We present observations of the optical afterglow of GRB 170817A, made by the Hubble Space Telescope, between 2018 February and August, up to one year after the neutron star merger GW170817. The ...afterglow shows a rapid decline beyond 170 days, and confirms the jet origin for the observed outflow, in contrast to more slowly declining expectations for "failed-jet" scenarios. We show here that the broadband (radio, optical, X-ray) afterglow is consistent with a structured outflow where an ultra-relativistic jet, with a Lorentz factor of Γ 100, forms a narrow core (∼5°) and is surrounded by a wider angular component that extends to ∼15°, which is itself relativistic (Γ 5). For a two-component model of this structure, the late-time optical decline, where F ∝ t− , is = 2.20 0.18, and for a Gaussian structure the decline is = 2.45 0.23. We find the Gaussian model to be consistent with both the early ∼10 days and late 290 days data. The agreement of the optical light curve with the evolution of the broadband spectral energy distribution, and its continued decline, indicates that the optical flux is arising primarily from the afterglow and not any underlying host system. This provides the deepest limits on any host stellar cluster with a luminosity 4000 L (MF606W −4.3).
We present Hubble Space Telescope (HST) and Chandra imaging, combined with Very Large Telescope MUSE integral field spectroscopy of the counterpart and host galaxy of the first binary neutron star ...merger detected via gravitational-wave emission by LIGO and Virgo, GW170817. The host galaxy, NGC 4993, is an S0 galaxy at z = 0.009783. There is evidence for large, face-on spiral shells in continuum imaging, and edge-on spiral features visible in nebular emission lines. This suggests that NGC 4993 has undergone a relatively recent ( 1 Gyr) "dry" merger. This merger may provide the fuel for a weak active nucleus seen in Chandra imaging. At the location of the counterpart, HST imaging implies there is no globular or young stellar cluster, with a limit of a few thousand solar masses for any young system. The population in the vicinity is predominantly old with 1% of any light arising from a population with ages < 500 Myr . Both the host galaxy properties and those of the transient location are consistent with the distributions seen for short-duration gamma-ray bursts, although the source position lies well within the effective radius ( r e ∼ 3 kpc), providing an re-normalized offset that is closer than ∼ 90 % of short GRBs. For the long delay time implied by the stellar population, this suggests that the kick velocity was significantly less than the galaxy escape velocity. We do not see any narrow host galaxy interstellar medium features within the counterpart spectrum, implying low extinction, and that the binary may lie in front of the bulk of the host galaxy.
Children with uncomplicated severe acute malnutrition (SAM) are treated at home with ready-to-use therapeutic foods (RUTFs). The current RUTF dose is prescribed according to the weight of the child ...to fulfil 100% of their nutritional needs until discharge. However, there is doubt concerning the dose, as it seems to be shared, resulting in suboptimal cost-efficiency of SAM treatment. We investigated the efficacy of a reduced RUTF dose in community-based treatment of uncomplicated SAM.
We undertook a randomised trial testing the non-inferiority of weight gain velocity of children with SAM receiving (a) a standard RUTF dose for two weeks, followed by a reduced dose thereafter (reduced), compared with (b) a standard RUTF dose throughout the treatment (standard). A mean difference of 0.0 g/kg/day was expected, with a non-inferiority margin fixed at -0.5 g/kg/day. Linear and logistic mixed regression analyses were performed, with study site and team as random effects. Between October 2016 and July 2018, 801 children with uncomplicated SAM aged 6-59 months were enrolled from 10 community health centres in Burkina Faso. At admission, the mean age (± standard deviation SD) was 13.4 months (±8.7), 49% were male, and the mean weight was 6.2 kg (±1.3). The mean weight gain velocity from admission to discharge was 3.4 g/kg/day and did not differ between study arms (Δ 0.0 g/kg/day; 95% CI -0.4 to 0.4; p = 0.92) confirming non-inferiority (p = 0.013). However, after two weeks, the weight gain velocity was significantly lower in the reduced dose with a mean of 2.3 g/kg/day compared with 2.7 g/kg/day in the standard dose (Δ -0.4 g/kg/day; 95% CI -0.8 to -0.02; p = 0.041). The length of stay (LoS) was not different (p = 0.73) between groups with a median of 56 days (interquartile range IQR 35-91) in both arms. No differences were found between reduced and standard arm in recovery (52.7% and 55.4%; p = 0.45), referral (19.2% and 20.1%; p = 0.80), defaulter (12.2% and 8.5%; p = 0.088), non-response (12.7% and 12.5%; p = 0.95), and relapse (2.4% and 1.8%; p = 0.69) rates, respectively. However, the reduced RUTF dose had a small 0.2 mm/week (95% CI 0.04 to 0.4; p = 0.015) negative effect on height gain velocity with a mean height gain of 2.6 mm/week with reduced and 2.8 mm/week with standard RUTF dose. The impact was more pronounced in children under 12 months of age (interaction, p = 0.019) who gained 2.8 mm/week with reduced and 3.1 mm/week with standard dose (Δ -0.4 mm/week; 95% CI -0.6 to -0.2; p < 0.001). Limitations include not blinding participants to the RUTF dose received and excluding all children with negative appetite test. The results are generalisable for relatively food secure contexts with a young SAM population.
