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Breakthrough Listen is a 10-yr initiative to search for signatures of technologies created by extraterrestrial civilisations at radio and optical wavelengths. Here, we detail the digital data recording system deployed for Breakthrough Listen observations at the 64-m aperture CSIRO Parkes Telescope in New South Wales, Australia. The recording system currently implements two modes: a dual-polarisation, 1.125-GHz bandwidth mode for single-beam observations, and a 26-input, 308-MHz bandwidth mode for the 21-cm multibeam receiver. The system is also designed to support a 3-GHz single-beam mode for the forthcoming Parkes ultra-wideband feed. In this paper, we present details of the system architecture, provide an overview of hardware and software, and present initial performance results.
We present multi–epoch VLBI observations of the methanol and water masers in the high–mass star formation region G 339.884−1.259, made using the Australian Long Baseline Array (LBA). Our sub–milliarcsecond precision measurements trace the proper motions of individual maser features in the plane of the sky. When combined with the direct line–of–sight radial velocity (vlsr), these measure the 3 D gas kinematics of the associated high–mass star formation region, allowing us to probe the dynamical processes to within 1000 AU of the core.
An antenna in geostationary orbit was used for VLBI observations at 2.3 GHz, in combination with ground antennas in Australia and Japan. 23 of the 25 observed sources were detected on orbiter-ground baselines, with baseline lengths as large as 2.15 earth diameters. Brightness temperatures between 1012 K and 4 × 1012 K were measured for 10 sources.
We present results from a multiwavelength study of the blazar PKS 1954–388 at radio, UV, X-ray, and gamma-ray energies. A RadioAstron observation at 1.66 GHz in June 2012 resulted in the detection of interferometric fringes on baselines of 6.2 Earth-diameters. This suggests a source frame brightness temperature of greater than 2 × 1012 K, well in excess of both equipartition and inverse Compton limits and implying the existence of Doppler boosting in the core. An 8.4-GHz TANAMI VLBI image, made less than a month after the RadioAstron observations, is consistent with a previously reported superluminal motion for a jet component. Flux density monitoring with the Australia Telescope Compact Array confirms previous evidence for long-term variability that increases with observing frequency. A search for more rapid variability revealed no evidence for significant day-scale flux density variation. The ATCA light-curve reveals a strong radio flare beginning in late 2013, which peaks higher, and earlier, at higher frequencies. Comparison with the Fermi gamma-ray light-curve indicates this followed ~ 9 months after the start of a prolonged gamma-ray high-state—a radio lag comparable to that seen in other blazars. The multiwavelength data are combined to derive a Spectral Energy Distribution, which is fitted by a one-zone synchrotron-self-Compton (SSC) model with the addition of external Compton (EC) emission.
Liability to substance use disorder (SUD) is largely nonspecific to particular drugs and is related to behavior dysregulation, including reduced cognitive control. Recent data suggest that cognitive mechanisms may be influenced by exposure to neurotropic infections, such as human herpesviruses. In this study, serological evidence of exposure to human herpesvirus Herpes simplex virus Type 1 (HSV-1), cytomegalovirus (CMV), and Epstein–Barr virus (EBV) as well as Toxoplasma gondii was determined in childhood (age ~11 years) in 395 sons and 174 daughters of fathers with or without SUD. Its relationships with a cognitive characteristic (IQ) in childhood and with risk for SUD in adulthood were examined using correlation, regression, survival, and path analyses. Exposure to HSV-1, EBV, and T. gondii in males and females, and CMV in males, was associated with lower IQ. Independent of that relationship, EBV in females and possibly in males, and CMV and possibly HSV-1 in females were associated with elevated risk for SUD. Therefore, childhood neurotropic infections may influence cognitive development and risk for behavior disorders such as SUD. The results may point to new avenues for alleviating cognitive impairment and SUD risk.
