Projects

The research projects offered in ASPIRE cover a wide range of topics. You can choose up to three projects when you apply via the form (in descending order of interest).

CV

Unleashing Vampire White Dwarfs; White Dwarfs Draining Mass from Other White Dwarfs
Dr. Jan van Roestel (jvanroes@caltech.edu; use ASPIRE in subject)

White dwarf stars are the most common type of stellar remnant. In very rare cases, binary star evolution can form white dwarf-white dwarf binary systems. As the white dwarfs orbit each other, they emit gravitational waves and slowly spiral inwards and get closer and closer. In some cases, one white dwarf can start to transfer mass to the other white dwarf star, so-called Helium cataclysmic variable systems (also called `AM CVn’ stars). About 80 of these He-CV systems have been found in the last 40 years, but we still do not know how exactly they are created and what their properties are, how many there are in our Galaxy, and how strong their gravitational wave emissions are.

OBJECTIVE: Because of the mass-transfer process, He-CV stars can show outbursts, where the star gets 100 times brighter than normal for a few days. The main objective is to find all outbursting Helium-CVs in data from the Zwicky Transient Facility: a robotic survey telescope that images the entire night sky every 2 nights. The student will get familiar with ZTF data and the different kinds of outbursting stars ZTF is observing. Once the student knows what to look for; they will develop an automated method (in python) to identify the He-CVs in the data. The student will apply this code to the entire ZTF archival dataset and also to data as it comes in to detect outbursting He-CVs in real-time. If successful and with some luck, promising candidates can be observed with followup telescopes. If you want to get some background information: in this youtube video I talk a bit about ZTF and AM CVn stars.

PREREQUISITES: No previous knowledge of the field is required. Knowledge in coding with Python is preferred but not mandatory.

RESOURCES: A normal computer/laptop should suffice, with a working Python installation.

Triple star

A Study of Tides in Hierarchical Triples
Dr. Yan Gao (ygbcyy@star.sr.bham.ac.uk)

Many stars live in multiple stellar systems, which consist of two or more stars dynamically bound to each other. Of these multiple stellar systems, those consisting of two stars are called binaries, while those consisting of three stars are called triples. Binaries are relatively well-studied, but we know preciously little about the physical processes that occur in triples. Yet we know that triples are connected to many astrophysical phenomena. Notably, many observed gravitational wave events were caused by the merging of two stellar-mass black holes, which could only have come about from the evolution of a binary system consisting of two very massive stars, and it has been demonstrated that most binary systems consisting of two massive stars are part of a triple. This behooves us to understand their evolution in the context of a triple, and such knowledge can only be attained by understanding the physics of triples. Among triple stellar systems, the most commonly seen is the hierarchical triple system. The defining characteristic of a hierarchical triple system is that two of the three stars are in a tight orbit with each other, while the third star orbits the two in a much wider orbit. Recent studies have uncovered irregular behavior within such triples that is due to tidal effects, but which have no analogy in binary physics. As such, understanding such behavior can be quite a challenge. This is where the student's ingenuity is required. Previous work has uncovered much about how a hierarchical triple's orbital parameters and other properties influence the effects of tertiary tides, but the influence of orbital eccentricity is, as of yet, unstudied. If the student is capable of designing a way to understand this influence, it should leave a lasting contribution to our knowledge of this tidal effect, and by extension, hierarchical triples and triples in general.

OBJECTIVE: The student will be expected to modify existing code to study certain tidal effects unique to hierarchical triple systems. The goal of the study is to understand how these tidal effects affect the host system, as well as constrain their magnitude.

PREREQUISITES: Basic knowledge of Newtonian Gravity and Mechanics is mandatory. A decent grasp of stellar evolution would be helpful but not crucial. Programming experience is strongly recommended, preferably in Fortran. The student is expected to have computer access.

RESOURCES: One helpful supervisor who will explain relevant concepts, plus algorithms that could be modified to produce the desired results.

Magnetar

Hunting for Transient Sources in Radio Images
Dr. Antonia Rowlinson (b.a.rowlinson@uva.nl)

Radio transient astronomy has taken off during the past decade, thanks to excellent new radio telescopes coming online and increases in computational power. Exciting detections of strange sources that still need identifying have been made including the Galactic Burster, a LOFAR transient, dispersed transients by AARTFAAC and recently an MWA discovery of a possible unusually slow magnetar. Each detection leads to the chance of discovering a whole new population of transient sources. In this project you will take data obtained by survey experiments from a world class radio telescope, either LOFAR or MeerKAT, and search for new transient sources on timescales ranging from seconds to months. You will process these data using our successful transient detection pipeline and help develop new techniques using machine learning with our team.

