Author Archives: ecasseditor

by Dr. Zhao Jiaqi (or Jake Zhao)
Thesis defended on August 6, 2025
Department of Physics, University of Alberta
Thesis advisor: Prof. Craig Henke

Abstract:

There is no doubt that the Universe is full of fascinating phenomena. The Chandra X-ray Observatory (Chandra), with its unprecedented angular resolution and sensitivity, has opened a new window for observing, studying, and appreciating the Universe in X-rays.
This thesis presents X-ray studies of millisecond pulsars (MSPs) in the globular cluster (GC) Omega Centauri (Omega Cen), diffuse X-ray emission from the GC Terzan 5, and a young neutron star (NS) in the supernova remnant Cassiopeia A (Cas A), utilizing Chandra datasets. We first search for X-ray counterparts to 18 MSPs newly discovered in Omega Cen. Using Chandra ACIS-I datasets with a total exposure time of 290.9 ks, we identify 11 confident X-ray counterparts to these MSPs, based on their positions, spectral properties, and X-ray colors. Additionally, we find clear correlations between the X-ray luminosities and minimum companion masses, as well as mass functions, of spider pulsars, and provide empirical fits to these relations. Next, we look into the diffuse X-ray emission from the field of Terzan 5, using deep Chandra ACIS-S observations with a total exposure time of 641.6 ks. We report the detection of a diffuse X-ray component genuinely associated with Terzan 5, and explore its possible nature through spectral analysis. Finally, we reexamine the rapid cooling of the Cas A NS utilizing newly obtained as well as archival Chandra HRC-S datasets. We detect significant declines in the surface temperature and X-ray flux of the NS, leading to an independent verification of its cooling rate. We also infer the maximal critical temperature of neutron superfluidity in the core of the Cas A NS.

by Dr. Margaret Ridder
Thesis defended on August 28, 2025
Department of Physics, University of Alberta
Thesis advisor: Prof. Craig Henke

Abstract:

Cataclysmic variables (CVs) are binary systems in which a white dwarf accretes from a low-mass donor star via Roche lobe overflow. They have been studied for well over a century, but the origin of their radio emission remains uncertain. In this thesis, I present the discovery of two unusual CVs in the Very Large Array Sky Survey (VLASS): QS Vir, a low-accretion rate pre-CV, and V2400 Oph, a diskless intermediate polar. In addition, I conduct follow-up radio and X-ray observations of QS Vir, finding two highly circularly polarized radio flares, which I attribute to a coherent plasma emission process such as electron-cyclotron maser emission or plasma radiation. Finally, I perform spectral, temporal, and polarization analysis on a sample of 6 other CVs at higher frequencies. I find a total of three flare events with high fractional circular polarization from two CVs, and find steady, spectrally steep radio emission from V2400 Oph. For most CVs, we see a flat gyrosynchrotron component that is at times accompanied by a coherent, flaring component for most CVs. The only CV that exhibits a synchrotron-like spectrum in this thesis is V2400 Oph.

By Eric Steinbring (Canadian Gemini Office, National Research Council Herzberg Astronomy & Astrophysics)

Upcoming Call-for-Proposal Deadlines

Reminder: The Regular-Semester 2026A Call for Proposals deadline is Tuesday 2 October at 4 PM PDT (7 PM EDT). There are 166 hours on the North and 182 hours on the South that Canada-based researchers can apply for, including proposals for Subaru, available via exchange time. Note that the deadlines of the partners differ, and when submitting together with your international collaborators within a joint-proposal (as Canadian researchers so often do) the Principal Investigator should submit before their partner-TAC deadline. Don’t confuse that with the usual monthly Fast Turnaround (FT) Call for smaller proposals, at noon Hawai`i time on Monday 30 September, which also happens to be our National Day for Truth and Reconciliation here in Canada.

Other Observing Time Available for Important Science

Did you know that Gemini holds a significant fraction of its observing time in reserve, especially for risky, high-reward science? This Director’s Discretionary Time (DDT)  is roughly 130 hours per semester, that can be applied for at any time at either telescope; typically, observations which are important-enough not to wait for the regular-semester (or FT) process to competitively grant it. Our US-based colleagues regularly request more than half of DDT, although any scientist from anywhere in the world can apply; and more than a quarter of further requests do not originate from within a Gemini partner country. Note that this is entirely separate from Canada’s 18% partner-share of observing time. But historically, Canadians don’t request much DDT, and in the last 5 years a mere 3.7% of DDT requests came from here (although nearly all have been successful!). Note also that a recent DD community-initiative has started related to time-domain science, which may be of interest. It’s worth keeping in mind for when you have important science to get done.

