Day 1489

Wednesday.

1810.0896
Challenging a Newtonian prediction through Gaia wide binaries
Hernandez, et al

Under Newtonian dynamics, the relative motion of the components of a binary star should follow Kepler's laws and show a Delta v ~ delta r^{-1/2} scaling with separation, Delta r.  Once orientation effects and a distribution of ellipticities are accounted for, dynamical evolution can be modeled to include the effects of Galactic tides and stellar mass perturbers, over the lifetime of the solar neighborhood.  This furnishes a prediction for the relative velocity between the components of a binary and their projected separation.  Taking a carefully selected small sample of 83 solar neighborhood wide binaries from the work of Shaya & Olling (2011) for the Hipparcos catalogue, identify these same stars in the recent Gaia DR2, to test the prediction mentioned using the latest and most accurate astrometry available.  The results are consistent with the Newtonian prediction for projected separations below 7000 AU, but inconsistent with it at large separations, where accelerations are expected to be lower than the critical a0=1.2e-10 m/s^2 value of MONDian gravity.  This result challenges Newtonian gravity at low accelerations and shows clearly the appearance of gravitational anomalies of the type usually attributed to dark matter at galactic scales, now at much smaller stellar scales.


1810.09505
What does a successful postdoctoral fellowship publication record look like?
Pepper, et al

Obtaining a prize postdoctoral fellowship in astronomy and astrophysics involves a number of factors, many of which cannot be quantified.  One criterion that can be measured is the publication record of an applicant.  The publication records of pst fellowship recipients may, therefore, provide some quantitative guidance for future prospective applicants.  Investigate the publication patterns of recipients of the NASA prize postdoctoral fellowships in the Hubble, Einstein, and Sagan programs from 2014 through 2017, using the NASA ADS reference system.  Tabulated their publications at the point where fellowship applications were submitted, and find that the 133 fellowship recipients in that time frame had a median of 6±2 first-author publications, and 14±6 co-authored publications.  The full range of first author papers is 1 to 15, and for all papers ranges from 2 to 76, indicating very diverse publication patterns.  Thus, while fellowship recipients generally have strong publication records, the distribution of both first-author and co-authored papers is quite broad; there is no apparent threshold of publications necessary to obtain these fellowships.  Also examined the post-PhD publication rates for each of the three fellowship programs, between male and female recipients, across the four years of the analysis and find no consistent trends.  Hope that these findings will prove a useful reference to future junior scientists.


1810.09702
A new method for calibration of gain variation in detector system
Goda, Matsuo

Transit spectroscopy of habitable planets orbiting late-type stars requires high relative spectro-photometric accuracy between wavelengths during transit/eclipse observation.  The spectra-photometric signal is not affected only by image movement and deformation due to wavefront error but also by electrical variation in the detector system.  These time-variation components, coupled to the transit signal, distort the measurements of atmospheric composition in transit spectroscopy.  Propose a new concept for improvement of spectra-photometric accuracy through the calibration of the time-variation components in the detector system by developing densified pupil spectroscopy that provides multiple spectra of the star-planet system.  Owing to a group of pixels exposed by the object light (i.e., science pixels), pixel-to-pixel variations can be smoothed out through an averaging operation, thus only common time-variation components per the science pixels remain.  In addition, considering that the detector plane is optically conjugated to the pupil plane, a pupil mask can completely block astronomical light incoming into residual pixels.  The common time-variation components are reconstructed with the residual pixels and reduced into a random term.  Applying the densified pupil spectrograph with a mid-infrared detector system to a large space cryogenic telescope such as the Origins Space Telescope, show that the system nearly achieves photon-noise limited performance and detects absorption features through transmission spectroscopy and secondary eclipse of terrestrial planets orbiting M-type stars at 10 pc with 60 transit observations.  Thus, the proposed method contributes to the measurement of planetary habitability and biosignatures of the nearby transiting habitable candidates.