OBJECTIVE: The key goal of this project is to search for and identify transient and variable sources in a radio image dataset by applying existing techniques developed for other datasets. The second objective is to develop and trial new techniques to filter transient candidates. The student will learn to process radio images and how to handle systematic effects in these data.

PREREQUISITES: Some knowledge of Python is required.

RESOURCES: The student will be connecting to computer resources in Amsterdam, so a standard computer or laptop is sufficient. Linux or OS operating system is ideal; however, there will be alternative options for Windows users. A reliable internet connection is required.

FRB

Probing the low-frequency emission of fast radio bursts
Dr. Pragya Chawla (p.chawla@uva.nl)

Fast radio bursts (FRBs) are extremely energetic, extragalactic flashes of radio emission. The origin of these micro-to-millisecond duration bursts is currently unknown, making them one of the most puzzling phenomena in the field of astrophysics today. Most FRB sources are known to emit radiation at frequencies above 400 MHz, with only a handful of sources detected at lower frequencies. Detection of more sources at low frequencies is particularly important to uncover the origin of FRBs, as low-frequency observations can help characterize the environments that FRBs inhabit and constrain the mechanisms which generate these bursts.

OBJECTIVE: The project aims at developing a better picture of low-frequency FRB emission by searching for FRBs in observations conducted with the Low Frequency Array (LOFAR) telescope located in the Netherlands. The observations were conducted as part of the LOFAR tied-array all-sky survey (LOTAAS) in the frequency range of 120-150 MHz. We intend to search for emission in this frequency range at the locations of FRB sources which are known to emit at higher frequencies. The student will develop scripts in Python and Bash to access and search the LOTAAS data. During the course of the project, the student will learn standard techniques used in FRB searches and also help adapt the existing tools to efficiently search for low-frequency FRB emission.

PREREQUISITES: No prior knowledge of the field is required but experience with programming in Python is preferred.

RESOURCES: The computationally intensive aspects of the FRB search will be performed on the Dutch supercomputer Snellius. A standard laptop/desktop computer with a reliable internet connection is required.

BinaryProtostar

Studying Accretion onto Binary Protostars
Swapnil Shankar and Dr. Philipp Moesta (s.shankar@uva.nl)

Within the last decade radio observations of protostellar binary systems at submillimeter wavelengths have enabled detailed spectral studies of their structures at high angular resolution. Observations have revealed significant morphological and kinematic structure in the circumstellar disk (CSD) and circumbinary disk (CBD) in these systems. In parallel, theoretical works have provided an interpretative framework for some of these observational data - the importance of the eccentricity of the orbit on the inner size of the CBD in particular. Recent numerical studies have provided theoretical understanding for the description of the structure within the CBD, and the morphology and variability of the flows between the CBD and CSD.

OBJECTIVE: In this project, you will perform simulations of accretion onto binary protostars using a 2D viscous Hydrodynamics code. The aim is to investigate the accretion dynamics onto primary and secondary stars when they have unequal mass ratios. You will also analyze the outputs from the simulations with respect to shock formation and observational signatures. This project will give you experience in working with remote systems and advance your programming skills, along with the theoretical knowledge.

PREREQUISITES: No specific knowledge of the field is required. However, knowledge of Python or similar programming tools is required. Familiarity with Linux is preferred. Knowledge of latex to write documents is also useful.

RESOURCES: Access to a normal laptop/workstation and a stable internet connection is required to login to the group computer. Having linux/unix on the laptop would be very useful.

MWC656

Hunt for Galactic Stellar Black Holes and Exotic Helium Stars
Dr. Tomer Shenar (t.shenar@uva.nl)

Stellar-mass black holes are notoriously difficult to find. Even though hundreds of millions are expected to lurk in our Galaxy, only a handful are known. Black holes orbiting massive stars in binary systems are of special interest. Such systems are thought to represent a key evolutionary phase of black-hole mergers that are continuously detected wih modern gravitational-wave observatories. The few known Galactic binaries hosting a black hole are generally X-ray bright systems in which the black hole accretes material from a nearby mass-donor star. However, such systems are expected too represent the tip of the iceberg of a much larger population of X-ray quiescent black-hole binaries. One of the only such binaries ever reported is the enigmatic binary system MWC 656, which comprises a rapidly rotating B-type star orbiting a hidden companion. This system is the focus of the project.

OBJECTIVE: The objective of the project is straight forward: find out if there is truly a black hole in MWC 656. The alternative hypothesis is that the companion is a so-called helium star, having been stripped through a previous mass-transfer event with its companion star. To explore this hypothesis, the student will make use of several high-resolution spectra obtained with the HERMES spectrograph of the MERCATOR telescope and implement the technique of spectral disentangling to unveil the hidden companion.

PREREQUISITES: Rudimentary knowledge of python beneficial.

RESOURCES: Any machine that can run standard python scripts is sufficient.