For G160M observations, please consult Chapter 9 of the COS Instrument Handbook to estimate overheads and the number of exposures per orbit, and consequently the correct lifetime position. Use of LP4 with G160M requires justification in the "Special Requirements" section of the Phase I PDF. Use of the default LP6 with G160M requires no justification. Proposals can be submitted with the warning present.0Assigned ID: 4095
----- Attempting Submission 1 (Tue May 23 12:48:09 GMT 2023) -----
HST Phase I Proposal 4095 successfully submitted.
Receipt: # 4095-1
----- Attempting Submission 2 (Wed May 24 12:30:33 GMT 2023) -----The use of COS G160M is explained in the proposal.Updated the timing requirements on both vistis.-16015292----- Attempting Submission 2 (Wed Nov 01 11:50:29 GMT 2023) -----
----- Attempting Submission 3 (Tue Aug 13 08:46:30 GMT 2024) -----
HST Phase II Proposal 17842 successfully submitted.
Receipt: # 17842-3
----- Attempting Submission 4 (Tue Aug 13 11:41:01 GMT 2024) -----Expanding shocks and the emergence of the compact object in Supernova 1987ABy a fortunate turn of events, SN 1987A, the brightest supernova (SN) since 1604, exploded just a few years before the launch of HST. This has allowed HST to monitor the evolution from the very beginning as the SN evolves into a remnant, proving astronomers with a unique laboratory for SN physics. The most recent observations show major changes in the interaction with the iconic triple-ring nebula of circumstellar material. The dense, inner ejecta are just starting to crash into the equatorial ring, while the shocks further out in the system are gradually revealing the mass-loss history of the progenitor star. Furthermore, JWST has recently detected the first clear electromagnetic signal from the compact object created in the explosion, though its properties are yet to be determined. We request imaging in narrow and broad filters over the next three cycles, as well as a COS spectrum in Cycle 31, to study the shock interaction and compact object. The observations will be used to determine the conditions in the shock region, the properties of the circumstellar medium, and constrain the main competing scenarios for the compact object. Annual observations are needed to track the rapid evolution of the shocks and the emerging emission from the compact object. Taken together, this will allow the properties of the progenitor and compact object to be connected for the first time. The HST observations are also indispensable for interpreting other multiwavelength observations of SN 1987A.The requested observervations include 6 orbits with WFC3/UVIS and 11 orbits with COS.
WFC3 Imaging:
We request imaging in F625W, F502N, F657N and F763M in cycle 31. The first three filters are needed to measure the propagation of all the shock components and connect to the previous monitoring, while F763M will be used to search for signs of the compact object.
To obtain a similar S/N as the previous observations, considering the fading of the system, we require one orbit each for F625W and F657N, and two orbits for F502N. The most interesting line from the compact object in the F763M filter is the [Ar III] 7753 line. Model predictions give a typical luminosity ~0.1* the [Ar II] 6.99 um luminosity, which results in a flux of 9 * 10^-17 erg cm^-2 s^-1. With a FWHM of 200 km s^-1, this results in a S/N ~14 in 6000 s. We therefore request two orbits with F763M to search for the compact object.
Since 2003, all ACS and WFC3 imaging have used a fixed dither strategy to improve the spatial resolution, which will be repeated for consistency.
COS spectrum:
We will observe SN 1987A using central wavelength settings of the G130M (1291, 1318) and G160M (1600, 1611, 1623) gratings, which ensures continuous wavelength coverage at relatively constant S/N, and effectively performs a focal plane split to minimize fixed pattern noise. The 1318 setting for G130M is needed to provide continuous wavelength coverage across the full G130M spectral region and to compare with previous epochs of COS
data. The limited spatial resolution of COS (about 1" in a 2.5" aperture) leaves some spatialspectral ambiguity in the deep spectral data. However, different emission components can be separated based on different line widths and Doppler shifts. While STIS would provide spatial information, its lower sensitivity makes it unsuitable for our objectives. We require a similar S/N as in the COS spectrum from 2017 (Fig. 7) to model the shocked emission from the ring and search for possible new lines from the compact object.
Assuming that the UV flux from the ring has faded by 30% since 2017 (as in the optical), we require 3.5 orbits with G130M and 7 orbits with G160M. Combining these, and including extra time to account for the overheads introduced in Cycle 30 by the extra wavelength calibration at LP6, we require 11 orbits for the COS observations. We have run the Bright Object Tools and no bright object violations are detected. This, combined with the offset acquisition, makes the observations safe to execute.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. Co-PIs J. Larsson and C. Fransson have been leading these efforts in recent years. 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 JWST, VLT and ALMA. J. Larsson will lead the data analysis of the proposed observations, while C. Fransson will lead the theoretical modeling.Stellar Physics and Stellar Types6falsefalsetruefalsefalsefalsefalsefalseSUPPORTEDEXT-MEDIUMSNRThis object was generated by the targetselector and retrieved from the SIMBAD database.J2000J2000WFC3/UVISImagingNoNoF625WWFC3/UVISImagingNoNoF657NWFC3/UVISImagingNoNoF502NWFC3/UVISImagingNoNoF438WWFC3/UVISImagingNoNoF763MCOS/FUVSpectroscopicNoNoG130M1291COS/FUVSpectroscopicNoNoG130M1318COS/FUVSpectroscopicNoNoG160M1600COS/FUVSpectroscopicNoNoG160M1611COS/FUVSpectroscopicNoNoG160M1623POS-TARGDITHER0.173LINE0.112falsefalse81.785423.884WFC3-UVIS-DITHER-BOX1false/Users/jlarsson/astro/proposals/hst/87a_2023/phase2/cycle32/OP-cache/sn87a_cycle32_17842-v01.xmlTiming link suitability includes constraints ([Sequence (01 02) within 14.0 days])The scheduling data was generated by CASM 32.1.1.CASM was run in Phase II mode.The orienation constraints are set to make sure that the diffraction spikes from "Star 3" (Fig. 1 of the proposal) do not overlap with the emission from the SN.(Tic-Visit
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