The Asteroid Terrestrial impact Last Alert System (ATLAS) system consists of two 0.5 m Schmidt telescopes with cameras covering 29 square degrees at plate scale of 1.86 arcsec per pixel. Working in ...tandem, the telescopes routinely survey the whole sky visible from Hawaii (above δ > − 50 ° ) every two nights, exposing four times per night, typically reaching o < 19 magnitude per exposure when the moon is illuminated and c < 19.5 magnitude per exposure in dark skies. Construction is underway of two further units to be sited in Chile and South Africa which will result in an all-sky daily cadence from 2021. Initially designed for detecting potentially hazardous near earth objects, the ATLAS data enable a range of astrophysical time domain science. To extract transients from the data stream requires a computing system to process the data, assimilate detections in time and space and associate them with known astrophysical sources. Here we describe the hardware and software infrastructure to produce a stream of clean, real, astrophysical transients in real time. This involves machine learning and boosted decision tree algorithms to identify extragalactic and Galactic transients. Typically we detect 10-15 supernova candidates per night which we immediately announce publicly. The ATLAS discoveries not only enable rapid follow-up of interesting sources but will provide complete statistical samples within the local volume of 100 Mpc. A simple comparison of the detected supernova rate within 100 Mpc, with no corrections for completeness, is already significantly higher (factor 1.5 to 2) than the current accepted rates.
Summary
The 2001 Report of the National Confidential Enquiry into Perioperative Deaths recommended that an echocardiogram should be performed on patients with aortic stenosis prior to anaesthesia. In ...this study we present the patient details, management and outcome of the 272 hip fracture patients with a previously undiagnosed murmur and echocardiographically proven aortic stenosis admitted from 2001–2005 in our hospital. The patients with aortic stenosis were significantly older, and had significantly lower Abbreviated Mental Test Scores, than the control group of 3698 hip fracture patients without aortic stenosis. There were significant trends toward general anaesthesia over spinal anaesthesia, and use of invasive monitoring of blood pressure, as the severity of the aortic stenosis increased. There were no significant trends towards higher 30‐day or 1‐year mortality rates as the severity of the aortic stenosis increased. Resources for rapid pre‐operative echocardiograms should be made available for hip fracture patients as the results have significant implications for their subsequent anaesthetic management.
ABSTRACT
We present multiwavelength follow-up observations of the ATLAS discovered faint Iax supernova SN 2020kyg that peaked at an absolute magnitude of Mg ≈ −14.9 ± 0.2, making it another member of ...the faint Iax supernova population. The bolometric light curve requires only ≈7 × 10−3 M⊙ of radioactive 56Ni, with an ejected mass of Mej ∼ 0.4 M⊙ and a low kinetic energy of E ≈ 0.05 ± 0.02 × 1051 erg. We construct a homogeneous volume-limited sample of 902 transients observed by ATLAS within 100 Mpc during a 3.5 yr span. Using this sample, we constrain the rates of faint Iax (Mr ≳ −16) events within 60 Mpc at $12^{+14}_{-8}{{\ \rm per\ cent}}$ of the SN Ia rate. The overall Iax rate, at $15^{+17}_{-9}{{\ \rm per\ cent}}$ of the Ia rate, is dominated by the low-luminosity events, with luminous SNe Iax (Mr ≲ −17.5) like 2002cx and 2005hk, accounting for only $0.9^{+1.1}_{-0.5}{{\ \rm per\ cent}}$ of the Ia rate (a 2σ upper limit of approximately 3 per cent). We favour the hybrid CONe WD + He star progenitor channel involving a failed deflagration of a near Chandrasekhar mass white dwarf, expected to leave a bound remnant and a surviving secondary companion, as a candidate explanation for faint Iax explosions. This scenario requires short delay times, consistent with the observed environments of SNe Iax. Furthermore, binary population synthesis calculations have suggested rates of $1\!-\!18{{\ \rm per\ cent}}$ of the SN Ia rate for this channel, consistent with our rate estimates.
ABSTRACT
Time domain astronomy was revolutionized with the discovery of the first kilonova, AT2017gfo, in August 2017, which was associated with the gravitational wave signal GW170817. Since this ...event, numerous wide-field surveys have been optimizing search strategies to maximize their efficiency of detecting these fast and faint transients. With the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), we have been conducting a volume-limited survey for intrinsically faint and fast-fading events to a distance of D ≃ 200 Mpc. Two promising candidates have been identified from this archival search, with sparse data – PS15cey and PS17cke. Here, we present more detailed analysis and discussion of their nature. We observe that PS15cey was a luminous, fast-declining transient at 320 Mpc. Models of BH–NS mergers with a very stiff equation of state could possibly reproduce the luminosity and decline but the physical parameters are extreme. A more likely scenario is that this was an AT2018kzr-like merger event. PS17cke was a faint and fast-declining event at 15 Mpc. We explore several explosion scenarios of this transient including models of it as a NS–NS and BH–NS merger, the outburst of a massive luminous star, and compare it against other known fast-fading transients. Although there is uncertainty in the explosion scenario due to difficulty in measuring the explosion epoch, we find PS17cke to be a plausible kilonova candidate from the model comparisons.
Abstract
In Smith et al. we published estimates of the volumetric rate of supernovae within 100 Mpc. These were incorrect and we present the correct values in this corrigendum.
Corrigendum Smith, K. W.; Smartt, S. J.; Young, D. R. ...
Publications of the Astronomical Society of the Pacific,
02/2021, Letnik:
133, Številka:
1020
Journal Article
Recenzirano
In Smith et al. we published estimates of the volumetric rate of supernovae within 100 Mpc. These were incorrect and we present the correct values in this corrigendum.
