The second data release from the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) survey was opened to the astronomical community on January 28th, 2019, and is available from the MAST archives. Pan-STARRS1 (PS1) is the first part of Pan-STARRS to be completed and is the basis for both Data Release 1 (DR1; 2016 December 19) and Data Release 2 (DR2). Links to access the PS1 DR2 data as well as the PS1 documentation can be found at https://panstarrs.stsci.edu.
The PS1 archive includes images and catalogs from several defined surveys, including observations of three quarters of the sky (the 3Pi Survey, which is available in DR2) carried out several times per filter and over a four-year time span. PS1 DR2 is the first release to include the time-dependent photometry, astrometry, and images collected by PS1. The total data volume of the release is approximately 1.6 petabytes, including a 150-terabyte database along with the single-epoch and stacked images. The catalog includes more than 2.5 billion objects having detections at two or more epochs. In total, there are more than 70 billion detections with an average of ~50 epochs for each object (~10 epochs per filter).
MAST provides a number of tools to help users explore the data products of the PS1 archive:
A simple image search form for retrieving image cutouts and full images for both the stacked and single-epoch images.
A powerful new catalog search form provides a simple tool to search the catalogs for objects near a sky position. The new interface features the ability to constrain searches on any catalog parameters along with an easy-to-use API for scripted access.
The PS1 catalog astrometry and photometry are well calibrated, with median astrometric errors for brighter sources (18–19 mag) compared with Gaia are about 20 milliarcsec (the astrometric calibration is based on the Gaia reference frame). Systematic photometric errors are about 7 millimag.
Beginning this week, the MAST website will receive a large number of updates over the course of 2019. This ongoing project will include new page organization, designs, and layouts in an effort to modernize MAST's look, and make it easier to navigate MAST's many tools and services. The current rollout includes the MAST front page, several major MAST-hosted missions, and the High-Level Science Products landing page, among others, with further updates in the near-future.
Our first updated individual HLSP page is also available for UVUDF, with more on the way. The legacy site remains available while we transition, and all your bookmarks should continue to work as they have, but if you have any questions, concerns, or other feedback on the new pages please contact the Archive Helpdesk!
These are the first multi-sector data sets released, and contain products (light curves and figures) associated with the transit-signal threshold crossing events (TCEs) found by the TESS mission pipeline after stitching together multiple sectors of light curves on each target.
A number of Jupyter notebook tutorials are also available to provide some guidance on working with the different data products from TESS. Additional questions on accessing TESS public data through MAST may be directed to the Archive Helpdesk.
ASTRAL is a combination of Large Treasury Projects in HST Cycles 18 and 21, involving dozens of investigators. The objective was to collect full-coverage ultraviolet (1150–3150 Å) spectra of representative bright stars over a range of temperatures, using HST’s high-performance Space Telescope Imaging Spectrograph (STIS). These UV “atlases” complement state-of-the-art ground-based optical and infrared spectra of the same objects. Harboring resonance transitions of key light elements and important metals, UV spectra can diagnose diverse phenomena, from the massive winds of hot stars to the multi-MK coronal outer envelopes of cool stars. The fine spectral resolution available with STIS allows us to de-blend close lines and extract Doppler velocity information.
Between 2010 and 2018, ASTRAL projects observed 37 different stars with STIS, recently adding two new types: four F/G metal-poor turn-off stars and two calibration hot white dwarfs. Multiple visits provided time domain coverage and mitigated a number of instrumental effects. Recently, all the ASTRAL spectra were re-processed through CALSTIS using updated and custom reference files. Then, the outputs were corrected to improve the wavelength scales by applying a high-order distortion correction; to compensate for “spectral bending,” which can occur with the narrowest STIS slits if the focus had drifted; and to optimize the echelle blaze shift. Next, multiple exposures in the same grating setting were combined, and the many grating settings covering the full UV range were stitched together. An illustration of the far-UV segments of the original ASTRAL sample, plus Alpha Cen AB, is shown in Figure 1.
In 2018, a new high-level data product was introduced to help visualize the processing steps for each observation at the “sub-exposure” level. These sub-exposure products can be found at the bottom of the data tree for each target. An example is shown in Figure 2.
Details and caveats concerning the observing strategy and processing steps, and a portal to the datasets, can be found at https://archive.stsci.edu/prepds/astral/ and http://casa.colorado.edu/~ayres/ASTRAL/. ASTRAL is intended to support diverse explorations for many years to come. Because it might be decades before the next generation high-resolution UV spectrometer flies, it is vital to carry out archive-minded projects like ASTRAL now, while we still have access to a remarkable instrument such as STIS. Additional questions about the ASTRAL collection and accessing the contents may be sent to the MAST Archive Helpdesk.
New and updated High-Level Science Product collections at MAST include a new set of corrections to GALEX spectral fluxes, Kepler light curves optimized for asteroseismology, and new planetary candidates from TESS.
GALEX-FLUXCAL (Bohlin & Bianchi 2019), a collection of 18 IUE spectral energy distributions (SEDs) on the CALSPEC scale that provide a correction to GALEX spectral fluxes, available in both text and FITS formats. This HLSP also includes the correction in 50 Angstrom bins from 1300 - 3000 Angstroms. While GALEX spectrophotometry is repeatable to only 10-20% in regions of good sensitivity, the average flux correction presented here has a precision of ~3%.
The KEPSEISMIC collection provides Kepler light curves optimized for asteroseismology. For each pixel in the pixel-data file, a reference weighted flux value is computed as the 99.9th percentile of the flux divided by its error representing a measure of the signal-to-noise ratio. The resultant light curve is processed through the implementation of the KADACS software, which corrects for outliers, jumps, and drifts, properly concatenates the independent Kepler Quarters in a star-by-star basis. It also fills the gaps shorter than 20 days in long cadence data following in-painting techniques based on a multi-scale cosine transform. The resulting light curves are high-pass filtered at 20, 55 days (quarter by quarter) and 80 days (using the full light curve at once) yielding three different light curves for each target. The team has provided the detrended light curves, the power spectra, and preview plots for more than 28,000 Kepler stars, and more will be released soon.
New TESS-DATA-ALERTS from Sector 4, identified from the Sector 4 Full Frame Images by the MIT Quick Look Pipeline. Since these are FFI-based, no 2-min. cadence data are provided as part of the HLSP update. The Sector 4 FFIs are publicly available at MAST.
If you are thinking about contributing a High-Level Science Product of your own, please fill out the HLSP Interest Form to get started. HLSPs archived on MAST enjoy permanent hosting space, additional visibility, and, often, increased citation rates. Any further questions on the process can be sent to the Archive Helpdesk.
This newsletter is a MAST publication produced by Greg Snyder, Peter Forshay, and Jonathan Hargis, on behalf of the entire MAST staff, who welcome your comments and suggestions.
The Mikulski Archive for Space Telescopes (MAST) is a NASA funded project to support and provide to the astronomical community a variety of astronomical data archives, with the primary focus on scientifically related data sets in the optical, ultraviolet, and near-infrared parts of the spectrum. MAST is located at the Space Telescope Science Institute (STScI).