gPhoton: THE GALEX PHOTON DATA ARCHIVE

Million, Chase; Fleming, Scott W.; Shiao, Bernie; Seibert, Mark; Loyd, R. O. Parke; Tucker, M. A.; Smith, M. A.; Thompson, R.; White, R. L.

doi:10.3847/1538-4357/833/2/292

Cited by 65 publications

(81 citation statements)

References 24 publications

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“…Time-tagged photon data has recently become available for GALEX (Million et al 2016a), including a Python toolkit to search for and interact with this high cadence data product called gPhoton (Million et al 2016b). This allows us to resample the GALEX main survey data into any desired cadence.…”

Section: Galex Observationsmentioning

confidence: 99%

The GALEX View of “Boyajian’s Star” (KIC 8462852)

Davenport

Covey

Clarke

et al. 2018

ApJ

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The enigmatic star KIC 8462852, informally known as "Boyajian's Star", has exhibited unexplained variability from both short timescale (days) dimming events, and years-long fading in the Kepler mission. No single physical mechanism has successfully explained these observations to date. Here we investigate the ultraviolet variability of KIC 8462852 on a range of timescales using data from the GALEX mission that occurred contemporaneously with the Kepler mission. The wide wavelength baseline between the Kepler and GALEX data provides a unique constraint on the nature of the variability. Using 1600 seconds of photon-counting data from four GALEX visits spread over 70 days in 2011, we find no coherent NUV variability in the system on 10-100 second or months timescales. Comparing the integrated flux from these 2011 visits to the 2012 NUV flux published in the GALEX-CAUSE Kepler survey, we find a 3% decrease in brightness for KIC 8462852. We find this level of variability is significant, but not necessarily unusual for stars of similar spectral type in the GALEX data. This decrease coincides with the secular optical fading reported by Montet & Simon (2016). We find the multi-wavelength variability is somewhat inconsistent with typical interstellar dust absorption, but instead favors a R V = 5.0 ± 0.9 reddening law potentially from circumstellar dust.

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Section: Galex Observationsmentioning

confidence: 99%

The GALEX View of “Boyajian’s Star” (KIC 8462852)

Davenport

Covey

Clarke

et al. 2018

ApJ

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“…Software: gPhoton (Million et al 2016), Astropy (Astropy Collaboration 2013), matplotlib (Hunter 2007), and SciPy (Jones et al 2001)…”

Section: Acknowledgementsmentioning

confidence: 99%

Searching for Short-timescale Variability in the Ultraviolet with the GALEX gPhoton Archive. I. Artifacts and Spurious Periodicities

Vega

Bianchi

2018

ApJS

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In order to develop and test a methodology to search for UV variability over the entire GALEX database down to the shortest time scales, we analyzed time-domain photometry of ∼ 5000 light curves of ∼ 300 bright (m FUV , m NUV ≤ 14) and blue (m FUV − m NUV < 0) GALEX sources. Using the gPhoton database tool, we discovered and characterized instrumentally-induced variabilities in time-resolved GALEX photometry, which may severely impact automated searches for short-period variations. The most notable artifact is a quasi-sinusoidal variation mimicking light curves typical of pulsators, seen occasionally in either one or both detectors, with amplitudes of up to 0.3 mag and periods corresponding to the periodicity of the spiral dithering pattern used during the observation (P∼120 sec). Therefore, the artifact may arise from small-scale response variations. Other artifacts include visit-long "sagging" or "hump" in flux, occurring when the dithering pattern is not a spiral, or a one-time change in flux level during the exposure. These instrumentally-caused variations were not reported before, and are not due to known (and flagged) artifacts such as hot spots, which can be easily eliminated. To characterize the frequency and causality of such artifacts, we apply Fourier transform analysis to both light curves and dithering patterns, and examine whether artificial brightness variations correlate with visit or instrumental parameters. Artifacts do not correlate with source position on the detector. We suggest methods to identify artifact variations and to correct them when possible.

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“…A comprehensive overview of the original GALEX calibration pipeline and available data products is discussed in Morrissey et al (2005Morrissey et al ( , 2007 and Million et al (2016). In 2011 NASA ceased direct support for GALEX and transferred ownership to the California Institute of Technology for the so-called "CAUSE" phase, during which time data was collected and retained by each project's principal investigators until the spacecraft's decommission.…”

Section: Galexmentioning

confidence: 99%

“…1258+013 13 Million et al (2016) and on the project webpage 1 . Our work was conducted using version 1.28.2 of the gPhoton software.…”

Section: Gphotonmentioning

confidence: 99%

White dwarf variability with gPhoton: pulsators

Tucker

Fleming

Pelisoli

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present results from a search for short time-scale white dwarf variability using gPhoton, a time-tagged database of GALEX photon events and associated software package. We conducted a survey of 320 white dwarf stars in the McCook-Sion catalogue, inspecting each for photometric variability with particular emphasis on variability over time-scales less than ∼ 30 minutes. From that survey, we present the discovery of a new pulsating white dwarf: WD 2246-069. A Ca II K line is found in archival ESO spectra and an IR excess is seen in WISE W 1 and W 2 bands. Its independent modes are identified in follow-up optical photometry and used to model its interior structure. Additionally, we detect UV pulsations in four previously known pulsating ZZ Ceti-type (DAVs). Included in this group is the simultaneous fitting of the pulsations of WD 1401-147 in optical, near-ultraviolet and far-ultraviolet bands using nearly concurrent Whole Earth Telescope and GALEX data, providing observational insight into the wavelength dependence of white dwarf pulsation amplitudes.

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gPhoton: THE GALEX PHOTON DATA ARCHIVE

Cited by 65 publications

References 24 publications

The GALEX View of “Boyajian’s Star” (KIC 8462852)

The GALEX View of “Boyajian’s Star” (KIC 8462852)

Searching for Short-timescale Variability in the Ultraviolet with the GALEX gPhoton Archive. I. Artifacts and Spurious Periodicities

White dwarf variability with gPhoton: pulsators

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