On 2019 August 14, the LIGO and Virgo interferometers detected a high-significance event labelled S190814bv. Preliminary analysis of the GW data suggests that the event was likely due to the merger ...of a compact binary system formed by a BH and a NS. ElectromagNetic counterparts of GRAvitational wave sources at the VEry Large Telescope (ENGRAVE) collaboration members carried out an intensive multi-epoch, multi-instrument observational campaign to identify the possible optical/near infrared counterpart of the event. In addition, the ATLAS, GOTO, GRAWITA-VST, Pan-STARRS and VINROUGE projects also carried out a search on this event. Our observations allow us to place limits on the presence of any counterpart and discuss the implications for the kilonova (KN) possibly generated by this NS-BH merger, and for the strategy of future searches. Altogether, our observations allow us to exclude a KN with large ejecta mass $M\gtrsim 0.1\,\mathrm{M_\odot}$ to a high ($>90\%$) confidence, and we can exclude much smaller masses in a subsample of our observations. This disfavours the tidal disruption of the neutron star during the merger. Despite the sensitive instruments involved in the campaign, given the distance of S190814bv we could not reach sufficiently deep limits to constrain a KN comparable in luminosity to AT 2017gfo on a large fraction of the localisation probability. This suggests that future (likely common) events at a few hundreds Mpc will be detected only by large facilities with both high sensitivity and large field of view. Galaxy-targeted observations can reach the needed depth over a relevant portion of the localisation probability with a smaller investment of resources, but the number of galaxies to be targeted in order to get a fairly complete coverage is large, even in the case of a localisation as good as that of this event.
We present the ATLAS discovery and initial analysis of the first 18 days of the unusual transient event, ATLAS18qqn/AT2018cow. It is characterized by a high peak luminosity (∼1.7 × 1044 erg s−1), ...rapidly evolving light curves (>5 mag rise to peak in ∼3.5 days), and hot blackbody spectra, peaking at ∼27,000 K that are relatively featureless and unchanging over the first two weeks. The bolometric light curve cannot be powered by radioactive decay under realistic assumptions. The detection of high-energy emission may suggest a central engine as the powering source. Using a magnetar model, we estimated an ejected mass of 0.1-0.4 M , which lies between that of low-energy core-collapse events and the kilonova, AT2017gfo. The spectra cooled rapidly from 27,000 to 15,000 K in just over two weeks but remained smooth and featureless. Broad and shallow emission lines appear after about 20 days, and we tentatively identify them as He i although they would be redshifted from their rest wavelengths. We rule out that there are any features in the spectra due to intermediate mass elements up to and including the Fe group. The presence of r-process elements cannot be ruled out. If these lines are due to He, then we suggest a low-mass star with residual He as a potential progenitor. Alternatively, models of magnetars formed in neutron star mergers, or accretion onto a central compact object, give plausible matches to the data.
Human immunodeficiency virus (HIV) persists indefinitely in individuals with HIV who receive antiretroviral therapy (ART) owing to a reservoir of latently infected cells that contain ...replication-competent virus
. Here, to better understand the mechanisms responsible for latency persistence and reversal, we used the interleukin-15 superagonist N-803 in conjunction with the depletion of CD8
lymphocytes in ART-treated macaques infected with simian immunodeficiency virus (SIV). Although N-803 alone did not reactivate virus production, its administration after the depletion of CD8
lymphocytes in conjunction with ART treatment induced robust and persistent reactivation of the virus in vivo. We found viraemia of more than 60 copies per ml in all macaques (n = 14; 100%) and in 41 out of a total of 56 samples (73.2%) that were collected each week after N-803 administration. Notably, concordant results were obtained in ART-treated HIV-infected humanized mice. In addition, we observed that co-culture with CD8
T cells blocked the in vitro latency-reversing effect of N-803 on primary human CD4
T cells that were latently infected with HIV. These results advance our understanding of the mechanisms responsible for latency reversal and lentivirus reactivation during ART-suppressed infection.
We present multi-wavelength follow-up observations of the ATLAS discovered faint Iax supernova SN 2020kyg that peaked at an absolute magnitude of \(M_g \approx -14.9 \pm 0.2\), making it another ...member of the faint Iax supernova population. The bolometric light curve requires only \(\approx 7 \times 10^{-3}\) M\(_{\odot}\) of radioactive \(^{56}\)Ni, with an ejected mass of \(M_{\rm ej} \sim 0.4\) M\(_{\odot}\) and a low kinetic energy of \(E \approx 0.05 \pm 0.02 \times 10^{51}\) erg. We construct a homogeneous volume-limited sample of 902 transients observed by ATLAS within 100 Mpc during a 3.5 year span. Using this sample, we constrain the rates of faint Iax (\(M_r \gtrsim -16\)) events within 60 Mpc at \(12^{+14}_{-8}\%\) of the SN Ia rate. The overall Iax rate, at \(15^{+17}_{-9}\%\) of the Ia rate, is dominated by the low-luminosity events, with luminous SNe Iax (\(M_r \lesssim -17.5\)) like 2002cx and 2005hk accounting for only \(0.9^{+1.1}_{-0.5}\%\) of the Ia rate (a 2\(\sigma\) upper limit of approximately 3\%). We favour the hybrid CONe WD + He star progenitor channel involving a failed deflagration of a near Chandrasekhar mass white dwarf, expected to leave a bound remnant and a surviving secondary companion, as a candidate explanation for faint Iax explosions. This scenario requires short delay times, consistent with the observed environments of SNe Iax. Furthermore, binary population synthesis calculations have suggested rates of \(1-18\%\) of the SN Ia rate for this channel, consistent with our rate estimates.
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