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  1. Abstract

    We performed radio searches for the “spider” millisecond pulsar (MSP) candidates 4FGL J0935.3+0901, 4FGL J1627.7+3219, and 4FGL J2212.4+0708 using the Green Bank Telescope in an attempt to detect the proposed radio counterpart of the multi-wavelength variability seen in each system. We observed using the VEGAS spectrometer, centered predominantly at 2165 MHz; however, we were also granted observations at 820 MHz for 4FGL J1627.7+3219. We performed acceleration searches on each data set usingPRESTOas well as additional jerk searches of select observations. We see no evidence of a radio counterpart in any of the observations for each of the three systems at this time. Additional observations, perhaps at different orbital phases (e.g., inferior conjunction), may yield detections of an MSP in the future. Therefore, we urge continued monitoring of these systems to fully characterize the radio nature, however faint or variable, of each system.

     
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  2. Abstract Hot subdwarf stars are mostly stripped red giants that can exhibit photometric variations due to stellar pulsations, eclipses, the reflection effect, ellipsoidal modulation, and Doppler beaming. Detailed studies of their light curves help constrain stellar parameters through asteroseismological analyses or binary light-curve modeling and generally improve our capacity to draw a statistically meaningful picture of this enigmatic stage of stellar evolution. From an analysis of Gaia DR2 flux errors, we have identified around 1200 candidate hot subdwarfs with inflated flux errors for their magnitudes—a strong indicator of photometric variability. As a pilot study, we obtained 2 minute cadence TESS Cycle 2 observations of 187 candidate hot subdwarfs with anomalous Gaia flux errors. More than 90% of our targets show significant photometric variations in their TESS light curves. Many of the new systems found are cataclysmic variables, but we report the discovery of several new variable hot subdwarfs, including HW Vir binaries, reflection-effect systems, pulsating sdBV s stars, and ellipsoidally modulated systems. We determine atmospheric parameters for select systems using follow-up spectroscopy from the 3 m Shane telescope. Finally, we present a Fourier diagnostic plot for classifying binary light curves using the relative amplitudes and phases of their fundamental and harmonic signals in their periodograms. This plot makes it possible to identify certain types of variables efficiently, without directly investigating their light curves, and may assist in the rapid classification of systems observed in large photometric surveys. 
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