Optical observations of a SN 2002cx-like peculiar supernova SN 2013en in UGC 11369

We present optical observations of a SN 2002cx-like supernova SN 2013en in UGC 11369, spanning from a phase near maximum light (t= +1 d) to t= +60 d with respect to the R-band maximum. Adopting a distance modulus of mu=34.11 +/- 0.15 mag and a total extinction (host galaxy+Milky Way) of $A_V \sim1.5$ mag, we found that SN 2013en peaked at $M(R)\sim -18.6$ mag, which is underluminous compared to the normal SNe Ia. The near maximum spectra show lines of Si II, Fe II, Fe III, Cr II, Ca II and other intermediate-mass and iron group elements which all have lower expansion velocities (i.e., ~ 6000 km/s). The photometric and spectroscopic evolution of SN 2013en is remarkably similar to those of SN 2002cx and SN 2005hk, suggesting that they are likely to be generated from a similar progenitor scenario or explosion mechanism.Comment: 8 pages, 8 figures, 3 tables, accepted for publication in MNRA

The Very Young Type Ia Supernova 2013dy: Discovery, and Strong Carbon Absorption in Early-Time Spectra

The Type Ia supernova (SN Ia) 2013dy in NGC 7250 (d ~ 13.7 Mpc) was discovered by the Lick Observatory Supernova Search. Combined with a prediscovery detection by the Italian Supernova Search Project, we are able to constrain the first-light time of SN 2013dy to be only 0.10 +/- 0.05 d (2.4 +/- 1.2 hr) before the first detection. This makes SN 2013dy the earliest known detection of an SN Ia. We infer an upper limit on the radius of the progenitor star of R_0 < 0.25 R_sun, consistent with that of a white dwarf. The light curve exhibits a broken power law with exponents of 0.88 and then 1.80. A spectrum taken 1.63 d after first light reveals a C II absorption line comparable in strength to Si II. This is the strongest C II feature ever detected in a normal SN Ia, suggesting that the progenitor star had significant unburned material. The C II line in SN 2013dy weakens rapidly and is undetected in a spectrum 7 days later, indicating that C II is detectable for only a very short time in some SNe Ia. SN 2013dy reached a B-band maximum of M_B = -18.72 +/- 0.03 mag ~17.7 d after first light.Comment: Accepted for Publication in ApJ Letter

Physical properties of the trans-Neptunian binary 2000 YW₁₃₄

The study of trans-Neptunian binaries (TNBs) remains one of the most active areas of progress in understanding the solar system beyond Neptune. TNBs have been found in every dynamical population of the trans-Neptunian region (Noll et al. 2020), with proportions ranging from 29 % in the cold classical population to 5.5 % for the remaining classes combined (Brunini 2020). The formation of the contact TNB Arrokoth is one of the challenges that formation models face nowadays. The current angular momentum of Arrokoth is too low and the current binary formation scenarios, by either rotational fission or streaming instability (Nesvorný et al. 2019), require also loss of angular momentum (McKinnon et al. 2020). Additionally, formation mechanisms of close binaries may be distinct from those for the wider pairs. As the angular momentum of a system approaches that of an object spinning near its critical rotation period, rotational fission is the most likely explanation for their formation (Descamps et al. 2008), which is thought to be the case for the proposed satellites of Varuna and 2002 TC302 systems (Fernández-Valenzuela et al. 2019; Ortiz et al. 2020). If close TNBs turn out to be common for objects rotating close to the breakup limit, that could reveal important clues about angular momentum evolution during accretion for TNOs (Petit et al. 2011). However, characterizing binary systems at such distances is challenging. From the ~120 known TNBs, only around 40 have their mutual orbit fully determined, let alone physical characterization. 2000 YW134 is a TNB in a 3:8 resonance with an orbital semi-major axis of 57.4 au (a rare occurrence). On February 23rd, 2022, it occulted the Gaia EDR3 star 627356458358636544 (V = 17.1 mag). The stellar occultation was initially predicted using the JPL orbit solution #24, and updated using data from the 1.5-m and 1.23-m telescopes at Sierra Nevada and Calar Alto Observatories, using the same methodology as explained in Ortiz et al (2020). From the 17 observatories involved, seven reported positive chords, with five of them corresponding to the main body and the other two chords corresponding to its satellite. We are currently working on the analysis of these data in order to obtain the physical properties that characterize the system. Preliminary results show that the lower limit for the equivalent projected diameter of the satellite is twice the previously estimated size from HST observations (Stephens et al. 2006). We will also compare our results with the area-equivalent diameter and albedo obtained using thermal data from Herschel and Spitzer observations (Farkas-Takács et al. 2020)

Pluto's lower atmosphere and pressure evolution from ground-based stellar occultations, 1988-2016

