For G160M observations, please consult Chapter 9 of the COS Instrument Handbook to estimate overheads and the number of exposures per orbit, and consequently the correct lifetime position. Use of LP4 with G160M requires justification in the "Special Requirements" section of the Phase I PDF. Use of the default LP6 with G160M requires no justification. Proposals can be submitted with the warning present.
For G160M observations, please consult Chapter 9 of the COS Instrument Handbook to estimate overheads and the number of exposures per orbit, and consequently the correct lifetime position. Use of LP4 with G160M requires justification in the "Special Requirements" section of the Phase I PDF. Use of the default LP6 with G160M requires no justification. Proposals can be submitted with the warning present.
For G160M observations, please consult Chapter 9 of the COS Instrument Handbook to estimate overheads and the number of exposures per orbit, and consequently the correct lifetime position. Use of LP4 with G160M requires justification in the "Special Requirements" section of the Phase I PDF. Use of the default LP6 with G160M requires no justification. Proposals can be submitted with the warning present.
For G160M observations, please consult Chapter 9 of the COS Instrument Handbook to estimate overheads and the number of exposures per orbit, and consequently the correct lifetime position. Use of LP4 with G160M requires justification in the "Special Requirements" section of the Phase I PDF. Use of the default LP6 with G160M requires no justification. Proposals can be submitted with the warning present.
For G160M observations, please consult Chapter 9 of the COS Instrument Handbook to estimate overheads and the number of exposures per orbit, and consequently the correct lifetime position. Use of LP4 with G160M requires justification in the "Special Requirements" section of the Phase I PDF. Use of the default LP6 with G160M requires no justification. Proposals can be submitted with the warning present.
For G160M observations, please consult Chapter 9 of the COS Instrument Handbook to estimate overheads and the number of exposures per orbit, and consequently the correct lifetime position. Use of LP4 with G160M requires justification in the "Special Requirements" section of the Phase I PDF. Use of the default LP6 with G160M requires no justification. Proposals can be submitted with the warning present.Resubmission with a couple fixes to text.1820698081Assigned ID: 5067
----- Attempting Submission 1 (Fri Mar 22 23:42:30 GMT 2024) -----
HST Phase I Proposal 5067 successfully submitted.
Receipt: # 5067-1
----- Attempting Submission 2 (Mon Mar 25 15:43:55 GMT 2024) -----We will use the default LP6 for the G160M mode.0----- Attempting Submission 1 (Thu Aug 08 21:57:52 GMT 2024) -----Far Ultraviolet Doppler Tomography of a T Tauri Dipper DiskTo understand the formation of the thousands of planets discovered on close orbits around other stars, protoplanetary disks kindred to the ones which gave rise to these systems must be studied at <1 au scales. The inner regions of most disks cannot be spatially resolved, but they can be studied by their line-rich UV spectra, and with time-series observations that capture variability on the timescale of orbits in the inner disk. We propose multi-epoch far ultraviolet (FUV) spectroscopy of the T Tauri ``dipper" star EP Chamaeleontis (RECX-11) with HST and COS when the Transiting Exoplanet Survey Satellite monitors the star in the optical for 27 days during Cycle 32. RECX-11 exhibits persistent quasi-periodic dimming due to dusty structures close to the star; these may also shadow the disk, producing its observed infrared variability. An FUV spectrum of EP Cha contains Lyman alpha-pumped fluorescent lines from molecular hydrogen in the inner disk gas, and the profiles of these lines contain velocity information uniquely resolvable by COS. Partial shadowing of the disk will induce periodic shifts and distortion of line profiles detectable in time-series spectra, and spatial information about the shadows and disk geometry can be retrieved by a ``tomographic" analysis. By performing these observations in parallel with TESS this shadowing can be related to the structures responsible for dimming. We will also use the line intensities to reconstruct the Lyman-alpha irradiation and any variation due to intervening gas. This investigation will harness the unique capabilities of HST and build on the Ultraviolet Legacy Library of Young Stars as Essential Standards (ULLYSES).We will employ the COS G130M (cenwave 1291) and G160M (cenwave 1577) gratings to reach both high spectral resolution and sufficient sensitivity to achieve the needed measurement precision of line profiles. The COS M-modes are chosen over the STIS G140L grating because STIS G140L does not have sufficient spectral resolution to isolate the FUV continuum in molecule-rich disks. TESS will monitor EP Cha during Sector 93 (3-29 June 2025) in Year 7 of its mission, and derived data products will include 200-sec cadence photometry in the TESS bandpass (600-1000 