Simultaneous analysis of X-ray energy spectrum analysis and time series analysis to explore the universe's origin of binary black holes! ~ Graduate University of Physical Sciences Graduate Award Interview Dean's Award: Tomoteru Omama ~ | Greetings people. Space and astronautics research information portal

May 16, 2024 |

Tomoki Ohmama, a third-year doctoral student at the Graduate University of Advanced Studies (completed March 2024), received the Graduate School of Physical Sciences Dean's Award at the Graduate University of Advanced Studies.
In a face-to-face interview, we asked Mr. Tomoteru Ohmama, who is expected to continue his success in the future, for an overview of the award-winning research and his thoughts on the award.

What type of research received the award “Simultaneous X-ray spectrum and timing analysis of the binary black hole MAXI J1820+070 using the space state model”?

First, a black hole binary is a system in which two celestial bodies, a black hole and a star such as the Sun, are close together and orbiting each other. Because the black hole has strong gravity, the gas from the star orbits around the black hole, forming a disk called an accretion disk and falling down. Black holes don't emit light themselves, but their accretion disks and various other structures do, so they can be observed in the X-ray range, and we are trying to infer the surrounding structure from this information.
The reason for studying the structure surrounding them is that black holes have strong gravity, so it is believed that the structure surrounding them is affected by the theory of general relativity (general relativity) proposed by Einstein, and the effect of the theory depends on the structure surrounding the black hole. In other words, it's important to use some method to estimate the surrounding structure, so we track that using the X-ray scope.

The reason for X-rays is that the area around the black hole contains very high energy and the radiation can be seen in a high energy range called X-rays, so by observing the X-rays we can explore the surrounding structure near the black hole. Because you can.
To explain more, X-rays contain temporal information such as when they arrive at the detector, and energy information such as how much energy the detected X-rays have. We will basically treat these two pieces of information as data by formatting them correctly. However, until now, time and energy have been treated as independent data. There are two problems caused by this. The first is to analyze temporal fluctuations in how the brightness of the X-ray band changes over time, using energy information to decompose the structure into the physical components that make up the structure surrounding the black hole. On the other hand, if you only look at the energy information, you can see the differences in fluctuations for each energy band, but you cannot see the time fluctuations for each physical component.
Therefore, in this research, I first considered a framework that deals with time and energy at the same time, then developed an approach that estimates fluctuations in the physical components themselves from observational results, and compiled my doctoral thesis.

How attractive is this research?

Until now, the prevailing approach has been for astronomers to imagine such an image exists, and then check for inconsistencies by comparing that image with observational data, but this research takes a different approach – the so-called data-driven approach, which involves extracting hidden information from an analysis of Data and scan the image from there.

What will be revealed as research into black holes progresses?

The binary black hole we dealt with this time was one of many in the galaxy, and we had previously used the EHT (Event Horizon Telescope) to build a global collaboration and imaging VLBI millimeter-wave/sub-millimeter-wave observing network. Black Hole Shadows The black hole imaged by this international project is located at the center of the galaxy. It is believed to be a supermassive black hole affecting the entire universe, and it is expected that there is an accretion disk-like structure around the black hole at the center of the galaxy. In this way, I believe this research on black hole binaries can be applied and inferred to the structure surrounding the black hole at the center of the galaxy, which will lead to further discussions about the origin of the universe.

What was the most challenging part of this research, including obtaining the data?

Although the data is publicly available and obtainable, research using statistical models like this is not very common in the field of astronomy. Therefore, the result of this research was the result of repeated trial and error from different aspects while reading different materials. I had to feel my way through the darkness, and I felt like there was light, but I didn't even know if it was really light.
This research also uses statistical model, but since statistical models obtain probability values, it is necessary to handle probabilities well. Traditional programming is good at handling fixed data, but in order to deal with data that can be obtained probabilistically, it is necessary to make full use of probabilistic programming languages ​​that extend them to deal with probabilities. In order to master it, in addition to traditional knowledge of programming, it was necessary to mobilize all knowledge in the field of statistics and mathematics. However, since it was a relatively new concept, there wasn't a lot of material available, so I had to read software manuals and tutorials to implement it, which was very difficult.

Please tell us how you felt when you received the award.

I thought it would go fairly well until I completed my dissertation and it was accepted as a doctoral thesis, but I honestly didn't know how much it would be evaluated. However, by receiving this award, I received confirmation that I was doing good research, which gave me a sense of security that 'I didn't do anything wrong' and 'I was doing research that was interesting from the perspective of others.'' We are connected.

The world is becoming more and more overflowing with data, so I believe that the people who process it will be the stars of the future.

I agree. They say there's a shortage of data scientists, and I think this has been said for over five years, but it seems like there's still a shortage of data scientists. This is because the amount of data being captured continues to increase, and I believe that these types of jobs and skills will become more necessary in the future.

Please tell us your goals and future prospects!

In the future, I will deal with social data in a private company. It may seem like completely different data, but when you look at it as data, there are similarities in the randomness and characteristics of the data. This time, the research looked into the natural sciences of physics, but in the future, I hope we can use data to create products that make people more comfortable and happy, for example from a humanities and social sciences perspective. I'm really excited that I can use the skills I've gained through data analysis to give back Beautiful to the community.

Finally, do you have any desire to deepen your research on black holes?

I agree. Maybe while analyzing data at work, you might think: “This method could be used with black holes,” and maybe you also work on black hole data on weekends. This may just be my wish, but my ideal life would be to return to ISAS in the future and be able to apply the knowledge I have gained in different places in astronomy. To this end, I would like to expand my horizons by working in other fields, receiving different incentives, and acquiring diverse skills and knowledge.

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