News

Welcome to O4!

On 24th of May, LIGO, in unison with KAGRA, started operations for its fourth observing run, O4. After over two years of upgrades and maintenance work, LIGO is back with an improved detection capability, and will be able to observe neutron star mergers at upto 190 Mpc from us. In the couple of weeks since the start, the LVK has already made a handful of likely astrophysical event observations and alerted the astronomy community via GraceDB and GCN . The excitement has just begun, and we look forward to hundreds of confirmed merger. However, for the events that I am most interested in, BNS (binary neutron star mergers) and BH-NS (black hole-neutron star mergers) the estimate is that only a handful of detections will be made.
With the start of O4, I also had the absolute delight of performing real-time analysis for the binary black hole candidate event S230601bf ( GraceDB link ) for the LIGO team working on Parameter Estimation as part of a rota group. I served for the week of 28/May to 4/June.
- June 2023

Gave a seminar talk

I talked about Multi-Messenger Astrophysics and the detectability of BNS merger properties via gravitational and electromagnetic waves. Talk title: "Multi-messenger Astrophysics: Gravitational waves of quark matter EOSs and ejecta parameter estimation with kilonovamodelling". Link to the pdf : CCRG_talk - March 2023.

New Paper on kilonovae and GW170817

We released a new article on kilonovae surrogate models and parameter estimation comparisons for EM- and GW- based observation.[ Link to the open access paper]
We have developed new surrogate models for light curves resulting from kilonova and perform parameter estimation with them to reveal important agreement/disagreement between GW- and EM- estimates for the neutron star merger (NSM) GW170817/AT2017gfo ejecta material.
What are surrogate models? These are substitute model for a mathematical function. In this case for estimating light curves from a particular set of NS-merger ejecta parameters. Performing full ratiative transfer simulations takes 1/2 hr on 10x128 cores ~ 20,000 threads, i.e. lots of t or $$$. To avoid the costs these Gaussian Process Regression based surrogates substitute for the complete simulation and can interpolate the LCs rapidly, ~5 mins, on local PCs!
Why is building surrogates important? Due to the speed benefits mentioned above, But also because NSMs have been known to produce a broad range of ejecta material based on theoretical (more like numerical) estimates. They suggest a range of ejecta masses, velocities, distribution in space, and depend heavily on simulation setup and nuclear physics. This results in uncertainties in the kilonova signal prediction working in the forward direction. I.e. NSM simulation -> ejecta mass, distribution, espansion rate estimation -> kilonova LCs. Our surrogates make that '->' between ejecta and kilonova LCs essentially trivial!
Vice-versa the uncertainties also makes it challenging to predict the NS parameters starting from the kilonova observation and working backwards. I.e. kilonova LCs observation -> estimating ejecta mass, distribution, expansion rate-> NS parameters. Our surrogates help here as well, hence making rapid parameter inference calculations possible.
Next, we perform ejecta parameter estimation with these surrogate models to obtain the ejecta component masses and velocities for the event AT2017gfo/GW170817. We find that the EM-predicted ejecta and the GW-predicted ejecta properties do come closer into agreement due to the additional ejecta forms, but still disagree somewhat. The disagreement is especially striking in the masses, while the velocities remain unconstrained either way (Fig. 6).
We also show the capabilities of our surrogate models that can produce LCs for a range of ejecta component form (shapes [dubbed 'morphology' in the paper]) expansion rate, observation azimuthal direction, and at any broadband filter within a range of wavelengths.
With LIGO's next observing run starting early next year, it will be exciting to see many more multi-messenger events observed that, via means of studies such as this, will constrain the physics of the formation of the ejecta, and will shed light into the origin of heavy elements.
The surrogates can be found here Link to the Github repo , the radiative transfer simulations at Link to the Zenodo repo , and the paper at Phys. Rev. Res. 5, 013168 (2023) - November 2022 .

My research in popular news media

The popular-science magazine New Scientist ran an article on one of my papers from Notre Dame. Link of the first news The paper the article is about is this on PRD. My PhD advisor Prof. Grant Mathews was interviewed for this article. A snapshot of the article can be found here. He also gave a talk the APS-DNP meeting this year and the talk was selected as a featured talk for the conference. See link of the second news - October 2022.

Postdoc at RIT

I am excited to announce that I am now a Postdoctoral researcher at the Center for Computational Relativity and Gravitation, at Rochester Institute of Technology working with Dr. Richard O'Shaughnessy (link to his website) on neutron star merger ejecta properties, kilonovae and nuclear equations of state.

Defended my Ph.D.

Very pleased to let you know that on 7/June/2022 I defended my Ph.D. at Notre Dame with my advisor being Prof. Grant Mathews. My dissertation title was Relativistic matter in Neutron Star mergers and Big bang nucleosynthesis, and it encompassed the neutron star merger paper I submitted recently and the work on big bang nucleosynthesis I have done over few years (see paper links in my CV for reference to what I am talking about). - June 2022

Invited talk at the ET workshop

Einstein toolkit workshop website. The talk discussed the workflow of preparing binary neutron star initial data using LORENE. The workflow for various different EoS formats, and grid systems were shown along with necessary unit discussion. A full recording can be viewed for reference on ET's YouTube channel. Please direct questions to my email. - July 2021

Recieved the CRC Graduate award

Original news article news article. Official award website.
The award recognizes "outstanding contributions in the areas of computational sciences and visualization. Such contributions may include, but are not limited to: Applications of high performance computation and/or visualization technology Development of algorithms, codes, software environments, or other tools for better using high performance computing and/or visualization." - June 2021

Co-hosted the MidWest Relativity Meeting on 22-24 October, 2020

The Center for Astrophysics at Notre Dame University (CANDU) hosted the 30th Mid-West Relativity (Virtual) Meeting on 22-24 Oct, 2020. The meeting was attended by more than 150 relativists located around the world, delivering over 80 talks in topics covering different research topics in General Relativity. Meeting website.

Research talks

Some of the recorded research talks of mine can be viewed on youtube:
3. Einstein Toolkit workshop (17/June/2022)
2. Einstein Toolkit workshop (28/July/2021)
1. Marcel Grossman 16 (8/July/2021)
(P.S.: Other talks in these meetings are also very interesting by excellent scholars, do view them as well.)

Interesting meetings

IPAM- UCLA is conducting a very interesting series of conferences on Gravitational waves and Multi messenger astrophysics. 13 Sept- 17 Dec 2021 Link

Resources

I plan on posting useful resources on understanding different concepts and physics here. To start-off: A set of pages on entropy, NSE and its role in nucleosynthesis by Bradley Meyer https://ned.ipac.caltech.edu/level5/Sept01/Meyer/Meyer2.html

Less used active emails:
atul.kedia at ligo.org
akedia at alumni.nd.edu
atulkedia at iitb.ac.in
atulkedia93 at iitbombay.org
atulkedia93 at gmail.com
atul.subhashkedia at mail.utoronto.ca


Fun Facts

I am an amateur geography enthusiast (primarily the US geography), and enjoy reading about quirky, unusual, unpopular places and about demographic trends. I'm also interested in public transit and long distance travel on trains and buses, and consequently enjoy visiting cities with good public transit network and walkability. Hoping the US gets more high-speed rail soon! Keeping an eye out on the Southeast High Speed Rail Corridor from Washington, D.C. to Raleigh, N.C. to Atlanta and Jacksonville Wikipedia link.

I also enjoy playing sports, and at different stages have been fond of playing football/soccer, badminton, squash, racquetball, table tennis/ping pong, billiards/pool, and most recently pickleball.