Nuclear and Orbital Characterization of the Transition Object (4015) 107P/Wilson-Harrington

Comet 107P/Wilson-Harrington, cross-listed as asteroid 4015, is one of the original transition objects whose properties do not neatly fit into a cometary or asteroidal origin. Discovered in a period of apparently gas-dominated activity in 1949, it was subsequently lost and recovered as the inactive asteroid 1979 VA. We obtained new and re-analyzed archival observations of the object, compared to meteorites, and conducted new orbital integrations in order to understand the nature of this object and to understand where it falls on the asteroid-comet continuum. Wilson-Harrington's reflectance spectrum is approximately neutral from visible to near-infrared wavelengths, but has a reflectance maximum near 0.8-0.9 microns. The object's spectrum is well matched by laboratory spectra of carbonaceous chondrite meteorites like the CM Murchison or the CI Ivuna. The object's phase curve is compatible with either an asteroidal or cometary origin, and its recent orbital history has no periods with high enough temperatures to have altered its surface. While it is possible that some unknown process has acted to change the surface from an originally cometary one, we instead prefer a fundamentally asteroidal origin for Wilson-Harrington which can explain its surface and orbital properties. However, this would require a way to maintain significant (hyper-)volatile supplies on the near-Earth objects beyond what is currently expected. Wilson-Harrington's similar meteorite affinity and possible orbital link to sample return targets (162173) Ryugu and (101955) Bennu suggest that the returned samples from the Hayabusa-2 and OSIRIS-REx missions might hold the key to understanding this object.Comment: 22 pages, 5 figures, accepted for publication in the AAS's Planetary Science Journal (PSJ

Self-Efficacy, Motivation, and Academic Success: Learners With ADHD in Online Universities

Research on traditional or brick and mortar universities suggests that there is an association between self-efficacy, intrinsic motivation (IM), extrinsic motivation (EM), and academic success in higher education. What is not yet clear is whether self-efficacy and motivation (IM and EM) are associated with academic success in online universities. The purpose of this study was to examine whether there is an association between self-efficacy, motivation (IM and EM), and academic success for learners with attention deficit hyperactivity disorder (ADHD) who attend online universities. The possible role of self-efficacy in mediating the relationship between IM and EM and academic success was also examined. Bandura’s theory of self-efficacy provided the theoretical framework for this study. The survey instrument included demographic questions, grade point average score, and items from the General Self-Efficacy Scale and the Academic Motivation Scale. A convenience sample of 52 students who attended an online university completed the survey anonymously on SurveyMonkey. Regression analysis indicated there were no statistical significance between the variables. Mediation analysis indicated statistical significance between self-efficacy and IM, which is consistent with the literature. However, overall mediation effects were nonsignificant. The findings indicate that other factors such as peer relationships are equally important to consider in the development of learning activities that influence learner engagement, persistence, and academic success. The study’s implications for positive social change include informing university staff about strategies to support the retention and academic success of students with ADHD who attend online universities

Near-infrared observations of active asteroid (3200) Phaethon reveal no evidence for hydration

Asteroid (3200) Phaethon is an active near-Earth asteroid and the parent body of the Geminid Meteor Shower. Because of its small perihelion distance, Phaethon's surface reaches temperatures sufficient to destabilize hydrated materials. We conducted rotationally resolved spectroscopic observations of this asteroid, mostly covering the northern hemisphere and the equatorial region, beyond 2.5-micron to search for evidence of hydration on its surface. Here we show that the observed part of Phaethon does not exhibit the 3-micron hydrated mineral absorption (within 2-sigma). These observations suggest that Phaethon's modern activity is not due to volatile sublimation or devolatilization of phyllosilicates on its surface. It is possible that the observed part of Phaethon was originally hydrated and has since lost volatiles from its surface via dehydration, supporting its connection to the Pallas family, or it was formed from anhydrous material

Near-Infrared Spectroscopy Of The Nucleus Of Low-Activity Comet P/2016 BA14_{14} During Its 2016 Close Approach

The Near-Earth Comet P/2016 BA$_{14}$ (PanSTARRS) is a slow-rotatating nearly-dormant object, a likely dynamical twin of 252P/LINEAR, and was recently shown to have a mid-infrared spectrum very dissimilar to other comets. BA$_{14}$ also recently selected one of the back-up targets for the ESA's \textit{Comet Interceptor}, so a clearer understanding of BA$_{14}$'s modern properties would not just improve our understanding of how comets go dormant, but could also aid planning for a potential spacecraft visit. We present observations of BA$_{14}$ taken on two dates during its 2016 Earth close approach with the NASA Infrared Telescope Facility, both of which are consistent with direct observations of its nucleus. The reflectance spectrum of BA$_{14}$ is similar to 67P/Churyumov-Gerasimenko, albeit highly phase-reddened. Thermal emission contaminates the reflectance spectrum at longer wavelengths, which we correct with a new Markov Chain Monte Carlo thermal modeling code. The models suggest $BA_{14}$'s visible geometric albedo is $p_V=0.01-0.03$, consistent with radar observations, its beaming parameter is typical for NEOs observed in its geometry, and its reflectrance spectrum is red and linear throughout H and K band. It appears very much like a "normal" comet nucleus, despite its mid-infrared oddities. A slow loss of fine grains as the object's activity diminished might help to reconcile some of the lines of evidence, and we discuss other possibilities. A spacecraft flyby past BA$_{14}$ could get closer to the nucleus than with a more active target, and we highlight some science questions that could be addressed with a visit to a (nearly-)dormant comet.Comment: 18 pages, 3 figures, accepted for publication in the Planetary Science Journal on April 1, 202

