Electronic Telegram No. 3690 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION CBAT Director: Daniel W. E. Green; Hoffman Lab 209; Harvard University; 20 Oxford St.; Cambridge, MA 02138; U.S.A. e-mail: cbatiau@eps.harvard.edu (alternate cbat@iau.org) URL http://www.cbat.eps.harvard.edu/index.html Prepared using the Tamkin Foundation Computer Network STRONG [Fe II] SOURCE IN SCORPIUS Bruce McCollum, Frederick Bruhweiler, The Catholic University of America (CUA); Seppo Laine, California Institute of Technology; Lee Rottler, Pisgah Astronomical Research Institute; and Glenn Wahlgren, CUA, report the discovery of an uncataloged, possibly transient strong infrared [Fe II] emission source in Scorpius. The source was discovered in Hubble Space Telescope WFC3 images obtained on 2012 Feb. 19 and 20 in the F160W and F164N filters. The F160W filter covers 1.4-1.7 microns and approximates the Johnson H bandpass. The F164N filter is is 0.209 micron wide, centered on the [Fe II] emission feature at 1.64 microns. The object's flux density in the F164N filter is 3.37 mJy. The object has an anomalously low F160W/F164N flux ratio of 9.57 +/- 0.11. This flux ratio is within a few percent of that seen in another object in the field that is known to be a strong [Fe II] emission source, suggesting strong [Fe II] emission in the new object. Also, the F160W/F164N flux ratio of eight other stars, not known to have significant [Fe II] emission in the same image, is 17.02 +/- 0.73, where the uncertainty reflects the spread of intrinsic fluxes rather than the photometric uncertainty in each object (a few percent). The ratios in the eight other stars are thus all relatively similar and are all approximately what would be expected from the relative bandpass widths of the F160W and F164N filters, assuming also some intrinsic differences in the spectral-energy distributions without significant [Fe II] emission. The object was also imaged on 2012 Feb. 21 in the WFC3 F673N filter, which is 2.3 nm wide and centered on the [S II] 671.7-/673.1-nm emission line; its flux density in the F673N filter is 0.253 mJy. The fact that the flux in the [Fe II] band is 16 times greater than in the [S II] band is most easily explained if most of the flux in the F160W band results from strong [Fe II] emission above the continuum. It is concluded that the object has unusually strong [Fe II] 1.64-micron emission. The object's F160W magnitude is [AB] = 15.87 +/- 0.05. The [Fe II] source is located at R.A. = 17h57m33s.32, Decl. = -30d43'12".2 (equinox 2000.0). Spitzer satellite images in the IRAC 3.6- and 4.5-micron channels obtained on 2012 May 19 show no source at that location; the IRAC images imply upper limits of 1 mJy at 3.6 microns and 0.03 mJy at 4.5 microns. No source at these coordinates is seen in digitized red and blue plates from the European Southern Observatory/Sciece and Engineering Research Council and the Palomar Sky Survey, which indicates limiting blue magnitudes of about 20 and red magnitudes of about 20. Also no source is seen in 2MASS images (down to limiting magnitudes of J = 15.8, K = 15.1, and K_s = 14.2) or in the DENIS survey (which conservatively gives a limiting I magnitude of about 17 in this crowded region near the Galactic center). V1309 Sco = N Sco 2008 is visible and distinct nearby in the same WFC3 images; both V1309 Sco and the new source are bright in the WFC3 [Fe II] filter, relative to the F160W filter brightness, and the authors have confirmed strong [Fe II] emission at 1.64 microns in V1309 Sco by obtaining spectra recently of V1309 Sco. A search of all online catalogues does not find any other objects closer than 2" from the above position. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2013 CBAT 2013 November 7 (CBET 3690) Daniel W. E. Green