On Thursday, December 15th, alumnus Miguel Martinez spoke on the mergers of triple systems within clustered and isolated environments in space.

Stars are complex, more so than we originally thought. Initially, most of the information disseminated around stars was related to seasons or navigation. However, in more recent millennia, we’ve started to focus on the science behind those lights in the sky–something Miguel Martinez (CC ‘19) is aiming to do.

A Columbia University alumnus, Miguel Martinez is now a graduate student working with the Fred Rasio group at Northwestern University where he is studying massive star clusters. Massive star clusters are “groups of stars that are gravitationally bound together” and are eight times larger than the sun by mass. These tight groups of stars have various configurations, and Martinez is investigating mainly how triple mergers are related to black hole mergers.

According to Martinez, triples can exist in a variety of different environments. There is an inner binary of two black holes orbited by an outer orbit known as a tertiary. This hierarchical structure allows scientists to approximate much information.

An example of a triple. Two black holes (represented by the dots) make up the smaller, inner orbit, and a third distant star is in the outer orbit.

Lots of research has been done on what triples can do, and ultimately they have three main features:

  1. Eccentricity: Extremely rapid loss of energy from waves
  2. Spin-orbit misalignment: The orientation of the structures can change and look different than the represented image
  3. Asymmetric Mergers

But ultimately, why do we care about them? Martinez stated, “we care about them because we see them.” These massive stars are observable. Most massive stars have a multiplicity fraction, which is the fraction of the star systems with multiple stars, greater than one. 60-80% of OB stars, a type of massive stars, are triples, with the rest consisting of higher-ordered configurations. These massive blue stars, though they have a short lifespan, were studied considering only binary stars for a long time. Now, however, triples are considered. This complicated addition is important because, while binaries are presented within triples, triples have specific properties as noted. 

There have been a lot of observations of triple star systems, but in Martinez’s paper, he wanted to look at them in the field and break down the triple mergers in time steps. None of the triple papers before had looked at the mass-ratio distribution. Through this study, they were able to understand the properties of asymmetric mergers from triples. He did want to make an important note that not all black-hole mergers result from triples and triples do not specifically cause these mergers based on his current research. 

Martinez and his group will continue to research this exciting area of study.

Star system via Wikimedia Commons

Triple drawing via Bwog Staff