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Iyer, Nirmal
Publications (4 of 4) Show all publications
Pearce, M., Eliasson, L., Iyer, N., Kiss, M., Kushwah, R., Larsson, J., . . . Xie, E. (2019). Science prospects for SPHiNX - A small satellite GRB polarimetry mission. Astroparticle physics, 104, 54-63
Open this publication in new window or tab >>Science prospects for SPHiNX - A small satellite GRB polarimetry mission
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2019 (English)In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 104, p. 54-63Article in journal (Refereed) Published
Abstract [en]

Gamma-ray bursts (GRBs) are exceptionally bright electromagnetic events occurring daily on the sky. The prompt emission is dominated by X-/gamma-rays. Since their discovery over 50 years ago, GRBs are primarily studied through spectral and temporal measurements. The properties of the emission jets and underlying processes are not well understood. A promising way forward is the development of missions capable of characterising the linear polarisation of the high-energy emission. For this reason, the SPHiNX mission has been developed for a small-satellite platform. The polarisation properties of incident high-energy radiation (50-600 keV) are determined by reconstructing Compton scattering interactions in a segmented array of plastic and Gd3Al2Ga3O12(Ce) (GAGG(Ce)) scintillators. During a two-year mission, similar to 200 GRBs will be observed, with similar to 50 yielding measurements where the polarisation fraction is determined with a relative error <= 10%. This is a significant improvement compared to contemporary missions. This performance, combined with the ability to reconstruct GRB localisation and spectral properties, will allow discrimination between leading classes of emission models. 

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2019
Keywords
Polarimetry, X-ray, Gamma-ray burst, Small satellite
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-238522 (URN)10.1016/j.astropartphys.2018.08.007 (DOI)000447479300004 ()
Funder
Swedish National Space Board, 232/16
Note

QC 20181106

Available from: 2018-11-06 Created: 2018-11-06 Last updated: 2018-11-06Bibliographically approved
Pearce, M., Eliasson, L., Iyer, N., Kiss, M., Kushwah, R., Larsson, J., . . . Xie, F. (2019). Science prospects for SPHiNX – A small satellite GRB polarimetry mission. Astroparticle physics, 104, 54-63
Open this publication in new window or tab >>Science prospects for SPHiNX – A small satellite GRB polarimetry mission
Show others...
2019 (English)In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 104, p. 54-63Article in journal (Refereed) Published
Abstract [en]

Gamma-ray bursts (GRBs) are exceptionally bright electromagnetic events occurring daily on the sky. The prompt emission is dominated by X-/γ-rays. Since their discovery over 50 years ago, GRBs are primarily studied through spectral and temporal measurements. The properties of the emission jets and underlying processes are not well understood. A promising way forward is the development of missions capable of characterising the linear polarisation of the high-energy emission. For this reason, the SPHiNX mission has been developed for a small-satellite platform. The polarisation properties of incident high-energy radiation (50–600 keV) are determined by reconstructing Compton scattering interactions in a segmented array of plastic and Gd3Al2Ga3O12(Ce) (GAGG(Ce)) scintillators. During a two-year mission, ∼ 200 GRBs will be observed, with ∼ 50 yielding measurements where the polarisation fraction is determined with a relative error ≤ 10%. This is a significant improvement compared to contemporary missions. This performance, combined with the ability to reconstruct GRB localisation and spectral properties, will allow discrimination between leading classes of emission models.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Gamma-ray burst, Polarimetry, Small satellite, X-ray, Ellipsometry, Polarimeters, Polarization, Satellites, Stars, X rays, Gamma ray bursts, Gamma-ray bursts (GRBs), High energy emission, High energy radiation, Linear polarisation, Scattering interactions, Small-satellite, Temporal measurements, Gamma rays
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-236345 (URN)10.1016/j.astropartphys.2018.08.007 (DOI)2-s2.0-85052499332 (Scopus ID)
Funder
Swedish National Space Board, 232/16
Note

