Alert Notice 763: V505 Ori to be observed with HST - coverage needed now

January 3, 2022

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
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- Young Stellar Objects:
Note that these forum threads may NOT be the same as for other Alert Notices related to the ODYSSEUS program.

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Further to AAVSO Alert Notice 725, Dr. Frederick Walter (Stony Brook University) informs us that HST observations of the YSO V505 Ori, one of the targets in the ULLYSES/ODYSSEUS campaign, have been scheduled. AAVSO observers' assistance is requested in muti-color monitoring of this pre-main sequence target before, during, and after the HST observations. As always with HST observations, a positive V observation is crucial 24 hours before the scheduled start time to allow the HST team to make a go/nogo decision.

V505 Ori was scheduled to be observed in December 2020 with HST, but those observations were postponed because data from AAVSO observers showed that the target had faded by about two magnitudes in B.

The HST observations of V505 Ori will be carried out on 2022 January 08 1108 - 1213 UT and 2022 January 09 0607 - 1010 UT.

AAVSO Alert Notices 725, 728, 731, 733, 737, 741, 748, 751, 756, and 760 also cover targets in the ULLYSES/ODYSSEUS campaign; some also give detailed information about the campaign itself.

Dr. Walter provides the following information:

"Please obtain digital BVRI observations nightly now through January 9 [ideally through January 12 to provide more context for the time of the HST observations]. Multiple observations per night will help us reconstruct the light curve. There will not be any TESS observations. Exact simultaneity with the HST observations would be nice, but is not required.The most useful observations will let us reconstruct the light curve in the days leading up to the HST observations in order to assess the accretion history.

"B and V are more valuable than R and I because stellar variability is more prominent at short wavelengths, but all 4 bands help us determine the extinction law, and the nature of the obscuring material. Visual observations are welcome in order to supplement the light curve."

Coordinates (2000.0): 05 38 27.26 -02 45 09.7   mean V~14.2 V   range 14.1-17.2 V

Charts with comparison stars for V505 Ori may be created using the AAVSO Variable Star Plotter (VSP).

Please submit observations to the AAVSO International Database, using the name V505 ORI, in a timely manner, and as soon as possible if any substantial brightening or fading is seen.

Observers are encouraged to subscribe to the forum threads above and use them to discuss any interesting observations and post questions or comments for Dr. Walter.

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen using material provided by Dr. Walter.



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