Reducing the RUTF dose provided to children with SAM after two weeks of treatment did not reduce overall weight or mid-upper arm circumference (MUAC) gain velocity nor affect recovery or lengthen treatment time. However, it led to a small but significant negative effect on linear growth, especially among the youngest. The potential effect of reducing the RUTF dose in a routine program on treatment outcomes should be evaluated before scaling up.
ISRCTN registry ISRCTN50039021.
Abstract
During the Zwicky Transient Facility (ZTF) Phase I operations, 78 hydrogen-poor superluminous supernovae (SLSNe-I) were discovered in less than 3 yr, constituting the largest sample from a ...single survey. This paper (Paper I) presents the data, including the optical/UV light curves and classification spectra, while Paper II in this series will focus on the detailed analysis of the light curves and modeling. Our photometry is primarily taken by ZTF in the
g
,
r
, and
i
bands, and with additional data from other ground-based facilities and Swift. The events of our sample cover a redshift range of
z
= 0.06 − 0.67, with a median and 1
σ
error (16% and 84% percentiles) of
z
med
=
0.265
−
0.135
+
0.143
. The peak luminosity covers −22.8 mag ≤
M
g
,peak
≤ −19.8 mag, with a median value of
−
21.48
−
0.61
+
1.13
mag. The light curves evolve slowly with a mean rest-frame rise time of
t
rise
= 41.9 ± 17.8 days. The luminosity and timescale distributions suggest that low-luminosity SLSNe-I with a peak luminosity ∼−20 mag or extremely fast-rising events (<10 days) exist, but are rare. We confirm previous findings that slowly rising SLSNe-I also tend to fade slowly. The rest-frame color and temperature evolution show large scatters, suggesting that the SLSN-I population may have diverse spectral energy distributions. The peak rest-frame color shows a moderate correlation with the peak absolute magnitude, i.e., brighter SLSNe-I tend to have bluer colors. With optical and UV photometry, we construct the bolometric luminosity and derive a bolometric correction relation that is generally applicable for converting
g
,
r
-band photometry to the bolometric luminosity for SLSNe-I.
Abstract
We present analysis of the light curves (LCs) of 77 hydrogen-poor superluminous supernovae (SLSNe I) discovered during the Zwicky Transient Facility Phase I operation. We find that the ...majority (67%) of the sample can be fit equally well by both magnetar and ejecta–circumstellar medium (CSM) interaction plus
56
Ni decay models. This implies that LCs alone cannot unambiguously constrain the physical power sources for an SLSN I. However, 23% of the sample show inverted V-shape, steep-declining LCs or features of long rise and fast post-peak decay, which are better described by the CSM+Ni model. The remaining 10% of the sample favors the magnetar model. Moreover, our analysis shows that the LC undulations are quite common, with a fraction of 18%–44% in our gold sample. Among those strongly undulating events, about 62% of them are found to be CSM-favored, implying that the undulations tend to occur in the CSM-favored events. Undulations show a wide range in energy and duration, with median values (and 1
σ
errors) being as
1.7
%
−
0.7
%
+
1.5
%
E
rad
,
total
and
28.8
−
9.1
+
14.4
days, respectively. Our analysis of the undulation timescales suggests that intrinsic temporal variations of the central engine can explain half of the undulating events, while CSM interaction (CSI) can account for the majority of the sample. Finally, all of the well-observed He-rich SLSNe Ib either have strongly undulating LCs or the LCs are much better fit by the CSM+Ni model. These observations imply that their progenitor stars have not had enough time to lose all of the He-envelopes before supernova explosions, and H-poor CSM are likely to present in these events.
Superluminous supernovae (SLSNe) of Type Ic have a tendency to occur in faint host galaxies which are likely to have low mass and low metallicity. PTF12dam is one of the closest and best-studied ...superluminous explosions that has a broad and slowly fading light curve similar to SN 2007bi. Here we present new photometry and spectroscopy for PTF12dam from 200–500 d (rest frame) after peak and a detailed analysis of the host galaxy (SDSS J142446.21+461348.6 at z = 0.107). Using deep templates and image subtraction we show that the light curve can be fit with a magnetar model if escape of high-energy gamma rays is taken into account. The full bolometric light curve from −53 to +399 d (with respect to peak) cannot be fit satisfactorily with the pair-instability models. An alternative model of interaction with a dense circumstellar material (CSM) produces a good fit to the data although this requires a very large mass (∼13 M⊙) of hydrogen-free CSM. The host galaxy is a compact dwarf (physical size ∼1.9 kpc) and with M
g
= −19.33 ± 0.10, it is the brightest nearby SLSN Ic host discovered so far. The host is a low-mass system (2.8 × 108 M⊙) with a star formation rate (5.0 M⊙ yr−1), which implies a very high specific star formation rate (17.9 Gyr−1). The remarkably strong nebular emission provide detections of the O iii λ4363 and O ii λλ7320, 7330auroral lines and an accurate oxygen abundance of 12 + log (O/H) = 8.05 ± 0.09. We show here that they are at the extreme end of the metallicity distribution of dwarf galaxies and propose that low metallicity is a requirement to produce these rare and peculiar SNe.
