The GFCAT: a catalog of ultraviolet variables observed by GALEX with sub-minute resolution

We have performed the first systematic search of the full GALEX data archive for astrophysical variability on timescales of seconds to minutes by rebinning data across the whole mission to 30-second time resolution. The result is the GALEX Flare Catalog (GFCAT) which describes 1426 ultraviolet variable sources, including stellar flares, eclipsing binaries, $\delta$ Scuti and RR Lyrae variables, and Active Galactic Nuclei (AGN). Many of these sources have never previously been identified as variable. We have also assembled a table of observations of ultraviolet flares and accompanying statistics and measurements, including energies, and of candidate eclipsing stars. This effort was enabled by a significantly-enhanced version of the gPhoton software for analyzing time-domain GALEX data; this gPhoton2 package is available to support follow-on efforts.Comment: accepted in ApJS; data available as a MAST High Level Science Product via https://dx.doi.org/10.17909/8d57-169

New Time-Resolved, Multi-Band Flares In The GJ 65 System With gPhoton

Characterizing the distribution of flare properties and occurrence rates is important for understanding habitability of M dwarf exoplanets. The GALEX space telescope observed the GJ 65 system, composed of the active, flaring M stars BL Cet and UV Cet, for 15900 seconds (~4.4 hours) in two ultraviolet bands. The contrast in flux between flares and the photospheres of cool stars is maximized at ultraviolet wavelengths, and GJ 65 is the brightest and nearest flaring M dwarf system with significant GALEX coverage. It therefore represents the best opportunity to measure low energy flares with GALEX. We construct high cadence light curves from calibrated photon events and find 13 new flare events with NUV energies ranging from 10^28.5 - 10^29.5 ergs and recover one previously reported flare with an energy of 10^31 ergs. The newly reported flares are among the smallest M dwarf flares observed in the ultraviolet with sufficient time resolution to discern light curve morphology. The estimated flare frequency at these low energies is consistent with extrapolation from the distributions of higher-energy flares on active M dwarfs measured by other surveys. The largest flare in our sample is bright enough to exceed the local non-linearity threshold of the GALEX detectors, which precludes color analysis. However, we detect quasi-periodic pulsations (QPP) during this flare in both the FUV and NUV bands at a period of ~50 seconds, which we interpret as a modulation of the flare's chromospheric thermal emission through periodic triggering of reconnection by external MHD oscillations in the corona.Comment: 22 pages, 20 figures, Jupyter Python notebooks to reproduce figures and tables available on GitHub at https://github.com/MillionConcepts/gfcat_gj6

A search for rapidly pulsating hot subdwarf stars in the GALEX survey

NASA's Galaxy Evolution Explorer (GALEX) provided near- and far-UV observations for approximately 77 percent of the sky over a ten-year period; however, the data reduction pipeline initially only released single NUV and FUV images to the community. The recently released Python module gPhoton changes this, allowing calibrated time-series aperture photometry to be extracted easily from the raw GALEX data set. Here we use gPhoton to generate light curves for all hot subdwarf B (sdB) stars that were observed by GALEX, with the intention of identifying short-period, p-mode pulsations. We find that the spacecraft's short visit durations, uneven gaps between visits, and dither pattern make the detection of hot subdwarf pulsations difficult. Nonetheless, we detect UV variations in four previously known pulsating targets and report their UV pulsation amplitudes and frequencies. Additionally, we find that several other sdB targets not previously known to vary show promising signals in their periodograms. Using optical follow-up photometry with the Skynet Robotic Telescope Network, we confirm p-mode pulsations in one of these targets, LAMOST J082517.99+113106.3, and report it as the most recent addition to the sdBVr class of variable stars.Comment: 11 Pages, 8 Figures, Accepted for publication in the Astrophysical Journa

Extending Optical Flare Models to the UV: Results from Comparing of TESS and GALEX Flare Observations For M Dwarfs

