Improving LSST Photometric Calibration with Gaia Data

We consider the possibility that the Gaia mission can supply data which will improve the photometric calibration of LSST. After outlining the LSST calibra- tion process and the information that will be available from Gaia, we explore two options for using Gaia data. The first is to use Gaia G-band photometry of selected stars, in conjunction with knowledge of the stellar parameters Teff, log g, and AV, and in some cases Z, to create photometric standards in the LSST u, g, r, i, z, and y bands. The accuracies of the resulting standard magnitudes are found to be insufficient to satisfy LSST requirements when generated from main sequence (MS) stars, but generally adequate from DA white dwarfs (WD). The second option is combine the LSST bandpasses into a synthetic Gaia G band, which is a close approximation to the real Gaia G band. This allows synthetic Gaia G photometry to be directly compared with actual Gaia G photometry at a level of accuracy which is useful for both verifying and improving LSST photometric calibration.Comment: Accepted for publication in PAS

First Results from the rapid-response spectrophotometric characterization of Near-Earth Objects

As part of our multi-observatory, multi-filter campaign, we present \rmi color observations of 82 Near-Earth Objects (NEOs) obtained with the RATIR instrument on the 1.5m robotic telescope at the San Pedro Martir's National Observatory in Mexico. Our project is particularly focused on rapid response observations of small ($\lesssim 850$ m) NEOs. The rapid response and the use of spectrophotometry allows us to constrain the taxonomic classification of NEOs with high efficiency. Here we present the methodology of our observations and our result, suggesting that the ratio of C-type to S-type asteroids in a size range of $\sim$30-850m is 1.1, which is in accordance with our previous results. We also find that 10$\%$ of all NEOs in our sample are neither C- nor S-type asteroidsComment: 31 pages, 4 tables, 10 figure

ANTARES: Progress towards building a `Broker' of time-domain alerts

The Arizona-NOAO Temporal Analysis and Response to Events System (ANTARES) is a joint effort of NOAO and the Department of Computer Science at the University of Arizona to build prototype software to process alerts from time-domain surveys, especially LSST, to identify those alerts that must be followed up immediately. Value is added by annotating incoming alerts with existing information from previous surveys and compilations across the electromagnetic spectrum and from the history of past alerts. Comparison against a knowledge repository of properties and features of known or predicted kinds of variable phenomena is used for categorization. The architecture and algorithms being employed are described

Absolute Magnitudes and Colors of RR Lyrae stars in DECam Passbands from Photometry of the Globular Cluster M5

We characterize the absolute magnitudes and colors of RR Lyrae stars in the globular cluster M5 in the ugriz filter system of the Dark Energy Camera (DECam). We provide empirical Period-Luminosity (P-L) relationships in all 5 bands based on 47 RR Lyrae stars of the type ab and 14 stars of the type c. The P-L relationships were found to be better constrained for the fundamental mode RR Lyrae stars in the riz passbands, with dispersion of 0.03, 0.02 and 0.02 magnitudes, respectively. The dispersion of the color at minimum light was found to be small, supporting the use of this parameter as a means to obtain accurate interstellar extinctions along the line of sight up to the distance of the RR Lyrae star. We found a trend of color at minimum light with pulsational period that, if taken into account, brings the dispersion in color at minimum light to < 0.016 magnitudes for the (r-i), (i-z), and (r-z) colors. These calibrations will be very useful for using RR Lyrae stars from DECam observations as both standard candles for distance determinations and color standards for reddening measurements.Comment: Accepted for publication in A

Sub-percent Photometry: Faint DA White Dwarf Spectophotometric Standards for Astrophysical Observatories