Prenatal maternal obesity has been linked to adverse childhood neuropsychiatric outcomes, including increased symptoms of attention deficit hyperactivity disorder (ADHD), internalizing and externalizing problems, affective disorders and neurodevelopmental problems but few studies have studied neuropsychiatric outcomes among offspring born to very severely obese women or assessed potential familial confounding by maternal psychological distress.
We evaluated neuropsychiatric symptoms in 112 children aged 3–5 years whose mothers had participated in a longitudinal study of obesity in pregnancy (50 very severe obesity, BMI ⩾40 kg/m2, obese class III and 62 lean, BMI 18.5–25 kg/m2). The mothers completed the Conners’ Hyperactivity Scale, Early Symptomatic Syndrome Eliciting Neurodevelopmental Clinical Examination Questionnaire (ESSENCE-Q), Child's Sleep Habits Questionnaire (CSHQ), Strengths and Difficulties Questionnaire (SDQ), and Child Behavior Checklist (CBCL) to assess child neuropsychiatric symptoms. Covariates included child's sex, age, birthweight, gestational age, socioeconomic deprivation levels, maternal age, parity, smoking status during pregnancy, gestational diabetes and maternal concurrent symptoms of anxiety and depression assessed using State Anxiety of Spielberger State-Trait Anxiety Index (STAI) and General Health Questionnaire (GHQ), respectively.
Children exposed to prenatal maternal very severe obesity had significantly higher scores in the Conners’ Hyperactivity Scale; ESSENCE-Q; total sleep problems in CSHQ; hyperactivity, conduct problems and total difficulties scales of the SDQ; higher externalizing and total problems, anxious/depressed, aggressive behaviour and other problem syndrome scores and higher DSM-oriented affective, anxiety and ADHD problems in CBCL. Prenatal maternal very severe obesity remained a significant predictor of child neuropsychiatric problems across multiple scales independent of demographic factors, prenatal factors and maternal concurrent symptoms of anxiety and depression.
Prenatal maternal very severe obesity is a strong predictor of increased neuropsychiatric problems in early childhood.
The 20 → 3−1 E-type transition of 13CH3OH at 14.78 GHz has been detected towards four continuum sources: Sgr B2, two positions in Sgr A (the peaks of the ' + 20 km/s' and the '40 km/s' clouds), and W33. The NASA Deep Space Network 70-m antenna near Canberra, Australia, which has a 66 arcsec beam at this frequency, was used. A comparison of the 13C and 12C profiles for Sgr B2 indicates a rest frequency of 14,782.27 ± .03 MHz, 0.12 MHz above the laboratory value of Haque et al. (1974). For the Galactic Centre sources, the 12C/13C abundance ratios derived using the simplest assumptions lie in the range 30–40, higher than the 20–25 range derived from H2CO observations. For W33 the apparent value of ∼ 50 is lower than the value of ∼100 derived by Henkel et al. (1983) from H2CO. There may be no discrepancy, however, as W33 contains two velocity components — the higher velocity one at 36 km/s is more prominent in CH3OH and the lower 33 km/s more prominent in H2CO.
We describe the performance of the Boolardy Engineering Test Array, the prototype for the Australian Square Kilometre Array Pathfinder telescope. Boolardy Engineering Test Array is the first aperture synthesis radio telescope to use phased array feed technology, giving it the ability to electronically form up to nine dual-polarisation beams. We report the methods developed for forming and measuring the beams, and the adaptations that have been made to the traditional calibration and imaging procedures in order to allow BETA to function as a multi-beam aperture synthesis telescope. We describe the commissioning of the instrument and present details of Boolardy Engineering Test Array’s performance: sensitivity, beam characteristics, polarimetric properties, and image quality. We summarise the astronomical science that it has produced and draw lessons from operating Boolardy Engineering Test Array that will be relevant to the commissioning and operation of the final Australian Square Kilometre Array Path telescope.
