Issue |
A&A
Volume 664, August 2022
|
|
---|---|---|
Article Number | A165 | |
Number of page(s) | 10 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361/202243870 | |
Published online | 25 August 2022 |
TUVO-21acq: A new cataclysmic variable discovered through a UV outburst⋆,⋆⋆
1
Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam, The Netherlands
e-mail: d.modiano@uva.nl
2
South African Astronomical Observatory, PO Box 9 Observatory Road, Observatory, 7935 Cape Town, South Africa
3
Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
4
Department of Physics, University of the Free State, PO Box 339 Bloemfontein 9300, South Africa
5
Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
6
Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
Received:
26
April
2022
Accepted:
19
June
2022
Outbursts from cataclysmic variables, such as dwarf novae (DNe), are prevalent throughout the galaxy and are known to emit strongly in the ultraviolet (UV). However, the UV emission of DN outbursts has not been studied extensively compared with the optical. Detailed characterisation of the physical processes responsible for outburst behaviour requires further UV data, because the UV probes the inner regions of the accretion disc. Here we report, as part of our recently launched Transient UV Objects (TUVO) project, the discovery of TUVO-21acq, a new transient which we detected in the UV using data from the Ultraviolet Optical Telescope (UVOT) aboard Swift. We detected two separate outbursts and used the UVOT data to constrain source properties, focusing on the amplitudes and timescales of the outbursts. We found that during the first outburst the source increased in brightness by at least 4.1, 2.4, and 3.5 mag and during the second outburst by 4.4, 3.4, and 3.6 mag in the UVW1, UVM2, and UVW2 bands, respectively. The outburst durations were in the range of 6–21 days and 11–46 days, and we determined an upper limit for the recurrence time of 316 days. To further characterise the source, we obtained an optical spectrum during quiescence with the Southern African Large Telescope (SALT). The spectrum exhibited hydrogen Balmer series and helium emission lines, and a flat overall spectral shape. We confirm the nature of the source as an accreting white dwarf which underwent DN outburst based on photometric and spectroscopic properties. This study serves as a proof of concept for the TUVO project strategy, demonstrating that it has the capability of discovering and classifying new, interesting UV transients. We also discuss the implications of our findings for our understanding of the physics underlying DN outbursts, in particular with respect to the UV emission. We examine the need for simultaneous UV and optical observations during the onset of DN outbursts in order to help answer remaining questions as to the characteristics and implications of the UV delay, for example.
Key words: methods: data analysis / methods: observational / ultraviolet: stars / binaries: close / stars: dwarf novae / novae / cataclysmic variables
SALT spectrum is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/664/A165
A reproduction package for this paper is available at https://doi.org/10.5281/zenodo.6483027
© D. Modiano et al. 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe-to-Open model. Subscribe to A&A to support open access publication.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.