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Abstract If Type Ia supernovae (SNe Ia) result from a white dwarf being ignited by Roche-lobe overflow from a nondegenerate companion, then as the SN explosion runs into the companion star its ejecta will be shocked, causing an early blue excess in the lightcurve. A handful of these excesses have been found in single-object studies, but inferences about the population of SNe Ia as a whole have been limited because of the rarity of multiwavelength follow-up within days of explosion. Here we present a 3 yr investigation yielding a nearly unbiased sample of nine nearby (z < 0.01) SNe Ia with exemplary early data. The data are multiwavelength, coveringUBVgriand Neil Gehrels Swift Observatory UV bandpasses, and also early, with an average first epoch 16.0 days before maximum light. Of the nine objects, three show early blue excesses. We do not find enough statistical evidence to reject the null hypothesis that SNe Ia predominantly arise from Roche-lobe-overflowing single-degenerate systems (p= 0.94). When looking at the objects’ colors, we find the objects are almost uniformly near-UV–blue, in contrast to earlier literature samples which found that only a third of SNe Ia are near-UV–blue, and we find a seemingly continuous range ofB − Vcolors in the days after explosion, again in contrast with earlier claims in the literature. This study highlights the importance of early, multiwavelength, high-cadence data in determining the progenitor systems of SNe Ia and in revealing their diverse early behavior. 

Effective communication in science is recognized as an important component of training for STEM professionals. This project focuses specifically on improving scientific communication to achieve this goal. Two learning communities that pair STEM research and inquiry activities in biology and chemistry with a public speaking course are being implemented with intentional and sustained instruction and mastery experiences to develop students’ science communication skills. The hypothesis is that instruction on how to communicate science effectively can result in an increase in students' understanding, confidence, and identity as a scientist. This can result in greater student engagement in the major and improved retention in STEM disciplines. Our aim is to test this curriculum intervention to determine its effectiveness in improving student communication ability and achievement. 

A combination of strategies was implemented to reduce barriers to transfer from associate to baccalaureate programs, and baccalaureate degree completion. These strategies include creation of the STEM Transfer Collaborative (STC). an adaption of the CUNY Pathways articulation initiative. Components of the STC include articulation agreements, shared professional development to align pedagogy and curriculum, outreach and collaboration by both the sending and receiving college faculty to begin transfer preparation and support before transfer occurs, and regular updates to community college faculty on the success of their transfer students. The second strategy employed is Momentum to the Baccalaureate (MB), an adaption of the CUNY Accelerated Study in Associate Programs (ASAP). MB provides support for junior and senior-level transfer students who are either community colleges associate degree graduates (external transfer) or associate degree graduates who transferred to bachelor’s programs at the same comprehensive college they earned their associate degree at, which has a 2+2 degree structure (internal transfer). Components of MB include personalized mentoring, advisement, and monthly stipends to students who maintain full-time enrollment and good academic standing. Participating majors include computer engineering technology, computer systems technology, construction management and civil engineering technology, electrical engineering technology, and applied chemistry. Propensity matching was used to evaluate the effectiveness of these strategies. Participating campuses are part of the City University of New York (CUNY), and include six community colleges (Borough of Manhattan Community College, Bronx Community College, Guttman Community College, Hostos Community College, Kingsborough Community College, and LaGuardia Community College), five of which are Hispanic Serving Institutions (HSIs), and New York City College of Technology (City Tech), also an HSI, which offers associate and bachelor’s programs (2+2 structure). Our first cohort of 40 students started upper-level studies in fall 2019, and has completed 2 years (four semesters) of post-associate degree study. The second cohort of 40 students, started in fall 2020, and has completed one year (two semesters) of post-associate degree study. Cohort 1 students receiving MB, supports had a significantly higher graduation rate after two years than the college average. Additionally, for cohort 1, the STC seems to have reduced “transfer shock,” the typical drop in GPA the first semester after transfer. There was no statistical difference in GPA, credits completed and semester-to-semester persistence of internal and external transfers in the MB program. Cohort 1 external transfer students who received support though MB also had a statistically significant improvement in their semester GPAs for their first 3 semesters at City Tech compared to matched students who were not provided support in the junior and senior years. There was no statistically significant difference by the 4th semester. Cohort 2 internal transfers receiving MB supports in their junior year had a statistically significant improvement in credits earned and persistence compared to a matched cohort without MB supports. There was no statistically significant improvement of external transfers compared to a matched cohort, who did not receive MB supports The inability of external transfer students to come to campus due to the pandemic, may have negated the sense of community and belonging that MB was intended to create. Overall, these preliminary results suggest that targeted pre-transfer and post-transfer supports improve transfer student outcomes. This project (NSF grant #1832457) was funded through the NSF Division of Education, Improving Undergraduate STEM Education: Hispanic-Serving Institutions Program. 

