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3. The ZTF Source Classification Project: III. A Catalog of Variable Sources

Author

Healy, Brian F., Coughlin, Michael W., Mahabal, Ashish A., Laz, Theophile Jegou du, Drake, Andrew, Graham, Matthew J., Hillenbrand, Lynne A., van Roestel, Jan, Szkody, Paula, Zielske, LeighAnna, Guiga, Mohammed, Hassan, Muhammad Yusuf, Hughes, Jill L., Nir, Guy, Parikh, Saagar, Park, Sungmin, Purohit, Palak, Rebbapragada, Umaa, Reed, Draco, Warshofsky, Daniel, Wold, Avery, Bloom, Joshua S., Masci, Frank J., Riddle, Reed, and Smith, Roger

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Solar and Stellar Astrophysics
Abstract

The classification of variable objects provides insight into a wide variety of astrophysics ranging from stellar interiors to galactic nuclei. The Zwicky Transient Facility (ZTF) provides time series observations that record the variability of more than a billion sources. The scale of these data necessitates automated approaches to make a thorough analysis. Building on previous work, this paper reports the results of the ZTF Source Classification Project (SCoPe), which trains neural network and XGBoost machine learning (ML) algorithms to perform dichotomous classification of variable ZTF sources using a manually constructed training set containing 170,632 light curves. We find that several classifiers achieve high precision and recall scores, suggesting the reliability of their predictions for 209,991,147 light curves across 77 ZTF fields. We also identify the most important features for XGB classification and compare the performance of the two ML algorithms, finding a pattern of higher precision among XGB classifiers. The resulting classification catalog is available to the public, and the software developed for SCoPe is open-source and adaptable to future time-domain surveys., Comment: 23 pages, 12 figures, accepted to ApJS. Catalog available at https://zenodo.org/doi/10.5281/zenodo.8410825

Published
2023

8. A radio-detected Type Ia supernova with helium-rich circumstellar material

Author

Kool, Erik C., Johansson, Joel, Sollerman, Jesper, Moldón, Javier, Moriya, Takashi J., Schulze, Steve, Chomiuk, Laura, Harris, Chelsea, Pérez-Torres, Miguel, Mattila, Seppo, Lundqvist, Peter, Graham, Matthew, Yang, Sheng, Perley, Daniel A., Strotjohann, Nora Linn, Fremling, Christoffer, Gal-Yam, Avishay, Lezmy, Jeremy, Maguire, Kate, Omand, Conor, Smith, Mathew, Andreoni, Igor, Bellm, Eric C., De, Kishalay, Bloom, Joshua S., Groom, Steven L., Kasliwal, Mansi M., Masci, Frank, Medford, Michael, Park, Sungmin, Purdum, Josiah, Reynolds, Tom M., Riddle, Reed, Robert, Estelle, Ryder, Stuart D., Sharma, Yashvi, and Stern, Daniel

Subjects
Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Solar and Stellar Astrophysics
Abstract

Type Ia supernovae (SNe Ia) are thermonuclear explosions of degenerate white dwarf (WD) stars destabilized by mass accretion from a companion star, but the nature of their progenitors remains poorly understood. A way to discriminate between progenitor systems is through radio observations; a non-degenerate companion star is expected to lose material through winds or binary interaction prior to explosion, and the SN ejecta crashing into this nearby circumstellar material (CSM) should result in radio synchrotron emission. However, despite extensive efforts, no SN Ia has ever been detected at radio wavelengths, which suggests a clean environment and a companion star that is itself a degenerate WD star. Here we report on the study of SN 2020eyj, a SN Ia showing helium-rich CSM, as revealed by its spectral features, infrared emission and, for the first time in a SN Ia, a radio counterpart. Based on our modeling, we conclude the CSM likely originates from a single-degenerate (SD) binary system where a WD accretes material from a helium donor star, an often hypothesized formation channel for SNe Ia. We describe how comprehensive radio follow-up of SN 2020eyj-like SNe Ia can improve the constraints on their progenitor systems., Comment: 62 pages, 10 figures, 4 tables

Published
2022
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14. A radio-detected type Ia supernova with helium-rich circumstellar material

