Added 3 arcsec to POSTARG-Y for all primary exposures with the FUVMAMA to counteract the fact that the APT does not accurately reflect the 3 arcsec offset of targets in this mode (to avoid repeller wire shadow). ----- Attempting Submission 1 (Tue Jun 17 16:18:49 GMT 2008) ----- Phase II Proposal 11665 (11665.apt) successfully submitted. ----- Attempting Submission 2 (Wed Jul 02 16:18:03 GMT 2008) ----- ----- Attempting Submission 3 (Mon Sep 29 17:55:33 GMT 2008) ----- Assigned ID: 131 ----- Attempting Submission 1 (Thu Mar 06 14:11:26 GMT 2008) ----- The Formation Mechanisms of Extreme Horizontal Branch Stars Blue hook stars are a class of hot (~35,000 K) subluminous extreme horizontal branch (EHB) stars that have been recently discovered using HST ultraviolet images of the massive globular clusters omega Cen and NGC 2808. These stars occupy a region of the HR diagram that is unexplained by canonical stellar evolution theory. Using new theoretical evolutionary and atmospheric models, we have shown that the blue hook stars are very likely the progeny of stars that undergo extensive internal mixing during a late helium core flash on the white dwarf cooling curve. This "flash mixing" produces an enormous enhancement of the surface helium and carbon abundances (relative to the abundance pattern that existed on the main sequence), which suppresses the observed flux in the far-UV. Because stars born with a high helium abundance are more likely to evolve into hot horizontal branch stars, flash mixing is more likely to occur in those massive clusters capable of helium self-enrichment. However, a high initial helium abundance, by itself, is not sufficient to explain the presence of a blue hook population - flash mixing of the envelope is also required. We propose far-UV spectroscopy of normal and subluminous EHB stars in NGC 2808 that will unambiguously test this new formation mechanism. These observations will easily detect the helium and carbon enhancements predicted by flash mixing and will therefore determine if flash mixing represents a new evolutionary channel for populating the hot end of the EHB. More generally, our observations will help to clarify the role of helium self-enrichment in producing blue horizontal branch morphologies and multiple main sequences in massive globular clusters. Finally, these results will provide new insight into the origin and abundance anomalies of the hot helium-rich subdwarf B and O stars in the Galactic field.
The spectra of approximately 30 HB stars will be obtained by placing the STIS 52x2 arcsec slit at 3 positions, with 5 orbits spent in each position. To help with scheduling, each position is observed in two visits of 2 and 3 orbits. Each 3-orbit visit consists of an ACQ on an offset star, an offset to one of these 3 positions, a brief CCD image through the slit to obtain accurate positions of the stars relative to the slit midline, and the G140L spectroscopy. The 2-orbit visit is similar but does not repeat the image through the slit. The 5 spectroscopic exposures taken at each position dither the slit to different positions parallel to the slit, to smooth the detector response and remove hot pixels in both the prime (STIS) and parallel (WFC3) data. This field has been imaged by STIS previously, and is safe for FUVQTZ imaging or spectroscopy. In parallel, we will obtain 5-band WFC3 imaging in the UVIS (F390W, F555W, and F814W) and IR (F110W and F160W) channels. Exposure times have been staggered to increase dynamic range. Dithering options are limited by the prime science, but will be sufficient for data masking and PSF resampling in one axis. RESOLVED STELLAR POPULATIONS 12 false 0.0 0.0 false false false false false AVAILABLE STELLAR CLUSTER GLOBULAR CLUSTER The V-mag and flux values are for the most UV-bright object in the field (NGC2808-UIT1), with previous UV imaging and spectroscopy by STIS. This object wil not be in the slit in this program. Orient of the slit for this target should be 25.5+/-180. B-V=0.1, F-CONT(1425)=5E-14, E(B-V)=0.23 J2000 09 12 3.7600 -64 51 37.24 J2000 STELLAR CLUSTER GLOBULAR CLUSTER The V-mag and flux values are for the most UV-bright object in the field (NGC2808-UIT1), with previous UV imaging and spectroscopy by STIS. This object wil not be in the slit in this program. Orient of the slit for this target should be 325.5+/-180. B-V=0.1, F-CONT(1425)=5E-14, E(B-V)=0.23 J2000 09 12 3.7600 -64 51 37.24 J2000 STELLAR CLUSTER GLOBULAR CLUSTER The V-mag and flux values are for the most UV-bright object in the field (NGC2808-UIT1), with previous UV imaging and spectroscopy by STIS. This object wil not be in the slit in this program. Orient of the slit for this target should be 14.8+/-180. B-V=0.1, F-CONT(1425)=5E-14, E(B-V)=0.23 J2000 09 12 3.7600 -64 51 37.24 J2000 STAR K III-I This star was used as the acquisition object in an earlier program by Wayne Landsman (7436) to obtain STIS spectroscopy of the UV-bright post-AGB star NGC2808-UIT1. B-V=1.74 J2000 09 12 3.7600 -64 51 37.24 J2000 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/CCD Imaging No No 50CCD STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/CCD Imaging No No 50CCD STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/CCD Imaging No No 50CCD WFC3/UVIS Imaging No No F390W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F814W WFC3/IR Imaging No No F110W WFC3/IR Imaging No No F160W WFC3/UVIS Imaging No No F390W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F814W WFC3/IR Imaging No No F110W WFC3/IR Imaging No No F160W WFC3/UVIS Imaging No No F390W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F814W WFC3/IR Imaging No No F110W WFC3/IR Imaging No No F160W The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. /private/tmp/OPVisit56479.xml (Tic-Visit :proposal-id 11665 :visit-id "01" :proposal-version -1 :trans-version "20080807" :date "29-Sep-2008 13:35:39.