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Swift UV/X-ray non-detection of the recurrent nova M31N 2007-11f

ATel #10040; M. Henze (CSIC-IEEC), P. Sin (UPC-IEEC), G. Sala (UPC-IEEC), K. Hornoch (Ondrejov)
on 2 Feb 2017; 13:29 UT
Credential Certification: Martin Henze (henze@ice.cat)

Subjects: Optical, Ultra-Violet, X-ray, Nova, Transient

A new nova candidate was recently reported as M31N 2016-12e (ATels #9912, #9942) and was subsequently identified (ATel #10001) as the second observed eruption of the Andromeda galaxy nova M31N 2007-11f (ATel #1312). Therefore, M31N 2007-11f can be classified as a recurrent nova (RN) in M31. It is the 18th known RN in our neighbour galaxy (see Shafter et al. 2015 and ATel #7116 for the previous RNe.)

Here we report follow-up observations in the UV and X-ray bands with the Swift satellite (Gehrels et al. 2004). A 2.8-ks target of opportunity observation was obtained starting on 2017-01-29.629 UT (MJD 57782.629), which is about 33 days after the optical discovery of the eruption (see the table below). No source was detected in the Swift UV/optical telescope (UVOT; Roming et al. 2005) data down to a 3σ limit of 20.7 mag in the uvw1 band (central wavelength of 260 nm). Similarly, nothing is visible in the X-ray telescope (XRT; Burrows et al. 2005) data with a 3σ upper limit of 3.7 × 10-3 ct/s.

The relatively rapid decline of the UV light curve is consistent with the fast evolution of the optical brightness. In general, RNe with their massive white dwarfs have shorter X-ray visibility phases (tens to a hundred days) than the average (M31) nova (hundreds to thousands of days; see Henze et al. 2014). However, only the most extreme RNe have X-ray phases that end before day 33: namely M31N 2008-12a (around day 19; see Darnley et al. 2016, ATels #6604, #8062) and V745 Sco (around day 10 compared to M31 novae; see Page et al. 2015). Therefore, we suspect that the X-ray phase of M31N 2007-11f is still to commence.

In addition, we note that the Ondrejov telescope (OND) observing dates in ATel #10001 were mistakenly shifted by 0.5 day. Below we reproduce the table from ATel #10001 using the corrected dates.

 
Date [UT]      | Mag   | Err  | Filter    | Telescope 
2016-12-26.811 | >20.5 |      | R         | OAJ 
2016-12-27.872 | 16.7  | 0.2  | R         | OAJ 
2016-12-28.736 | 17.3  | 0.1  | R         | OND 
2016-12-28.831 | 17.6  | 0.3  | R         | OAJ 
2016-12-29.724 | 18.0  | 0.1  | R         | OND 
2016-12-30.830 | 18.0  | 0.3  | R         | OAJ 
2016-12-30.841 | 17.2  | 0.3  | Hα        | OAJ 
2017-01-01.681 | 18.4  | 0.2  | R         | OND 
2017-01-05.780 | 18.8  | 0.2  | R         | OND 
2017-01-06.806 | 19.0  | 0.3  | R         | OND 
2017-01-10.704 | 19.1  | 0.3  | R         | OND 
2017-01-15.751 | >20.0 |      | R         | OND 
2017-01-19.725 | >20.9 |      | R         | OND 


We are grateful to the Swift Team for the scheduling of the ToO observations, in particular N. Gehrels, the duty scientists, and the science planners.