0 Assigned ID: 711 ----- Attempting Submission 1 (Fri Apr 05 20:23:50 GMT 2019) ----- 1. This plan is nearly a copy of visits used in program 15812, Jan-May 2020. ----- 2. Brightness limits for STIS/MAMA are worth noting for this object. See various comments for Visit 4. Here our safety precautions are the same as we used in some previous MAMA observations.l ----- 3. The Target Confirmation Charts Tool is useless for Eta Carinae, because it's in a very crowded region with bright nebulosity, which GSC was apparently unable to cope with. See point 5 below. BOT is also useless, for similar reasons. See comments for visit 4. ----- 4. Like all successful HST programs on this target since 1998, the acquisition uses special catalog ZZZQ. Comparisons with Gaia show that ZZZQ is very good except for a small number of unusually bad stars. If we can get information on which acquisition/guide stars will be chosen, then we can confirm whether they're OK (and they probably will be). So far, ZZZQ has never failed; but we are especially worried for this program because it concerns a one-time event. ----- -1465223303 ----- Attempting Submission 1 (Wed Jul 24 18:13:30 GMT 2019) ----- ----- Attempting Submission 2 (Tue Jun 23 21:31:48 GMT 2020) ----- Eta Car, the only giant eruption survivor that can be studied well, has been unsteady in recovering from the 1830-1870 explosion. About 20 years ago its spectroscopic and photometric trends dramatically accelerated -- signaling a rapid decrease in the primary mass loss rate. This is a novel clue to the stellar interior's thermal and rotational disequilibrium following the eruption. Meanwhile, "spectroscopic events" occur at 5.54-year intervals marking the companion star's periastron. HST showed that the basic nature of these events changed between 2003 and 2014 --but we do not know whether this change was temporary, or permanent, or the precursor to something more extreme. Hence the next spectroscopic event, in early 2020, is crucial. For reasons noted in the proposal, ground-based instruments have inadequate spatial resolution for this purpose, and can't observe the UV. 2020 will be our last opportunity for HST spectroscopy, and the star will be irreversibly changed when suitable instruments become available sometime in the future. Therefore we propose an adequate set of STIS/CCD and STIS/MAMA observations. They will be valuable for a wide range of topics including stellar instabilities, colliding-wind physics, and abnormal emission-line processes as well as eta Car's recovery from a giant eruption. Eta Car's periastron spectroscopic event occurred in January-April 2020, and was observed in HST program 15812. This program, 16176, consists of 2 visits to sample the spectrum well after the event. We followed a similar procedure for the preceding event in 2014-2015. ** These are expected to be the last HST observations of eta Carinae, 30 years after the first ones. ** -- ---- ((( Original description for program 15812, written in 2019, follows below. ))) ---- Eta Car's periastron spectroscopic event will occur mainly in January-April 2020. This program samples it with STIS-CCD in 7 one-orbit visits, plus a single orbit for STIS-MAMA near the middle of the event. Much later, 2 more orbits in Cycle 28 will show the post-event state of the object. --- Each CCD visit includes several critical wavelength intervals. Approximately in decreasing order of spectroscopic priority, these are -- (1) Interval 4570-4840 A using grating G430M. This includes the exotic HeII 4687 flash, the EUV-excited N II 4600 multiplet, a significant He I feature, and useful low-excitation features. (2) 6490-7040 A using G750M. The H-alpha line profile changes dramatically during an event, and so does He I 6680. This also provides photometry of the red continuum. (3) 2760-2910 A using G230MB. This includes the bright Mg II emission feature, plus necessary UV continuum photometry. (4) 3800-4070 A using G430M. This range includes a variety of diagnostics including high-order Balmer lines, Ca H & K, and He I. In addition, we also use low-dispersion gratings G230LB and G430L for photometry across the broad wavelength range 1700-5500 A. A secondary purpose of the low-dispersion spectrum is to detect any major unexpected changes outside the main wavelength ranges listed above. --- Incidentally, these slit spectra also provide useful information about ejecta located 0.2 to 4 arcsec from the star. (But the star is far more important for our goals.) --- The STIS-CCD exposure times range from 0.2 to 150 seconds (totals of CR-SPLITS). For practical reasons