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 5125904 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11665 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11665 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3198 :al-overhead-at-end 126 :internal-dur-at-end 804 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11665 :visit-id "01" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3336 :al-overhead-at-end 126 :internal-dur-at-end 804 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11665 :visit-id "01" :orbit-number 3 :pcs-time 195 :si-vis-utilization 3336 :al-overhead-at-end 126 :internal-dur-at-end 1066 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) true 3 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. /private/tmp/OPVisit56480.xml (Tic-Visit :proposal-id 11665 :visit-id "02" :proposal-version -1 :trans-version "20080807" :date "29-Sep-2008 13:35:43.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 3108976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11665 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11665 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3198 :al-overhead-at-end 126 :internal-dur-at-end 804 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11665 :visit-id "02" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3336 :al-overhead-at-end 126 :internal-dur-at-end 608 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. /private/tmp/OPVisit56481.xml (Tic-Visit :proposal-id 11665 :visit-id "03" :proposal-version -1 :trans-version "20080807" :date "29-Sep-2008 13:35:48.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 5125904 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11665 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11665 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3198 :al-overhead-at-end 126 :internal-dur-at-end 804 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11665 :visit-id "03" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3336 :al-overhead-at-end 126 :internal-dur-at-end 804 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11665 :visit-id "03" :orbit-number 3 :pcs-time 195 :si-vis-utilization 3336 :al-overhead-at-end 126 :internal-dur-at-end 1066 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) true 3 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. /private/tmp/OPVisit56482.xml (Tic-Visit :proposal-id 11665 :visit-id "04" :proposal-version -1 :trans-version "20080807" :date "29-Sep-2008 13:35:50.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 3108976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11665 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11665 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3198 :al-overhead-at-end 126 :internal-dur-at-end 804 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11665 :visit-id "04" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3336 :al-overhead-at-end 126 :internal-dur-at-end 608 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. /private/tmp/OPVisit56483.xml (Tic-Visit :proposal-id 11665 :visit-id "05" :proposal-version -1 :trans-version "20080807" :date "29-Sep-2008 13:35:55.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 5125904 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11665 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11665 :visit-id "05" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3198 :al-overhead-at-end 126 :internal-dur-at-end 804 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11665 :visit-id "05" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3336 :al-overhead-at-end 126 :internal-dur-at-end 804 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11665 :visit-id "05" :orbit-number 3 :pcs-time 195 :si-vis-utilization 3336 :al-overhead-at-end 126 :internal-dur-at-end 1066 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) true 3 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. /private/tmp/OPVisit56484.xml (Tic-Visit :proposal-id 11665 :visit-id "06" :proposal-version -1 :trans-version "20080807" :date "29-Sep-2008 13:35:58.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 3108976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11665 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11665 :visit-id "06" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3198 :al-overhead-at-end 126 :internal-dur-at-end 804 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11665 :visit-id "06" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3336 :al-overhead-at-end 126 :internal-dur-at-end 608 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3531 :pcs-gap 0 ) true 2 0