Classical T Tauri stars (CTTS) show strong, broad and asymmetric FUV emission lines. Neither the width, nor the line profile is understood. Likely, different mechanisms influence the line profile; the best candidates are accretion, winds and stellar activity. We propose to monitor the CIV 1548/1550 Ang doublet in the nearby, bright CTTS TW Hya and to correlate it with i) the cool wind, as seen in COS NUV MgII line profiles, ii) the photometric period from joint ground-based monitoring, iii) the accretion rate as determined from the UV continuum and iv) the Ha line profile from independent ground-based observations. We request 10 orbits distributed over a few weeks to cover the typical time scales of stellar rotation, accretion and winds. With this data we can identify the FUV emission region, test for the presence of a hot wind, identify its properties, and characterize the variability of the accretion region.

We concentrate here on the Civ doublet at 1548/1550 A, the brightest hot FUV line, which we will observe with the G160M grating, set on central wavelength 1577 A. Several other important features are covered in the wavelength range of this grating: i) Si iv 1392/1403 A is a second hot ion line we will use for comparison. ii) Si ii 1527/1533 A, He ii 1640 A and Ci 1656 A probe the presence of cooler material. iii) Between the lines we obtain a continuum measurement to calculate the mass accretion rate. Supporting data are needed from the NUV G285M grating, set to central wavelength 2676 A. It covers i) the Mg ii 2796 A line, which is absorbed on the blue side, so that we know the minimum and maximum speed of the cool wind, and ii) provides continuum measurements between 2520 and 2820 A. Together with the FUV from the G160M grating we can thus fit the shape of the continuum and calculate the contemporary mass accretion rate according to the models of Calvet & Gullbring (1998). We ask for 10 HST orbits unevenly spaced over a few weeks (see comments to each visit). Each orbit will have an identical layout of observations with target acquisition, G285M and G160M exposures. According to the ETC TW Hya can be observed in the ACQ/IMAGE mode, if the BOA is used, but target Acquisition is faster in spectroscopic mode, because the overhead is reduced. The coordinates of our target are well known (to 0.01 arcsec), so we can save the time for ACQ/SEARCH (see COS ISR 2010-14). The existing HST/STIS spectra allow us to estimate the required exposure time in the COS bandpass reliably and to verify that no safety contraint for COS will be violated. The first 12 min will be used for a single NUV exposure with the G285M grating. This exposure time is sufficient to reach a SNR 20 per resolution element at 2594 A, i.e. blueward of the wind absorption in the Mg ii line. The maximum SNR in the NUV without flatfielding is 50, a value we will reach only in the line center. This allows us to determine the maximum speed of the wind observed in this ion. At the same time we pick up enough signal in the continuum to calculate the mass accretion rate according to the models of Calvet & Gullbring (1998).To answer the observational questions we need to achieve a SNR comparable to previous observations. However, in the FUV fixed-pattern noise limitsthe SNR to 18 per exposure per resolution element, so we need to obtain spectra at different settings of FP-POS. We will use FP-POS=2,3,4, because in position 1 the Si iv 1392 A line falls right on the edge of the detector. For the line center of Civ the limiting SNR is reached in < 2 min, however each exposure shall last 7 min to obtain the required signal in the wings of the Civ line (blueward of the maximum wind speed and at +300 km/s were emission variability has been observed before) and in the weaker lines, while keeping the instrumental overhead low. Including the initial grating change, the FP-POS changes and setup and readout for each exposure in total 33 min will be spent on the FUV exposures. It is the purpose of this proposal to determine the time scale of the FUV line variations. Photometric and spectral variability has been observed over periods of years in the past and there is an ongoing program for three observations of TW Hya (Proposal ID: 11608), spaced by a few months. Thus the new observations only need to cover the shorter time scale. This can be achieved by unevenly spacing out the visits over a few weeks with most visits within a short time frame e.g. with visits on days 1, 1, 1, 2, 2, 3, 5, 10, 15, 30 or 1, 5, 9, 10, 10, 10, 11, 15, 20, 30. However, there is no particular order required, it can be chosen to fit scheduling needs as long as is covers short and long timescales. Therefore, we