In this series of posts, we sit down with some of the plenary speakers for the 240th AAS meeting to learn more about them and their research. You can see a complete schedule of their calls hereand read our other interviews here!
“Magnetars are the perpetrators of (almost) everything” is the title and Astrobit from a few years ago, and Dr. Scholz, one of the topics in today’s Astrobites feature, generally tends to agree.
Today’s post will jointly focus on the work and career of Dr. Victoria Kaspi, Professor of Physics at McGill University, and her former student and associate, Dr. Paul Scholz, a Postdoctoral Fellow at the Dunlap Institute for Astronomy and Astrophysics at the Dunlap Institute for Astronomy and Astrophysics at University of Toronto. As chief investigator for Canadian Hydrogen Intensity Mapping Experiment (CHIME) Dr. Kaspi is one of many astronomers working to solve the mystery fast radio bursts (FRB) – extremely fast and energetic emission bursts that we observe in the radio band – and to find out how to use these phenomena to answer basic questions about the universe. The CHIME instrument is a unique stationary radio telescope that constructs very wide density maps of hydrogen almost immediately, making it ideal for both large-scale science – for example, to measure the expansion history of the universe – and at rapid scales – for example to study rare transient or periodically issuing objects such as FRB and pulsars.
The strength of Dr. Kaspi’s scientific collaborations are obvious as she will receive two awards at AAS this year, focusing on two different areas of her expertise. On behalf of the entire CHIME collaboration, she and Dr. Scholz receive the Berkeley Prize for the discovery of a very brilliant radio broadcast from a magnetar (a dense stellar remnant with an unusually strong magnetic field) within our galaxy and the large catalog of FRBs compiled by the CHIME team. Until their observation, the FRB had been a purely extragalactic phenomenon and their origin was an open question, so their discovery showed us that the words from that Astrobite a few years ago may be true – magnetars can produce radiobureaus so that we can see them from extragalactic distances, and therefore some FRBs can be magnetars. Dr. Scholz remembers the moment when they first made that observation and tells of his excitement: “it was one of those moments when it felt like nature threw something at you and it tells you something – it is [the kind of observation] it has consequences as soon as you see it ”. That observation was actually groundbreaking in the area of FRB and has opened the door to the possibility of more such discoveries within our own galaxy.
Dr. Kaspi also receives the Shaw Prize, which she is awarded together with her colleague Dr. Chryssa Kouveliotou, for their independent work with magnetars. Dr. Kaspi led research on observational anomalous X-ray pulsars who lacks a clear understanding of the origin of X-rays – her observational work showed that these were also performed by magnetars. By continuing to monitor the sources, they discovered that this phenomenon was quite normal and provided insight into the range of possible magnetic phenomenologies and what causes these systems.
In college at McGill University, Dr. Kaspi intends to pursue a career in particle physics, especially after a summer at CERN in Switzerland. Thereafter, her postgraduate studies at Princeton required students to do some kind of project that differed from their planned degree project. At the time, she thought astronomy was cool but had no real experience with it. So she found herself as a freshman in physics who had to learn what “RA” and “Dec.” means (axes of the standard astronomical coordinate system). In fact, Dr. Kaspi remembers a lot of the astronomy she knows today as she learned it by teaching it! Her first astronomy project was an observation pulsar program – and she loved it. She remembers being impressed by using a large telescope and collecting data, and realized that she liked it much more than her previous projects in particle physics.
Now Professor at McGill University, Dr. Kaspi has expanded this work with pulsars and then magnetars to work to answer the question: what is FRB? Recent work on the CHIME collaboration has shown that some can be magnetars, but we do not know what they all are. Dr. Kaspi explained that it is useful to divide it into smaller issues. For example, do all FRBs have individual peaks in their signal, suggesting that they are catastrophic events? Are there different classes for producing FRBs, and are FRBs a homogeneous, more uniform population or a heterogeneous, mixed population?
