Dear colleagues,

We are pleased to announce the Version 1 0 release of Epoch 2 of the cluster MACSJ0717 5+3745, after the completion of the full total of 140 orbits of WFC3/IR and ACS imaging on the main cluster and parallel field from our Frontier Fields program (13498, PI: J Lotz), as well as including archival data from program ID 12103 (PI: M Postman), 13389 (PI: B Siana), and 13459 (PI : T Treu) These v1 0 mosaics have been fully recalibrated relative to the v0 5 mosaics that we have been releasing during this epoch in March and April 2015 For ACS, the v1 0 mosaics incorporate new bias and dark current reference files, created with the new postflash approach to improve low-level noise, along with CTE correction and bias destriping, and also include a set of mosaics that have been processed with the new selfcal approach to better account for the low-level dark current structure The WFC3/IR v1 0 mosaics have improved masking for persistence and bad pixels, and in addition include a set of mosaics that have been corrected for time-variable sky emission that can occur during the orbit and can otherwise impact the up-the-ramp count-rate fitting if not properly corrected Further details are provided in the readme file, which can be obtained along with all the mosaics at the following location:

• Latest mosaics: http://archive stsci edu/pub/hlsp/frontier/macs0717/images/hst/v1 0-epoch2/
• All mosaics: http://archive stsci edu/prepds/frontier/macs0717 html

More general information about the data for this project can be obtained from our Frontier Fields MAST archive website: * http://archive stsci edu/prepds/frontier/ as well as our main Frontier Fields HST project website: * http://www stsci edu/hst/campaigns/frontier-fields/ and our Frontier Fields astronomer's blog and other social media: * https://blogs stsci edu/hstff/ * https://twitter com/MAST_News/ * https://facebook com/MASTArchive/

We hope that these high-level science products are useful for your research, and we welcome any suggestions or questions that you may have about them

Best regards, Anton Koekemoer and the STScI Frontier Fields Team http://archive stsci edu/prepds/frontier/ http://www stsci edu/hst/campaigns/frontier-fields/Contact

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