Every year, over 4 million children are treated for severe acute malnutrition with varying program performance. This study sought to explore the predictors of time to recovery from and non-response ...to outpatient treatment of SAM.
Children with weight-for-height z-score (WHZ) <-3 and/or mid-upper arm circumference (MUAC) <115 mm, without medical complications were enrolled in a trial (called MANGO) from outpatient clinics in Burkina Faso. Treatment included a weekly ration of ready-to-use therapeutic foods. Recovery was declared with WHZ ≥-2 and/or MUAC ≥125 mm, for two weeks without illness. Children not recovered by 16 weeks were considered as non-response to treatment. Predictors studied included admission characteristics, morbidity and compliance during treatment and household characteristics. Cox proportional hazard models were fitted and restricted mean time to recovery calculated. Logistic regression was used to analyse non-response to treatment.
Fifty-five percent of children recovered and mean time to recovery was eight weeks while 13% ended as non-response to treatment. Independent predictors of longer time to recovery or non-response included low age, being admitted with WHZ <-3, no illness nor anaemia at admission, illness episodes during treatment, skipped or missed visits, low maternal age and not practising open defecation. Eighty-four percent of children had at least one and 59% at least two illness episodes during treatment. This increased treatment duration by 1 to 4 weeks. Thirty-five percent of children missed at least one treatment visit. One missed visit predicted 3 weeks longer and two or more missed visits 5 weeks longer treatment duration.
Both longer time to recovery and higher non-response to treatment seem most strongly associated with illness episodes and missed visits during treatment. This indicates that prevention of illnesses would be key to shortening the treatment duration and that there is a need to seek ways to facilitate adherence.
In this paper we report the results of the first ~four years of spectroscopic and photometric monitoring of the Type IIn supernova SN 2015da (also known as PSN J13522411+3941286, or iPTF16tu). The ...supernova exploded in the nearby spiral galaxy NGC 5337 in a relatively highly extinguished environment. The transient showed prominent narrow Balmer lines in emission at all times and a slow rise to maximum in all bands. In addition, early observations performed by amateur astronomers give a very well-constrained explosion epoch. The observables are consistent with continuous interaction between the supernova ejecta and a dense and extended H-rich circumstellar medium. The presence of such an extended and dense medium is difficult to reconcile with standard stellar evolution models, since the metallicity at the position of SN 2015da seems to be slightly subsolar. Interaction is likely the mechanism powering the light curve, as confirmed by the analysis of the pseudo bolometric light curve, which gives a total radiated energy ≳ 10
51
erg. Modeling the light curve in the context of a supernova shock breakout through a dense circumstellar medium allowed us to infer the mass of the prexisting gas to be ≃ 8
M
⊙
, with an extreme mass-loss rate for the progenitor star ≃0.6
M
⊙
yr
−1
, suggesting that most of the circumstellar gas was produced during multiple eruptive events. Near- and mid-infrared observations reveal a fluxexcess in these domains, similar to those observed in SN 2010jl and other interacting transients, likely due to preexisting radiatively heated dust surrounding the supernova. By modeling the infrared excess, we infer a mass ≳ 0.4 × 10
−3
M
⊙
for the dust.
ABSTRACT
We present spectroscopy of the ejecta of SN 1987A in 2017 and 2018 from the Hubble Space Telescope and the Very Large Telescope, covering the wavelength range between 1150 and $10\, 000$ Å. ...At 31 yr, this is the first epoch with coverage over the ultraviolet-to-near-infrared range since 1995. We create velocity maps of the ejecta in the H α, Mg ii λλ2796, 2804 and O i λλ6302, 6366 (vacuum) emission lines and study their morphology. All three lines have a similar morphology, but Mg ii is blueshifted by ∼1000 km s−1 relative to the others and stronger in the north-west. We also study the evolution of the line fluxes, finding a brightening by a factor of ∼9 since 1999 in Mg ii, while the other line fluxes are similar in 1999 and 2018. We discuss implications for the power sources of emission lines at late times: thermal excitation due to heating by the X-rays from the ejecta–ring interaction is found to dominate the ultraviolet Mg ii lines, while the infrared Mg ii doublet is powered mainly by Ly α fluorescence. The X-ray deposition is calculated based on merger models of SN 1987A. Far-ultraviolet emission lines of H2 are not detected. Finally, we examine the combined spectrum of recently discovered hotspots outside the equatorial ring. Their unresolved Balmer emission lines close to zero velocity are consistent with the interaction of fast ejecta and a clumpy, slowly moving outflow. A clump of emission in this spectrum, south of the equatorial ring at ∼1500 km s−1, is likely associated with the reverse shock.
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