Abstract We present a JWST MIRI medium-resolution spectrometer spectrum (5–27μm) of the Type Ia supernova (SN Ia) SN 2021aefx at +415 days pastB-band maximum. The spectrum, which was obtained during the iron-dominated nebular phase, has been analyzed in combination with previous JWST observations of SN 2021aefx to provide the first JWST time series analysis of an SN Ia. We find that the temporal evolution of the [Coiii] 11.888μm feature directly traces the decay of⁵⁶Co. The spectra, line profiles, and their evolution are analyzed with off-center delayed-detonation models. Best fits were obtained with white dwarf (WD) central densities ofρ_c= 0.9−1.1 × 10⁹g cm⁻³, a WD mass ofM_WD= 1.33–1.35M_⊙, a WD magnetic field of ≈10⁶G, and an off-center deflagration-to-detonation transition at ≈0.5M_⊙seen opposite to the line of sight of the observer (−30°). The inner electron capture core is dominated by energy deposition fromγ-rays, whereas a broader region is dominated by positron deposition, placing SN 2021aefx at +415 days in the transitional phase of the evolution to the positron-dominated regime. The formerly “flat-tilted” profile at 9μm now has a significant contribution from [Niiv], [Feii], and [Feiii] and less from [Ariii], which alters the shape of the feature as positrons mostly excite the low-velocity Ar. Overall, the strength of the stable Ni features in the spectrum is dominated by positron transport rather than the Ni mass. Based on multidimensional models, our analysis is consistent with a single-spot, close-to-central ignition with an indication of a preexisting turbulent velocity field and excludes a multiple-spot, off-center ignition. 

ABSTRACT We report the All-Sky Automated Survey for SuperNovae discovery of the tidal disruption event (TDE) ASASSN-23bd (AT 2023clx) in NGC 3799, a LINER galaxy with no evidence of strong active galactic nucleus (AGN) activity over the past decade. With a redshift of z = 0.01107 and a peak ultraviolet (UV)/optical luminosity of (5.4 ± 0.4) × 1042 erg s−1, ASASSN-23bd is the lowest-redshift and least-luminous TDE discovered to date. Spectroscopically, ASASSN-23bd shows H α and He i emission throughout its spectral time series, there are no coronal lines in its near-infrared spectrum, and the UV spectrum shows nitrogen lines without the strong carbon and magnesium lines typically seen for AGN. Fits to the rising ASAS-SN light curve show that ASASSN-23bd started to brighten on MJD 59988$$^{+1}_{-1}$$, ∼9 d before discovery, with a nearly linear rise in flux, peaking in the g band on MJD $$60 \, 000^{+3}_{-3}$$. Scaling relations and TDE light curve modelling find a black hole mass of ∼106 M⊙, which is on the lower end of supermassive black hole masses. ASASSN-23bd is a dim X-ray source, with an upper limit of $$L_{0.3-10\, \mathrm{keV}} \lt 1.0\times 10^{40}$$ erg s−1 from stacking all Swift observations prior to MJD 60061, but with soft (∼0.1 keV) thermal emission with a luminosity of $$L_{0.3-2 \, \mathrm{keV}}\sim 4\times 10^{39}$$ erg s−1 in XMM-Newton observations on MJD 60095. The rapid (t < 15 d) light curve rise, low UV/optical luminosity, and a luminosity decline over 40 d of ΔL40 ≈ −0.7 dex make ASASSN-23bd one of the dimmest TDEs to date and a member of the growing ‘Low Luminosity and Fast’ class of TDEs.