specify only very rough constraints on the timing of the individual visits. STAR FORMATION 12 false 0.0 1.0 false false false false false false SUPPORTED STAR T TAURI STAR WIND J2000 11 01 51.9063 -34 42 17.02 J2000 COS/FUV Spectroscopic No No G160M 1577 COS/NUV Spectroscopic No No G285M 2676 COS/FUV Spectroscopic No No G160M 1577 COS/NUV Spectroscopic No No G285M 2676 COS/FUV Spectroscopic No No G160M 1577 COS/NUV Spectroscopic No No G285M 2676 COS/FUV Spectroscopic No No G160M 1577 COS/NUV Spectroscopic No No G285M 2676 COS/FUV Spectroscopic No No G160M 1577 COS/NUV Spectroscopic No No G285M 2676 COS/FUV Spectroscopic No No G160M 1577 COS/NUV Spectroscopic No No G285M 2676 COS/FUV Spectroscopic No No G160M 1577 COS/NUV Spectroscopic No No G285M 2676 Timing link suitability includes constraints ([Group (01 02) Within 30.0 days] [Group (01 03) Within 30.0 days] [Group (01 04) Within 30.0 days] [Group (01 05) Within 30.0 days] [Group (01 06) Within 30.0 days] [Group (01 07) Within 30.0 days] [Group (01 08) Within 30.0 days] [02 After 01 by 1.0 to 2.0 days] [03 After 01 by 2.0 to 3.0 days] [04 After 01 by 3.0 to 4.0 days] [05 After 01 by 5.0 to 10.0 days]) The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. It is the purpose of this proposal to determine the time scale of the FUV line variations. Photometric and spectral variability has been observed over periods of years in the past and there is an ongoing program for three observations of TW~Hya (Proposal ID: 11608), spaced by a few months. Thus the new observations only need to cover the shorter time scale. This can be achieved by unevenly spacing out the visits over a few weeks with most visits within a short time frame e.g. with visits on days 1, 1, 1, 2, 2, 3, 5, 10, 15, 30 or 1, 2 ,5, 5, 5, 6, 10, 12, 18, 30 or 1, 10, 15,18, 20, 24, 25, 25, 25, 28. However, there is no particular order required, it can be chosen to fit scheduling needs. We have specified some time relations between the visits, but is is acutally more flexible than that. Choose any order and spacing within 30 days with a few vitis wintin a few days to study short time scales and a few further apart. (Tic-Visit :proposal-id 12315 :visit-id "01" :proposal-version -1 :trans-version "20100505" :date "06-Jul-2010 11:28:41.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 3 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 1183168 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12315 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12315 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2942 :al-overhead-at-end 0 :internal-dur-at-end 59 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12315 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 3053 :al-overhead-at-end 0 :internal-dur-at-end 50 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) (Tic-Orbit :proposal-id 12315 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 3053 :al-overhead-at-end 0 :internal-dur-at-end 362 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) true 3 0 Timing link suitability includes constraints ([Group (01 02) Within 30.0 days] [02 After 01 by 1.0 to 2.0 days]) The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. It is the purpose of this proposal to determine the time scale of the FUV line variations. Photometric and spectral variability has been observed over periods of years in the past and there is an ongoing program for three observations of TW~Hya (Proposal ID: 11608), spaced by a few months. Thus the new observations only need to cover the shorter time scale. This can be achieved by unevenly spacing out the visits over a few weeks with most visits within a short time frame e.g. with visits on days 1, 1, 1, 2, 2, 3, 5, 10, 15, 30 or 1, 2 ,5, 5, 5, 6, 10, 12, 18, 30 or 1, 10, 15,18, 20, 24, 25, 25, 25, 28. However, there is no particular order required, it can be chosen to fit scheduling needs. We have specified some time relations between the visits, but is is acutally more flexible than that. Choose any order and spacing within 30 days with a few vitis wintin a few days to study short time scales and a few further apart. (Tic-Visit :proposal-id 12315 :visit-id "02" :proposal-version -1 :trans-version "20100505" :date "01-Jul-2010 12:07:40.