A descPre-outburst observations of T CrB with ALMAriptive title
ATel #16781; Gloria Sala (UPC, Spain), Dirk Petry (ESO, Germany), Jochen Greiner (MPE, Germany), Steven Shore (UniPi, Italy), Thomas Stanke (MPE, Germany)
on 20 Aug 2024; 18:19 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Gloria Sala (gloria.sala@upc.edu)
Subjects: Radio, Millimeter, Sub-Millimeter, Cataclysmic Variable, Nova
T CrB is the closest known recurrent nova, with its white dwarf accreting from a red giant companion. In preparation for its next outburst, expected before the end of 2024 (Schaefer 2019, AAS abstract #234; Luna et al. 2020, ApJ 902, L14; related ATels e.g. #16337, #16336), we have obtained pre-burst mm/sub-mm snapshot observations with the ALMA observatory.
So far, final results from observations in 3 bands (5 minutes on-source time each), performed on 10 August 2024 with the ALMA 12M main array, are available. In all three bands, a faint point source at the position of T CrB is detected with at least 4 sigma significance. Details are given in the following table:
Band Centre Freq. (GHz) Flux Density (micro-Jy)
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3 107.9 216 (+/-48)
4 136.4 205 (+/-38)
7 359.5 440 (+/-110)
Observations were also obtained in ALMA bands 1 and 6, and results will be reported in a future publication when the calibration and analysis for these bands is completed.
The spectral energy distribution between Bands 3 and 7 is consistent with a powerlaw with a (positive) index of approximately 0.6. Once the measurements from all five bands are available, this can be constrained further and interpreted.
High-resolution spectra were taken in all bands, mostly at the location of CO, SiO and HCN lines (with 4 km/s, 0.45 km/s and 1.3 km/s spectral resolution respectively), but so far, there is no indication of any line emission.
We gratefully acknowledge the superb support by the ESO and ALMA teams. Our proposal for several multi-band post-burst ALMA ToO observations of T CrB until two months after the burst has been accepted.
