ABSTRACT
Neptunian Trojans (NTs), trans-Neptunian objects in 1:1 mean-motion resonance with Neptune, are generally thought to have been captured from the original trans-Neptunian protoplanetary disc ...into co-orbital resonance with the ice giant during its outward migration. It is possible, therefore, that the colour distribution of NTs is a constraint on the location of any colour transition zones that may have been present in the disc. In support of this possible test, we obtained g, r, and i-band observations of 18 NTs, more than doubling the sample of NTs with known visible colours to 31 objects. Out of the combined sample, we found ≈4 objects with g –i colours of >1.2 mags placing them in the very red (VR) category as typically defined. We find, without taking observational selection effects into account, that the NT g – i colour distribution is statistically distinct from other trans-Neptunian dynamical classes. The optical colours of Jovian Trojans and NTs are shown to be less similar than previously claimed with additional VR NTs. The presence of VR objects among the NTs may suggest that the location of the red to VR colour transition zone in the protoplanetary disc was interior to 30 – 35 au.
We present the complete set of ultra-violet, optical and near-infrared photometry and spectroscopy for SN 2012ca, covering the period from 6 d prior to maximum light, until 531 d after maximum. The ...spectroscopic time series for SN 2012ca is essentially unchanged over 1.5 yr, and appear to be dominated at all epochs by signatures of interaction with a dense circumstellar medium (CSM) rather than the underlying supernova (SN). SN 2012ca is a member of the set of type of the ambiguous IIn/Ia-CSM SNe, the nature of which have been debated extensively in the literature. The two leading scenarios are either a Type Ia SN exploding within a dense CSM from a non-degenerate, evolved companion, or a core-collapse SN from a massive star. While some members of the population have been unequivocally associated with Type Ia SNe, in other cases the association is less certain. While it is possible that SN 2012ca does arise from a thermonuclear SN, this would require a relatively high (between 20 and 70 per cent) efficiency in converting kinetic energy to optical luminosity, and a massive (~2.3-2.6 M...) circumstellar medium. On the basis of energetics, and the results of simple modelling, we suggest that SN 2012ca is more likely associated with a core-collapse SN. This would imply that the observed set of similar SNe to SN 2012ca is in fact originated by two populations, and while these are drawn from physically distinct channels, they can have observationally similar properties. (ProQuest: ... denotes formulae/symbols omitted.)
The two rings of (50000) Quaoar Pereira, C. L.; Sicardy, B.; Morgado, B. E. ...
Astronomy and astrophysics (Berlin),
05/2023, Letnik:
673
Journal Article
Recenzirano
Odprti dostop
Context.
Quaoar is a classical trans-Neptunian object (TNO) with an area-equivalent diameter of 1100 km and an orbital semi-major axis of 43.3 astronomical units. Based on stellar occultations ...observed between 2018 and 2021, an inhomogeneous ring (Q1R, i.e., Quaoar’s first ring) has been detected around this body.
Aims.
A new stellar occultation by Quaoar was observed on August 9, 2022, with the aim of improving Quaoar’s shape models and the physical parameters of Q1R, while searching for additional material around the body.
Methods.
The occultation provided nine effective chords across Quaoar, pinning down its size, shape, and astrometric position. Large facilities, such as Gemini North and the Canada-France-Hawaii Telescope (CFHT), were used to obtain high acquisition rates and signal-to-noise ratios. The light curves were also used to characterize the Q1R ring (radial profiles and orbital elements).
Results.
Quaoar’s elliptical fit to the occultation chords yields the limb with an apparent semi-major axis of 579.5 ± 4.0 km, apparent oblateness of 0.12 ± 0.01, and area-equivalent radius of 543 ± 2 km. Quaoar’s limb orientation is consistent with Q1R and Weywot orbiting in Quaoar’s equatorial plane. The orbital radius of Q1R is refined to a value of 4057 ± 6 km. The radial opacity profile of the more opaque ring profile follows a Lorentzian shape that extends over 60 km, with a full width at half maximum (FWHM) of ∼5 km and a peak normal optical depth of 0.4. Besides the secondary events related to the already reported rings, new secondary events detected during the August 2022 occultation in three different data sets are consistent with another ring around Quaoar with a radius of 2520 ± 20 km, assuming the ring is circular and co-planar with Q1R. This new ring has a typical width of 10 km and a normal optical depth of ∼0.004. Just as Q1R, it also lies outside Quaoar’s classical Roche limit.
Neptunian Trojans (NTs), trans-Neptunian objects in 1:1 mean-motion resonance with Neptune, are generally thought to have been captured from the original trans-Neptunian protoplanetary disk into ...co-orbital resonance with the ice giant during its outward migration. It is possible, therefore, that the colour distribution of NTs is a constraint on the location of any colour transition zones that may have been present in the disk. In support of this possible test, we obtained \(g\), \(r\), and \(i\)-band observations of 18 NTs, more than doubling the sample of NTs with known visible colours to 31 objects. Out of the combined sample, we found \(\approx\)4 objects with \(g\)-\(i\) colours of \(>\)1.2 mags placing them in the very red (VR) category as typically defined. We find, without taking observational selection effects into account, that the NT \(g\)-\(i\) colour distribution is statistically distinct from other trans-Neptunian dynamical classes. The optical colours of Jovian Trojans and NTs are shown to be less similar than previously claimed with additional VR NTs. The presence of VR objects among the NTs may suggest that the location of the red to VR colour transition zone in the protoplanetary disk was interior to 30-35 au.