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 417600 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12315 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12315 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2942 :al-overhead-at-end 0 :internal-dur-at-end 371 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) true 1 0 Timing link suitability includes constraints ([Group (01 03) Within 30.0 days] [03 After 01 by 2.0 to 3.0 days]) The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. It is the purpose of this proposal to determine the time scale of the FUV line variations. Photometric and spectral variability has been observed over periods of years in the past and there is an ongoing program for three observations of TW~Hya (Proposal ID: 11608), spaced by a few months. Thus the new observations only need to cover the shorter time scale. This can be achieved by unevenly spacing out the visits over a few weeks with most visits within a short time frame e.g. with visits on days 1, 1, 1, 2, 2, 3, 5, 10, 15, 30 or 1, 2 ,5, 5, 5, 6, 10, 12, 18, 30 or 1, 10, 15,18, 20, 24, 25, 25, 25, 28. However, there is no particular order required, it can be chosen to fit scheduling needs. We have specified some time relations between the visits, but is is acutally more flexible than that. Choose any order and spacing within 30 days with a few vitis wintin a few days to study short time scales and a few further apart. (Tic-Visit :proposal-id 12315 :visit-id "03" :proposal-version -1 :trans-version "20100505" :date "01-Jul-2010 12:07:44.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 417600 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12315 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12315 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2942 :al-overhead-at-end 0 :internal-dur-at-end 371 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) true 1 0 Timing link suitability includes constraints ([Group (01 04) Within 30.0 days] [04 After 01 by 3.0 to 4.0 days]) The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. It is the purpose of this proposal to determine the time scale of the FUV line variations. Photometric and spectral variability has been observed over periods of years in the past and there is an ongoing program for three observations of TW~Hya (Proposal ID: 11608), spaced by a few months. Thus the new observations only need to cover the shorter time scale. This can be achieved by unevenly spacing out the visits over a few weeks with most visits within a short time frame e.g. with visits on days 1, 1, 1, 2, 2, 3, 5, 10, 15, 30 or 1, 2 ,5, 5, 5, 6, 10, 12, 18, 30 or 1, 10, 15,18, 20, 24, 25, 25, 25, 28. However, there is no particular order required, it can be chosen to fit scheduling needs. We have specified some time relations between the visits, but is is acutally more flexible than that. Choose any order and spacing within 30 days with a few vitis wintin a few days to study short time scales and a few further apart. (Tic-Visit :proposal-id 12315 :visit-id "04" :proposal-version -1 :trans-version "20100505" :date "01-Jul-2010 12:07:46.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 417600 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12315 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12315 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2942 :al-overhead-at-end 0 :internal-dur-at-end 371 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) true 1 0 Timing link suitability includes constraints ([Group (01 05) Within 30.0 days] [05 After 01 by 5.0 to 10.0 days]) The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. It is the purpose of this proposal to determine the time scale of the FUV line variations. Photometric and spectral variability has been observed over periods of years in the past and there is an ongoing program for three observations of TW~Hya (Proposal ID: 11608), spaced by a few months. Thus the new observations only need to cover the shorter time scale. This can be achieved by unevenly spacing out the visits over a few weeks with most visits within a short time frame e.g. with visits on days 1, 1, 1, 2, 2, 3, 5, 10, 15, 30 or 1, 2 ,5, 5, 5, 6, 10, 12, 18, 30 or 1, 10, 15,18, 20, 24, 25, 25, 25, 28. However, there is no particular order required, it can be chosen to fit scheduling needs. We have specified some time relations between the visits, but is is acutally more flexible than that. Choose any order and spacing within 30 days with a few vitis wintin a few days to study short time scales and a few further apart. (Tic-Visit :proposal-id 12315 :visit-id "05" :proposal-version -1 :trans-version "20100505" :date "01-Jul-2010 12:07:49.