Additional spectroscopic observations and Swift monitoring of the M31 nova iPTF16bqy (ASASSN-16hf)

ATel #9329; K. Chinetti (Caltech), M. J. Darnley (LJMU), K. L. Page (Leicester), S. C. Williams (Lancaster)
on 5 Aug 2016; 20:55 UT
Credential Certification: Matt Darnley (M.J.Darnley@ljmu.ac.uk)

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We report additional spectroscopic observations of the M31 nova, iPTF16bqy (ASASSN-16hf, ATels #9245, #9248). iPTF16bqy was initially classified as a Fe II nova based on spectra obtained 2016 July 14 and 15 (ATel #9248), about two days after discovery. Additional follow-up spectroscopy with the SPRAT spectrograph (Piascik et al. 2014) on the 2m Liverpool Telescope (Steele et al. 2004) was obtained on 2016 July 25.064 UT, August 3.09, and August 5.11.

The July 25 spectrum, about thirteen days after initial discovery, showed weaker Fe II (multiplets 42, 48, 49) lines that had previously dominated the spectra. Along with the continued strong Balmer (Hα-δ) lines, there were weak indications of N III (4638 Å), He II (4686 Å), and N II (5001 Å). These findings were confirmed with the August 3 and 5 spectra, taken about twenty-two days after discovery. These spectra show clear lines of N III (4638 Å), He II (4686 Å), N II (5001, 5679 Å), [N II] (5755 Å), and Fe II (multiplets 42, 48, 49). There is also a very tentative He I (6678 Å) detection. The presence of the helium and nitrogen indicate that this may be a "hybrid" nova, which are Fe II novae that evolve into He/N novae typically within a few weeks after eruption. The additional appearance of the forbidden line of [N II] indicates the nova may already be beginning to enter the nebular phase.

iPTF16bqy has also been monitored as a target of opportunity by Swift since July 19. As of August 3, no X-ray source has been detected by Swift/XRT at the position of the nova. Weekly Swift/UVOT observations continue to yield a UV light curve.

This work is part of an international undergraduate internship supported by the NSF PIRE GROWTH program.