The Southern Hemisphere VLBI Experiment (SHEVE) program is aimed at producing high-resolution images of southern radio sources. The radio telescopes of the present SHEVE array are described below and some recent results presented.
During the time elapsed since the last general assembly of the I.A.U., many activities have been pursued by the astronomers engaged in research work in the wide fields of problems concerning nebulae and clusters. In fact a number of important discoveries have been made and earlier work has been extended in a way to consolidate earlier views or revise them. The embarras de richesse in this field and the extremely short time available for the compilation of a report make it impossible to present anything else than a few short notes partly written by heart and only intended to express personal views on the question of how the research work on nebulae and clusters might be carried on.
The following report is mainly restricted to work done since the last meeting of the I.A.U., but in a few cases it has been necessary to mention earlier results.
Intra-day variability (IDV) of active galactic nuclei (AGN) has been detected from gamma-ray energies to radio wavelengths. At high energies, such variability appears to be intrinsic to the sources themselves. However, at radio wavelengths, brightness temperatures as high as 1018 to 1021 K are encountered if the IDV is intrinsic to the source. We discuss here the accumulating evidence showing that, at radio wavelengths where the highest brightness temperatures are encountered, interstellar scintillation (ISS) is the principal mechanism causing IDV. While ISS reduces the implied brightness temperatures, they still remain uncomfortably high.
We have found large amplitude intraday variability in the radio quasar PKS 0405–385 on timescales less than an hour. If intrinsic to the source, the inferred brightness temperature is TB ~ 1021 K, far exceeding the inverse Compton limit for a static synchrotron source. We argue that our data are in agreement with interstellar scintillations of a source component which is < 5μarcsec in size.
PKS 1934–638 is an archetypal GPS source, peaking at 1.4 GHz and exhibits almost no flux density variability. VLBI images at frequencies of .843, 2.3, 4.8, & 8.4 were made with the southern hemisphere VLBI array and they reveal that the source is a 42 mas compact double. There is no detectable change in separation over the last 20 years, yielding an upper limit of ~ 0.03c ± 0.2c on any expansion velocity. The spectral shapes of the two components are remarkably similar, despite indications of finer structure on longer baselines. Magnetic field calculations indicate fields of a few mGauss and the results are consistent with equipartition.
The mechanism providing the 35-day period found in optical and X-ray light curves of the eclipsing low-mass X-ray binary Her X-l is considered to be the precession of a tilted and twisted accretion disc about the neutron star. We have obtained spectrophotometric observations of this system. The majority of line absorption and emission originates on or near the mass-losing primary, with distributions over the inner face of the star consistent with irradiation from the environs of the compact object. After suitable corrections for heating, the neutron star is found have a mass of 1.6±0.3M⊙, in contrast to the last radial velocity study which found a value less than 1.0 M⊙ . Rotational velocity measurements, while insufficiently precise to reject the older mass estimate, suggest that the rotational period of HZ Her differs from the synchronous rate by no more than 20%. Using a recently determined figure for the effective temperature of the unheated face, the distance to Her X-l is estimated at 6.7±0.4kpc, higher than prior estimates. The systemic velocity is found to be –69±6km s−1. In order to to determine the plausibility of the twisted disc model we reconstruct the expected shadow of the disc across the heated inner face of the donor star to compare with observation. Large scale emission structure is reproduced, but the model fails to synthesize finer observational details. HeII λ4686 Å emission is detected and found to be distributed closely about the neutron star, and is a likely tracer of the accretion flow.
This is a progress report on the ATCA IDV survey of compact, flat or inverted spectrum radio sources. We found that four sources: PKS 0405–385, PKS 1034–293, PKS 1144–397, and PKS 1519–273 out of the sample of 125 show high flux density variability on the daily timescale. The characteristics of observed IDV are discussed and we reflect on its possible origin.
