Repeated Stellar Wind Line Variability in O Stars in the SMC

0 Assigned ID: 3489 ----- Attempting Submission 1 (Fri Mar 25 20:05:32 GMT 2022) ----- HST Phase I Proposal 3489 successfully submitted. Receipt: # 3489-1 0 Repeated Stellar Wind Line Variability in O Stars in the SMC Massive stars dominate the space surrounding them, as the source of ionising flux, by the feedback from their winds and from dramatic cataclysmic events such as supernova. Understanding the physics of massive star winds is critical to various fields of astrophysics. A large area of tension is the so-called weak wind problem, with measured mass-loss rates from stellar winds from late O stars being lower than hydrodynamical predictions. In particular, it is suggested that the weak wind problem affects earlier O types within the low-metallicity galaxies, such as the SMC, compared to the Milky Way. However, for low-metallicity stars, these conclusions are based on only a very small number of analyzed stars. By inspecting the archival UV spectra of the commonly cited stars, we find that the wind lines of these stars are often variable. This variability appears to be cyclic, and hence resembling the ambiguous variability observed in Galactic O stars on time scales comparable to the rotational periods. This cyclic variability is commonly explained by the presence of large scale co-rotating structures within stellar winds. In low metallicity stars, this type of variability has never yet been studied but is urgently needed. We propose a highly efficient series of long slit UV spectrograph observations of seven late O type stars in NGC 346, the most massive star cluster in the SMC. Taken over 15 orbits, these observations will be equally spaced to monitor the variability of the CIV doublet 1548.2 - 1550.8 wind lines over multiple rotation periods of the targets. This will finally resolve questions about the structure of stellar winds at low metallicity. On each visit we will take 3 STIS G140M observations, covering 1513-1567A in the UV, of 6 O Stars. We will revisit them every 11 orbits until a total of 15 visits have been made. This is a revision of the Phase 1 proposal which proposed 7 O stars. This would have required mid-orbit reorientation. The time constraints needed to target acquire after such an orientation change would have limited our exposure time. Instead, we lose one of our lowest priority targets and observe in the same orientation throughout each visit. We target acquire NGC-346-NMC-17 (O8V) for accurate positioning of our first long slit exposure, and we use relative RA and DEC shifts to position our other two observations accurately. Coordinates are ICRS J2016 coordinates from Gaia DR3, verified on sky from archival Hubble F225W images. The relative offsets are confirmed in the same IRCS frame. We note the 3arcsec offset required due to the repeller wire (STIS IHB 7.6.1) and the fiducial bar, brought by this shift on to the used portion of the MAMA detector, the lowest Y axis position fiducial bar (STIS IHB 13.2.6) and ensure neither obscures our targets. The proper motion (PM) of NMC-17 is taken from Gaia DR3 and used to aid target acquisition. For the our other two slits, only one target within each has a proper motion. However, all objects are thought to be members of NGC 346 and this is shown by the common proper motion, as all three known proper motions are within the ranges PMRA 0.4 to 0.8 mas/yr and PMDEC -0.9 to -1.6 mas/yr. The inherited PMRA 0.8 mas/yr and PMDEC -1.6 mas/yr of NMC-17 is acceptable for the two other positions as the largest movement we might expect from the PM adjusted J2016 epoch during Cycle 30 is 0.01arcseconds. An orientation of either 79degrees or 259degrees North through East gives us best coverage of our targets. Due to the offset of the slit to the MAMA sensor, we cannot specify both, and so 259degrees is selected due to having the greater schedulability. This is given as 304degrees for our visits due to the 45degrees offset of STIS from the +U3 axis (P2PI Table 6.2). Due to the multiple objects within each slit and the requirement for a constant angle throughout each visit, not every target is centred within the dispersal axis. Despite this, experience of working with STIS G140M observations has shown that the loss of data in the dispersal direction is minimal and will not impact upon our science goals. We note that changing schedulability down to 80 percent does not reduce the the schedulability of our observations and enables us to exceed our target exposure time. Each visit is scheduled for a factor of 11 visits (+1/-1 visit) from Visit 1. This is to ensure that the program is not interrupted if one observation is missed due to technical reasons. Prof. L Oskinova is an expert in massive star stellar winds and has much experience with spectroscopic studies of massive stars. Mr. M. Rickard is a third-year PhD student with the subject of his PhD being the stellar winds of massive stars, with his first paper submitted for publication, detailing analysis of UV Spectrograph observations of O stars compared to Co-Moving Frame (CMF) model fits. Mr. D. Pauli is a second-year PhD student and has already published a paper on the observed wind profiles in massive star binaries. Prof. W. -R. Hamann, Prof. D. Massa and Prof. R. Prinja are leading experts in UV spectroscopy of stellar winds and stellar wind modelling. Dr. V. Ramachandran and Dr. R. Hainich have each published extensively on massive star observations and the model fitting of these observations. D. Pauli et al. 2022, A&A, 659, A9 The earliest O-type eclipsing binary in the Small Magellanic Cloud, AzV 476: A comprehensive analysis reveals surprisingly low stellar masses Ramachandran et al., 2019, A&A 625, A104 Testing massive star evolution, star formation history, and feedback at low metallicity. Spectroscopic analysis of OB stars in the SMC Wing Massa et al., 2019, ApJ, 873, 81 Coordinated UV and X-Ray Spectroscopic Observations of the O-type Giant ksi Per Hainich et al., 2019, A&A 621, 85 PoWR grids of non-LTE model atmospheres for OB-type stars of various metallicities Ramachandran, V.; Hamann, W.