HST-WFPC2 imaging of the young star V1331 Cyg revealed several dust arcs seen in scattered light which were caused by short-lived strong winds arising from FU Ori-like outbursts. Most notably the brightest outer arc is encircled by an expanding CO ring which implies that the otherwise extremely well mixed gas and dust components were separated according to particle mass. This is presumably due to the dependence of the wind ram pressure on the ratio of particle cross section and mass as well as the brief acceleration period. Thus, we suspect that a FU Ori outburst acts as a cosmic mass spectrometer. In order to verify this hypothesis, we apply for 2nd epoch imaging to reveal the color gradient across the bright dust arc which will be induced by the grain sorting. Furthermore, the current imagery will allow us to prove directly the expansion of the arc by measuring its proper motion. The proposed observations represent new diagnostics for what concerns studies of young stellar objects.

Our observations are focused on two science goals: measuring the outward proper motion of the shell seen between radii of 10 to 16 arcsec from the star, and measuring its broadband colors to constrain the dust sorting process by the wind. The first goal requires deep imaging in the F606W filter in the WF3 camera, for direct comparison with the epoch 2000 WFPC2 observations. Two 1100s CR-SPLIT exposures will provide enhanced sensitivity over the 1st epoch observations. Thus, the astrometric accuracy is primarily limited by the archival data. In order to register the 1st and 2nd epoch frames, we will use the six faint stars covered by the WF3 FOV. We require images in at least two broad-band filters in order to measure colors of the reflection nebulosity. These should be over as broad a color baseline as possible in order to provide the greatest leverage on the dust scattering properties, which in turn constrain the grain sorting properties of the wind. The WFPC2 F814W and F450W filters will be used. Two 1100s CR-SPLIT F814W exposure will fill out the second orbit. With the star's B-V color of 0.8mag (Herbig and Bell 1988) and the reduced throughput at F450W, another two orbits will be devoted to obtain two 2300s exposures in F450W. Extrapolating from the existing F606W image, this strategy will yield a S/N>5 in each WF3 pixel on the extended shell, and S/N of 10 or better in F606W and F814W. 2x2pixel rebinning will be employed in the measurements of color gradients in the shell. Short exposures in each filter will be used to centroid the images. V1331 Cyg is near the CVZ, with some visibility all year long (modulo the moon). STAR FORMATION 12 false 0.0 0.0 false false false false false SUPPORTED STAR T TAURI STAR G V-IV This object was generated by the targetselector and retrieved from the SIMBAD database.This object was generated by the targetselector and retrieved from the SIMBAD database. HBC302 GSC03596-00959 J2000 21 01 9.2100 +50 21 44.80 J2000 WFPC2 Imaging No F606W WFPC2 Imaging No F814W WFPC2 Imaging No F450W The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 11976 :visit-id "01" :proposal-version -1 :trans-version "20080807" :date "27-Jan-2009 10:21:20.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 4 :saa-model "26" :si-bright-earth-limb-angle 20.0 :data-volume 448160 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11976 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11976 :visit-id "01" :orbit-number 1 :pcs-time 355 :si-vis-utilization 2760 :al-overhead-at-end 120 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11976 :visit-id "01" :orbit-number 2 :pcs-time 355 :si-vis-utilization 2760 :al-overhead-at-end 120 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11976 :visit-id "01" :orbit-number 3 :pcs-time 355 :si-vis-utilization 2760 :al-overhead-at-end 120 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) (Tic-Orbit :proposal-id 11976 :visit-id "01" :orbit-number 4 :pcs-time 355 :si-vis-utilization 2760 :al-overhead-at-end 120 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) false 4 0 STAR WILL BE SATURATED. STAR WILL BE SATURATED. STAR WILL BE SATURATED. STAR WILL BE SATURATED.