A Compton reflection dominated spectrum in a peculiar accreting neutron star

We report on a puzzling event occurred during a long BeppoSAX observation of the slow-rotating binary pulsar GX 1+4. During this event, lasting about 1 day, the source X-ray flux was over a factor 10 lower than normal. The low-energy pulsations disappeared while at higher energies they were shifted in phase. The spectrum taken outside this low-intensity event was well fitted by an absorbed cut-off power law, and exhibited a broad iron line at ~6.5 keV probably due to the blending of the neutral (6.4 keV) and ionised (6.7 keV) K_alpha iron lines. The spectrum during the event was Compton reflection dominated and it showed two narrow iron lines at ~6.4 keV and ~7.0 keV, the latter never revealed before in this source. We also present a possible model for this event in which a variation of the accretion rate thickens a torus-like accretion disc which hides for a while the direct neutron star emission from our line of sight. In this scenario the Compton reflected emission observed during the event is well explained in terms of emission reflected by the side of the torus facing our line of sight.Comment: 10 pages; to be published in MNRA

A puzzling event during the X-ray emission of the binary system GX 1+4

We report on a long X-ray observation of the slow-rotating binary pulsar GX 1+4. BeppoSAX observed, in the 0.1-200 keV energy range, an event in which the source flux dropped for almost a day, and then recovered. During this event only the high-energy emission was found to be pulsed and the pulsations were shifted in phase of ~0.2 . The spectrum during the event was well fitted by a Compton-reflection model. A broad iron line at ~6.55 keV was present outside of the event, where instead two narrow emission lines at ~6.47 keV and ~7.05 keV were detected. The pulse profile was highly variable as a function of both energy and time. We interpret this low-flux event as an occultation of the direct X-ray emission, due to the increase of a torus-like accretion disk; we then discuss similarities between this source and the recently discovered highly absorbed INTEGRAL sources.Comment: accepted for publication in Advances in Space Researc

Lower mitochondrial energy production of the thigh muscles in patients with low-normal ankle-brachial index

Background--Lower muscle mitochondrial energy production may contribute to impaired walking endurance in patients with peripheral arterial disease. A borderline ankle-brachial index (ABI) of 0.91 to 1.10 is associated with poorer walking endurance compared with higher ABI. We hypothesized that in the absence of peripheral arterial disease, lower ABI is associated with lower mitochondrial energy production. Methods and Results--We examined 363 men and women participating in the Baltimore Longitudinal Study of Aging with an ABI between 0.90 and 1.40. Muscle mitochondrial energy production was assessed by post-exercise phosphocreatine recovery rate constant (kPCr) measured by phosphorus magnetic resonance spectroscopy of the left thigh. A lower post-exercise phosphocreatine recovery rate constant reflects decreased mitochondria energy production.The mean age of the participants was 71\uc2\ub112 years. A total of 18.4% had diabetes mellitus and 4% were current and 40% were former smokers. Compared with participants with an ABI of 1.11 to 1.40, those with an ABI of 0.90 to 1.10 had significantly lower post-exercise phosphocreatine recovery rate constant (19.3 versus 20.8 ms-1, P=0.015). This difference remained significant after adjusting for age, sex, race, smoking status, diabetes mellitus, body mass index, and cholesterol levels (P=0.028). Similarly, post-exercise phosphocreatine recovery rate constant was linearly associated with ABI as a continuous variable, both in the ABI ranges of 0.90 to 1.40 (standardized coefficient=0.15, P=0.003) and 1.1 to 1.4 (standardized coefficient=0.12, P=0.0405). Conclusions--An ABI of 0.90 to 1.10 is associated with lower mitochondrial energy production compared with an ABI of 1.11 to 1.40. These data demonstrate adverse associations of lower ABI values with impaired mitochondrial activity even within the range of a clinically accepted definition of a normal ABI. Further study is needed to determine whether interventions in persons with ABIs of 0.90 to 1.10 can prevent subsequent functional decline

Highly ionized Fe K emission lines from the LINER galaxy M 81

We present spectral and timing results from a long (130 ks) XMM-NEWTON EPIC observation of the nucleus of the Seyfert/LINER galaxy M 81. During the observation the X-ray flux varied by 20%, but there was no significant change in spectral shape. The 2-10 keV spectrum is well described by a power law continuum and three narrow Fe K emission lines at 6.4, 6.7 and 6.96 keV. The three emission lines have equivalent widths of 39, 47, and 37 eV respectively. The ratios of the three lines are thus more similar to those observed from the Galactic Centre region than to those typically observed from Seyfert galaxies. The high ionization lines most likely originate either from photoionized gas within 0.1 pc of the nucleus of M 81, or from a non-thermal distribution of cosmic-ray electrons interacting with the 0.2-0.6 keV thermal plasma which is found in the bulge of M 81.Comment: Accepted for publication in A&