-R.; Hainich, R.; et al, 2018, A&A 615, 40 Stellar population of the superbubble N 206 in the LMC. II. Parameters of the OB and WR stars, and the total massive star feedback Hainich, R.; Oskinova, L. M.; Shenar, T.; et al., 2018, A&A, 609, 94 Observational properties of massive black hole binary progenitors Ramachandran, Varsha; Hainich, R.; Hamann, W.-R.; et al., 2018, A&A 609, 7 Stellar population of the superbubble N 206 in the LMC. I. Analysis of the Of-type stars Ramachandran, V.; Oskinova, L. M.; Hamann, W. -R. 2021 A&As, 646, A16, Discovery of O stars in the tidal Magellanic Bridge. Stellar parameters, abundances, and feedback of the nearest metal-poor massive stars and their implication for the Magellanic System ecology Stellar Physics and Stellar Types 6 false false true false false false false false SUPPORTED EXT-STAR MAIN SEQUENCE O NO SSN-18 MPG-487 J2000 EXT-STAR MAIN SEQUENCE O NO EXT-STAR MAIN SEQUENCE O NO STIS/FUV-MAMA Spectroscopic No No G140M 1540 1656944478820 Timing link suitability includes constraints ([02 After 01 by 0.7 to 0.8 days] [03 After 01 by 1.4 to 1.5 days] [04 After 01 by 2.1 to 2.2 days] [05 After 01 by 2.8 to 3.0 days] [06 After 01 by 3.6 to 3.7 days] [07 After 01 by 4.3 to 4.4 days] [08 After 01 by 5.0 to 5.2 days] [09 After 01 by 5.8 to 5.9 days] [10 After 01 by 6.5 to 6.6 days] [11 After 01 by 7.2 to 7.3 days] [12 After 01 by 7.9 to 8.1 days] [13 After 01 by 8.7 to 8.8 days] [14 After 01 by 9.4 to 9.5 days] [15 After 01 by 10.1 to 10.3 days]) The scheduling data was generated by CASM 30.3. CASM was run in Phase II mode. 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UV observations of 3 long slits covering 6 massive O star dwarfs 1692138959000 304.0 (Tic-Visit :proposal-id 17104 :visit-id "02" :proposal-version -1 :trans-version "20220516" :date "04-Jul-2022 15:21:19.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 226576 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17104 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17104 :visit-id "02" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2766 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3161 :pcs-gap 0 ) false 1 0 1656944481064 Timing link suitability includes constraints ([03 After 01 by 1.4 to 1.5 days]) The scheduling data was generated by CASM 30.3. CASM was run in Phase II mode. UV observations of 3 long slits covering 6 massive O star dwarfs 1692224480000 304.0 (Tic-Visit :proposal-id 17104 :visit-id "03" :proposal-version -1 :trans-version "20220516" :date "04-Jul-2022 15:21:20.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 226576 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17104 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17104 :visit-id "03" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2766 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3161 :pcs-gap 0 ) false 1 0 1656944482159 Timing link suitability includes constraints ([04 After 01 by 2.1 to 2.2 days]) The scheduling data was generated by CASM 30.3. CASM was run in Phase II mode. UV observations of 3 long slits covering 6 massive O star dwarfs 1692309992000 304.0 (Tic-Visit :proposal-id 17104 :visit-id "04" :proposal-version -1 :trans-version "20220516" :date "04-Jul-2022 15:21:22.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 226576 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17104 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17104 :visit-id "04" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2766 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3161 :pcs-gap 0 ) false 1 0 1656944483225 Timing link suitability includes constraints ([05 After 01 by 2.8 to 3.0 days]) The scheduling data was generated by CASM 30.3. CASM was run in Phase II mode. UV observations of 3 long slits covering 6 massive O star dwarfs 1692389798000 304.0 (Tic-Visit :proposal-id 17104 :visit-id "05" :proposal-version -1 :trans-version "20220516" :date "04-Jul-2022 15:21:23.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 226576 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17104 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17104 :visit-id "05" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2766 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3161 :pcs-gap 0 ) false 1 0 1656944484297 Timing link suitability includes constraints ([06 After 01 by 3.6 to 3.7 days]) The scheduling data was generated by CASM 30.3. CASM was run in Phase II mode. UV observations of 3 long slits covering 6 massive O star dwarfs 1692481001000 304.0 (Tic-Visit :proposal-id 17104 :visit-id "06" :proposal-version -1 :trans-version "20220516" :date "04-Jul-2022 15:21:24.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 226576 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17104 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17104 :visit-id "06" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2766 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3161 :pcs-gap 0 ) false 1 0 1656944485357 Timing link suitability includes constraints ([07 After 01 by 4.3 to 4.4 days]) The scheduling data was generated by CASM 30.3. CASM was run in Phase II mode. UV observations of 3 long slits covering 6 massive O star dwarfs 1692555100000 304.0 (Tic-Visit :proposal-id 17104 :visit-id "07" :proposal-version -1 :trans-version "20220516" :date "04-Jul-2022 15:21:25.