In addition to understanding these basic characteristics of FRB, Dr. Kaspi and her team on using FRB as new cosmological probes with new technologies. One such way is to study reionization, the last major phase change of the universe, when it was transformed from primarily neutral gas to ionized gas. FRBs are huge probes of ionized gas, as they can help detect proliferation through the inhomogeneity of gas in the early universe.
Dr. Scholz began his career in science in the same way as Dr. Kaspi – he entered his undergraduate program at the University of Victoria and studied physics. After a few terms of co-ops (Canadian equivalents to REU) where he had the opportunity to dip his toes in the field, he began to seriously consider astronomy research as a viable career. This interest led him to graduate school at McGill University, where he was supervised by Dr. Kaspi and worked with X-ray observations of magnetars. As he neared the end of his PhD in 2015, he found himself inadvertently drawn into the world of FRB when he and his group discovered first recurring FRB while processing some pulsar observations from the Pulsar Arecibo L-band Feed Array (PALFA) instrument. By chance, he was already in the process of applying for postdoctoral positions in the hope of studying the exciting new subject FRBs, so this was a superior segue in that area.
Since graduating with a doctorate, he has completed a postdoctoral fellowship at the Dominion Radio Astrophysical Observatory (DRAO) where he was part of the team that oversaw the development and construction of the CHIME instrument. Given that CHIME is designed to continuously monitor large parts of the sky for FRBs, the instrument receives several terabytes of data – equivalent to a few portable hard drives – per second, so it cannot possibly store all the data for subsequent analysis. Instead, Dr. Scholz described that the real beauty of the telescope’s construction lies in its software pipeline, which helps deal with the “fire hose of [the data intake rate]”. Near the instrument are a few hundred computers – housed in a pair of radio frequency protection freight containers – that immediately analyze data so that it is only saved when an FRB has occurred.
Dr. Scholz, who is now a postdoctoral fellow at the Dunlap Institute, has continued his work on software and data analysis pipelines for the CHIME FRB instrument, but has also come full circle when once again working with magnetars and looking for high-energy observation equivalents to the FRB observations. made with CHIME.
In addition to research, Dr. realized Kaspi the importance of trying to help pave the way for future generations of scientists. During her studies, she remembers that she “felt a lot of anxiety” and remembered that she advocated more women’s bathrooms in the physics building – there was one in the whole building at that time, compared to many men’s toilets in comfortable places. Still, she says that even though this type of breakthrough is important, you can not do everything, and it is much better to focus on doing certain things really well. “The years go by very fast!” she remarked.
Dr. Scholz recognizes the value of cooperatives in helping him identify his passion for astronomy, and advises students to explore their interests by trying research as early as they can. In addition – and perhaps a little more playfully – he advises prospective astronomers to always document their code.
Throughout the interview, Dr. emphasized Kaspi his students’ excellence and the whole CHIME collaboration. “They are the lifeblood and energy of the group. Well, I guess I still have some energy …” she joked. Among her many students is Ketan Sand, who wrote an essay with CHIME data to analyze a periodically recurring FRB, and astrobitur Alice Curtin Dr. Kaspi also highlighted a recent analysis by student Alex Josephy, who examined the celestial distribution of the FRB and found no obvious correlation with the galactic plane to determine if the FRB population is contaminated with nearby intermittent radiopulsars.
Find out more about the work of the CHIME team and the FRBs they demystify at the Berkeley Prize Plenary (Thursday, June 16, 2022 at 4:40 p.m. PT – 5:30 p.m.) and about magnetars at the Shaw Prize Special Session (Monday, June 13, 2022 at 10.00 PT – 11.30 PT).
Astrobite written together by Sahil Hegde and Olivia Cooper
Astrobite edited by Graham Doskoch
Selected Image Credit: American Astronomical Society
About Sahil Hegde
I am a first year doctoral student in astrophysics at UCLA. I currently use semi-analytical models to study the formation of the first stars and galaxies in the universe. I graduated from Columbia University and am originally from the San Francisco Bay Area. Outside of astronomy, you will find me playing tennis, surfing (read: wiping out) and playing board games / TTRPG!
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