From the combination of VLBI phase-referenced observations and Hipparcos satellite data, we have found evidence of a low-mass object orbiting the late-type star AB Doradus. The mass of the new object is near the hydrogen burning limit and will constitute a precise point for calibrating the low end of the main sequence. This represents the first detection of a low-mass stellar companion using the VLBI technique, which could become an important tool in future searches for planets and brown dwarfs orbiting other stars.
Glucocorticoids and serotonin may mediate the link between maternal environment, fetal brain development and ‘programming’ of offspring behaviors. The placenta regulates fetal exposure to maternal hormonal signals in animal studies, but few data address this in humans. We measured prospectively maternal depressive symptoms during pregnancy and mRNAs encoding key gene products determining glucocorticoid and serotonin function in term human placenta and explored associations with infant regulatory behaviors.
Bi-weekly self-ratings of the Center for Epidemiologic Studies Depression Scale from 12th to 13th gestational week onwards and term placental mRNAs of 11beta-hydroxysteroid dehydrogenase type 2 (HSD2B11), type 1 (HSD1B11), glucocorticoid (NR3C1), mineralocorticoid receptors (NR3C2) and serotonin transporter (SLC6A4) were obtained from 54 healthy mothers aged 32.2 ± 5.3 years with singleton pregnancies and without pregnancy complications. Infant regulatory behaviors (crying, feeding, spitting, elimination, sleeping and predictability) were mother-rated at 15.6 ± 4.2 days.
Higher placental mRNA levels of HSD2B11 [0.41 standard deviation (s.d.) unit increase per s.d. unit increase; 95% confidence interval (CI) 0.13–0.69, p = 0.005], HSD1B11 (0.30, 0.03–0.57, p = 0.03), NR3C1 (0.44, 0.19–0.68, p = 0.001) and SLC6A4 (0.26, 0.00–0.53, p = 0.05) were associated with more regulatory behavioral challenges of the infant. Higher placental NR3C1 mRNA partly mediated the association between maternal depressive symptoms during pregnancy and infant regulatory behaviors (p < 0.05).
Higher placental expression of genes regulating feto-placental glucocorticoid and serotonin exposure is characteristic of infants with more regulatory behavioral challenges. Maternal depression acts, at least partly, via altering glucocorticoid action in the placenta to impact on offspring regulatory behaviors.
Both maternal obesity and disordered mood have adverse effects on pregnancy outcome. We hypothesized that maternal very severe obesity (SO) is associated with increased anxiety and depression (A&D) symptoms during pregnancy, with adverse effects on gestational weight gain (GWG), postpartum mood and postpartum weight retention (PPWR) and explored any mediation by circulating glucocorticoids.
We measured A&D symptoms with validated questionnaires at weeks 17 and 28 of pregnancy and 3 months postpartum in 135 lean [body mass index (BMI) ⩽25 kg/m2] and 222 SO (BMI ⩾40 kg/m2) pregnant women. Fasting serum cortisol was measured by radioimmunoassay; GWG and PPWR were recorded.
A&D symptoms were higher in the SO group during pregnancy and postpartum despite adjusting for multiple confounders including previous mental health diagnosis (p < 0.05), and were non-linearly correlated with total GWG (anxiety R2 = 0.06, p = 0.037; depression R2 = 0.09, p = 0.001). In the SO group only, increased maternal anxiety (β = 0.33, p = 0.03) and depression (β = 0.19, p = 0.04) symptoms at week 17 of pregnancy were associated with increased PPWR, independent of total GWG and breastfeeding. Anxiety symptoms at week 28 of pregnancy, but not depression, were non-linearly correlated with serum cortisol level at week 36 of pregnancy (R2 = 0.06, p = 0.02). Cortisol did not mediate the link between A&D symptoms and GWG.
Maternal SO was associated with increased A&D symptoms, and with adverse effects on GWG and PPWR independent of circulating glucocorticoids. Strategies to optimize GWG and postpartum weight management in SO women should include assessment and management of maternal mood in early pregnancy.