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.
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: 6199
----- Attempting Submission 1 (Wed Apr 09 02:09:29 GMT 2025) -----
HST Phase I Proposal 6199 successfully submitted.
Receipt: # 6199-1
----- Attempting Submission 2 (Thu Apr 10 20:01:52 GMT 2025) -----I have read the warning.0----- Attempting Submission 1 (Fri Aug 08 16:51:30 GMT 2025) -----
----- Attempting Submission 2 (Wed Oct 15 15:14:36 GMT 2025) -----
HST Phase II Proposal 18101 successfully submitted.
Receipt: # 18101-2
----- Attempting Submission 3 (Wed Nov 05 19:45:08 GMT 2025) -----A New Approach to Determine the Ionizing Fluxes of Rapidly Rotating Oe Stars at Low MetallicityOe rapidly-rotating main-sequence emission-line stars can dominate the ionization of H II regions, particularly at low metallicity, where they are relatively common and reach earlier (hotter) types. When line emission fills-in their key optical absorption lines, it is extremely challenging to infer their spectral type, effective temperature/Teff, and ionizing spectrum using conventional optical analysis. FUV spectra offer the only route for constraining these fundamental stellar properties. However, few FUV spectra of Oe stars are available, and most of them are of stars in complex regions that prevent us from using their associated nebulae to validate their ionizing fluxes. We have used data from the integral field spectroscopic survey, SDSS-V Local Volume Mapper, to identify two SMC-field Oe stars with relatively isolated H II regions. The stars have high-quality optical spectra from 6-8 m class telescopes and are likely to sample different temperature regimes (one early- and one late-type). We request HST/COS G130M+G160M observations of these stars in order to cover the crucial 1160-1190 and 1550 Ang spectral regions. The FUV spectra will enable us to assess the impact of rapid rotation on their ionizing fluxes and to infer stellar wind properties. Due to their isolation, the Oe star H II regions can be used to validate the stellar ionizing fluxes predicted from models fit to the HST/COS spectra. Our study will be the first that combines stellar and nebular spectra to constrain the highly uncertain contribution of Oe stars, known to be more common at low metallicity, to the ionizing fluxes/feedback of their host galaxies.We will observe two rapidly-rotating O-type main sequence stars in the SMC, AzV 255 or LHA-115-S-31 (~O7V) and N80A or OGLE-SMC725.11.009683 (~O3V).
We will use COS G130M (cenwave=1291) + G160M (cenwave=1611) for the first target (AzV 255), which has fluxes of 4.2e-13 erg/s/cm2 at 1300 A and 3.0e-13 at 1500 A, Gaia G=13.54 mag, and E(B-V)~0.04 mag.
We will use COS G140L and cenwave = 800 for the second star, which is fainter (1.1e-14 erg/s/cm2 at 1300 Ang, Gaia G=17.84 mag) and more reddened (E(B-V)~0.3 mag).
To avoid going over the brightness limits during the TA of N80A, which is located near a bright star, we will acquire instead an offset star (Gaia DR3 4687529716356335360, renamed N80A-OFFSET), which is a B1V star that has a V-band magnitude of 15.56 and E(B-V)~0.04 mag.
For all exposure time calculations we will use Castelli and Kurucz Models models of the stars and the Milky Way extinction law to redden the models prior to their renormalization to the above observed reddened fluxes or magnitudes.
For the TA of AzV 255, we use the BOA, MIRROB, the ACQ/IMAGE mode, and the recommended SNR=30 when using the BOA. For the TA of N80A-OFFSET, we use the PSA, MIRRORB, the ACQ/IMAGE mode, and the recommended SNR=20 (5s) when using the PSA.
Guided by O-star observations from ULLYSES, we need spectroscopic observations to have a minimum SNR=20/six-pixel resel (G130M/1291 at 1150 Ang and G160M/1611 at 1590 Ang). For N80A we require a similar SNR=20 with G140L/800 at 1169 Ang. For this, the G130M and G160M science exposure times for AzV 255 need to be 276 s and 434 s, respectively; and for N80A, 1,369 s.
For AzV 255, the overhead times (in s) for the guide star acquisition and TA, G130M, and G160M exposures are 420, 206 and 1706, and 1706+117 s, respectively.
Thus, overall, we will use 2 (2) orbits for observing N80A (AzV 255) with COS.Aida Wofford has led multiple HST proposals, including proposals that use STIS and COS. She is an expert on massive stars, stellar populations and nearby galaxies. She has priviledged access to SDSS-V LVM observations.
Paul Crowther has decades of expertise in UV+optical spectroscopic analysis of OB and related stars with model atmosphere codes such as CMFGEN.
