Assigned ID: 77
----- Attempting Submission 1 (Tue Feb 22 17:13:00 GMT 2011) -----
HST Phase I Proposal 77 (astrogo.apt) successfully submitted.I'm not understanding the "BOT" results, which seem to suggest all 4 of my targets are O5 V
stars that are too bright?! I've used the STIS exposure time calculators to verify the observations
are safe, and these calculations are attached with this submission for each exposure. (The
only possibly questionable exposure is the E230H exposure for HD30652 (see comment with
that exposure).----- Attempting Submission 1 (Fri Jul 01 17:02:45 GMT 2011) -----
HST Phase II Proposal 12596 (astrogo.apt) successfully submitted.
----- Attempting Submission 2 (Mon Aug 13 14:27:00 GMT 2012) -----In Search of a Young Solar WindThere are three main reasons why we would very much like to know how the coronal winds emanating from the Sun and other solar-like stars evolve with time. 1. Stellar winds have important effects on planetary atmospheres, with Mars being a particularly important example in our own solar system. 2. Stellar winds may contribute to the dissipation of debris disks. 3. Stellar winds play a central role in the angular momentum and activity evolution of cool main sequence stars. The best way to investigate stellar wind evolution is to detect and measure the winds of solar-like stars of various ages to see how they change with time. Unfortunately, detecting coronal winds is extremely difficult. The only detections to date come from high resolution HST Lyman-alpha spectra of nearby stars, which sometimes show absorption from the stellar "astrospheres" (i.e., interaction regions between stellar winds and the ISM). The amount of absorption can be used as a diagnostic of the stellar wind strength. There are 13 astrospheric detections so far, but unfortunately there are still no unambiguous detections for any true young, solar analogs. We here propose to try to rectify this situation by observing four young, very active solar-like stars with HST/STIS, in the hopes that at least one or two will yield an astrospheric detection that can finally tell us what coronal winds are like for young F and G stars. Success would mean a major step forward in being able to address the question of how winds evolve for solar-like stars, and how that affects the planets and disks that surround them.We will observe our 4 stars with STIS for 2 orbits each. We acquire each of our rather bright stars with a 0.1 second exposure onto the STIS/CCD with the F28X50OII filter. An accurate wavelength scale is important for our purposes so we will perform a peakup into the narrow 0.2"x0.09" aperture. A dispersed light peakup is required for our bright targets and we use a 0.1 s exposure with the G430M grating for the peakups. After acquisition, the first orbit will generally consist of an E230H spectrum of the 2574-2851 Angstrom wavelength range, through the 0.2"x0.09" aperture. We require this spectrum to study the velocity structure of the ISM towards our targets using the narrow interstellar Mg II h & k lines near 2800 Angstrom and Fe II at 2600 Angstroms. This information is needed to maximize our ability to accurately model the interstellar H I Lyman-alpha absorption and search for the presence of an astrospheric absorption signature for which the ISM cannot account (Wood et al. 2005b).
The second orbit of each target visit will be used for an E140M spectrum of the 1150-1700 Angstrom wavelength range through the 0.2"x0.2" aperture, which will contain the primary line of interest: H I Lyman-alpha at 1216 Angstroms. All but one of our targets are comfortably in compliance with STIS/MAMA bright object limits, as verified using both Table 13.44 in the STIS Instrument Handbook and the online STIS exposure time calculator. The exception is HD 30652. The E230H exposure for this star exceeds the total image count rate limit unless we replace the 0.2"x0.09" aperture with the tiny 0.1"x0.03" slit. An extra peakup is required to center the star in this tiny aperture. Note also that the E230H exposure will not be necessary for HD 72905, as one already exists in the HST archive. Thus, both orbits will be used for the E140M exposure in this case. The E230H observation will provide the highest resolution spectrum of the Mg II and Fe II absorption lines. The E140M grating does not have quite the resolution of E230H, but its resolution is good enough to study the H I Lyman-alpha line profile in
the detail that we require.
