0Assigned ID: 447
----- Attempting Submission 1 (Fri Mar 06 11:27:24 GMT 2020) -----
HST Phase I Proposal 447 successfully submitted.
Receipt: # 447-1
----- Attempting Submission 2 (Fri Mar 06 15:40:36 GMT 2020) -----0----- Attempting Submission 1 (Wed Jun 24 01:05:06 GMT 2020) -----
----- Attempting Submission 2 (Wed Jul 06 22:41:43 GMT 2022) -----The ever-changing face of SN 1987ASN 1987A is the great supernova (SN) of the HST era. An unbroken string of observations is the essential tool for detecting change and establishing a uniform legacy archive. Recent imaging has shown dramatic changes in the ejecta and the interaction with the circumstellar material. After a steady increase in flux, the inner circumstellar ring reached a maximum in 2009 and is now fading rapidly as it is destroyed by shocks. At the same time, diffuse emission and new spots outside the inner ring are becoming visible, gradually revealing previously unseen material that extends toward the outer rings. Monitoring this emission is required to understand the formation of the rings and the mass-loss history of the progenitor star. In addition, the expanding innermost ejecta reveal asymmetries and mixing in the explosion. As the ejecta expand, X-rays from the inner ring penetrate into the metal-rich core, which results in a brightening in the optical band. We request imaging in narrow and broad filters over the next three cycles to follow these developments. Annual observations are needed to monitor the rapid evolution of the shocks. Imaging in additional filters in one of the cycles will provide flux measurements crucial to estimating the energy budget of the ejecta, that, perhaps, will begin to reveal the elusive compact object. The HST observations have a unique blend of photometric fidelity and angular resolution that make them the indispensable partner to ongoing X-ray, sub-mm ALMA, and ground-based optical/NIR observations. They are also an important complement to the JWST GTO observations in 2022.We request imaging with WFC3/UVIS in Cycles 28, 29, and 30. The total time requested is 4 + 9 + 4 = 17 orbits.
Monitoring:
We request imaging with F438W, F625W, F502N, and F657N in all three cycles. With these observations, we will follow the light curve and morphology of the ejecta, the ER, and the new spots and diffuse gas outside the ER. To obtain a similar quality as the previous observations, we need half an orbit each for the broad filters, one orbit for F657N and two orbits for F502N. This amounts to 4 X 3 = 12 orbits over three years. Since 2003, all ACS and WFC3 imaging has used a fixed dither strategy to improve the resolution of the HST PSF. Using the same dither strategy and the empirical PSFs by Anderson (2016), we will use PSF-matched difference imaging (Sugerman 2005) across the full ACS/WFC3 dataset and search for faint changes in the rings and outer structures.
Additional filters in Cycle 29:
We request imaging with F275W, F336W, F555W, F814W and F280N in Cycle 29 only, which is expected to be close in time to the planned JWST GTO observations. In the event of a significant delay in the JWST launch, we would request the STScI Director to move these observations to Cycle 30. The HST observations in this cycle will give complete coverage of the wavelength interval between 2300A-10000A. The primary science objectives for the broad filters are the energy budget for the ejecta and compact object, but the observations will also measure the other emission components in the system, which can verify our models for the shock interaction. The last time that SN 1987A was observed in all these filters was in 2009. We request a full orbit each in F275W and F336W, which is a significant improvement compared to the 400 s UV-band exposures in the 2009 epoch. The longer exposures are motivated by the relatively low transmission as well as the fact that these filters are important for estimating limits on the compact object. We will need one orbit to cover F555W and F814W.
The narrow F280N filter covering the Mg II lambda-2800 lines has not previously been used for SN 1987A, though it is known from STIS spectra that the ejecta are strong in Mg II (Larsson et al. 2013). As described above, these lines can also help refine the shock models for the new spots. The F280N filter will cover almost all ejecta emission inside 2500 km/s, while the highest velocities will be included in the F275W image. Given the filter throughput and the expected strength of the lines, we require two orbits for F280N.Our team has extensive experience in HST observations of SN 1987A, with many of the team members having been involved since the launch of HST. The expertise within the team covers everything from HST data reduction and analysis to theoretical modeling. Many of the team members are also involved in other multiwavelength observations of SN 1987A, including VLT, ALMA, and NuSTAR. In the last decade, we have written more than 15 papers based on our HST observations, including one in Nature and one in Science. Co-PIs J. Larsson and C. Fransson have been leading these efforts in recent years. J. Larsson will lead the data analysis of the proposed observations, while C. Fransson will lead the theoretical modeling. C. Fransson and our team member P. Bouchet are also members of the collaboration for the JWST GTO observations of SN 1987A. They will ensure the coordination of the analysis of JWST and HST data.Stellar Physics and Stellar Types6falsefalsetruefalsefalsefalsefalsefalseSUPPORTEDEXT-STARSUPERNOVAThis object was generated by the targetselector and retrieved from the SIMBAD database.J2000J2000WFC3/UVISImagingNoNoF438WWFC3/UVISImagingNoNoF625WWFC3/UVISImagingNoNoF657NWFC3/UVISImagingNoNoF502NWFC3/UVISImagingNoNoF275WWFC3/UVISImagingNoNoF280NWFC3/UVISImagingNoNoF336WWFC3/UVISImagingNoNoF555WWFC3/UVISImagingNoNoF814WPOS-TARGDITHER0.173LINE0.112falsefalse81.785423.884WFC3-UVIS-DITHER-BOX1falseTiming link suitability includes constraints ([Sequence (01 02 03) within 7.0 days])The scheduling data was generated by CASM 30.3.CASM was run in Phase II mode.1695440244000259.0(Tic-Visit
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