nm), sufficient for resolving any details in the lightcurve. Our COS observing strategy relies on the persistent 2.45-day quasi-periodicity of EP Cha, but we will not know a priori the time of inferior conjunction of an occulting structure. A "desirement" is that all COS observations occur within the same 2.45-day interval, but the requirement is only that they take place within the Sector 93 window and that they are spaced by at least 45 degrees of phase or 5 HST orbits. The number of complete observations (6) is set by the requirement of capturing significant profile variability with a 95% confidence, which Fig. 7b suggests occurs over the superior half of the phase. Paired spectra in the G130M and G160M modes must be taken as closely together as possible to minimize profile variation between them. Integration times are set by the requirement to detect and accurate fit multiple H2 lines and resolve small changes in FWHM of ~10 km/s due to shadowing by a inner disk wall or single occulting structure and thus achieve a precision of 3 km/s. Assuming 10 lines are averaged and since the median FWHM error in the archival COS spectra is about 15 km/s, this means an increase in SNR by ~50% or about a doubling of the integration times from 1604 and 1306 (for 130M and 160M, respectively) to nearly an hour. EP Cha is at a declination of -78 deg and can be observed for 58 min during an orbit, and minus 7 min for total overhead for target acquisition leaves 3060 sec, sufficient for science integration. We thus propose six visits of two consecutive orbits (G130M+G160M), a total of 12 orbits. COS Instrument Safety: EPCha was safely observed by COS at FUV wavelengths. We have used the STScI on-line Exposure Time Calculators to verify observational safety based on the archival COS spectra. EPCha is well within the safety limit of the COS FUV XDL detector using the COS G130M and COS G160M modes. EP Cha is a K-type star, so flare protection rules imposed for M dwarfs are not applicable.PI Eric Gaidos has expertise on the evolution of low-mass stars, their disks, and planetary systems. He has been studying the ``dipper" star phenomenon for the past seven years, has (co-)authored 10 papers on the topic, and has significant experience with the analysis of TESS light curves. He was the PI of a Cycle 17 Swift Guest Investigation (1720006) that observed RECX-11 (EP Cha) in X-ray simultaneously with TESS. He was also the PI of Las Cumbres Observatory Global Telescope (LCOGT) Key Project 2020-007 on ``dipper" stars that dedicated thousands of hours of 0.4-m and 1-m telescope network time to time-series photometry and spectroscopy of these objects.
Co-I Dr. Kevin France has been the PI of HST-COS spectroscopic programs observing accreting protostars (12876, 15070), and directed the spectral and temporal analysis for similar investigation of disk-bearing stars (e.g., France et al. 2011, 2014, 2017; Schindhelm et al. 2012a, b; McJunkin et al. 2014, 2016; Hoadley et al. 2015, 2017; Arulanantham et al. 2018, 2020). He is intimately familiar with HST-COS instrument, data, and analysis procedures. Dr. France was also the PI of the HST MUSCLES Treasury Survey (GO13650) and MEATS (GO16166) Survey to study the spectral and temporal properties of exoplanet host stars (France et al. 2016, 2018; Loyd et al. 2016; Youngblood et al. 2016). He is the co-PI of the follow-on Mega-MUSCLES (GO15071) and Mega-MEATS (16701) Surveys that focused on activity in stars optimal for planetary characterization with JWST. He was a member of the COS instrument and science teams, developing numerous community tools for spectral and temporal analysis of COS data, and has authored over 70 refereed publications on cool stars, exoplanets, and planet-forming disks using UV spectra from HST.
Co-I Dr. Nicole Arulanantham has previously led and directed studies of Lyman$\alpha$, FUV continuum, and UV-fluorescent molecular gas emission from YSOs and disks, including targets in the ULLYSES program (Arulanantham et al. 2018, 2020, 2021, 2023; Chang et al. 2024). She has also conducted a similar joint spectral and photometric analysis with multi-epoch optical/near-IR data from the dipper disk KH 15D (Arulanantham et al. 2017).Exoplanets and Exoplanet FormationStellar Physics and Stellar Types6falsefalsetruefalsefalsefalsefalsefalseSUPPORTEDSTART TAURI STARYSONOThis object was generated by the targetselector and retrieved from the SIMBAD database.J2000J2000COS/FUVSpectroscopicNoNoG130M1291COS/FUVSpectroscopicNoNoG160M1577COS/FUVSpectroscopicNoNoG130M1291COS/FUVSpectroscopicNoNoG160M1577COS/FUVSpectroscopicNoNoG130M1291COS/FUVSpectroscopicNoNoG160M1577COS/FUVSpectroscopicNoNoG130M1291COS/FUVSpectroscopicNoNoG160M1577COS/FUVSpectroscopicNoNoG130M1291COS/FUVSpectroscopicNoNoG160M1577COS/FUVSpectroscopicNoNoG130M1291COS/FUVSpectroscopicNoNoG160M1577/Users/ericgaidos/Documents/OP-cache/HST5067-v01.xmlTiming link suitability includes constraints ([02 After 01 by 0.4 to 8.6 days])The scheduling data was generated by CASM 32.1.1.CASM was run in Phase II mode.(Tic-Visit
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