0Assigned ID: 4347
----- Attempting Submission 1 (Wed May 24 14:47:04 GMT 2023) -----
HST Phase I Proposal 4347 successfully submitted.
Receipt: # 4347-1
----- Attempting Submission 2 (Wed May 24 22:48:39 GMT 2023) -----The target for visit 04 was replaced with a new target consistent with the science goals. Again, an offset acquisition has been set up for this visit due to a bright object nearby.
Visits 05 and 06 have been separately confirmed.2091255809----- Attempting Submission 1 (Fri Sep 15 03:43:44 GMT 2023) -----
HST Phase II Proposal 17488 successfully submitted.
Receipt: # 17488-1
----- Attempting Submission 2 (Fri Sep 15 19:22:19 GMT 2023) -----
HST Phase II Proposal 17488 successfully submitted.
Receipt: # 17488-2
----- Attempting Submission 3 (Fri Sep 15 19:50:31 GMT 2023) -----
HST Phase II Proposal 17488 successfully submitted.
Receipt: # 17488-3
----- Attempting Submission 4 (Tue Oct 24 15:46:35 GMT 2023) -----
----- Attempting Submission 5 (Sat Aug 03 23:58:59 GMT 2024) -----
----- Attempting Submission 6 (Fri Aug 30 11:30:45 GMT 2024) -----
----- Attempting Submission 7 (Mon Sep 09 23:49:38 GMT 2024) -----Unraveling the mystery of the rare 2175 A extinction bump in the SMCUnderstanding the properties of dust extinction is fundamental to answer questions ranging from how dust grains form to what drives galaxy evolution. The dust extinction curve at ultraviolet (UV) wavelengths is known to vary widely in the Local Group and beyond, but the reason is still not fully understood. It is an open question how, and physical conditions of the interstellar medium (ISM) may affect extinction curve features such as the far-UV rise and the properties of the 2175A bump. The Small Magellanic Cloud (SMC) is key to studying such variations since it is our best nearby analog to low-metallicity and high-redshift observations, there are plenty of observations of its ISM, and spatially-resolved individual stars and dust/gas complexes enable analyzing correlations between environment and dust extinction properties. The limited number of high-quality SMC UV extinction curve measurements needs to be supplemented with new targeted measurements of sightlines in a variety of ISM physical conditions. We propose to measure UV extinction curves and the HI column densities of a carefully selected sample of 6 reddened, hot stars to evaluate the dependence on environment of the 2175A bump and the FUV rise. These stars have a high probability of a strong bump in their extinction curves based on modeling their spectral energy distributions from an existing large photometric survey in the SMC Southwest Bar. Our proposed sample will triple the UV extinction curve database of SMC sightlines with a strong bump from 3 to 9 improving the statistical significance of correlations of bump properties with environment.HST STIS is the most suitable instrument for our proposed observations. We propose to obtain STIS low-resolution spectra with the 52x2 slit and the G140L grating (to measure the FUV extinction curve rise and obtain Ly-alpha to measure the HI column density) and the G230L grating (to measure the properties of the 2175 A feature). STIS will be able to perform the observations significantly faster than COS. Our targets have 17.62 <= F475W <= 19.47 mag and extinction in the V band of 0.91 <= AV <= 1.6. These correspond to V-band magnitudes from 17.54 to 19.43 mag. We require a S/N of ~ 10 at R = 10 since from previous STIS UV spectra work we know these criteria will allow us to measure the detailed properties of the bump and the strength of the FUV rise.
Using the STIS exposure time calculator, we find that the faintest object will require a 2452s/2407s exposure in G230L/G140L respectively. This and two other objects will require 2 orbits each when taking into consideration the instrument overheads. Our brightest object will require 271s/424s in G230L/G140L respectively, which along with two other bright objecrs will require one orbit each.
In total, for the 6 targets in our sample we request 9 HST orbits.Dr. Petia Yanchulova Merica-Jones, Dr. Marjorie Decleir, Dr. Karl Gordon, Dr. Karin Sandstrom, and Dr. Dries Van De Putte are all experts in studies of SMC dust extinction properties.Stellar Populations and the Interstellar Medium6falsefalsefalsefalsefalsefalsefalsefalseSUPPORTEDEXT-STARB0-B2 III-IJ2000EXT-STARB3-B5 V-IVJ2000EXT-STARB3-B5 V-IVJ2000EXT-STARB0-B2 V-IVreplaced original S4 which was located in the N13 nebula due to bright UV sources and extended emission nearby. The new target is brighter and is does not appear to have other bright nearby objects of concern.J2000J2000EXT-STARB3-B5 V-IVReplaced SMIDGE-S5 with a star with similar parameters for the science proposed, and better observation parameters:
J004606.4704-731728.978
Target is 9.4" away from a brighter object with V=17.7 mag. Is within or close to 5" away from objects with V=19.7 mag and 19.1 mag, resepctively.
log(T) = 4.14 dex; log(g) = 3.52 dex; Av = 1.15; Rv = 2.74; => E(B-V) =~ 0.38J2000J2000EXT-STARB0-B2 V-IVJ2000J2000EXT-STARK III-I2MASS J00462720-7321013 1 00 46 27.203 -73 21 01.40 RGB*_Candidate MIR|NIR|RB? B= 18.390 V=17.090 J=14.966 H=14.247 K=14.269J2000STIS/NUV-MAMASpectroscopicNoNoG230L2376STIS/FUV-MAMASpectroscopicNoNoG140L1425STIS/NUV-MAMASpectroscopicNoNoG230L2376STIS/FUV-MAMASpectroscopicNoNoG140L1425STIS/NUV-MAMASpectroscopicNoNoG230L2376STIS/FUV-MAMASpectroscopicNoNoG140L1425STIS/NUV-MAMASpectroscopicNoNoG230L2376STIS/FUV-MAMASpectroscopicNoNoG140L1425STIS/NUV-MAMASpectroscopicNoNoG230L2376STIS/FUV-MAMASpectroscopicNoNoG140L1425STIS/NUV-MAMASpectroscopicNoNoG230L2376STIS/FUV-MAMASpectroscopicNoNoG140L1425The scheduling data was generated by CASM 32.1.1.CASM was run in Phase II mode./private/var/folders/th/45l2486x16lgmh0k83j7x2d80002lc/T/OPVisit9485278939497798968.xml1724824551000322.7393459177867(Tic-Visit
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