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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.
Anxiety disorders are common, and cognitive–behavioural therapy (CBT) is a first-line treatment. Candidate gene studies have suggested a genetic basis to treatment response, but findings have been inconsistent.
To perform the first genome-wide association study (GWAS) of psychological treatment response in children with anxiety disorders (n = 980).
Presence and severity of anxiety was assessed using semi-structured interview at baseline, on completion of treatment (post-treatment), and 3 to 12 months after treatment completion (follow-up). DNA was genotyped using the Illumina Human Core Exome-12v1.0 array. Linear mixed models were used to test associations between genetic variants and response (change in symptom severity) immediately post-treatment and at 6-month follow-up.
No variants passed a genome-wide significance threshold (P=5×10–8) in either analysis. Four variants met criteria for suggestive significance (P<5×10–6) in association with response post-treatment, and three variants in the 6-month follow-up analysis.
This is the first genome-wide therapygenetic study. It suggests no common variants of very high effect underlie response to CBT. Future investigations should maximise power to detect single-variant and polygenic effects by using larger, more homogeneous cohorts.
We previously reported an association between 5HTTLPR genotype and
outcome following cognitive–behavioural therapy (CBT) in child anxiety
(Cohort 1). Children homozygous for the low-expression short-allele
showed more positive outcomes. Other similar studies have produced mixed
results, with most reporting no association between genotype and CBT
To replicate the association between 5HTTLPR and CBT outcome in child
anxiety from the Genes for Treatment study (GxT Cohort 2,
n = 829).
Logistic and linear mixed effects models were used to examine the
relationship between 5HTTLPR and CBT outcomes. Mega-analyses using both
cohorts were performed.
There was no significant effect of 5HTTLPR on CBT outcomes in Cohort 2.
Mega-analyses identified a significant association between 5HTTLPR and
remission from all anxiety disorders at follow-up (odds ratio 0.45,
P = 0.014), but not primary anxiety disorder
The association between 5HTTLPR genotype and CBT outcome did not
replicate. Short-allele homozygotes showed more positive treatment
outcomes, but with small, non-significant effects. Future studies would
benefit from utilising whole genome approaches and large, homogenous
Based on our deep image of Sgr A using broadband data observed with the VLA† at 6 cm, we present a new perspective of the radio bright zone at the Galactic center. We further show the radio detection of the X-ray Cannonball, a candidate neutron star associated with the Galactic center SNR Sgr A East. The radio image is compared with the Chandra X-ray image to show the detailed structure of the radio counterparts of the bipolar X-ray lobes. The bipolar lobes are likely produced by the winds from the activities within Sgr A West, which could be collimated by the inertia of gas in the CND, or by the momentum driving of Sgr A*; and the poloidal magnetic fields likely play an important role in the collimation. The less-collimated SE lobe, in comparison to the NW one, is perhaps due to the fact that the Sgr A East SN might have locally reconfigured the magnetic field toward negative galactic latitudes. In agreement with the X-ray observations, the time-scale of ∼1 × 104 yr estimated for the outermost radio ring appears to be comparable to the inferred age of the Sgr A East SNR.
Deep imaging of the Sgr A complex at 6 cm wavelength with the B and C configurations of the Karl G. Jansky VLA† has revealed a new population of faint radio filaments. Like their brighter counterparts that have been observed throughout the Galactic center on larger scales, these filaments can extend up to ∼10 parsecs, and in most cases are strikingly uniform in brightness and curvature. Comparison with a survey of Paschen-α emission reveals that some of the filaments are emitting thermally, but most of these structures are nonthermal: local magnetic flux tubes illuminated by synchrotron emission. The new image reveals considerable filamentary substructure in previously known nonthermal filaments (NTFs). Unlike NTFs previously observed on larger scales, which tend to show a predominant orientation roughly perpendicular to the Galactic plane, the NTFs in the vicinity of the Sgr A complex are relatively randomly oriented. Two well-known radio sources to the south of Sgr A – sources E and F – consist of numerous quasi-parallel filaments that now appear to be particularly bright portions of a much larger, strongly curved, continuous, nonthermal radio structure that we refer to as the “Southern Curl”. It is therefore unlikely that sources E and F are Hii regions or pulsar wind nebulae. The Southern Curl has a smaller counterpart on the opposite side of the Galactic center – the Northern Curl – that, except for its smaller scale and smaller distance from the center, is roughly point-reflection symmetric with respect to the Southern Curl. The curl features indicate that some field lines are strongly distorted, presumably by mass flows. The point symmetry about the center then suggests that the flows originate near the center and are somewhat collimated.
We present our recent efforts to unveil and understand the origin of massive stars outside the three massive star clusters in the Galactic center. From our Hubble/NICMOS survey of the Galactic center, we have identified 180 Paschen-α emitting sources, most of which should be evolved massive stars with strong optically thin stellar winds. Recently, we obtained Gemini GNIRS/NIFS H- and K-band spectra of eight massive stars near the Arches cluster. From their radial velocities, ages and masses, we suggest that in our sample, two stars are previous members of the Arches cluster, while other two stars embedded in the H1/H2 Hii regions formed in-situ.
Microbial metabolism has the potential to control the biogeochemistry of redox-active radionuclides in a range of geodisposal scenarios. In this study, sediments from a high pH lime workings site were incubated under carefully controlled anaerobic conditions, at a range of alkali pH values with added electron donors and electron acceptors, to explore the limits and rates of bioreduction in a sediment system analogous to intermediate-level nuclear waste. There was a clear succession in the utilization of electron acceptors (in the order nitrate > Fe(III)-citrate > Fe(III) oxyhydroxide > sulfate), in accordance with calculated free energy yields and Eh values over the pH range 10–12. The rate and extent of bioreduction decreased at higher pH, with an upper limit for the processes studied at pH 12. The biochemical limits for such processes are discussed, alongside the potential impact of such forms of microbial metabolism on the solubility of a range of redox active radionuclides that will feature heavily in the safety case for the geological disposal of intermediate-level nuclear waste.