The eclipsing accreting white dwarf Z chameleontis as seen with TESS

Court, JMC; Scaringi, S; Rappaport, S; Zhan, Z; Littlefield, C; Castro Segura, N; Knigge, C; Maccarone, T; Kennedy, M; Szkody, P; Garnavich, P

Abstract

We present results from a study of TESS observations of the eclipsing dwarf nova system Z Cha, covering both an outburst and a superoutburst. We discover that Z Cha undergoes hysteretic loops in eclipse depth – out-of-eclipse flux space in both the outburst and the superoutburst. The direction that these loops are executed in indicates that the disc size increases during an outburst before the mass transfer rate through the disc increases, placing constraints on the physics behind the triggering of outbursts and superoutbursts. By fitting the signature of the superhump period in a flux-phase diagram, we find the rate at which this period decreases in this system during a superoutburst for the first time. We find that the superhumps in this source skip evolutionary stage ‘A’ seen during most dwarf nova superoutbursts, even though this evolutionary stage has been seen during previous superoutbursts of the same object. Finally, O–C values of eclipses in our sample are used to calculate new ephemerides for the system, strengthening the case for a third body in Z Cha and placing new constraints on its orbit.

Citation

Court, J., Scaringi, S., Rappaport, S., Zhan, Z., Littlefield, C., Castro Segura, N., Knigge, C., Maccarone, T., Kennedy, M., Szkody, P., & Garnavich, P. (2019). The eclipsing accreting white dwarf Z chameleontis as seen with TESS. Monthly Notices of the Royal Astronomical Society, 488(3), 4149-4160. https://doi.org/10.1093/mnras/stz2015

• Journal Article Type: Article
• Acceptance Date: Jul 11, 2019
• Online Publication Date: Jul 31, 2019
• Publication Date: 2019-09
• Deposit Date: Dec 31, 2020
• Publicly Available Date: Apr 9, 2021
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 488
• Issue: 3
• Pages: 4149-4160
• DOI: https://doi.org/10.1093/mnras/stz2015
• Public URL: https://durham-repository.worktribe.com/output/1283087