Author

Kool, Erik C., Johansson, Joel, Sollerman, Jesper, Moldón, Javier, Moriya, Takashi J., Mattila, Seppo, Schulze, Steve, Chomiuk, Laura, Pérez-Torres, Miguel, Harris, Chelsea, Lundqvist, Peter, Graham, Matthew, Yang, Sheng, Perley, Daniel A., Strotjohann, Nora Linn, Fremling, Christoffer, Gal-Yam, Avishay, Lezmy, Jeremy, Maguire, Kate, Omand, Conor, Smith, Mathew, Andreoni, Igor, Bellm, Eric C., Bloom, Joshua S., De, Kishalay, Groom, Steven L., Kasliwal, Mansi M., Masci, Frank J., Medford, Michael S., Park, Sungmin, Purdum, Josiah, Reynolds, Thomas M., Riddle, Reed, Robert, Estelle, Ryder, Stuart D., Sharma, Yashvi, and Stern, Daniel

Published
2023
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22. Electrically controllable diffractive optical elements fabricated by direct laser writing on a carbon nanotube network film

Author

Min Taeyol, Yim Jong Hyuk, Park Sungmin, Ha Seongju, Lee Soonil, and Yeom Dong-Il

Subjects
carbon nanotube (cnt) network film, diffractive optical elements, fresnel zone plates, tunable thin film lens, Physics, QC1-999
Abstract

A randomly connected single-walled carbon nanotube (CNT) network film is suggested as an optically homogenous thin film to implement a tunable diffractive optical element with a subwavelength thickness. A Fresnel zone plate (FZP) as a thin-film lens is successfully realized by mask-free direct laser writing onto the CNT network film with a thickness of 450 nm. The fabricated FZP exhibits an intense three-dimensional focus having lateral and axial focal sizes of 0.95λ and 7.10λ, respectively, at the wavelength of 1550 nm. Furthermore, we show that the intensities at focal points of the first and second diffraction orders can be significantly modulated by 72% and 40% through ion-gel gating between +1.8 V and −1.8 V. These results may offer the potential for electro-optic tunability in multifocal diffraction flat optics and the like.

Published
2022
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27. The ZTF Source Classification Project. III. A Catalog of Variable Sources

Author

Healy, Brian F., primary, Coughlin, Michael W., additional, Mahabal, Ashish A., additional, Jegou du Laz, Theophile, additional, Drake, Andrew, additional, Graham, Matthew J., additional, Hillenbrand, Lynne A., additional, van Roestel, Jan, additional, Szkody, Paula, additional, Zielske, LeighAnna, additional, Guiga, Mohammed, additional, Hassan, Muhammad Yusuf, additional, Hughes, Jill L., additional, Nir, Guy, additional, Parikh, Saagar, additional, Park, Sungmin, additional, Purohit, Palak, additional, Rebbapragada, Umaa, additional, Reed, Draco, additional, Warshofsky, Daniel, additional, Wold, Avery, additional, Bloom, Joshua S., additional, Masci, Frank J., additional, Riddle, Reed, additional, and Smith, Roger, additional

Published
2024
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28. Tunable quantum critical point and detached superconductivity in Al-doped CrAs

Author

Park, Sungmin, Shin, Soohyeon, Kim, Sung-Il, Thompson, Joe D., and Park, Tuson

Subjects
Condensed Matter - Superconductivity
Abstract

The origin of unconventional superconductivity and its relationship to a T=0 K continuous quantum phase transition (a quantum critical point, QCP), which is hidden inside the dome of a superconducting state, have long been an outstanding puzzle in correlated superconductors. The observation and tuning of the hidden QCP, which is critical in resolving the mystery, however, has been rarely reported due to lack of ideal systems. The helical antiferromagnet CrAs provides an example in which a dome of superconductivity appears at a pressure where its magnetic transition goes to zero temperature. Here we report the tuning of a projected critical point in CrAs via Al chemical doping (Al-CrAs) and separation of the magnetic critical point from the pressure-induced superconducting phase. When CrAs is doped with Al, its AFM ordering temperature TN increases from 260 K to 270 K. With applied pressure, TN decreases and extrapolates to zero Kelvin near 4.5 kbar, which is shifted from 8 kbar for undoped CrAs. A funnel of anomalously enhanced electron scattering and a non-Fermi liquid resistivity underscore an AFM QCP near 4.5 kbar in Al-CrAs. Pressure-induced superconductivity, in contrast, is almost independent of Al doping and forms a dome with essentially the identical maximum Tc and same optimal pressure as in pure CrAs. The clear separation between the tuned AFM QCP and Tc maximum in Al-CrAs suggests that superconductivity is independent of the AFM QCP, illustrating subtleties in the interplay between superconductivity and quantum criticality in correlated electron systems., Comment: S. Park and S. Shin contributed equally to this work

Published
2018
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