We have established a network of 19 faint (16.5 mag $< V <$19 mag) northern and equatorial DA white dwarfs as spectrophotometric standards for present and future wide-field observatories. Our analysis infers SED models for the stars that are tied to the three CALSPEC primary standards. Our SED models are consistent with panchromatic Hubble Space Telescope ($HST$) photometry to better than 1%. The excellent agreement between observations and models validates the use of non-local-thermodynamic-equilibrium (NLTE) DA white dwarf atmospheres extinguished by interstellar dust as accurate spectrophotometric references. Our standards are accessible from both hemispheres and suitable for ground and space-based observatories covering the ultraviolet to the near infrared. The high-precision of these faint sources make our network of standards ideally suited for any experiment that has very stringent requirements on flux calibration, such as studies of dark energy using the Large Synoptic Survey Telescope (LSST) and the Wide-Field Infrared Survey Telescope ($WFIRST$).Comment: 46 pages, 23 figures, 8 tables, accepted for publication in ApJ

Perfecting our set of spectrophotometric standard DA white dwarfs

We verified for photometric stability a set of DA white dwarfs with Hubble Space Telescope magnitudes from thenear-ultraviolet to the near-infrared and ground-based spectroscopy by using time-spaced observations from theLas Cumbres Observatory network of telescopes. The initial list of 38 stars was whittled to 32final ones, whichcomprise a high-quality set of spectrophotometric standards. These stars are homogeneously distributed around thesky and are all fainter thanr~16.5 mag. Their distribution is such that at least two of them would be available tobe observed from any observatory on the ground at any time at airmass less than 2. Light curves and differentvariability indices from the Las Cumbres Observatory data were used to determine the stability of the candidatestandards. When available, Pan-STARRS1, Zwicky Transient Facility, and TESS data were also used to confirmthe star classification. Our analysis showed that four DA white dwarfs may exhibit evidence of photometricvariability, while afifth is cooler than our established lower temperature limit, and a sixth star might be a binary. Insome instances, due to the presence of faint nearby red sources, care should be used when observing a few of thespectrophotometric standards with ground-based telescopes. Light curves andfinding charts for all the stars areprovided.This study was supportedby NASA through grant O1904 from the Space TelescopeScience Institute, which is operated by AURA, Inc., underNASA contract NAS 5-26555 and the Space Telescope ScienceInstitute. The analysis was also supported by the DDRF grantD0001.82481. E.O. was also partially supported by the NSFthrough grant AST-1815767. R.R. received funding from thepostdoctoral fellowship program Beatriu de Pinós, funded bythe Secretary of Universities and Research(Government ofCatalonia)and by the Horizon 2020 program of research andinnovation of the European Union under the Maria Skło-dowska-Curie grant agreement No. 801370. C.S. is supportedby the US DOE through award DE-SC0007881. This work hasmade use of data from the European Space Agency(ESA)mission Gaia(https://www.cosmos.esa.int/gaia), processedby the Gaia Data Processing and Analysis Consortium(DPAC;https://www.cosmos.esa.int/web/gaia/dpac/consortium).Funding for the DPAC has been provided by nationalinstitutions, in particular the institutions participating in theGaia Multilateral Agreement. This publication makes use ofVOSA, developed under the Spanish Virtual Observatoryproject supported by the Spanish MINECO through grantAyA2017-84089. VOSA has been partially updated by usingfunding from the European Union’s Horizon 2020 Research andInnovation Programme, under grant Agreement No. 776403(EXOPLANETS-A). This work includes data from the AsteroidTerrestrial-impact Last Alert System(ATLAS)project. ATLAS isprimarily funded to search for near-earth asteroids through NASAgrants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575;byproducts of the NEO search include images and catalogs fromthe survey area. The ATLAS science products have been madepossible through the contributions of the University of HawaiiInstitute for Astronomy, the Queen’s University Belfast, the SpaceTelescope Science Institute, and the South African AstronomicalObservatory. G.N. and K.M. gratefully acknowledge support fromNASA under grant 80NSSC20K0453 issued through theNNH18ZDA001N Astrophysics Data Analysis Program(ADAP).Facilities:LCO, HST(WFC3), Gaia, ATLAS, TESS,Pan-STARRS, ZTFPeer ReviewedPostprint (published version