NICHOLAS J. RUFFINI

A HYPER-RUNAWAY WHITE DWARF IN GAIA DR2 AS A TYPE IAX SUPERNOVA PRIMARY REMNANT CANDIDATE

Observations of stellar remnants linked to Type Ia and Type Iax supernovae are necessary to fully understand their progenitors. Multiple progenitor scenarios predict a population of kicked donor remnants and partially-burnt primary remnants, both moving with relatively high velocity. But only a handful of examples consistent with these two predicted populations have been observed. Here we report the likely first known example of an unbound white dwarf that is consistent with being the fully-cooled primary remnant to a Type Iax supernova. The candidate, LP 93-21, is travelling with a galactocentric velocity of v_gal ~ 605 km/s, and is gravitationally unbound to the Milky Way. We rule out an extragalactic origin. The Type Iax supernova ejection scenario is consistent with its peculiar unbound trajectory, given anomalous elemental abundances are detected in its photosphere via spectroscopic follow-up. This discovery reflects recent models that suggest stellar ejections likely occur often. Unfortunately the intrinsic faintness of white dwarfs, and the uncertainty associated with their direct progenitor systems, makes it difficult to detect and confirm such donors.

NASA Planetary Data System, PDS4 Data Collection, 2018

HALE-BOPP VISUAL LIGHTCURVE

This dataset contains visual magnitudes of comet C/1995 O1 (Hale-Bopp) that were obtained from the International Comet Quarterly and processed to provide a secular lightcurve from -7 AU (pre-perihelion) to +8 AU (post-perihelion). The original apparent magnitudes from 17 observers were corrected for geocentric distance and phase angle, and then combined in a systematic way that yielded a self-consistent consensus fit. In analyzing visual data from multiple observers, the questions inevitably arise of which data to reject, and under what justification, and whether combining data from observers, each with their own systematic errors, leads to a biased result. Without instrumental calibration, there is no certain answer to these questions, and such calibration is not available for the observations discussed here. We estimated the shifts with a self-consistent statistical approach, leading to a sharper light curve and improving the precision of the measured slopes. The dataset includes the original apparent magnitudes, those corrected for geocentric distance and phase angle, and the final shifted and weighted values. The final secular lightcurve is the best produced to date for comet Hale-Bopp.