To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (~2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor.
The Binary Population and Spectral Synthesis suite of binary stellar evolution models and synthetic stellar populations provides a framework for the physically motivated analysis of both the integrated light from distant stellar populations and the detailed properties of those nearby. We present a new version 2.1 data release of these models, detailing the methodology by which Binary Population and Spectral Synthesis incorporates binary mass transfer and its effect on stellar evolution pathways, as well as the construction of simple stellar populations. We demonstrate key tests of the latest Binary Population and Spectral Synthesis model suite demonstrating its ability to reproduce the colours and derived properties of resolved stellar populations, including well-constrained eclipsing binaries. We consider observational constraints on the ratio of massive star types and the distribution of stellar remnant masses. We describe the identification of supernova progenitors in our models, and demonstrate a good agreement to the properties of observed progenitors. We also test our models against photometric and spectroscopic observations of unresolved stellar populations, both in the local and distant Universe, finding that binary models provide a self-consistent explanation for observed galaxy properties across a broad redshift range. Finally, we carefully describe the limitations of our models, and areas where we expect to see significant improvement in future versions.
Eta Carinae is one of the most massive observable binaries. Yet determination of its orbital and physical parameters is hampered by obscuring winds. However the effects of the strong, colliding winds changes with phase due to the high orbital eccentricity. We wanted to improve measures of the orbital parameters and to determine the mechanisms that produce the relatively brief, phase-locked minimum as detected throughout the electromagnetic spectrum. We conducted intense monitoring of the He ii λ4686 line in η Carinae for 10 months in the year 2014, gathering ~300 high S/N spectra with ground- and space-based telescopes. We also used published spectra at the FOS4 SE polar region of the Homunculus, which views the minimum from a different direction. We used a model in which the He ii λ4686 emission is produced by two mechanisms: a) one linked to the intensity of the wind-wind collision which occurs along the whole orbit and is proportional to the inverse square of the separation between the companion stars; and b) the other produced by the ‘bore hole’ effect which occurs at phases across the periastron passage. The opacity (computed from 3D SPH simulations) as convolved with the emission reproduces the behavior of equivalent widths both for direct and reflected light. Our main results are: a) a demonstration that the He ii λ4686 light curve is exquisitely repeatable from cycle to cycle, contrary to previous claims for large changes; b) an accurate determination of the longitude of periastron, indicating that the secondary star is ‘behind’ the primary at periastron, a dispute extended over the past decade; c) a determination of the time of periastron passage, at ~4 days after the onset of the deep light curve minimum; and d) show that the minimum is simultaneous for observers at different lines of sight, indicating that it is not caused by an eclipse of the secondary star, but rather by the immersion of the wind-wind collision interior to the inner wind of the primary.
We have recently released version 2.0 of the Binary Population and Spectral Synthesis (BPASS) population synthesis code. This is designed to construct the spectra and related properties of stellar populations built from ~200,000 detailed, individual stellar models of known age and metallicity. The output products enable a broad range of theoretical predictions for individual stars, binaries, resolved and unresolved stellar populations, supernovae and their progenitors, and compact remnant mergers. Here we summarise key applications that demonstrate that binary populations typically reproduce observations better than single star models.
Over the past two decades a clear relation between Gamma-Ray Bursts (GRBs) and some broad-lined Type Ic Supernovae (SNe) has been observed. The use of spectropolarimetry allows us to directly probe the 3D geometry of the unresolved ejecta of SNe, which can help us better understand the physics of their explosion and the SN-GRB connection. We present 7 epochs of spectropolarimetry of the broad-lined Type Ic SN 2014ad and highlight its similarities with SN 1998bw.
We gathered a multiwavelength dataset of two well-known LBVs. We found a complex mass-loss, with evidence of variability, such as has been seen previously. In addition, our data reveal signatures of collimated stellar winds. We propose a new scenario for these two stars where the nebula shaping is influenced by the presence of a companion star and/or fast rotation.
The role of episodic mass loss in evolved massive stars is one of the outstanding questions in stellar evolution theory. Integral field spectroscopy of nebulae around massive stars provide information on their recent mass-loss history. η Car is one of the most massive evolved stars and is surrounded by a complex circumstellar environment. We have conducted a three-dimensional morpho-kinematic analysis of η Car’s ejecta outside its famous Homunculus nebula. SHAPE modelling of VLT MUSE data establish unequivocally the spatial cohesion of the outer ejecta and the correlation of ejecta with the soft X-ray emission.
