TITLE: GCN CIRCULAR NUMBER: 7192 SUBJECT: Transient in NGC2770 / SN2008D: Metallicity of nearby HII regions DATE: 08/01/17 15:27:09 GMT FROM: Edo Berger at Princton U E. Berger and A. M. Soderberg (Princeton) report on behalf of a larger collaboration: "We used the ARC 3.5-m telescope at Apache Point Observatory to obtain spectroscopic observations of the X-ray transient in NGC2770 (GCN 7159). We obtained 4x1200 sec exposures with the DIS red+blue cameras providing a wavelength range of 3600-9000A. The spectra therefore cover a wide range of nebular emission lines relevant for metallicity measurements (i.e. [OII], H-beta, [OIII], H-alpha, [NII], and [SII]). Following the prescriptions of Kewley & Dopita (2002) we use several indicators (e.g. [NII]/[OII], R23) to measure the metallicity and ionization parameter of bright HII regions within +/-8 arcsec (about 1 kpc) of the X-ray transient position. We find metallicities of 12+log(O/H)=8.9+/-0.2, or about 0.6-1.6 times the solar metallicity. The error bar includes both the spread in metallicity and the systematic uncertainty between the various indicators. This value is higher, and more robust, than the estimate in GCN 7189 which relied on an assumed metallicity gradient."