation of their energy momentum tensors. The EoS parameter of the perfect fluid is also assumed to be constant. In addition to these we have used a special law of variation of Hubble parameter proposed by Berman that yields constant deceleration parameter. For two different values of the constant deceleration parameters we have obtained two different cosmological models. The physical behaviors of both the models have been discussed by using some physical parameters.

The present paper deals with cylindrically symmetric metric in the form of Marder (1958) with Saez-Ballester theory of gravitation in the presence of perfect fluid and dark energy. In order to obtain the deterministic solution of the field equations we have assumed that the expansion scalar in the model is proportional to the Eigen value of the shear tensor. We have also assumed that the two sources, here the perfect fluid and dark energy interact minimally with separate conservative parts of their energy momentum tensors together with the constant EoS parameter of the perfect fluid. The role of the dark energy in the present model with variable equation of state parameter is studied more in detail. Some physical properties of model are also discussed., Comment: 10 pages, no figure

Tilted and non tilted homogeneous plane symmetric C-field cosmological models are investigated. Using the method of Narlikar and Padmanabhan [4], the solutions have been presented when the creation field C is function of time t only. To get the deterministic model, we have assumed the supplementary condition between pressure and density . The behaviour of different stages of the universe has been studied in non tilted models. We have also investigated the behaviours of some physical parameters., Comment: 12 pages no figure

XTE J1908+094 is an X-ray transient black hole candidate in the Galactic plane that was observed in outburst in 2002 and 2013. Here we present multi-frequency radio and X-ray data, including radio polarimetry, spanning the entire period of the 2013 outburst. We find that the X-ray behaviour of XTE J1908+094 traces the standard black hole hardness-intensity path, evolving from a hard state, through a soft state, before returning to a hard state and quiescence. Its radio behaviour is typical of a compact jet that becomes quenched before discrete ejecta are launched during the late stages of X-ray softening. The radio and X-ray fluxes, as well as the light curve morphologies, are consistent with those observed during the 2002 outburst of this source. The polarisation angle during the rise of the outburst infers a jet orientation in agreement with resolved observations but also displays a gradual drift, which we associate with observed changes in the structure of the discrete ejecta. We also observe an unexpected 90deg rotation of the polarisation angle associated with a second component., Comment: Accepted for publication in MNRAS (13 pages, 6 figures, 2 tables)