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 226576 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17104 :visit-id "07" :obset-id "07" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17104 :visit-id "07" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2766 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3161 :pcs-gap 0 ) false 1 0 1656944486429 Timing link suitability includes constraints ([08 After 01 by 5.0 to 5.2 days]) The scheduling data was generated by CASM 30.3. CASM was run in Phase II mode. UV observations of 3 long slits covering 6 massive O star dwarfs 1692646288000 304.0 (Tic-Visit :proposal-id 17104 :visit-id "08" :proposal-version -1 :trans-version "20220516" :date "04-Jul-2022 15:21:26.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 226576 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17104 :visit-id "08" :obset-id "08" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17104 :visit-id "08" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2766 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3161 :pcs-gap 0 ) false 1 0 1656944487492 Timing link suitability includes constraints ([09 After 01 by 5.8 to 5.9 days]) The scheduling data was generated by CASM 30.3. CASM was run in Phase II mode. UV observations of 3 long slits covering 6 massive O star dwarfs 1692726083000 304.0 (Tic-Visit :proposal-id 17104 :visit-id "09" :proposal-version -1 :trans-version "20220516" :date "04-Jul-2022 15:21:27.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 226576 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17104 :visit-id "09" :obset-id "09" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17104 :visit-id "09" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2766 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3161 :pcs-gap 0 ) false 1 0 1656944488587 Timing link suitability includes constraints ([10 After 01 by 6.5 to 6.6 days]) The scheduling data was generated by CASM 30.3. CASM was run in Phase II mode. UV observations of 3 long slits covering 6 massive O star dwarfs 1692811576000 304.0 (Tic-Visit :proposal-id 17104 :visit-id "10" :proposal-version -1 :trans-version "20220516" :date "04-Jul-2022 15:21:28.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 226576 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17104 :visit-id "10" :obset-id "10" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17104 :visit-id "10" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2766 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3161 :pcs-gap 0 ) false 1 0 1656944490218 Timing link suitability includes constraints ([11 After 01 by 7.2 to 7.3 days]) The scheduling data was generated by CASM 30.3. CASM was run in Phase II mode. UV observations of 3 long slits covering 6 massive O star dwarfs 1692897068000 304.0 (Tic-Visit :proposal-id 17104 :visit-id "11" :proposal-version -1 :trans-version "20220516" :date "04-Jul-2022 15:21:30.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 226576 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17104 :visit-id "11" :obset-id "11" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17104 :visit-id "11" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2766 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3161 :pcs-gap 0 ) false 1 0 1656944491235 Timing link suitability includes constraints ([12 After 01 by 7.9 to 8.1 days]) The scheduling data was generated by CASM 30.3. CASM was run in Phase II mode. UV observations of 3 long slits covering 6 massive O star dwarfs 1692982558000 304.0 (Tic-Visit :proposal-id 17104 :visit-id "12" :proposal-version -1 :trans-version "20220516" :date "04-Jul-2022 15:21:31.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 226576 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17104 :visit-id "12" :obset-id "12" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17104 :visit-id "12" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2766 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3161 :pcs-gap 0 ) false 1 0 1656944492287 Timing link suitability includes constraints ([13 After 01 by 8.7 to 8.8 days]) The scheduling data was generated by CASM 30.3. CASM was run in Phase II mode. UV observations of 3 long slits covering 6 massive O star dwarfs 1693090845000 304.0 (Tic-Visit :proposal-id 17104 :visit-id "13" :proposal-version -1 :trans-version "20220516" :date "04-Jul-2022 15:21:32.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 226576 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17104 :visit-id "13" :obset-id "13" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17104 :visit-id "13" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2766 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3161 :pcs-gap 0 ) false 1 0 1656944493350 Timing link suitability includes constraints ([14 After 01 by 9.4 to 9.5 days]) The scheduling data was generated by CASM 30.3. CASM was run in Phase II mode. UV observations of 3 long slits covering 6 massive O star dwarfs 1693153536000 304.0 (Tic-Visit :proposal-id 17104 :visit-id "14" :proposal-version -1 :trans-version "20220516" :date "04-Jul-2022 15:21:33.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 226576 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17104 :visit-id "14" :obset-id "14" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17104 :visit-id "14" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2766 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3161 :pcs-gap 0 ) false 1 0 1718376454293 Timing link suitability includes constraints ([15 After 01 by 10.1 to 10.3 days]) The scheduling data was generated by CASM 30.3. 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