Results 61 to 70 of about 13,120 (212)

Organocatalytic C─O Bond Cleavage and Asymmetric Transformations via [1,3]‐Sigmatropic Rearrangement

Advanced Science, Volume 12, Issue 29, August 7, 2025.
A direct asymmetric strategy for fulfilling the functional group transfer by aryl ether cleavage and migration is developed, representing the first Brønsted base‐catalyzed asymmetric [1,3]‐sigmatropic rearrangement reaction. The resulting chiral benzofuran products generated through this strategy exhibit significant 3D‐dimensionality and demonstrate ...
Lei Peng, Yu Chang, Liangchen Yin, Jinbang Zhang, Xuli Feng, Pengfei Wang, Wenling Qin, Hailong Yan   +7 more
wiley   +1 more source

On the progenitor of the Type Ic supernova 2002ap

Astrophysical Journal, 2002
This letter presents wide-field optical and and NIR UBVRI,Halpha,K' images of the galaxy M74 which were taken between 0.6-8.3 years before the discovery of the Type Ic SN2002ap. We have located the position of the SN on these images with an accuracy of 0.3''. We find no sign of a progenitor object on any of the images.
Smartt, S., Vreeswijk, P.M., Ramirez-Ruiz, E., Gilmore, G.F, Meikle, W.P.S., Ferguson, A.M.N., Knapen, J.H.   +6 more
openaire   +4 more sources

Hubble Space Telescope Deep Upper Limits Rule out a Surviving Massive Binary Companion to the Type Ic Supernova 2012fh

The Astrophysical Journal
Current explanations of the mass-loss mechanism for stripped-envelope supernovae (SNe) remain divided between single and binary progenitor systems. Here we obtain deep ultraviolet (UV) imaging with the Hubble Space Telescope (HST) of the Type Ic SN ...
Benjamin F. Williams, Emmanouil Zapartas, Ori D. Fox, K. Azalee Bostroem, Jianing Su, Brad Koplitz, Schuyler D. Van Dyk, Maria R. Drout, Dimitris Souropanis, Dan Milisavljevic, Stuart D. Ryder, Selma E. de Mink, Nathan Smith, Andrew Dolphin, Alexei V. Filippenko, Jeff J. Andrews, Max M. Briel, Seth Gossage, Matthias U. Kruckow, Camille Liotine, Philipp M. Srivastava, Elizabeth Teng   +21 more
doaj   +1 more source

Circumstellar Emission from Type Ib and Ic Supernovae [PDF]

The Astrophysical Journal, 2006
The presumed Wolf-Rayet star progenitors of Type Ib/c supernovae have fast, low density winds and the shock waves generated by the supernova interaction with the wind are not expected to be radiative at typical times of observation. The injected energy spectrum of radio emitting electrons typically has an observed index p=3, which is suggestive of ...
Chevalier, Roger A., Fransson, Claes
openaire   +2 more sources

Managing and mitigating future public health risks: Planetary boundaries, global catastrophic risk, and inclusive wealth

Risk Analysis, Volume 45, Issue 7, Page 1607-1631, July 2025.
Abstract There are two separate conceptualizations for assessing existential risks: Planetary Boundaries (PBs) and global catastrophic risks (GCRs). While these concepts are similar in principle, their underpinning literatures tend not to engage with each other.
Eoin McLaughlin, Matthias Beck
wiley   +1 more source

The Energy Sources, the Physical Properties, and the Mass-loss History of SN 2017dio

The Astrophysical Journal
We study the energy sources, the physical properties of the ejecta and the circumstellar medium (CSM), and the mass-loss history of the progenitor of SN 2017dio, which is a broad-lined Ic (Ic-BL) supernova (SN) having unusual light curves (LCs) and ...
Deng-Wang Shi, Shan-Qin Wang, Wen-Pei Gan, En-Wei Liang   +3 more
doaj   +1 more source

Probing Shock Breakout and Progenitors of Stripped-Envelope Supernovae through Their Early Radio Emissions

, 2012
We study properties of early radio emission from stripped-envelope supernovae (those of type IIb/Ib/Ic). We suggest there is a sub-class of stripped-envelope supernovae in their radio properties, including optically well-studied type Ic supernovae (SNe ...
Maeda, Keiichi
core   +1 more source

A Radio Survey of Type Ib and Ic Supernovae: Searching for Engine‐driven Supernovae [PDF]

The Astrophysical Journal, 2003
The association of gamma-ray bursts (GRBs) and core-collapse supernovae (SNe) of Type Ib and Ic was motivated by the detection of SN 1998bw in the error box of GRB 980425 and the now-secure identification of a SN 1998bw-like event in the cosmological GRB 030329.
Berger, E., Kulkarni, S. R., Frail, D. A., Soderberg, A. M.   +3 more
openaire   +2 more sources

Mechanisms underlying the loss of migratory behaviour in a long‐lived bird

Journal of Animal Ecology, Volume 94, Issue 5, Page 1061-1075, May 2025.
White stork populations in Iberia are undergoing a profound change in their migratory patterns, becoming mostly resident. By combining census data, GPS‐tracking and genomic analyses, Andrade et al. link this behavioural change to inter‐generational shifts in the frequency of migratory and non‐migratory young individuals (likely associated with ...
Pedro Andrade, Aldina M. A. Franco, Marta Acácio, Sandra Afonso, Cristiana I. Marques, Francisco Moreira, Miguel Carneiro, Inês Catry   +7 more
wiley   +1 more source

Core-Collapse Supernovae and Host Galaxy Stellar Populations

, 2012
We have used images and spectra of the Sloan Digital Sky Survey to examine the host galaxies of 519 nearby supernovae. The colors at the sites of the explosions, as well as chemical abundances, and specific star formation rates of the host galaxies ...
Aldering, Arcavi, Arcavi, Bertin, Blanton, Blanton, Blondin, Blondin, Cappellaro, Chevalier, Chugai, Cool, Delahaye, Dilday, Djorgovski, Drout, Filippenko, Filippenko, Fioc, Fioc, Foley, Fryer, Gal-Yam, Habergham, Hardin, Heger, Hicken, Kelly, Kelly, Kewley, Kewley, Kudritzki, Levesque, Li, Maeder, Malesani, Marion, Matheson, Matheson, Matheson, Matheson, Maund, Mazzali, Miknaitis, Modjaz, Modjaz, Modjaz, Moustakas, Moustakas, Osterbrock, Patrick L. Kelly, Perlmutter, Pravdo, Prieto, Quimby, Quimby, Raskin, Riess, Robert P. Kirshner, Sako, Sanders, Sanders, Schlegel, Schlegel, Smartt, Soderberg, Stanek, Strauss, Thompson, Tremonti, Van Dyk, Van Dyk, Van Dyk, van Zee, Yoon, Yoon   +75 more
core   +1 more source