Edge-on, optically thin, debris disks provide unique opportunities to probe physical properties of the disk itself. Using the host star as the background source, trace atomic and molecular disk species can be detected in absorption. Redfield (2007) found that the recently discovered edge-on system, HD32297, has the strongest NaI absorption feature of any known debris disk, 5 times the level observed toward beta Pic, the canonical edge-on debris disk. Roberge et al. (2006) compiled the only comprehensive chemical inventory of a debris disk, using beta Pic, and found that carbon was surprisingly overabundant, which has important implications for the physical structure and support of a stable gas disk. What is severely lacking are comparison observations to determine if such an abundance pattern is typical of debris disk systems. HD32297 represents the best opportunity to make such a comparative study and perform a comprehensive gas inventory of a debris disk, due to its high NaI column density. The UV is critical for this work due to the large number of strong transitions (almost 50 ions and molecules are accessible) that are located in, and often only in, the UV. These observations will provide a much needed comparison dataset for addressing the gas chemistry of debris disk systems that are at the critical stage, near the end of planet formation, and in the process of clearing their interplanetary environments.

Target Selection and Availability: Edge-on debris disk systems are rare, and only a handful of local systems are known. These fortuitously aligned optically thin disks provide an opportunity to search for trace molecules along the long pathlength from the host star through the disk. HD32297, an A0 star, shows the largest NaI atomic absorption of any edge-on debris disk, 5 times that of beta Pic, and therefore is the best target to search for atomic and molecular absorption signatures caused by gas in the debris disk. Comparison Spectra: The separation of the interstellar and circumstellar absorption components (>4 km/s) is on the order of the resolution of the proposed observations (R ~ 110,000, or ~2.7 km/s), and therefore if both circumstellar and interstellar components are present for a particular transition, they will be partially resolved by the high resolution gratings of STIS. However, since they are not expected to be fully unblended, we will use two strategies to make an accurate measurement of the circumstellar component: (1) Comparison spectra of nearby stars (HD34203 and HD34204), which are located close to HD32297 in the sky (<5 degrees) and at a comparable distance will be observed in order to identify which transitions in fact do show significant interstellar absorption and at what strength. (2) For those that do show interstellar absorption we will use the velocity structure identified at ultra-high resolution in NaI by Redfield (2007) in order to accurately model the line profile shape by constraining the velocity difference between the two components which will be partially resolved at the high spectral resolution of STIS. The short comparison observations of nearby stars will be used to reconstruct the interstellar contribution to the full absorption profile observed toward HD32297 for some of the strongest atomic transitions. Two stars are selected, a bright (V = 5.5) A0V star (HD34203) which is located only 5.1 degrees from HD32297 and has an identical parallax that places it at ~112 pc. The second comparison star (HD34204) is a bright (V = 6.9) G5 star only ~2.5 arcminutes from HD32297 and located at a comparable distance of ~134 pc. Two comparison stars are selected because HD34203, the A0V star, exceeds the brightness limit in the near-UV, and therefore will only be used to obtain spectra in the far-UV settings, while HD34204, the G5 star, can be used to quickly obtain the near-UV comparison spectra. In addition, the two sight lines will provide an indication of any small-scale variations in the interstellar medium along these very similar sight lines. This will enable us to place a more stringent constraint on the strength of the ISM lines observed in the spectra of HD32297. Note that these comparison spectra need not be obtained in the same visit as HD32297. Also note that not all transitions that show circumstellar absorption will also show interstellar absorption (e.g., transitions from an excited level). Desired Spectral Resolution: This program benefits from the high spectral resolution (R ~ 110,000) available with STIS, and therefore will utilize the E140H and E230H gratings with the narrow slit (0.2x0.09). Redfield (2007) observed the NaI transition in the optical at ultra-high spectra resolution (R ~ 240,000) and was able to resolve the circumstellar and interstellar absorption profiles. The velocity