Quaoar is a classical Trans-Neptunian Object (TNO) with an area equivalent diameter of 1,100 km and an orbital semi-major axis of 43.3 astronomical units. Based on stellar occultations observed ...between 2018 and 2021, an inhomogeneous ring (Q1R, Quaoar's first ring) was detected around this body. Aims. A new stellar occultation by Quaoar was observed on August 9th, 2022 aiming to improve Quaoar's shape models and the physical parameters of Q1R while searching for additional material around the body. Methods. The occultation provided nine effective chords across Quaoar, pinning down its size, shape, and astrometric position. Large facilities, such as Gemini North and the Canada-France-Hawaii Telescope (CFHT), were used to obtain high acquisition rates and signal-to-noise ratios. The light curves were also used to characterize the Q1R ring (radial profiles and orbital elements). Results. Quaoar's elliptical fit to the occultation chords yields the limb with an apparent semi-major axis of \(579.5\pm4.0\) km, apparent oblateness of \(0.12\pm0.01\), and area-equivalent radius of \(543\pm2\) km. Quaoar's limb orientation is consistent with Q1R and Weywot orbiting in Quaoar's equatorial plane. The orbital radius of Q1R is refined to a value of \(4,057\pm6\) km. The radial opacity profile of the more opaque ring profile follows a Lorentzian shape that extends over 60 km, with a full width at half maximum (FWHM) of \(\sim5\) km and a peak normal optical depth of 0.4. Besides the secondary events related to the already reported rings, new secondary events detected during the August 2022 occultation in three different data sets are consistent with another ring around Quaoar with a radius of \(2,520\pm20\) km, assuming the ring is circular and co-planar with Q1R. This new ring has a typical width of 10 km and a normal optical depth of \(\sim\)0.004. Like Q1R, it also lies outside Quaoar's classical Roche limit.
We present the complete set of ultra-violet, optical and near-infrared photometry and spectroscopy for SN 2012ca, covering the period from 6~days prior to maximum light, until 531 days after maximum. ...The spectroscopic time series for SN 2012ca is essentially unchanged over 1.5 years, and appear to be dominated at all epochs by signatures of interaction with a dense circumstellar medium rather than the underlying supernova (SN). At late phases, we see a near infrared excess in flux which is possibly associated with dust formation, although without any signs of accompanying line shifts. SN 2012ca is a member of the set of type of the ambiguous IIn/Ia-CSM SNe, the nature of which have been debated extensively in the literature. The two leading scenarios are either a type Ia SN exploding within a dense CSM from a non-degenerate, evolved companion, or a core-collapse SN from a massive star. While some members of the population have been unequivocally associated with type Ia SNe, in other cases the association is less certain. While it is possible that SN 2012ca does arise from a thermonuclear SN, this would require a relatively high (between 20 and 70 per cent) efficiency in converting kinetic energy to optical luminosity, and a massive (~2.3-2.6 Msun) circumstellar medium. On the basis of energetics, and the results of simple modelling, we suggest that SN 2012ca is more likely associated with a core-collapse SN. This would imply that the observed set of similar SNe to SN 2012ca is in fact originated by two populations, and while these are drawn from physically distinct channels, they can have observationally similar properties.
Abstract
The Jupiter Trojan asteroid 128383 (2004 JW
52
) was recently reported to have optical colors that are incongruous with its dynamical class. New and archival observations show that this is ...not the case. This is a reminder that we must always rule out the possibility that the Point-Spread Function of a minor planet is blended with that of a background sidereal source in survey images before its colors in the associated survey catalog can be considered reliable.
Abstract We report on contemporaneous optical observations at ≈10 ms timescales from the fast radio burst (FRB) 20180916B of two repeat bursts (FRB 20201023 and FRB 20220908) taken with the ‘Alopeke ...camera on the Gemini-North telescope. These repeats have radio fluences of 2.8 and 3.5 Jy ms, respectively, approximately in the lower 50th percentile for fluence from this repeating burst. The ‘Alopeke data reveal no significant optical detections at the FRB position and we place 3 σ upper limits to the optical fluences of <8.3 × 10 −3 and <7.7 × 10 −3 Jy ms after correcting for line-of-sight extinction. Together, these yield the most sensitive limits to the optical-to-radio fluence ratio of an FRB on these timescales with η ν < 3 × 10 −3 by roughly an order of magnitude. These measurements rule out progenitor models where FRB 20180916B has a similar fluence ratio to optical pulsars, such as the Crab pulsar, or where optical emission is produced as inverse-Compton radiation in a pulsar magnetosphere or young supernova remnant. Our ongoing program with ‘Alopeke on Gemini-North will continue to monitor repeating FRBs, including FRB 20180916B, to search for optical counterparts on millisecond timescales.
Although alcohol and other drug use is increasingly the focus of policy and research efforts, there are challenges identifying and applying evidence-based strategies to minimise harms for alcohol and ...other drugs in health care and community settings. These challenges include limited available research, variability across settings, and lack of 'fit' between research evidence and their intended settings. In this commentary, we describe a novel approach to develop and evaluate tailored, sustainable strategies to enhance the uptake of evidence-based activities into health services and community settings. Our approach involves four key principles: (i) identifying evidence-based alcohol and other drug harm minimisation strategies; (ii) partnering with local experts to identify and tailor strategies; (iii) implementing strategies into existing practice/infrastructure to build in sustainability; and (iv) using sustainable co-designed outcome measures including value-based health-care principles to measure uptake, feasibility and acceptability, health outcomes and economic implications. We propose that this approach offers a way forward to enhance the relevance and suitability of research in health services and community settings and has potential to be applied in other sectors.
PDF
