Projects

Research projects with Daksha

The Daksha team welcomes participation from the scientific community in a variety of projects related to Daksha. Here we list a few representative collaboration opportunities. The details for a few of them are listed below. More topics and details will be added to this page from time to time.

• Soft X-ray GRB spectroscopy

• Time-resolved GRB spectroscopy

• Broadband spectroscopy of GRBs

• Detectability of extended emission and soft X-ray tails

• Studying Fast X-ray Transients with Daksha

• Studying known X-ray pulsars with Daksha

• Blind all-sky Pulsar searches with Daksha

• High Energy Counterparts to Neutron Star – Black Hole merger events

• Joint Sub-threshold searches for Gravitational Wave event counterparts

• Terrestrial Gamma-ray Flashes

• Temperature dependence of pixel noise in CZT detectors

Soft X-ray GRB spectroscopy

Overview

Gamma Ray Bursts (GRBs) have conventionally been studied in the hard X-ray and Gamma-Ray bands. Soft X-ray observations typically enter the picture only when studying afterglows. Some progress has recently been made in the soft X-ray prompt spectroscopy with data from Einstein Probe – but the overall soft X-ray spectra of GRBs remain poorly studied and understood.

Broadband spectra of GRBs are typically modelled with a phenomenological Band function or a synchrotron-like cutoff powerlaw. In both cases, a spectral peak or a break is predicted at high energies (hundreds of keV or higher). A disagreement exists between the observed prompt spectral shape and the theoretical synchrotron predictions from a non-thermal population of ultra relativistic electrons in the soft X-ray band. Studies of long GRB spectra by Oganesyan et al (2017) showed the presence of low energy breaks (~2 – 30 keV) as well. What is the cause of these soft breaks? Can they be modelled by marginally fast cooling in synchrotron regime? Or are they related to thermal emission?

There is no strong evidence for such soft spectral breaks in short GRBs. Is this a real physical effect, potentially related to their intrinsically harder spectra? Or is it just an observational bias resulting from the fewer number of photons in typical short GRBs? 

Goals

The goals of this project are:

1. Theoretical overview: Undertake a review of soft X-ray spectral models for GRB prompt spectra

2. Simulations for detectability: Undertake simplistic simulations of GRB spectra including soft components (for instance Xspec fakeit), and fit them using Daksha response files

3. Implications: Compile a manuscript discussing the possible detections / non-detections of such soft spectral components in Daksha, and their implications on our understanding of GRBs.

References

• “Detection of Low-energy Breaks in Gamma-Ray Burst Prompt Emission Spectra”, Oganesyan et al, 2017, The Astrophysical Journal, Volume 846, Issue 2, article id. 137, 22 pp. (2017). https://ui.adsabs.harvard.edu/abs/2017ApJ...846..137O/abstract 

• "Reconciling observed gamma-ray burst prompt spectra with synchrotron radiation?", Daigne et al., 2011 Astronomy and Astrophysics, Volume 526, id.A110, 13 pp https://ui.adsabs.harvard.edu/abs/2011A%26A...526A.110D/abstract 

• "Photospheric Emission as the Dominant Radiation Mechanism in Long-duration Gamma-Ray Bursts", Lazzati et al., 2013, The Astrophysical Journal, Volume 765, Issue 2, article id. 103, 7 pp. https://ui.adsabs.harvard.edu/abs/2013ApJ...765..103L/abstract 

• "Evidence of two spectral breaks in the prompt emission of gamma-ray bursts", Ravasio et al., 2019, Astronomy & Astrophysics, Volume 625, id.A60, 13 pp., https://ui.adsabs.harvard.edu/abs/2019A%26A...625A..60R/abstract 

Time-resolved GRB spectroscopy

Overview

Time-resolved prompt emission studies in Gamma-Ray Bursts (GRBs) reveal two critical unresolved patterns in spectral evolution. First, the spectral evolution from hard to soft energies suggests a complex emission mechanism: initial black body radiation from collapsing material transforms into non-thermal photons through internal shock interactions. Second, the correlation between luminosity and temperature indicates energy dissipation in Poynting flux-dominant outflows, with radiation primarily produced above the photosphere.

For short GRBs, critical open questions remain about the jet's propagation through merger ejecta. The cocoon formation and shock break-out process—characterized by a hard initial spike followed by a soft tail—provides a potential window into understanding neutron star merger dynamics. Crucial uncertainties persist about how the luminosity, duration, and spectral characteristics of these emissions relate to ejecta structure, jet properties, and potentially even the neutron star equation of state.

The fundamental scientific challenge is developing a unified physical model that can explain these complex emission mechanisms. Detailed, millisecond time-resolved spectroscopy across broad energy ranges—as enabled by missions like Daksha with micro-second resolution—represents the most promising path to resolving these outstanding questions in high-energy astrophysics.

Goals

The goals of this project are:

1. Consolidate theoretical models about GRB spectral evolution over short timescales, or among different pulses of GRBs

2. Simulate Daksha observations of such bursts (simulations tools are available from the core team)

3. Analyse the simulated data with Daksha response files to conclude how Daksha can measure the temporal evolution of spectral parameters, and the implications for our understanding of GRBs. Publish a manuscript about the same.

References

1. "Gamma-ray bursts from internal shocks in a relativistic wind: temporal and spectral properties", Daigne and Mochkovitch, 1998, MNRAS, Volume 296, Issue 2, pp. 275-286 https://ui.adsabs.harvard.edu/abs/1998MNRAS.296..275D/abstract 

2. "Time-resolved Analysis of Fermi Gamma-Ray Bursts with Fast- and Slow-cooled Synchrotron Photon Models", Burgess et al., 2014, The Astrophysical Journal, Volume 784, Issue 1, article id. 17, 18 pp. https://ui.adsabs.harvard.edu/abs/2014ApJ...784...17B/abstract  

3. "A reconnection switch to trigger gamma-ray burst jet dissipation", McKinney et al., 2012, MNRAS, Volume 419, Issue 1, pp. 573-607 https://ui.adsabs.harvard.edu/abs/2012MNRAS.419..573M/abstract 

Broadband spectroscopy of GRBs

Overview

GRB observations have typically been limited to the hard X-ray and Gamma ray regime, with very few observations of soft prompt emission from GRBs. Consequently, most theoretical GRB models also focus on only the high energy spectra. 

Many interesting questions about GRB physics will become accessible with the availability of broadband spectra Are there unique soft spectral signatures in GRBs? Do the soft and hard spectra arise from the same physical process, or different ones? Are these processes occurring in the same physical region, or are there different emission zones (for instance, photosphere and jet) giving rise to different emission components? How are these components related to each other? How are they expected to evolve with time?

Daksha, with its broadband spectral response, can obtain spectra of GRBs from 1 keV to beyond 1 MeV. The full utilisation of this rich data set is contingent upon having detailed spectroscopic models for GRB prompt emission. 

Goals

The goals of this project are:

1. Theoretical overview: Undertake a review of broadband spectral models for GRB prompt spectra

2. Simulations: Undertake simulations of GRB spectra including soft components (for instance Xspec fakeit), and fit them using Daksha response files

3. Implications: Compile a manuscript discussing the abilities of Daksha to distinguish between spectral models, and the implications on our understanding of GRBs.

References

1. "Evidence of two spectral breaks in the prompt emission of gamma-ray bursts", Ravasio et al., 2019, Astronomy & Astrophysics, Volume 625, id.A60, 13 pp., https://ui.adsabs.harvard.edu/abs/2019A%26A...625A..60R/abstract 

2. "The physics of gamma-ray bursts & relativistic jets", Pawan & Zhang, 2015, Physics Reports, Volume 561, p. 1-109. https://ui.adsabs.harvard.edu/abs/2015PhR...561....1K/abstract 

3. "Spectra and Light Curves of Gamma-Ray Burst Afterglows", Sari et al., 1998, The Astrophysical Journal, Volume 497, Issue 1, pp. L17-L20 https://ui.adsabs.harvard.edu/abs/1998ApJ...497L..17S/abstract