The electromagnetic counterpart of the binary neutron star merger LIGO/Virgo GW170817. I. Discovery of the optical counterpart using the Dark Energy Camera

We present the Dark Energy Camera (DECam) discovery of the optical counterpart of the first binary neutron star merger detected through gravitational wave emission, GW170817. Our observations commenced 10.5 hours post-merger, as soon as the localization region became accessible from Chile. We imaged 70 deg2 in the i and z bands, covering 93% of the initial integrated localization probability, to a depth necessary to identify likely optical counterparts (e.g., a kilonova). At 11.4 hours post-merger we detected a bright optical transient located 10:600 from the nucleus of NGC4993 at redshift z = 0:0098, consistent (for H0 = 70 km s-1 Mpc-1) with the distance of 40±8 Mpc reported by the LIGO Scientific Collaboration and the Virgo Collaboration (LVC). At detection the transient had magnitudes i=17.3 and z=17.4, and thus an absolute magnitude of Mi = -15.7, in the luminosity range expected for a kilonova. We identified 1,500 potential transient candidates. Applying simple selection criteria aimed at rejecting background events such as supernovae, we find the transient associated with NGC4993 as the only remaining plausible counterpart, and reject chance coincidence at the 99.5% confidence level. We therefore conclude that the optical counterpart we have identified near NGC4993 is associated with GW170817. This discovery ushers in the era of multi-messenger astronomy with gravitational waves, and demonstrates the power of DECam to identify the optical counterparts of gravitational-wave sources

Indução do estro no pós-parto em vacas primíparas Holandês-Zebu Induction of estrus in the postpartum of Holstein-Zebu heifers through norgestomet

Avaliou-se o efeito do peso corporal no início do tratamento com progestágeno sobre as características reprodutivas de vacas mestiças Holandês-Zebu no pós-parto. Foram utilizadas 64 vacas, divididas em quatro grupos: GI - vacas com peso corporal entre 390-458kg e submetidas a tratamento hormonal com norgestomet, GII - vacas com peso corporal entre 464-562kg e submetidas a tratamento hormonal com norgestomet, GIII - vacas com peso corporal entre 374-451kg (controle) e GIV - vacas com peso corporal entre 452-545kg (controle). Os animais do grupo II manifestaram o primeiro estro no pós-parto mais cedo que os demais (64,4 dias - GII vs. 109,4-GI; 143,2-GIII e 105,1-GIV dias), e apresentaram menor período de serviço (94,6 dias vs. 125,5; 160,9 e 131,0 dias, na mesma ordem de citação anterior). Quanto às taxas de manifestação de estro e de gestação final, não se verificaram diferenças (P>0,05) entre os tratamentos. Os animais do GII apresentaram o menor período de serviço e os do GIII, o maior (94,6 vs. 160,9). Não houve influência do tratamento hormonal nem do peso corporal sobre a produção de leite e duração da lactação. O uso do implante de progestágeno nos animais que apresentaram maiores peso e condição corporal no início do tratamento respondeu por menor intervalo entre o parto e o primeiro estro. O uso do progestágeno em animais mais leves esteve associado ao retorno mais rápido à atividade ovariana cíclica no pós-parto.<br>The experiment was carried out to evaluate the effect of two ranges of body weight and norgestomet treatment on the reproductive parameters of postpartum crossbred Holstein-zebu cows. Sixty four primiparous cows were randomly allocated to four treatments 40 days after calving: group I - cows with body weight ranging from 390 to 458kg and norgestomet treated; group II - cows with body weight ranging from 464 to 562kg and norgestomet treated; group III - cows with body weight ranging from 390 to 458kg (control); and group IV - cows with body weight ranging from 464 to 562kg (control). Progestagen auricular implants were mantained during 10 days and the cows were mated to bulls submitted to breeding soundness evaluation. Animals from treatment II showed estrus earlier than animals of the others treatments (II: 64.4; I: 109.4; III: 143.2 and IV: 105.1 days; P<0.05), and shorter open days (II: 94.6; I: 125.5; III: 160.9 and IV: 131.0 days; P<0.05). Estrus and pregnance rates did not differ between treatments (P>0.05). The hormonal treatment and the body weight did not affect the total and daily milk yield, and length of lactation (P>0.05). Progestagen treated, heavier and better body condition scored animals had shorter open days, and returned to postpartum ovarian ciclicity faster than lighter animals

On composite marginal likelihoods

Clustered data, Computational efficiency, Composite likelihood, Genetics, Longitudinal data, Missing data, Pairwise likelihood, Pseudolikelihood, Spatial data, Statistical efficiency, Survival analysis, Time series,

Multi-messenger Observations of a Binary Neutron Star Merger

International audienceOn 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim 1.7\,{\rm{s}}$ with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg(2) at a luminosity distance of ${40}_{-8}^{+8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 $\,{M}_{\odot }$. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim 40\,{\rm{Mpc}}$) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position $\sim 9$ and $\sim 16$ days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta