Swift Observatory UV Observations of the Continuing Outburst of V694 Mon
ATel #12670; B. McCollum (American Univ.), T. Torpin (CUA), F. C. Bruhweiler (American Univ.)
on 18 Apr 2019; 17:30 UT
Credential Certification: Bruce McCollum (mccollub@cua.edu)
Subjects: Ultra-Violet, Binary, Star, Variables
Referred to by ATel #: 16956
The recurrent symbiotic system V 694 Mon (MWC 560) began a new, major outburst in late
2018 (ATel #12227). This outburst is unexpected because it is only two years since the
previous major outburst which was in 2016. The 2016 outburst was the brightest in its ~100 year
photometric history. AAVSO reports show that the current outburst has
continued since late 2018 and has reached B = 9.3, which is only ~0.1 magnitude fainter than the peak of the 2016 outburst.
We obtained observations of MWC 560 with the Swift UVOT in three broad UV filters in Nov/Dec 2018 and April 2019. Measurements from these observations are in the table below. Fluxes and uncertainties are in erg cm-2 s-1 A-1. The central wavelength and FWHM of the filters used are, for the UVM2: 2231 A +/- 498 A, UVW2: 2030 A +/- 687 A, UVW1: 2634 A +/- 693 A.
Date |
Filter |
Flux |
Uncertainty |
28 Nov 2018 |
UVM2 |
4.49x10-13 | 3.0x10-15 |
1 Apr 2019 |
UVM2 |
4.55x10-13 | 2.9x10-15 |
28 Nov 2018 |
UVW2 |
3.50x10-13 | 7.6x10-15 |
3 Dec 2018 |
UVW2 |
4.49x10-13 | 7.6x10-15 |
8 Dec 2018 |
UVW2 |
3.50x10-13 | 7.6x10-15 |
1 Apr 2019 |
UVW2 |
3.35x10-13 | 8.9x10-15 |
3 Dec 2018 |
UVW1 |
2.27x10-13 | 7.0x10-15 |
No UV observations of the 2016 outburst have been published. The 1990 outburst, which was the brightest known until 2016, was observed spectroscopically at several epochs in the same wavelength range as the Swift filters by the International Ultraviolet Explorer (Michalitsanos et al. 1991, ApJ, 371, 761). The 1990 UV spectra generally show fluxes on the order of 10
-13 erg/cm2/s/A, approximately the same as what we observe with Swift in the current outburst.
We obtained a low resolution (R ~ 75) spectrum of MWC 560 on 1 April 2019 with the Swift UVOT grism. The spectrum shows strong, broad absorption from Mg II (2800 A) and Fe II (~2400 A and ~2600 A). These features were also prominent in IUE spectra during the 1990 outburst.
We thank the NASA Neil Gehrels Swift Observatory for performing these observations. We acknowledge with thanks the variable star observations from the AAVSO International Database contributed by observers worldwide which were used in planning these observations.