Last year we reported the discovery of a ring nebula called SBW1 around a blue supergiant star in our Galaxy. In almost every respect, it is a true "twin" of the equatorial ring nebula around SN 1987A: it has an identical physical radius of 0.2pc, a similar expansion speed and age, it is located in a massive HII region, the central star is an early B supergiant with the same luminosity as SN1987A's progenitor, and the ring's structure in our ground-based H-alpha images looks almost identical to early HST images of SN1987A's ring. The detailed density structure of SN1987A's ring on scales smaller than the limiting resolution of HST has become a pressing question, because the forward shock of the supernova is now colliding with that ring, causing it to brighten by 3 orders of magnitude and giving rise to a series of "hotspots" around the ring. HST/WFC3 images of SBW1 will provide a snapshot of an SN1987A-like ring before the supernova explodes, and will provide a detailed view of the important density inhomogeneities in the ring with a physical spatial resolution 10 times better than HST images of SN1987A (because SBW1 is 10 times closer to us). STIS spectra will allow us to directly measure the radial density structure of the ring. Both the overall radial density profile and the detailed structures of the clumps that give rise to the "hotspots" are critical factors in modeling the rapid evolution of SN1987A, and our proposed study of SBW1 will provide extremely valuable input for those models.

This program will obtain F656N, F658N, and F502N images with WFC3 of the ring nebula around SBW2, as well as STIS/CCD spectra including the H-alpha and [S II] emission lines. ISM AND CIRCUMSTELLAR MATTER 12 false 0.0 0.0 false false false false false SUPPORTED STAR B0-B2 III-I BE CIRCUMSTELLAR MATTER EMISSION LINE NEBULA RING J2000 10 40 19.4000 -59 49 9.70 J2000 WFC3/UVIS Imaging No No F658N WFC3/UVIS Imaging No No F656N WFC3/UVIS Imaging No No F502N STIS/CCD Spectroscopic No No G750M 6581 POS-TARG DITHER 0.145 LINE false false 2 46.84 WFC3-UVIS-DITHER-LINE 1 false The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. for imaging, central star is centered on CCD1, and only CCD1 is read out. use 2-pt dither for all, and CR-SPLIT for F656N and F658N. (Tic-Visit :proposal-id 11637 :visit-id "01" :proposal-version -1 :trans-version "20080624" :date "02-Jul-2008 14:58:45.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 1408272 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11637 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :cvz T :proposal-id 11637 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 4389 :al-overhead-at-end 216 :internal-dur-at-end 654 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 0 :low-sky "N" :pcs-visibility 0 :pcs-gap 0 ) true 1 0 not doing CR-SPLIT for the F502N images. The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. The slit will be offset by 0.3 arcsec on either side of the star, and the slit should be oriented at a position angle of +32d (or +122d) with a tolernce of +-5d. (Tic-Visit :proposal-id 11637 :visit-id "02" :proposal-version -1 :trans-version "20080624" :date "02-Jul-2008 13:25:40.0" :trans-errors '(:WARNINGS 6 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 147648 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11637 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :cvz T :proposal-id 11637 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 5061 :al-overhead-at-end 0 :internal-dur-at-end 342 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 0 :low-sky "N" :pcs-visibility 0 :pcs-gap 0 ) false 1 0 slit offset perp-to-slit, placing slit 0.3 arcsec off of star's position to avoid saturation of bright central star in long exposures. spatial offset placing slit 0.3 arcsec on other side of star.