Canfam GSD: De novo chromosome-length genome assembly of the German Shepherd Dog (Canis lupus familiaris) using a combination of long reads, optical mapping, and Hi-C

Background: The German Shepherd Dog (GSD) is one of the most common breeds on earth and has been bred for its utility and intelligence. It is often first choice for police and military work, as well as protection, disability assistance, and search-and-rescue. Yet, GSDs are well known to be susceptible to a range of genetic diseases that can interfere with their training. Such diseases are of particular concern when they occur later in life, and fully trained animals are not able to continue their duties. Findings: Here, we provide the draft genome sequence of a healthy German Shepherd female as a reference for future disease and evolutionary studies. We generated this improved canid reference genome (CanFam GSD) utilizing a combination of Pacific Bioscience, Oxford Nanopore, 10X Genomics, Bionano, and Hi-C technologies. The GSD assembly is ∼80 times as contiguous as the current canid reference genome (20.9 vs 0.267 Mb contig N50), containing far fewer gaps (306 vs 23,876) and fewer scaffolds (429 vs 3,310) than the current canid reference genome CanFamv3.1. Two chromosomes (4 and 35) are assembled into single scaffolds with no gaps. BUSCO analyses of the genome assembly results show that 93.0% of the conserved single-copy genes are complete in the GSD assembly compared with 92.2% for CanFam v3.1. Homology-based gene annotation increases this value to ∼99%. Detailed examination of the evolutionarily important pancreatic amylase region reveals that there are most likely 7 copies of the gene, indicative of a duplication of 4 ancestral copies and the disruption of 1 copy. Conclusions: GSD genome assembly and annotation were produced with major improvement in completeness, continuity, and quality over the existing canid reference. This resource will enable further research related to canine diseases, the evolutionary relationships of canids, and other aspects of canid biology

ESA Voyage 2050 white paper:A Polarized View of the Hot and Violent Universe

Since the birth of X-ray Astronomy, spectacular advances have been seen in the imaging, spectroscopic and timing studies of the hot and violent X-ray Universe, and further leaps forward are expected in the future. On the other hand, polarimetry is very much lagging behind: after the measurements of the Crab Nebula and Scorpius X-1, obtained by OSO-8 in the 70s, no more observations have been performed in the classical X-ray band, even if some interesting results have been obtained in hard X-rays and in soft gamma-rays. The NASA/ASI mission IXPE, scheduled for the launch in 2021, is going to provide for the first time imaging X-ray polarimetry in the 2-8 keV band thanks to its photoelectric polarimeter, coupled with ~25'' angular resolution X-ray mirrors. Its orders of magnitude improvement in sensitivity with respect to the OSO-8 Bragg polarimeter implies scientifically meaningful polarimetric measurements for at least the brightest specimens of most classes of X-ray sources. In 2027, the Chinese-led mission eXTP should also be launched. In addition to timing and spectroscopic instruments, eXTP will have on board photoelectric polarimeters very similar to those of IXPE, but with a total effective area 2-3 times larger. Building on IXPE results, eXTP will increase the number of sources for which significant polarimetric measurements could be obtained. However, further progresses, such as exploring a broader energy range, considering a larger effective area, improving the angular resolution, and performing wide-field polarization measurements, are needed to reach a mature phase for X-ray polarimetry. In the first part of this White Paper we will discuss a few scientific cases in which a next generation X-ray Polarimetry mission can provide significant advances. In the second part, a possible concept for a medium-class Next Generation X-ray Polarimetry (NGXP) mission will be sketched

The Australian dingo is an early offshoot of modern breed dogs

Dogs are uniquely associated with human dispersal and bring transformational insight into the domestication process. Dingoes represent an intriguing case within canine evolution being geographically isolated for thousands of years. Here, we present a high-quality de novo assembly of a pure dingo (CanFam_DDS). We identified large chromosomal differences relative to the current dog reference (CanFam3.1) and confirmed no expanded pancreatic amylase gene as found in breed dogs. Phylogenetic analyses using variant pairwise matrices show that the dingo is distinct from five breed dogs with 100% bootstrap support when using Greenland wolf as the outgroup. Functionally, we observe differences in methylation patterns between the dingo and German shepherd dog genomes and differences in serum biochemistry and microbiome makeup. Our results suggest that distinct demographic and environmental conditions have shaped the dingo genome. In contrast, artificial human selection has likely shaped the genomes of domestic breed dogs after divergence from the dingo