they are not done in order of scientific priority. In order to obtain sufficient schedulability throughout the January-April time interval, the usable time in each orbit is reduced by several minutes. --- In the MAMA visit, echelles E140M and E230M cover the entire attainable UV range 1300-3100 A,, using the FUV and NUV detectors respectively. Exposures of several hundred seconds give high S/N, so the combination fits well into one orbit. Regarding detector brightness limits, we apply a double test: specific count rates were found in earlier observations of the same type, and CCD visits 1 and 2 will give information about the current UV brightness level. See comments in Visit 4.. --- Concerning HST's gyro issue: 1-gyro operation would most likely cause a shortage of visibility windows during the 4-month event. In that case we would need to heavily revise the plan -- for instance, reducing the number of observations per visit might allow more time-windows, and/or we might need to accept sparser temporal sampling.. Meanwhile, depending on gyro performance and jitter amounts, we might need to use the 52x0.2 slit instead of 52x0.1. This would be acceptable for the main science goals. --- The PI, Dr. Kris Davidson has more than 20 years experience with HST data. He has led the numerous STIS proposals on eta Car since 1998 and the HST Treasury Program on eta Car, one of the first three treasury programs in 2003. He is responsible for program oversight and leads the analysis of the stellar wind from the CCD spectra. Dr John Marin has been a co-I on the eta Car programs since 2003. He is responsible for resonstruction of the multi-wavelength photometry and light curves. Co-I Dr. Kazunori Ishibashi is experienced with observations from X-ray through near-IR. He is primarily responsible for reduction of the STIS CCD and MAMA data and focuses on the analysis of UV spectra. Co-I Dr. Roberta Humphreys is an experienced HST user on this program as well as other HST programs on massive stars. This team has over 30 refereed publications on eta Car, most based on HST observations. Stellar Physics 0 false false true false false false false SUPPORTED STAR ETA CARINAE STAR Special catalog ZZZQ was prepared in 1989 because the original HST GSC was very poor in this crowded nebular region. Later GSC, and especially GAIA, would _probably_ be OK for Eta Car acquisition. However, ZZZQ was used for nearly every successful Eta Car HST observation 1991--2018, and it never failed. Absolute position of Eta Car is still uncertain at the 0.2 arcsec level, even with GAIA, because this object has asymmetric structure at every size scale. The RA and dec listed here were used for successful programs in 2014 and 2018. J2000 J2000 STIS/CCD Spectroscopic No No G750M 6768 STIS/CCD Spectroscopic No No G430M 3936 STIS/CCD Spectroscopic No No G430M 4706 STIS/CCD Spectroscopic No No G430L 4300 STIS/CCD Spectroscopic No No G230MB 2836 STIS/CCD Spectroscopic No No G230LB 2375 STIS/CCD Spectroscopic No No G750M 6768 STIS/CCD Spectroscopic No No G430M 3936 STIS/CCD Spectroscopic No No G430M 4706 STIS/CCD Spectroscopic No No G430L 4300 STIS/CCD Spectroscopic No No G230LB 2375 STIS/CCD Spectroscopic No No G230MB 2836 STIS/FUV-MAMA Spectroscopic No No E140M 1425 STIS/NUV-MAMA Spectroscopic No No E230M 1978 1592941999196 Timing link suitability includes constraints ([02 After 01 by 10.0 to 30.0 days]) The scheduling data was generated by CASM 28.2. CASM was run in Phase II mode. This visit was preceded by 7 CCD visits in program 15812, covering eta car's periastron event in 2020. Unlike them, this visit does not have severe timing requirements. -- Historical note: . Program 16176 will most likely be the last HST coverage of eta Car. For almost 30 years, in several respects this object was repeatedly the most successful stellar HST target -- mainly because it is bright enough, complex enough, and variable enough to demonstrate HST's capabilities for spatial resolution plus UV coverage. (Tic-Visit :proposal-id 16176 :visit-id "01" :proposal-version -1 :trans-version "20200518" :date "23-Jun-2020 14:53:18.0" :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 142672 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16176 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16176 :visit-id "01" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2491 :al-overhead-at-end 246 :internal-dur-at-end 320 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3389 :pcs-gap 0 ) true 1 0 Because of the crowded field, special catalog ZZZQ has been used for almost every successful HST acquisition of eta