QC 20181108

Available from: 2018-11-08 Created: 2018-11-08 Last updated: 2018-11-08Bibliographically approved
Pearce, M., Eliasson, L., Iyer, N., Kiss, M., Kushwah, R., Larsson, J., . . . Xie, F. (2019). Science prospects for SPHiNX - A small satellite GRB polarimetry mission. Astroparticle physics, 104, 54-63
Open this publication in new window or tab >>Science prospects for SPHiNX - A small satellite GRB polarimetry mission
Show others...
2019 (English)In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 104, p. 54-63Article in journal (Refereed) Published
Abstract [en]

Gamma-ray bursts (GRBs) are exceptionally bright electromagnetic events occurring daily on the sky. The prompt emission is dominated by X-/gamma-rays. Since their discovery over 50 years ago, GRBs are primarily studied through spectral and temporal measurements. The properties of the emission jets and underlying processes are not well understood. A promising way forward is the development of missions capable of characterising the linear polarisation of the high-energy emission. For this reason, the SPHiNX mission has been developed for a small-satellite platform. The polarisation properties of incident high-energy radiation (50-600 keV) are determined by reconstructing Compton scattering interactions in a segmented array of plastic and Gd3Al2Ga3O12(Ce) (GAGG(Ce)) scintillators. During a two-year mission, similar to 200 GRBs will be observed, with similar to 50 yielding measurements where the polarisation fraction is determined with a relative error <= 10%. This is a significant improvement compared to contemporary missions. This performance, combined with the ability to reconstruct GRB localisation and spectral properties, will allow discrimination between leading classes of emission models.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2019
Keywords
Polarimetry, X-ray, Gamma-ray burst, Small satellite
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-238104 (URN)10.1016/j.astropartphys.2018.08.007 (DOI)000447479300004 ()2-s2.0-85052499332 (Scopus ID)
Note

QC 20190111

Available from: 2019-01-11 Created: 2019-01-11 Last updated: 2019-01-11Bibliographically approved
Radhika, D., Sreehari, H., Nandi, A., Iyer, N. & Mandal, S. (2018). Broad-band spectral evolution and temporal variability of IGR J17091-3624 during its 2016 outburst: SWIFT and NuSTAR results. Astrophysics and Space Science, 363(9), Article ID 189.
Open this publication in new window or tab >>Broad-band spectral evolution and temporal variability of IGR J17091-3624 during its 2016 outburst: SWIFT and NuSTAR results
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2018 (English)In: Astrophysics and Space Science, ISSN 0004-640X, E-ISSN 1572-946X, Vol. 363, no 9, article id 189Article in journal (Refereed) Published
Abstract [en]

We report on the 2016 outburst of the transient Galactic Black Hole candidate IGR J17091-3624 based on the observation campaign carried out with SWIFT and NuSTAR. The outburst profile, as observed with SWIFT-XRT, shows a typical 'q'-shape in the Hardness Intensity Diagram (HID). Based on the spectral and temporal evolution of the different parameters, we are able to identify all the spectral states in the q-profile of HID and the Hardness-RMS diagram (HRD). Both XRT and NuSTAR observations show an evolution of low frequency Quasi periodic oscillations (QPOs) during the low hard and hard intermediate states of the outburst rising phase. We also find mHz QPOs along-with distinct coherent class variabilities (heartbeat oscillations) with different timescales, similar to the -class (observed in GRS 1915+105). Phenomenological modelling of the broad-band XRT and NuSTAR spectra also reveals the evolution of high energy cut-off and presence of reflection from ionized material during the rising phase of the outburst. Further, we conduct the modelling of X-ray spectra of SWIFT and NuSTAR in 0.5-79 keV to understand the accretion flow dynamics based on two component flow model. From this modelling, we constrain the mass of the source to be in the range of with 90% confidence, which is consistent with earlier findings.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Accretion, accretion disks, Black hole physics, X-rays: binaries, ISM: jets and outflows, Stars: individual: IGR J17091-3624
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:kth:diva-234580 (URN)10.1007/s10509-018-3411-1 (DOI)000442478500001 ()2-s2.0-85052240883 (Scopus ID)
Note

QC 20180917

Available from: 2018-09-17 Created: 2018-09-17 Last updated: 2018-09-17Bibliographically approved
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