Emergence of Infrared CO bands in V3890 Sgr and further narrowing of the emission lines.

ATel #13096; C. E. Woodward (University of Minnesota), D. P.K. Banerjee (PRL, India), A. Evans (Keele University), T. R. Geballe (Gemini Observatory), S. Starrfield (Arizona State University)
on 10 Sep 2019; 19:57 UT
Credential Certification: Dipankar P.K. Banerjee (dpkb12345@gmail.com)

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We report on 0.7-2.5 micron near-infrared observations of recurrent nova V3890 Sgr using the 3.2m NASA IRTF telescope. Spectra were obtained on 2019 Sept 7.3751 UT (with a 0.8 arcsec slit) and at a higher resolution on 2019 Sept 8.3756 (with a 0.3 arcsec slit, R = 2000 in sub-arcsecond seeing conditions) using SpeX in the cross-dispersed mode. The spectrum of 2019 Sept 8.3756 UT is rich with emission lines, most of which have been mentioned in ATEL #13088 and additionally several other fainter lines whose identification is in progress. Pfund series lines (16-5 to 28-5) are seen. A significant development is the detection of the 2-0, 3-1 and 4-2 first overtone CO bands in absorption with bandheads at 2.2935, 2.3227 and 2.3535 micron arising from the cool secondary star. There was a suggestion that these bands were already present in the earlier spectra discussed in ATel #13088. There does not appear to be convincing evidence for coronal lines yet, though a feature is seen at 2.4831 micron that matches well the expected position of [Si VII] 2.4833 micron. However the [Si VI] 1.9641 micron line is not convincingly seen.

The line widths have narrowed even further than reported in ATEL #13081 and ATEL #13088. The Pa-beta line profile is well reproduced by the sum of two gaussians viz. a broad component (FWHM ~3800 km/s) which forms the pedestal of the profile on which a narrow component (FWHM ~540 km/s) is superposed. The narrow component is itself split into two sub-components separated by ~ 650 km/s, with the blue sub-component being approximately one-third in strength compared to the red. This is seen in both the Pa-beta and Br-gamma profiles. The FWZI of the HI lines is ~8000 km/s. HeI 1.083 and He I 2.0581 micron lines also show a broad boxy pedestal (FWZI ~9000-10000 km/s for the 2.0581 micron line) on which is superposed a strong and narrow component with FWHM ~ 460 km/s (as measured for the 2.0581 micron line). All line-widths reported here are observed values and not deconvolved for the instrumental FWHM of ~150 km/s.

These observations were conducted under IRTF program 2019B005, and we thank Bobby Bus and Dave Griep (U. Hawaii, IfA) for their assistance.