separation was >4 km/s, which is slightly larger than the the highest resolution available with STIS (~2.7 km/s) indicating that the circumstellar and interstellar absorption components should still be partially resolved. Note that not all transitions will show interstellar transitions (e.g., molecular transitions and atomic transitions from an excited level). Indeed several ions (e.g., CI, AlI, SiII, SI, FeII) showed gas disk absorption in excited transitions toward beta Pic, with no contaminating interstellar feature (Lagrange et al. 1998). Desired Spectral Coverage: In order to observe the strongest transitions of almost 50 different ions and molecules, observations of almost the entire UV spectral range are required. Using the highest resolution gratings (i.e., E140H and E230H), this can be achieved using only 7 different settings. We propose to use the E140H grating centered at 1271 and 1526 Angstroms, in order to cover the far-UV spectral region, and the E230H grating centered at 1763, 2013, 2413, 2713, and 2962 Angstroms, in order to cover the near-UV spectral region. All critical transitions are covered by these settings, along with many more supporting transitions of the same ions and molecules but different opacities. All transitions of a given ion or molecule can be fit simultaneously in order to increase the dynamic range of the observed column density, as well as reduce the impact of systematic errors, such as continuum placement. Desired Signal-to-Noise: In order to detect a wide range of absorption features, a moderately high S/N is required. Lagrange et al. (1998) measured ~65 circumstellar absorption lines toward beta Pic from only ~180 Angstroms using spectra with a S/N of approximately 25. Likewise, CO and CI gas features in the beta Pic disk were analyzed by Roberge et al. (2000) with spectra taken with a S/N ~ 10. Although fainter than beta Pic, HD32297 is a significantly early spectral type (A0, as opposed to A6), and therefore has a strong UV continuum that extends well into the far-UV. We use the STIS Exposure Time Calculator, with (1) an A0V spectral model scaled to the brightness of HD32297 and (2) the well calibrated Vega spectrum, also an A0V star, scaled to the brightness of HD32297, in order to estimate the exposure time needed to achieve a S/N ~ 25 for each setting. The three shortest wavelength settings require roughly a full orbit in order to obtain the desired S/N, while the four longest wavelength settings can be paired, and the S/N for each setting can be obtained in roughly half an orbit. A single orbit is sufficient to obtain high S/N spectra of the comparison star spectra (three settings for HD34203, and two settings for HD34204). Brightness Limits: Our primary target, HD32297, will not violate the brightness limits of STIS, given we are observing in the highest resolution modes (E140H and E120H) and in a narrow slit (0.2x0.09). One of our comparison objects, HD34203, an even brighter A0 star, will only be observed at the shortest wavelengths (E140H centered at 1271 and 1526 Angstroms, and E230H only at the 1763 Angstrom setting) and through a very narrow slit (0.1x0.03). Our second comparison star, with a G5 spectral type, will not violate the brightness limit and will be used to cover the longer wavelength settings (E230H centered at 2713 and 2962 Angstroms), observed through the nominal slit (0.2x0.09). ISM AND CIRCUMSTELLAR MATTER 12 false 0.0 0.0 false false false false false false SUPPORTED STAR A0-A3 V-IV CIRCUMSTELLAR MATTER Coordinates and proper motion are from the Hipparcos Output Catalog. Fluxes derived from HST observations of stars of similar spectral type. Type=A0, B-V=0.199 +/- 0.014, E(B-V)=0.0, F-CONT(1271) = 1.4 +/- 0.4 E-14, F-CONT(1526) = 2.5 +/- 0.9 E-12, F-CONT(1763) = 4.3 +/- 1.1 E-12, F-CONT(2013) = 3.5 +/- 0.5 E-12, F-CONT(2413) = 2.4 +/- 0.2 E-12, F-CONT(2713) = 2.3 +/- 0.2 E-12, F-CONT(2962) = 2.3 +/- 0.2 E-12 BD+07D777 J2000 05 02 27.4366 +07 27 39.68 J2000 STAR A0-A3 V-IV Coordinates and proper motion are from the Hipparcos Output Catalog. Fluxes derived from HST observations of stars of similar spectral type. This target leads to a Health and Safety flag for the global count rate when run through the BOT. Hipparcos identifies this star as an A0V (Cowley+ 1969 label it a A0V and Osawa 1959 label it a A0III). The Hipparcos B-V color is consistent with a A0 star and is measured at -0.012 +/- 0.005. Although the BOT has the appropriate B-V color (listed at -0.01), it has an incorrect spectral type of "**O5V**". If the BOT is using the spectral type of an O5V star, then it is grossly overestimating the flux. Using stellar models and Vega (the canonical A0V star) as template spectra in the STIS ETC, there should be little to no risk of approaching the global count rate