Dear colleagues,

We are pleased to announce the release of the first new v0 5 HST mosaics obtained on the cluster MACSJ0717 5+3745, from the first 40 orbits of observations of this target from our Frontier Fields program ID 13498 (PI: J Lotz), also including archival ACS and WFC3/IR data (programs 9722 and 10420, PI : H Ebeling; programs 10493 and 10793, PI : A Gal-Yam; program 12103, PI : M Postman; program 13389, PI : B Siana; and program 13459, PI : T Treu), to provide the most complete full-depth mosaics in the ACS/WFC and WFC3/IR filters that are used for the Frontier Fields program, where all data have been fully reprocessed using the most current calibration files These mosaics have all been processed beyond the default pipeline calibration, in order to produce the best possible quality, science-ready full-depth mosaics For ACS, these mosaics incorporate CTE correction and bias destriping, as well as a set of mosaics that have been processed with the new selfcal approach to better correct for low-level dark current structure The WFC3/IR mosaics have been masked 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 All these mosaics are aligned to a common pixel grid as well as to an absolute astrometric frame based on pre-existing catalogs of this field 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/v0 5-20141014/
• 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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