ItemArticle

Spectral Evolution of GX 17+2 Using AstroSat and NICER Observations

Title
Spectral Evolution of GX 17+2 Using AstroSat and NICER Observations
Creator
Bhattacherjee, Sree; Misra, Ranjeev; Sarkar, Biplob; Jithesh, V.; Roy, Jayashree; Bhulla, Yashpal
Description
We study the spectral evolution of the Z-track source GX 17+2 using AstroSat and NICER observations taken between 2016 and 2020. The AstroSat observations cover the period when the source is in the normal branch (NB) and the flaring branch (FB), while for the NICER ones the variability can be associated with the FB branch. The source spectra at different regions of the branches are well described by accretion disk emission, blackbody surface emission, and a thermal Comptonization component. In the NB, the total bolometric unabsorbed flux remains constant and the variation is due to changes in the Comptonization, disk fluxes. In particular, the inferred luminosity (LT) and accretion rate ( M ? ) remain constant, while there is significant variation in the inner disk radii and fraction of disk photons entering the corona, indicating changes in the geometry of the system. On the other hand, in the FB, there is significant variation in luminosity from ?4.0 to ?7.0 1038 erg s?1. Despite this significant variation in luminosity and in the inner disk radii, the accretion efficiency, defined as ? = L T / M ? c 2 , remains nearly constant at ?0.20 throughout the evolution of the source, as expected for a neutron star system. 2025. The Author(s). Published by the American Astronomical Society.
Source
Astrophysical Journal;Volume;989;Issue;1;Article No.;23;
Date
01-01-2025
Publisher
Institute of Physics
Coverage
Bhattacherjee S., Department of Applied Sciences, Tezpur University, Assam, Napaam, 784028, India; Misra R., Inter-University Center for Astronomy and Astrophysics, Ganeshkhind, Pune, 411007, India; Sarkar B., Department of Applied Sciences, Tezpur University, Assam, Napaam, 784028, India; Jithesh V., Department of Physics and Electronics, Christ University, Hosur Main Road, Bengaluru, 560029, India; Roy J., Inter-University Center for Astronomy and Astrophysics, Ganeshkhind, Pune, 411007, India; Bhulla Y., Pacific Academy of Higher Education and Research University, Udaipur, 313003, India
Rights
All Open Access; Gold Open Access; Green Open Access
Relation
ISSN: 0004637X;
Format
online
Language
English
Type
Article

Citation

Bhattacherjee, Sree; Misra, Ranjeev; Sarkar, Biplob; Jithesh, V.; Roy, Jayashree; Bhulla, Yashpal, “Spectral Evolution of GX 17+2 Using AstroSat and NICER Observations,” CHRIST (Deemed To Be University) Institutional Repository, accessed June 19, 2026, https://archives.christuniversity.in/items/show/23586.

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