limit. Indeed, all estimates are <59,000 counts/sec over the entire detector. Type=A0V, B-V=-0.012 +/- 0.005, E(B-V)=0.0, F-CONT(1271) = 1.4 +/- 0.3 E-13, F-CONT(1526) = 4.0 +/- 0.4 E-11, F-CONT(1763) = 4.8 +/- 1.3 E-11 18ORI HR1718 J2000 05 16 4.1341 +11 20 28.87 J2000 STAR EMISSION LINE STAR G V-IV Coordinates and proper motion are from the Hipparcos Output Catalog. Fluxes derived from HST observations of stars of similar spectral type. Type=G5, B-V=0.958 +/- 0.009, E(B-V)=0.0, F-CONT(2713) = 4.7 +/- 0.9 E-13, F-CONT(2962) = 1.2 +/- 0.3 E-12, F-LINE(2796) = 1.4 +/- 0.7 E-12, W-LINE(2796) = 0.65 +/- 0.07 BD+07D778 J2000 05 02 31.4738 +07 25 26.51 J2000 STIS/FUV-MAMA Spectroscopic No No E140H 1271 STIS/FUV-MAMA Spectroscopic No No E140H 1526 STIS/NUV-MAMA Spectroscopic No No E230H 1763 STIS/NUV-MAMA Spectroscopic No No E230H 2013 STIS/NUV-MAMA Spectroscopic No No E230H 2413 STIS/NUV-MAMA Spectroscopic No No E230H 2713 STIS/NUV-MAMA Spectroscopic No No E230H 2962 STIS/FUV-MAMA Spectroscopic No No E140H 1271 STIS/FUV-MAMA Spectroscopic No No E140H 1526 STIS/NUV-MAMA Spectroscopic No No E230H 1763 STIS/NUV-MAMA Spectroscopic No No E230H 2713 STIS/NUV-MAMA Spectroscopic No No E230H 2962 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1282248329000 259.040017576091 (Tic-Visit :proposal-id 11569 :visit-id "01" :proposal-version -1 :trans-version "20080624" :date "02-Jul-2008 08:45:36.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 662832 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11569 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11569 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2909 :al-overhead-at-end 0 :internal-dur-at-end 115 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3242 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11569 :visit-id "01" :orbit-number 2 :pcs-time 195 :si-vis-utilization 3047 :al-overhead-at-end 0 :internal-dur-at-end 115 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3242 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11569 :visit-id "01" :orbit-number 3 :pcs-time 195 :si-vis-utilization 3047 :al-overhead-at-end 196 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3242 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11569 :visit-id "01" :orbit-number 4 :pcs-time 195 :si-vis-utilization 3047 :al-overhead-at-end 196 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3242 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11569 :visit-id "01" :orbit-number 5 :pcs-time 195 :si-vis-utilization 3047 :al-overhead-at-end 201 :internal-dur-at-end 321 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3242 :pcs-gap 0 ) true 5 0 SNR = 59 Brightest pixel = 1,812 e- ETC# = STIS77309 Brightest pixel = 42 e- Total counts = 1.8e5 e- ETC# = STIS77315 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1264075134000 91.71768518155568 (Tic-Visit :proposal-id 11569 :visit-id "02" :proposal-version -1 :trans-version "20080624" :date "02-Jul-2008 08:29:12.0" :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 262544 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11569 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11569 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2918 :al-overhead-at-end 0 :internal-dur-at-end 396 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3251 :pcs-gap 0 ) true 1 0 SNR = 119 Brightest pixel = 6,683 e- ETC# = STIS77295 Brightest pixel = 58 e- Total counts = 2.5e5 e- ETC# = STIS77391 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1282426636000 259.60392365165296 (Tic-Visit :proposal-id 11569 :visit-id "03" :proposal-version -1 :trans-version "20080624" :date "02-Jul-2008 08:29:16.0" :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 175536 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11569 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11569 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2909 :al-overhead-at-end 0 :internal-dur-at-end 396 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3242 :pcs-gap 0 ) true 1 0 SNR = 68 Brightest pixel = 2,067 e- ETC# = STIS77276 Brightest pixel = 50 e- Total counts = 1.6e5 e- ETC# = STIS77302 HOPR repeat of visit 3. (Tic-Visit :proposal-id 11569 :visit-id "53" :proposal-version -1 :trans-version "20100505" :date "21-Sep-2010 08:22:54.0" :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 175536 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11569 :visit-id "53" :obset-id "53" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11569 :visit-id "53" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2909 :al-overhead-at-end 0 :internal-dur-at-end 396 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3242 :pcs-gap 0 ) true 1 0 SNR = 68 Brightest pixel = 2,067 e- ETC# = STIS77276 Brightest pixel = 50 e- Total counts = 1.6e5 e- ETC# = STIS77302