Car since 1991. We use wavelength interval 7795 because it is relatively free of narrow emission lines produced in blobs at r = 0.2 arcsec. Shorter wavelengths would be better in other respects, but they can be perturbed by the extraneous off-center emission lines. Ultra-short exposure for bright H-alpha emission profile. WAVECAL=NO because we are explicitly managing the WCALs. Throughout this program we restrict SIZEAXIS2 to avoid buffer dump. Some H-alpha pixels will be saturated in this exposure. WAVECAL=NO because we are explicitly managing the WCALs. We use explicit WCALs for two reasons: (1) Some may be omitted if not needed for program goals, and (2) this may help to force a WCAL into the occultation period after last science exposure. Extremely important wvl interval for He II 4687 and rad-exc N II features. WAVECAL=NO because we manage the WCALs explicitly. WAVECA:L after orbit visibility time. 1592943506742 Timing link suitability includes constraints ([02 After 01 by 10.0 to 30.0 days]) The scheduling data was generated by CASM 28.2. CASM was run in Phase II mode. Re. MAMA brightness limits: In March 2020, visit 04 of program 15812 also used MAMA on this target. See notes and correspondence about that case. As we did in past MAMA observations of this star, we'll use the preceding CCD visit (STIS-CCD-8) to confirm that the UV has not brightened by a dangerous amount. -- Note that eta Car's progressive brightening has a timescale of years -- i.e., this is not an irregular variable in the context of MAMA safety limits. -- Additional detail: If the UV brightness approaches the safety limits, we can reduce the overall count rates by using a smaller MAMA aperture. -- (Tic-Visit :proposal-id 16176 :visit-id "02" :proposal-version -1 :trans-version "20200518" :date "23-Jun-2020 15:18:26.0" :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 174976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16176 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16176 :visit-id "02" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2529 :al-overhead-at-end 0 :internal-dur-at-end 394 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3389 :pcs-gap 0 ) true 1 0 This ACQ plan is copied from program 15067, done in 2018. This ACQ plan is copied from program 15067, done in 2018. Re. BRIGHTNESS LIMITS: -- ((Remarks written in 2019 for program 15812:)) ETC is only a rough guide for this object, because the spectrum is extremely complex and changes during the spectroscopic event. Real observed count rates are better. On 21 April 2018, E230M produced 6.6 cts/s in the maximum pixel, and 143,000 cts/s in the entire detector. On average, Eta Car is brightening about 12 percent per year in the UV -- EXCEPT that it has always become temporarily fainter during each spectroscopic event. --- In order to verify that Eta Car has not brightened by a dangerous amount, we will examine CCD-G230LB and CCD-G230MB data from visits 1 and 2. --- Note that this object is not a strong irregular variable in the sense used for brightness limits. Absorption lines have caused rapid UV _decreases_ in previous spectroscopic events, but there have been no strong rapid increases in UV emission. -- ((Later remarks, June 2020:)) Program 15812 followed the above plan and was successful. Its MAMA visit was done in March 2020. In the same way, program 16176 uses a fresh CCD visit to verify that the UV brightness is still safe for MAMA. If the brightness has become uncomfortably bright by late 2020 or early 2021, we can reduce the count rates by using a smaller MAMA aperture. -- ((Remarks written in 2019 for program 15812:)) Re. BRIGHTNESS LIMITS: ETC is only a rough guide for this object, because the spectrum is extremely complex and changes during the spectroscopic event. Real observed count rates are better. On 21 April 2018, E140M produced 0.5 cts/s in the maximum pixel, and 75,000 cts/s in the entire detector. On average, Eta Car is brightening about 12 percent per year in the UV -- EXCEPT that it has always become temporarily fainter during each spectroscopic event. --- In order to verify that Eta Car has not brightened by a dangerous amount, we will examine CCD-G230LB and CCD-G230MB data from visits 1 and 2. --- Note that this object is not a strong irregular variable in the sense used for brightness limits. Absorption lines have caused rapid UV _decreases_ in previous spectroscopic events, but there have been no strong rapid increases in UV emission. -- ((Remarks in June 2020, for program 16176:)) The above approach was successful, see comments for the NUV1978 observation, --