Physical Characterization of the December 2017 Outburst of the Centaur 174P/Echeclus

The Centaurs are the small solar system bodies intermediate between the active inner solar system Jupiter Family Comets and their inactive progenitors in the trans-Neptunian region. Among the fraction of Centaurs which show comet-like activity, 174P/Echeclus is best known for its massive 2005 outburst in which a large apparently active fragment was ejected above the escape velocity from the primary nucleus. We present visible imaging and near-infrared spectroscopy of Echeclus during the first week after its December 2017 outburst taken at the Faulkes North & South Telescopes and the NASA IRTF, the largest outburst since 2005. The coma was seen to be highly asymmetric. A secondary peak was seen in the near-infrared 2D spectra, which is strongly hinted at in the visible images, moving hyperbolically with respect to the nucleus. The retrieved reflectance spectrum of Echelcus is consistent with the unobscured nucleus but becomes bluer when a wider extraction aperture is used. We find that Echeclus's coma is best explained as dominated by large blue dust grains, which agrees with previous work. We also conducted a high-resolution orbital integration of Echeclus's recent evolution and found no large orbital changes that could drive its modern evolution. We interpret the second peak in the visible and near-infrared datasets as a large cloud of larger-than-dust debris ejected at the time of outburst. If Echeclus is typical of the Centaurs, there may be several debris ejection or fragmentation events per year on other Centaurs that are going unnoticed.Comment: Accepted for publication in the Astronomical Journal, 18 pages, 4 figures, 4 table

Characterisation of the new target of the NASA Lucy mission: asteroid 152830 Dinkinesh (1999 VD57)

The NASA Lucy mission is aimed at the study of the very interesting population of Jupiter Trojans, considered as time capsules from the origin of our solar system. During its journey, the mission will pass near a main belt asteroid, Donaldjohanson. Recently, NASA has announced that a new asteroid in the belt will also be visited by Lucy: 152830 Dinkinesh (1999 VD57). The main goal of this work is to characterise this newly selected target, asteroid Dinkinesh, in order to provide critical information to the mission team. To achieve it, we have obtained visible spectra, colour photometry, and time-series photometry of Dinkinesh, using several telescopes located at different observatories. For the spectra we used the 10.4m Gran Telescopio Canarias (GTC), in the island of La Palma (Spain); for the colour photometry the 4.3m Lowell Discovery Telescope (LDT), near Happy Jack, Arizona (USA) was used; and for the time-series photometry we used the 82cm IAC80 telescope located in the island of Tenerife (Spain). Both visible spectrum and reflectance values computed from colour photometry show that Dinkinesh is an S-type asteroid, i.e., it is composed mainly of silicates and some metal. According to observations done by the NEOWISE survey, S-type asteroids have typical geometric albedo of $p_V$ = 0.223 $\pm$ 0.073. From our time-series photometry, we obtained an asteroid mean magnitude $r'$ = 19.99 $\pm$ 0.05, which provides an absolute magnitude $H_{r'}$ = 17.53 $\pm$ 0.07 assuming $G$ = 0.19 $\pm$ 0.25 for S-types. Using our colour-photometry, we transformed $H_{r'}$ to $H_V$ = 17.48 $\pm$ 0.05. This value of absolute magnitude combined with the geometric albedo provides a mean diameter for Dinkinesh of $\sim$900 m, ranging between a minimum size of 542 m and a maximum size of 1309 m.Comment: 4 pages, 3 figures, Accepted for publication in A&

Physical Characterization of Active Asteroid (6478) Gault

Main belt asteroid (6478) Gault has been dynamically linked with two overlapping asteroid families: Phocaea, dominated by S-type asteroids, and Tamara, dominated by low-albedo C-types. This object has recently become an interesting case for study, after images obtained in late 2018 revealed that it was active and displaying a comet-like tail. Previous authors have proposed that the most likely scenarios to explain the observed activity on Gault were rotational excitation or merger of near-contact binaries. Here we use new photometric and spectroscopic data of Gault to determine its physical and compositional properties. Lightcurves derived from the photometric data showed little variation over three nights of observations, which prevented us from determining the rotation period of the asteroid. Using WISE observations of Gault and the near-Earth Asteroid Thermal Model (NEATM) we determined that this asteroid has a diameter $<$6 km. NIR spectroscopic data obtained with the Infrared Telescope Facility (IRTF) showed a spectrum similar to that of S-complex asteroids, and a surface composition consistent with H chondrite meteorites. These results favor a compositional affinity between Gault and asteroid (25) Phocaea, and rules out a compositional link with the Tamara family. From the spectroscopic data we found no evidence of fresh material that could have been exposed during the outburst episodes.Comment: 9 pages, 4 figures, accepted for publication in ApJ