The ultraviolet (UV) emission of stellar flares may have a pivotal role in the habitability of rocky exoplanets around low-mass stars. Previous studies have used white-light observations to calibrate empirical models which describe the optical and UV flare emission. However, the accuracy of the UV predictions of models have previously not been tested. We combined TESS optical and GALEX UV observations to test the UV predictions of empirical flare models calibrated using optical flare rates of M stars. We find that the canonical 9000 K blackbody model used by flare studies underestimates the GALEX NUV energies of field age M stars by up to a factor of 6.5$\pm$0.7 and the GALEX FUV energies of fully convective field age M stars by 30.6$\pm$10.0. We calculated energy correction factors that can be used to bring the UV predictions of flare models closer in line with observations. We calculated pseudo-continuum flare temperatures that describe both the white-light and GALEX NUV emission. We measured a temperature of 10,700 K for flares from fully convective M stars after accounting for the contribution from UV line emission. We also applied our correction factors to the results of previous studies of the role of flares in abiogenesis. Our results show that M stars do not need to be as active as previously thought in order to provide the NUV flux required for prebiotic chemistry, however we note that flares will also provide more FUV flux than previously modelled.Comment: 20 pages, 9 figures, 4 tables. Accepted for publication in the Monthly Notices of the Royal Astronomical Societ

The GALEX View of "Boyajian's Star" (KIC 8462852)

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 $\pm$ 0.9 reddening law potentially from circumstellar dust.Comment: 8 pages, 4 figures, ApJ Accepte

Concert recording 2015-11-30

[Track 01]. Danza brasiliera / Jorge Morel -- [Track 02]. Sunburst / Andrew York -- [Track 03]. Ladron broma / Chase Chamberlin -- [Track 04]. Etudes 1, 2, & 3 / Matteo Carcassi -- [Track 05]. Invitation / Bronislaw Kaper -- [Track 06]. Ami etude / Ferdinando Carulli -- Variation (slur study) / Mauro Giuliani -- [Track 07]. Tango / Isaac Albeniz -- [Track 08]. Invention no. 8 / J.S. Bach -- [Track 09]. Don\u27t get around much anymore / Duke Ellington -- [Track 10]. Turnaround / Omette Coleman -- [Track 11]. Julia Florida / Augustin Barrios -- [Track 12]. Estudio 9 / Fernando Sor -- [Track 13]. Billie\u27s bounce / C. Parker -- [Track 14]. Emily / J. Mandel -- [Track 15]. Lagrima, Adelita / F. Tarrega

OpenPlanetary, an "umbrella" non-profit organisation for open planetary science communities

OpenPlanetary, or simply "OP", is an international non-profit organisation that promotes open research in the planetary science and exploration communities: sharing ideas and collaborating on planetary research and data analysis problems, new challenges, and opportunities. OpenPlanetary started in 2015 as a way for participants of the ESA’s Planetary GIS Workshop to stay connected and exchange information related to and beyond this workshop. It expanded further by playing a similar role for the second USGS-hosted Planetary Data Workshop (PDW) in 2017. OpenPlanetary has continued to support the biannual PDW and provides a more persistent forum for participants to highlight presented topics and discussions from the workshops. In 2018, we established OpenPlanetary as a non-profit organisation (Association under 1901 French Law,) in order to provide us with a legal framework to sustainably fund our community framework, projects and activities, and to better serve the planetary science community as a whole. OpenPlanetary is governed by a Board of Directors, elected for two years, which (1) define the policy and general orientation, (2) initiate, endorse, lead, or contribute to the projects and activities, and (3) can make use of the funds of the Association for any endorsed project or activity; the Bureau contains a 3-person subset of the Board members (a president, treasurer, and secretary) and serves as the executive body of the Association

Mastcam multispectral database from the Curiosity rover’s traverse in the Gale crater, Mars (sols 2302-3672)

The Mars Science Laboratory (MSL) Curiosity rover has continued to explore the lower strata of Mt. Sharp in Gale Crater. Evidence for fluvial, lacustrine, and aeolian paleoenvironments has been found by multiple instruments. Curiosity’s multispectral imaging instrument, Mast Camera (Mastcam), is able to collect reflectance data covering visible to near-infrared wavelengths from 445 nm to 1013 nm. The primary control on Mastcam multispectral variability is the presence and amount of iron oxides. However, Mastcam can still make broad interpretations regarding mineralogy and diagenesis, especially when used in tandem with other instruments. This dataset includes Mastcam spectra from 266 observations, collected from sols 2302 to 3672 in Glen Torridon, Greenheugh pediment, and the clay-sulfate transition. Geologic metadata, like the type of rock surface and its position in stratigraphy, is included with each spectrum in the database, as well as image products (decorrelation and enhanced color stretches) that aided in our analyses, and context images that show where the spectra were extracted from