Twenty-six young men admitted to an Accident and Emergency Department for observation following a minor closed head injury (post-traumatic amnesia (PTA) less than 12 hours) were investigated within 24 hours of admission (day 0) and followed up at 10 days, 6 weeks and 1 year after the trauma.
Investigations at day 0 included physical examination, completion of post-concussional symptom and stress-arousal checklists, computerised EEG (CEEG) and auditory brainstem evoked potential (BAEP) recordings. These were repeated at ten days and six weeks. At 12 months follow-up, the Present State Examination (PSE) was carried out and a further post-concussional symptom checklist completed.
Post-concussional symptomatology declined progressively from day 0 but half had residual symptoms at 1 year. Seventy-two per cent ran an acute course with recovery by 6 weeks, 8% a chronic unremitting course and 20% initially improved but had an exacerbation of symptoms between 6 weeks and 12 months. The CEEG alpha-theta ratios decreased significantly between days 0 and 10, reaching a baseline thereafter. Measures of CEEG recovery from all channels correlated with symptom counts at six weeks; the slower the recovery the greater the symptoms. A relative delay in left temporal recovery was associated with residual psychiatric morbidity (PSE ID scores) at 12 months. Prolonged central brainstem conduction times occurred in 27% of patients at day 0. These correlated positively with PTA and degree of psychiatric morbidity (PSE ID scores) at 12 months.
Symptom chronicity was accompanied by continuing brainstem dysfunction, while the degree of transient cortical dysfunction appeared to have a direct influence in the intensity of early organic symptom reaction to the trauma. Levels of perceived stress at the time of the injury, or afterwards, were not related to symptom formation.
The aim of this study was to establish the prevalence of epilepsy in persons with Down's syndrome aged 19 years and over. A total of 191 adults with Down's syndrome were identified, giving a prevalence of 0.76/1000 (95% CI 0.75 to 0.77). Of these, 18 had epilepsy, giving a prevalence of 9.4% (95% CI 5.3% to 13.5%). The prevalence of epilepsy increased with age, reaching 46% in those over 50. The neurophysiological (EEG) findings of the epilepsy group were compared with those of a control group of Down's syndrome adults without epilepsy. Paroxysmal abnormalities consistent with a diagnosis of epilepsy were found in 80% of the epilepsy group, compared with only 13% of controls (P < 0.001). Epilepsy of late onset was associated with diffuse EEG abnormalities and clinical evidence of dementia. The age distribution and EEG findings suggest two independent processes in the causation of epilepsy: late-onset epilepsy associated with clinical evidence of dementia, and early-onset epilepsy in the absence of dementia.
Experiments were conducted from 1989 through 1991 to determine the effect of MSMA on efficacy of fluometuron, cyanazine, oxyfluorfen, lactofen, methazole, diuron, and linuron applied POST to entireleaf morningglory. In one set of experiments, applications were made at the cotyledon to three-leaf and four- to six-leaf stages of weed growth. In another set of experiments, applications were made at only one growth stage. Cyanazine, MSMA, or cyanazine plus MSMA were the most efficacious treatments, especially when application was delayed until the four- to six-leaf stage. Adding MSMA to all of the herbicides increased control of entireleaf morningglory, with the magnitude of improvement increasing as the application timing was delayed.
To investigate the integrity of the brain-stem in 20 mentally handicapped children who met the Rutter criteria for autism, brain-stem auditory evoked potentials were obtained for a range of stimulus intensities. Central conduction times (CCTs) were calculated for the Wave l–Wave V interval of the brain-stem potentials. In children under 14 years of age CCTs were normal. In children 14 years of age and over, three of four girls and eight of nine boys had CCTs exceeding normal limits when compared with a group of controls of normal intelligence, matched for age and sex. CCTs recorded from a group of non-autistic mentally handicapped children were within normal limits. The age distributions are consistent with a maturational defect in myelination within the brain-stem in autism, a defect which may have a much wider anatomical distribution throughout cortical and subcortical structures.