Sally Oey has a long track record of expertise with H II regions, photoionization, and nebular emission. She also has experience with massive star populations in the SMC and LMC, including a recent paper on an extreme and variable Oe star in the SMC.
Grace Telford is an expert in low-metallicity O stars and HII regions. Telford is PI of the Large Treasury HST/COS program GO-17491 to build a UV atlas of O stars below SMC metallicity, and has led UV+optical analyses using both stellar atmosphere (PoWR) and photoionization (Cloudy) modeling.
Jorick Vink is an expert in massive star evolution and atmosphere modelling at low metallicity. He is PI of the ESO Large Programme "XShooting Ullyses (XShootU) : Massive stars at low metallicity".
D. Pauli is a leading expert in the consistent non-LTE stellar atmosphere modelling of optical and UV spectra of O-type stars with particular focus on the analysis of massive stars and binaries in the Small Magellanic Cloud.
Gautham Sabhahit is an expert in the modeling of optical and UV spectra of massive stars.
Oskar Arangure is an expert in the analysis of LVM observations of H II regions in the Magellanic Clouds.
Christophe Morriset is an expert in the modeling of H II regions using Cloudy and the PI of pyNeb and pyCloudy.Stellar Physics and Stellar Types6falsetruefalsefalsefalsefalseSUPPORTEDEXT-STARMAIN SEQUENCE OOENOThis object was generated by the targetselector and retrieved from the SIMBAD database.
SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM.J2000J2000EXT-STARMAIN SEQUENCE OOENOThis object was generated by the targetselector and retrieved from the SIMBAD database.
The equatorial coordinates match those of Gaia DR3J2000J2000STARB0-B2 V-IVNOThe equatorial coordinates are from Gaia DR3S0W8275115GAIA-DR3-4687529716356335360J2000G = 15.50COS/NUVImagingNoNoMIRRORACOS/FUVSpectroscopicNoNoG130M1291COS/FUVSpectroscopicNoNoG160M1611COS/NUVImagingNoNoMIRRORACOS/FUVSpectroscopicNoNoG130M1291COS/FUVSpectroscopicNoNoG160M1611/Users/aidawofford/Downloads/OP-cache/18101_nov4-v01.xmlThe scheduling data was generated by CASM 33.1.CASM was run in Phase II mode.(Tic-Visit
:proposal-id 18101
:visit-id "01"
:proposal-version -1
:trans-version "20250624"
:date "05-Nov-2025 10:42:58.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
:number-of-orbits 2
:saa-model "31"
:si-bright-earth-limb-angle 20.0
:data-volume 661280
:tdrss-contact-duration 0
:coron NIL
)
(Tic-Obset
:proposal-id 18101
:visit-id "01"
:obset-id "01"
:pcs-mode "FGS"
)
(Tic-Orbit
:proposal-id 18101
:visit-id "01"
:orbit-number 1
:pcs-time 380
:si-vis-utilization 2667
:al-overhead-at-end 0
:internal-dur-at-end 114
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 3121
:pcs-gap 0
)
(Tic-Orbit
:proposal-id 18101
:visit-id "01"
:orbit-number 2
:pcs-time 380
:si-vis-utilization 2741
:al-overhead-at-end 0
:internal-dur-at-end 377
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 3121
:pcs-gap 0
)true20/Users/aidawofford/Downloads/OP-cache/18101_nov4-v02.xmlThe scheduling data was generated by CASM 33.1.CASM was run in Phase II mode.(Tic-Visit
:proposal-id 18101
:visit-id "02"
:proposal-version -1
:trans-version "20250624"
:date "05-Nov-2025 10:43:23.0"
:trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0
:FATAL-ERRORS 0 :CONTINUABLE-FATALS 0)
:number-of-orbits 2
:saa-model "31"
:si-bright-earth-limb-angle 20.0
:data-volume 121920
:tdrss-contact-duration 0
:coron NIL
)
(Tic-Obset
:proposal-id 18101
:visit-id "02"
:obset-id "02"
:pcs-mode "FGS"
)
(Tic-Orbit
:proposal-id 18101
:visit-id "02"
:orbit-number 1
:pcs-time 380
:si-vis-utilization 2741
:al-overhead-at-end 0
:internal-dur-at-end 57
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 3121
:pcs-gap 0
)
(Tic-Orbit
:proposal-id 18101
:visit-id "02"
:orbit-number 2
:pcs-time 380
:si-vis-utilization 2740
:al-overhead-at-end 0
:internal-dur-at-end 367
:dark-offset NIL
:dark-utilization 0
:max-dark-utilization 1920
:low-sky "N"
:pcs-visibility 3121
:pcs-gap 0
)true20