Justification may be needed for use of certain lifetime positions with G160M. See "Errors and Warnings" for more details.0Assigned ID: 2736
----- Attempting Submission 1 (Mon Mar 14 21:33:01 GMT 2022) -----Our proposed science requires to detect NIII lines which are at 1783.7A (observed frame). Thus we request G160M centered at 1623A.0----- Attempting Submission 1 (Fri Mar 25 00:14:50 GMT 2022) -----
HST Phase II Proposal 16931 successfully submitted.
Receipt: # 16931-1
----- Attempting Submission 2 (Fri Mar 25 18:36:22 GMT 2022) -----
HST Phase II Proposal 16931 successfully submitted.
Receipt: # 16931-2
----- Attempting Submission 3 (Mon Mar 28 16:03:04 GMT 2022) -----HST High Resolution UV Spectroscopy of the Second Closest Luminous SLSN-IInIn the nearby Universe ($<100$\,Mpc), superluminous supernovae with peak luminosities brighter than $-20$\,magnitude are extremely rare, with only a few in total. Recently, the Zwicky Transient Facility discovered and classified ZTF21ackxdos, the closest and brightest SLSN-IIn in more than a decade ($z=0.018, 78$\,Mpc). Its current apparent brightness is 14.5 and 17.7\,magnitudes in $r$ and {\it Swift} UVW2 (1928~\AA) respectively. Such high UV fluxes offer a rare and valuable opportunity for high resolution HST/UV spectroscopy. The rich suite of narrow UV emission lines from C, N and O at various ionization states offer the best diagnostics to obtain reliable measurements of CNO abundances and electron density of the circumstellar medium (CSM) ejected from the surface of the SN progenitor star. This type of observations was carried out only once before for a luminous SN IIn, SN\,2010jl at $z=0.01058$ (Fransson et al. 2014). The requested data will determine if the nitrogen in ZTF21ackxdos is highly enriched due to the CNO-cycle, similar to the case for SN\,2010jl, whose progenitor is thought to be a luminous blue variable (LBV). The high resolution COS spectra can resolve the UV lines down to $\la 100 $\,km\,s$^{-1}$ and together with the density provide a measurement of the mass loss rate, crucial for characterising this type of progenitors. ZTF21ackxdos will be visible by {\it HST} on April 7, 2022. We request one epoch of COS and STIS observations before the supernova becomes too faint.Our science goals require high resolution spectra. Therefore, we request G130M and G160M grating centered at 1309 and 1623A respectively. These two gratings will give a resolution between 20,000 - 24,000, with a wavelength scale of 0.01 - 0.012A per pixel and each resolution elements have 6 - 7 pixels. The STIS G230LB grating will cover the wavelength range of 1685 - 3065A with a resolution of ~700. This spectrum provides great complimentary data to both the far-UV COS and the optical X-shooter data and covers the strong Mg II 2800A doublet as well as the important C III] 1909A and [N II] 2143A lines.
At the time of the writing of this proposal, ZTF21ackxdos was observed by Swift twice, with UVW2 fluxes (1928A) of 17.73 and 17.78 magnitudes on Feb 23 and Feb 28, 2022 respectively. Assuming this declining rate, we anticipate that UVW2 apparent magnitude will be about 0.4 magnitude fainter on April 7, 2022. We use the Exposure Time Calculator (ETC) with the scaled HST COS and STIS spectra of SN 2010jl as the input data for our calculations. Here the scaling factors are derived by matching with the observed Swift broad band UV fluxes for ZTF21akcxdos and including the expected decline of 0.4 magnitude between Feb 23 and April 7, 2022. The results from ETC estimates are shown in Figure 3, where the SNR values for both COS and STIS are based on exposure time of 2500 seconds. The expected SNRs are 4 at
1230A, 6.3 at 1500A and 16.3 at 2500A for the three configurations respectively. We note that for high resolution COS spectra, rebinning can increase SNR by another factor of 2 - 3. The requested spectra should have SNR similar to what have been published for SN 2010jl
(Fransson et al. 2014). In summary, we request a total of 3 orbits to obtain one epoch of COS and STIS
observations for ZTF21ackxdos as soon as it is visible.The PI and all Co-Is are the members of the Zwicky Transient Facility. Dr. Yan is an expert in superluminous supernovae, and has taken HST COS/STIS UV spectra of 3 Type I SLSNe (Yan et al, 2017, 2018). Dr. Fransson is a theoretical expert on interaction driven supernova, and has written extensive modeling software for the application in the proposed program. Drs. Lunnan, Sollerman and Schulze are also experts in core collapse supernovae.Stellar Physics and Stellar TypesStellar Physics and Stellar Types0falseSUPPORTEDSTARSUPERNOVA TYPE IINOJ2000J2000COS/FUVSpectroscopicNoNoG130M1309COS/FUVSpectroscopicNoNoG160M1623STIS/CCDSpectroscopicNoNoG230LB2375/Users/lyan/proposals/HST-ddt/ztf21ackxdos/OP-cache/HST-DDT-phaseII-Mar24-v01.xmlThe scheduling data was generated by CASM 30.1.CASM was run in Phase II mode.(Tic-Visit
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