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 417600 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12315 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12315 :visit-id "05" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2942 :al-overhead-at-end 0 :internal-dur-at-end 371 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) true 1 0 Timing link suitability includes constraints ([Group (01 06) Within 30.0 days]) The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. It is the purpose of this proposal to determine the time scale of the FUV line variations. Photometric and spectral variability has been observed over periods of years in the past and there is an ongoing program for three observations of TW~Hya (Proposal ID: 11608), spaced by a few months. Thus the new observations only need to cover the shorter time scale. This can be achieved by unevenly spacing out the visits over a few weeks with most visits within a short time frame e.g. with visits on days 1, 1, 1, 2, 2, 3, 5, 10, 15, 30 or 1, 2 ,5, 5, 5, 6, 10, 12, 18, 30 or 1, 10, 15,18, 20, 24, 25, 25, 25, 28. However, there is no particular order required, it can be chosen to fit scheduling needs. We have specified some time relations between the visits, but is is acutally more flexible than that. Choose any order and spacing within 30 days with a few vitis wintin a few days to study short time scales and a few further apart. (Tic-Visit :proposal-id 12315 :visit-id "06" :proposal-version -1 :trans-version "20100505" :date "01-Jul-2010 12:07:52.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 417600 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12315 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12315 :visit-id "06" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2942 :al-overhead-at-end 0 :internal-dur-at-end 371 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) true 1 0 Timing link suitability includes constraints ([Group (01 07) Within 30.0 days]) The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. It is the purpose of this proposal to determine the time scale of the FUV line variations. Photometric and spectral variability has been observed over periods of years in the past and there is an ongoing program for three observations of TW~Hya (Proposal ID: 11608), spaced by a few months. Thus the new observations only need to cover the shorter time scale. This can be achieved by unevenly spacing out the visits over a few weeks with most visits within a short time frame e.g. with visits on days 1, 1, 1, 2, 2, 3, 5, 10, 15, 30 or 1, 2 ,5, 5, 5, 6, 10, 12, 18, 30 or 1, 10, 15,18, 20, 24, 25, 25, 25, 28. However, there is no particular order required, it can be chosen to fit scheduling needs. We have specified some time relations between the visits, but is is acutally more flexible than that. Choose any order and spacing within 30 days with a few vitis wintin a few days to study short time scales and a few further apart. (Tic-Visit :proposal-id 12315 :visit-id "07" :proposal-version -1 :trans-version "20100505" :date "01-Jul-2010 12:07:54.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 417600 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12315 :visit-id "07" :obset-id "07" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12315 :visit-id "07" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2942 :al-overhead-at-end 0 :internal-dur-at-end 371 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) true 1 0 Timing link suitability includes constraints ([Group (01 08) Within 30.0 days]) The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. It is the purpose of this proposal to determine the time scale of the FUV line variations. Photometric and spectral variability has been observed over periods of years in the past and there is an ongoing program for three observations of TW~Hya (Proposal ID: 11608), spaced by a few months. Thus the new observations only need to cover the shorter time scale. This can be achieved by unevenly spacing out the visits over a few weeks with most visits within a short time frame e.g. with visits on days 1, 1, 1, 2, 2, 3, 5, 10, 15, 30 or 1, 2 ,5, 5, 5, 6, 10, 12, 18, 30 or 1, 10, 15,18, 20, 24, 25, 25, 25, 28. However, there is no particular order required, it can be chosen to fit scheduling needs. We have specified some time relations between the visits, but is is acutally more flexible than that. Choose any order and spacing within 30 days with a few vitis wintin a few days to study short time scales and a few further apart. (Tic-Visit :proposal-id 12315 :visit-id "08" :proposal-version -1 :trans-version "20100505" :date "01-Jul-2010 12:07:57.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "31" :si-bright-earth-limb-angle 20.0 :data-volume 417600 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 12315 :visit-id "08" :obset-id "08" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 12315 :visit-id "08" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2942 :al-overhead-at-end 0 :internal-dur-at-end 371 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) true 1 0