An Eye and an Ear to What’s Happening at Gemini

Along with these quarterly articles from yours-truly, CASCA members all receive regular posts from the CGO via the e-mail exploder. But there are many other ways to keep on top of Gemini News, even if those won’t be in both of our official languages. For example, NOIRLab, together with providing regular updates on Rubin/LSST and the US ELT programs, also puts out many interesting press releases and other Gemini-related news items; see https://noirlab.edu/science/announcements. Be sure to sign up to receive their monthly newsletter, the NOIRLab eNews. You can also follow Gemini tweets on Twitter/X, although the US National Gemini Office now frequently posts instead to a popular alternative on the Web called Bluesky. BTW, “skeets” (=posts) from CASCA can now be seen at handle @casca.ca.web.brid.gy.

By Patrick Côté (NRC-Herzberg), Tyrone Woods (University of Manitoba)

• The Coalition for Canadian Astronomy:  The Coalition for Canadian Astronomy — which brings together representatives from the astronomical community (CASCA), the Association of Canadian Universities for Research in Astronomy (ACURA) and industry — is continuing its efforts to secure approval and funding for the mission. Their pre-budget submission, submitted in July, seeks immediate funding for an NRC-led Phase A+ study to be begin in early 2026. Their efforts emphasize the CASTOR mission’s potential for Canadian scientific leadership, international partnerships, national sovereignty, and capacity-building within the aerospace sector.
• Phase A+ Study. As the Coalition pushes for Phase A+ funding, NRC and CSA continue their discussions on a framework to jointly support such a study. NRC is devoting project management resources to develop statements of work for work packages, deliverables, and schedule. The highest priority items for development in this Phase will be the telescope system; the FSM pointing servo loop; the spacecraft bus design; cameras, detectors and electronics; and mission systems engineering. This study would serve three primary purposes: (1) demonstrate Canada’s commitment to the mission, solidify the partnership, & define partner contributions; (2) elevate the mission definition and costing to enable a future funding request as a fixed-firm-price mission; and (3) reduce cost uncertainty for subsequent development by retiring technical risk.
• Technology Development. Technology development for the mission, carried out in collaboration with international partners, is continuing along two fronts:
  • Detector Testing and Characterization of engineering-grade detectors for the mission is proceeding at NRC-HAA in Victoria; the newly refurbished Vacuum UV Calibration Facility at the University of Calgary; and the Centre for Electronic Imaging at the Open University in the UK. Cryogenic, in-vacuum characterization of the detectors and electronics will continue throughout this calendar year as the collaboration builds its understanding of the performance of these large-format, UV-enhanced CMOS detectors.
  • UVMOS Proto-typing. The three-year effort to build and test a prototype of a UV multi-object spectrograph (UVMOS) for the CASTOR mission is well underway (having started in spring 2024). The current schedule aims for the delivery of the prototype instrument to the Calgary test facility in 2027. This work, which is being carried out in collaboration with researchers in France, Colorado, Spain, Calgary and Manitoba, is advancing the technology readiness level of convex gratings, DMDs and CMOS detectors for operation at UV wavelengths. In July, a progress report on this project was presented at the “Towards the Habitable Worlds Observatory: Visionary Science and Transformational Technology” conference in Washington. Additional updates will be presented in talks at the upcoming “Network for UV Astronomy” meeting to be held in Marseille, in October.
• Science Planning Tools: Works continues on the FORECASTOR suite of science planning tools (Finding Optics Requirements and Exposure times for CASTOR). This effort is driven largely by undergraduate and graduate students. Recent and ongoing projects include the development of: data simulation and exposure time calculation tools for the UVMOS instrument, as part of the NRC Small Teams project; a tool to generate Target Access Reports for pointed and mapping programs; and software to simulate the detection and monitoring of moving objects within the solar system. This tool has implications for future facilities focused on space situational awareness.
• HWO Request for Information. CSA has issued a Request for Information inviting community input on possible Canadian contributions to NASA’s Habitable Worlds Observatory (HWO). The closing date for submissions is October 15. The HWO instrument suite has yet to be finalized but is currently expected to include: an optical/NIR coronagraph; a high-resolution UV/VIS and NIR Imager; and a UV Multi-Object Spectrograph (with a possible fourth instrument to be defined). As explained in the recent JATIS review paper, CASTOR can provide a scientific and technical pathway to a possible HWO contribution, should the Canadian community decide to pursue this option. Several members of the CASTOR team plan to provide a response to the RFI; contact the authors if you would like more information and wish to be involved.

For more information on the mission, see https://www.castormission.org