Context. The tenuous nitrogen (N2) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New Horizons spacecraft. Aims. The main goals of this study are (i) to construct a well calibrated record of the seasonal evolution of surface pressure on Pluto and (ii) to constrain the structure of the lower atmosphere using a central flash observed in 2015. Methods. Eleven stellar occultations by Pluto observed between 2002 and 2016 are used to retrieve atmospheric profiles (density, pressure, temperature) between altitude levels of ~5 and ~380 km (i.e. pressures from ~ 10 μbar to 10 nbar). Results. (i) Pressure has suffered a monotonic increase from 1988 to 2016, that is compared to a seasonal volatile transport model, from which tight constraints on a combination of albedo and emissivity of N2 ice are derived. (ii) A central flash observed on 2015 June 29 is consistent with New Horizons REX profiles, provided that (a) large diurnal temperature variations (not expected by current models) occur over Sputnik Planitia; and/or (b) hazes with tangential optical depth of ~0.3 are present at 4–7 km altitude levels; and/or (c) the nominal REX density values are overestimated by an implausibly large factor of ~20%; and/or (d) higher terrains block part of the flash in the Charon facing hemisphere

Lower atmosphere and pressure evolution on Pluto from ground-based stellar occultations, 1988-2016

Context. The tenuous nitrogen (N2) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New Horizons spacecraft. Aims: The main goals of this study are (i) to construct a well calibrated record of the seasonal evolution of surface pressure on Pluto and (ii) to constrain the structure of the lower atmosphere using a central flash observed in 2015. Methods: Eleven stellar occultations by Pluto observed between 2002 and 2016 are used to retrieve atmospheric profiles (density, pressure, temperature) between altitude levels of 5 and 380 km (i.e. pressures from 10 μbar to 10 nbar). Results: (i) Pressure has suffered a monotonic increase from 1988 to 2016, that is compared to a seasonal volatile transport model, from which tight constraints on a combination of albedo and emissivity of N2 ice are derived. (ii) A central flash observed on 2015 June 29 is consistent with New Horizons REX profiles, provided that (a) large diurnal temperature variations (not expected by current models) occur over Sputnik Planitia; and/or (b) hazes with tangential optical depth of 0.3 are present at 4-7 km altitude levels; and/or (c) the nominal REX density values are overestimated by an implausibly large factor of 20%; and/or (d) higher terrains block part of the flash in the Charon facing hemisphere

Lower atmosphere and pressure evolution on Pluto from ground-based stellar occultations, 1988-2016

Context. The tenuous nitrogen (N2) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New Horizons spacecraft. Aims. The main goals of this study are (i) to construct a well calibrated record of the seasonal evolution of surface pressure on Pluto and (ii) to constrain the structure of the lower atmosphere using a central flash observed in 2015. Methods. Eleven stellar occultations by Pluto observed between 2002 and 2016 are used to retrieve atmospheric profiles (density, pressure, temperature) between altitude levels of ∼5 and ∼380 km (i.e. pressures from ∼10 μbar to 10 nbar). Results. (i) Pressure has suffered a monotonic increase from 1988 to 2016, that is compared to a seasonal volatile transport model, from which tight constraints on a combination of albedo and emissivity of N2 ice are derived. (ii) A central flash observed on 2015 June 29 is consistent with New Horizons REX profiles, provided that (a) large diurnal temperature variations (not expected by current models) occur over Sputnik Planitia; and/or (b) hazes with tangential optical depth of ∼0.3 are present at 4-7 km altitude levels; and/or (c) the nominal REX density values are overestimated by an implausibly large factor of ∼20%; and/or (d) higher terrains block part of the flash in the Charon facing hemisphere. © E. Meza et al. 2019

Evaluation of a quality improvement intervention to reduce anastomotic leak following right colectomy (EAGLE): pragmatic, batched stepped-wedge, cluster-randomized trial in 64 countries

Background Anastomotic leak affects 8 per cent of patients after right colectomy with a 10-fold increased risk of postoperative death. The EAGLE study aimed to develop and test whether an international, standardized quality improvement intervention could reduce anastomotic leaks. Methods The internationally intended protocol, iteratively co-developed by a multistage Delphi process, comprised an online educational module introducing risk stratification, an intraoperative checklist, and harmonized surgical techniques. Clusters (hospital teams) were randomized to one of three arms with varied sequences of intervention/data collection by a derived stepped-wedge batch design (at least 18 hospital teams per batch). Patients were blinded to the study allocation. Low- and middle-income country enrolment was encouraged. The primary outcome (assessed by intention to treat) was anastomotic leak rate, and subgroup analyses by module completion (at least 80 per cent of surgeons, high engagement; less than 50 per cent, low engagement) were preplanned. Results A total 355 hospital teams registered, with 332 from 64 countries (39.2 per cent low and middle income) included in the final analysis. The online modules were completed by half of the surgeons (2143 of 4411). The primary analysis included 3039 of the 3268 patients recruited (206 patients had no anastomosis and 23 were lost to follow-up), with anastomotic leaks arising before and after the intervention in 10.1 and 9.6 per cent respectively (adjusted OR 0.87, 95 per cent c.i. 0.59 to 1.30; P = 0.498). The proportion of surgeons completing the educational modules was an influence: the leak rate decreased from 12.2 per cent (61 of 500) before intervention to 5.1 per cent (24 of 473) after intervention in high-engagement centres (adjusted OR 0.36, 0.20 to 0.64; P &lt; 0.001), but this was not observed in low-engagement hospitals (8.3 per cent (59 of 714) and 13.8 per cent (61 of 443) respectively; adjusted OR 2.09, 1.31 to 3.31). Conclusion Completion of globally available digital training by engaged teams can alter anastomotic leak rates. Registration number: NCT04270721 (http://www.clinicaltrials.gov)