Estimating expected S/N for our planned spectra requires first estimating Lyman-alpha and Mg II fluxes, which we can do by extrapolating from previously observed stars. Chromospheric line fluxes (such as Mg II and Lyman-alpha) are related to X-ray fluxes through the relation $f_{\rm chrom}\propto f_{\rm X}^{0.34}$ from Ayres et al. (1995). Thus, Lyman-alpha or Mg II fluxes for our stars can be estimated from the equation
\begin{equation}
f_{2}=f_{1} \left( \frac{d_{1}}{d_{2}} \right)^{2}
\left( \frac{L_{X2}}{L_{X1}} \right)^{0.34},
\end{equation}
where d_{2} and L_{X2} are the distances and X-ray luminosities listed in Table 1 for our target stars, and d_{1}, L_{X1}, and f_{1} are the distance, X-ray luminosity, and Lyman-alpha (or Mg II) flux observed from some reference star, respectively. Wood et al. (2005b) provide Lyman-alpha spectra for many stars. We use Chi1 Ori as the comparison star for our purposes here.
After acquisition, peakup, and observational overhead are considered, we expect about 28 minutes to be available in the first orbit for the E230H exposure. We expect this to be enough time to attain a more than sufficient S/N >50 at line center for the strong Mg II lines. After acquisition and overheads are considered, we expect our 1 orbit E140M exposure to be about 46 minutes in length, sufficient to achieve a S/N>15 within the H I Lyman-alpha line profile for all of our stars, which should be good enough for our purposes considering the broad width of the line.COOL STARS12false0.00.0falsefalsefalsefalseSUPPORTEDSTARF3-F9This object was generated by the targetselector and retrieved from the SIMBAD database.PI3-ORIJ2000J2000TYPE=F6V, F-LINE(2796)=2.7+/-0.7E-11, W-LINE(2796)=0.6, F-LINE(1216)=1.2+/-0.4E-11, W-LINE(1216)=0.8STARG V-IVThis object was generated by the targetselector and retrieved from the SIMBAD database.PI1-UMAJ2000J2000TYPE=G1.5V, F-LINE(2796)=8.2+/-2.0E-12, W-LINE(2796)=0.6, F-LINE(1216)=3.6+/-1.2E-12, W-LINE(1216)=0.8STARF3-F9This object was generated by the targetselector and retrieved from the SIMBAD database.V1119-TAUJ2000J2000TYPE=F8V, F-LINE(2796)=1.0+/-0.3E-11, W-LINE(2796)=0.6, F-LINE(1216)=4.6+/-1.5E-12, W-LINE(1216)=0.8STARG V-IVThis object was generated by the targetselector and retrieved from the SIMBAD database.HN-PEGJ2000J2000TYPE=G0V, F-LINE(2796)=5.9+/-1.5E-12, W-LINE(2796)=0.6, F-LINE(1216)=2.6+/-0.9E-12, W-LINE(1216)=0.8STIS/NUV-MAMASpectroscopicNoNoE230H2713STIS/FUV-MAMASpectroscopicNoNoE140M1425STIS/FUV-MAMASpectroscopicNoNoE140M1425STIS/NUV-MAMASpectroscopicNoNoE230H2713STIS/FUV-MAMASpectroscopicNoNoE140M1425STIS/NUV-MAMASpectroscopicNoNoE230H2713STIS/FUV-MAMASpectroscopicNoNoE140M1425/tmp/OPVisit2356383107123353839.xmlThe scheduling data was generated by CASM 20.0.CASM was run in Phase II mode.1344443684000255.593819739421(Tic-Visit
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)true20The total expected count rate is 161128/s, which is within 40% of the Bright Object Limit, so there is a warning. But this NUV continuum flux should not be variable. So as long as the count rate estimate is good, it should be OK. And I tried different models for this F6 V star in the exposure time calculator, and they are all very consistent./home/wood/marmoset/props/hst11/OP-cache/astrogo-v02.xmlThe scheduling data was generated by CASM 20.0.CASM was run in Phase II mode.(Tic-Visit
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