Çağatay Kerem Dönmez

Çağatay Kerem Dönmez

Who are you?

A research assistant in the Department of Physics in Middle East Technical University (METU). It is located in Ankara, the capital of Turkey. Despite the official naming, the position primarily involves teaching responsibilities.

I received my PhD from the same department in 2025.


What do you do in school? Splitting atoms? Self-torture?

Well, I work in astrophysics, currently focusing on X-ray binaries that contain a neutron star.


So you mean, self-torture???

No, not really... Maybe?

Well, a neutron star is basically the immensely compacted core of a massive dead star. I think no word in any language can truly convey how "immensely" compacted it is: The material of a neutron star is, on average, 100 000 000 000 000 times denser than water! Consequently, a typical neutron star has a mass comparable that of the Sun, yet is only 10 km in size.

Even though we often think of stars as single entities, many of them have companions. In such binary systems, the star pair orbits around each other. When a neutron star is in a binary system and when the conditions are right (e.g. the companion is huge or unstable, or the stars are very close), the neutron star can steal matter from its companion. Because the neutron star is so heavy and dense, the infalling matter accelerates wildly and gains an incredible amount of energy. Due to the violent interactions between the infalling matter and the neutron star, lots of high-energy X-rays are produced (Okaay, other types of "light" are produced as well, but right now X-rays are my bread and butter). By observing those X-rays, you can better understand the physics behind these weird objects. That's basically what we do.

In order to observe X-rays, a space telescope specifically designed to detect them is needed:

  • It needs to be sent into space because, luckily, Earth's atmosphere blocks all X-rays coming from the outer space.
  • It needs to be a special type of telescope, because you cannot manipulate X-rays like visible light. For example, you can create a lens to focus visible light, but X-rays either pass through or are absorbed by such a lens!
So, scientists come up with different designs for different purposes, and there are numerous X-ray space observatories orbiting the Earth. Securing observation time from these telescopes is extremely difficult, but thankfully, most of the data is publicly available immediately or after a proprietary period.


Any actual work, or just slacking?

As of August 2025, I have four peer-reviewed publications:

I defended my PhD thesis in June 2025, titled Pulse Profile Changes in Swift J0243.6+6124, MXB 0656-072 and GRO J1008-57.
I defended my master's thesis in February 2019, titled The Spectral and Temporal Properties of MAXI J1409-619.


Meh. Tell me more about yourself.

Born in an industrial, mid-sized city called Karadeniz Ereğli on the coast of Black Sea. Spent my life there until university.

My undergrad degree is actually in electrical and electronics engineering. I studied at Bilkent University (again in Ankara) and graduated in 2015.

I'm a casual


How to find you?

I am often in my office, Z22, at the Department of Physics. It's on the ground floor, in the middle of the long corridor.

You can also reach me at:

If you ever need my exact address, here it is:


Some other links