COPAS: Compact Objects and the Physics of Accretion Survey I. Accreting Binaries with P < 83 Minutes
Abstract
We present the first results from the Compact Objects and the Physics of Accretion Survey (COPAS), a high-cadence photometric survey focused on the detection of accreting white dwarf binaries mainly through their outbursts using TESS. From an initial sample of 2,054 cataclysmic variable (CV) candidates observed during TESS Cycle 6 and 7, we identify 11 systems with periods below 83 minutes. This includes 7 AM CVns and 4 CVs. Our Gemini spectroscopic data confirm ZTF18aaxuusk and ASASSN-21eo as AM CVns, while Gaia21akb is confirmed as a CV. We provide the first period measurements for 6 out of the 11 systems. Complementing our TESS data with ground-based observations, we measured superoutburst recurrence times of approximately one year for the AM CVn systems ASASSN-21in and ZTF18aaxuusk, and 1.8-2.0 years for the short-period CVs ASASSN-18rd and ASASSN-15ev. Using TESS, we also estimate the mass-ratio for ASASSN-19ct (q = 0.05 +/- 0.02), which is consistent with a highly evolved low-mass donor star. Though the number of ultracompact systems detected among the total sample is low (0.54%), and likely the result of observational biases and intrinsic population rareness, the reclassification of 5 systems as AM CVns highlights the importance of continuous monitoring to identify more systems through their outbursts and short periods.
Related
- The evolutionary history of ultra-compact accreting binaries. II. HST spectroscopy of two eclipsing AM CVn stars
- Population synthesis of low-mass binaries with wind-accreting neutron stars
- Balmer breaks in accreting super-massive black hole binaries
- Accreting Neutron Stars in Low-Mass X-ray Binaries
- Orbital evolution of asymmetric binaries within accreting environments
BibTeX
@misc{mendoza2026copas,
title = {{COPAS: Compact Objects and the Physics of Accretion Survey I. Accreting Binaries with P < 83 Minutes}},
author = {Wendy Mendoza and Liliana Rivera Sandoval and Jan Kára and Ryan J. Oelkers and Yuri Cavecchi and Thomas J. Maccarone and Manuel Pichardo Marcano and Meryem K. Dağ and Simone Scaringi and Kieran O'Brien and Martina Veresvarska and Christian Knigge},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.21150},
eprint = {2609.21150},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.21150},
}
RIS
TY - UNPB
TI - COPAS: Compact Objects and the Physics of Accretion Survey I. Accreting Binaries with P < 83 Minutes
AU - Wendy Mendoza
AU - Liliana Rivera Sandoval
AU - Jan Kára
AU - Ryan J. Oelkers
AU - Yuri Cavecchi
AU - Thomas J. Maccarone
AU - Manuel Pichardo Marcano
AU - Meryem K. Dağ
AU - Simone Scaringi
AU - Kieran O'Brien
AU - Martina Veresvarska
AU - Christian Knigge
PY - 2026
DA - 2026/09/17
PB - arXiv
DO - 10.48550/arxiv.2609.21150
UR - https://arxiv.org/abs/2609.21150
AB - We present the first results from the Compact Objects and the Physics of Accretion Survey (COPAS), a high-cadence photometric survey focused on the detection of accreting white dwarf binaries mainly through their outbursts using TESS. From an initial sample of 2,054 cataclysmic variable (CV) candidates observed during TESS Cycle 6 and 7, we identify 11 systems with periods below 83 minutes. This includes 7 AM CVns and 4 CVs. Our Gemini spectroscopic data confirm ZTF18aaxuusk and ASASSN-21eo as AM CVns, while Gaia21akb is confirmed as a CV. We provide the first period measurements for 6 out of the 11 systems. Complementing our TESS data with ground-based observations, we measured superoutburst recurrence times of approximately one year for the AM CVn systems ASASSN-21in and ZTF18aaxuusk, and 1.8-2.0 years for the short-period CVs ASASSN-18rd and ASASSN-15ev. Using TESS, we also estimate the mass-ratio for ASASSN-19ct (q = 0.05 +/- 0.02), which is consistent with a highly evolved low-mass donor star. Though the number of ultracompact systems detected among the total sample is low (0.54%), and likely the result of observational biases and intrinsic population rareness, the reclassification of 5 systems as AM CVns highlights the importance of continuous monitoring to identify more systems through their outbursts and short periods.
ER -