1,742 research outputs found
How to reconstruct the geometry of a Middle Triassic feeding system: clues from clinopyroxene textures in lava flows from Cima Pape (Southern Alps, Italy)
Pearson cross-correlation in the first four black hole binary mergers
We adopt the Pearson cross-correlation measure to analyze the LIGO Hanford and LIGO Livingston detector data streams around the events GW150914, GW151012,GW151226 and GW170104. We find that the Pearson cross-correlation method is sensitive to these signals, with correlations peaking when the black hole binaries reconstructed by the LIGO Scientific and Virgo Collaborations, are merging. We compare the obtained cross-correlations with the statistical correlation fluctuations arising in simulated Gaussian noise data and in LIGO data at times when no event is claimed. Our results for the significance of the observed cross-correlations are broadly consistent with those announced by the LIGO Scientific and Virgo Collaborations based on matched-filter analysis. In the same data, if we subtract the maximum likelihood waveforms corresponding to the announced signals, no residual cross-correlations persists at a statistically significant level
The environment of the SN-less GRB 111005A at z = 0.0133
The collapsar model has proved highly successful in explaining the properties
of long gamma-ray bursts (GRBs), with the most direct confirmation being the
detection of a supernova (SN) coincident with the majority of nearby long GRBs.
Within this model, a long GRB is produced by the core-collapse of a metal-poor,
rapidly rotating, massive star. The detection of some long GRBs in metal-rich
environments, and more fundamentally the three examples of long GRBs (GRB
060505, GRB 060614 and GRB 111005A) with no coincident SN detection down to
very deep limits is in strong contention with theoretical expectations. In this
paper we present MUSE observations of the host galaxy of GRB 111005A, which is
the most recent and compelling example yet of a SN-less, long GRB. At
z=0.01326, GRB 111005A is the third closest GRB ever detected, and second
closest long duration GRB, enabling the nearby environment to be studied at a
resolution of 270 pc. From the analysis of the MUSE data cube, we find GRB
111005A to have occurred within a metal-rich environment with little signs of
ongoing star formation. Spectral analysis at the position of the GRB indicates
the presence of an old stellar population (tau > 10 Myr), which limits the mass
of the GRB progenitor to M_ZAMS<15 Msolar, in direct conflict with the
collapsar model. Our deep limits on the presence of any SN emission combined
with the environmental conditions at the position of GRB 111005A necessitate
the exploration of a novel long GRB formation mechanism that is unrelated to
massive stars.Comment: Now accepted by A&A. Manuscript replaced to match accepted version.
Some additional discussion added, and velocity map of the host galaxy now
include
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