High-Energy Astrophysics

Ruchika
Dhaka

I study how matter falls onto black holes and neutron stars — probing accretion physics, X-ray binaries, and quasi-periodic oscillations with the world's X-ray observatories. Postdoctoral researcher at the Xinjiang Astronomical Observatory.

Postdoctoral Researcher · Xinjiang Astronomical Observatory PhD, IIT Kanpur ruchika@iitk.ac.in
01

About

I am a high-energy astrophysicist and a postdoctoral researcher at the Xinjiang Astronomical Observatory (XAO) in Urumqi, China. I completed my PhD in the Department of Physics at the Indian Institute of Technology Kanpur in 2025, and subsequently held a FARE Fellowship at IIT Kanpur before joining XAO.

My research investigates the physics of accretion onto compact objects. I combine spectral and timing analysis across X-ray missions to understand the geometry of accretion flows, the launching of relativistic jets, and the origin of quasi-periodic oscillations (QPOs) in black-hole and neutron-star binaries — with sources such as GRS 1915+105, GX 339−4, and Cyg X-3.

As Principal Investigator on observing programs with NICER, Swift, and IXPE, I design and lead my own observational campaigns, and I have held visiting fellowships at IUCAA Pune and at FORTH in Crete, Greece.

Ruchika Dhaka presenting her research on GRS 1915+105
Current
Postdoctoral Researcher, XAO Urumqi
Previously
FARE Fellow, IIT Kanpur
PhD Physics
IIT Kanpur · 2019–2025
M.Sc. Physics
IIT Kanpur · 2017–2019
B.Sc. Physics
University of Rajasthan, Jaipur
02

Research Interests

Accretion physics X-ray binaries Spectral & timing analysis Quasi-periodic oscillations Low-mass X-ray binaries Black-hole jets X-ray polarization Spectral state transitions
03

Selected Publications

01
Correlations between QPO frequencies and spectral parameters of GRS 1915+105 using AstroSat observations
Dhaka R., Misra R., Yadav J. S., Jain P. · MNRAS 524 (2), 2721–2732 · 2023
First author Cited by 13 DOI ↗
02
Exploring the broadband spectral and timing characteristics of GRS 1915+105 with AstroSat and NICER observations
Dhaka R., Misra R., Jain P., Yadav J. S. · ApJ 974 (1), 90 · 2024
First author Cited by 9 DOI ↗
03
Discovery of a new flaring class in GRS 1915+105 using AstroSat
Dhaka R., Yadav J. S., Misra R., Jain P. · ApJ 984 · 2025
First author Cited by 3 arXiv ↗
04
Accretion disc evolution in GX 339−4 across spectral states using NuSTAR, NICER, and Insight-HXMT observations
Dhaka R., Misra R., Chaurasia S. K. · MNRAS 547 (4), staf487 · 2026
First author New arXiv ↗
05
Spectral analysis of Cyg X-3 using simultaneous AstroSat and Insight-HXMT observations
Chaurasia S. K., Mall G., Dhaka R., Misra R., Pathak A. · ApJ 986 (1) · 2025
Co-author Cited by 2 arXiv ↗
06
Testing the jet model for the black-hole X-ray source GX 339−4 during the decay of the outburst
Dhaka R., Reig P., Kylafis N.
First author In preparation
04

Observing Proposals as PI

2024
Recent outburst of the neutron-star X-ray binary Aql X-1 NICER · DDT Program (PI)
2024
Evolution of the 2024 outburst of Aql X-1, 4-day monitoring cadence Swift · Targets of Opportunity (PI)
2024
Persistent high/soft state of LMC X-1 NICER · Cycle 7 Guest Observer (PI)
2024
High-energy polarization of Cygnus X-3: scattering & reflection models IXPE · Cycle 2 (PI)
2021
Simultaneous Insight-HXMT & AstroSat observations of black-hole binaries Insight-HXMT · AO4 (Co-I)
05

Invited Talks & Seminars

Ruchika Dhaka delivering a talk on GRS 1915+105

Presenting the spectral and timing evolution of GRS 1915+105

2024
MAXI 15-year workshop for time-domain astronomy Talk · Nihon University, Tokyo, Japan
2024
Spectral & timing evolution of black-hole X-ray binaries Invited seminar · ISAS / JAXA, Japan
2023
4th China–India Workshop on High Energy Astrophysics Talk · Fudan University, Shanghai, China
2023
Insights from QPOs and spectral states of GRS 1915+105 Invited seminar · University of Crete / IA-FORTH, Greece
2023
10th Microquasar Workshop Talk · Crete, Greece
2022
2nd & 3rd China–India Workshops on High Energy Astrophysics Talks · Fudan University & IUCAA
06

Fellowships & Recognition

2023
Arepalli Travel Grant, IIT Kanpur For international conference participation
2022–24
Visiting Fellow, IUCAA Pune & IA-FORTH, Crete
2021–
Institute Senior Research Fellowship, IIT Kanpur
2017
JAM all-India rank 196 · JEST all-India rank 247 National entrance examinations
07

Tools & Methods

X-ray Analysis
HEASOFT — IXPE, NICER, NuSTAR, AstroSat, Insight-HXMT
Programming
Python, C, MATLAB, Bash scripting
Methods
Spectral & timing analysis, machine learning
Languages
English, Hindi, Punjabi
08

Contact & References

Open to collaboration on X-ray binary spectroscopy, timing, and polarization studies.

ruchika@iitk.ac.in

ruchikadhaka1997@gmail.com

Dept. of Physics, IIT Kanpur, India

Prof. Pankaj Jain
Space Science & Astronomy, IIT Kanpur
Prof. Ranjeev Misra
Astronomy & Astrophysics, IUCAA Pune
Prof. J. S. Yadav
Space Science & Astronomy, IIT Kanpur
Prof. Sudip Bhattacharyya
Astronomy & Astrophysics, TIFR Mumbai
Dr. Pablo Reig
Senior Researcher, IA-FORTH, Greece