The 1989 and 2015 outbursts of V404 Cygni: a global study of wind-related optical features

The black hole transient V404 Cygni exhibited a bright outburst in June 2015 that was intensively followed over a wide range of wavelengths. Our team obtained high time resolution optical spectroscopy (~90 s), which included a detailed coverage of the most active phase of the event. We present a database consisting of 651 optical spectra obtained during this event, that we combine with 58 spectra gathered during the fainter December 2015 sequel outburst, as well as with 57 spectra from the 1989 event. We previously reported the discovery of wind-related features (P-Cygni and broad-wing line profiles) during both 2015 outbursts. Here, we build diagnostic diagrams that enable us to study the evolution of typical emission line parameters, such as line fluxes and equivalent widths, and develop a technique to systematically detect outflow signatures. We find that these are present throughout the outburst, even at very low optical fluxes, and that both types of outflow features are observed simultaneously in some spectra, confirming the idea of a common origin. We also show that the nebular phases depict loop patterns in many diagnostic diagrams, while P-Cygni profiles are highly variable on time-scales of minutes. The comparison between the three outbursts reveals that the spectra obtained during June and December 2015 share many similarities, while those from 1989 exhibit narrower emission lines and lower wind terminal velocities. The diagnostic diagrams presented in this work have been produced using standard measurement techniques and thus may be applied to other active low-mass X-ray binaries.Comment: Accepted for publication in MNRAS. 23 pages paper, plus a 9 pages appendix with extra tables and figures. 18 figures are included in the paper and 8 in the appendi

A population-based controlled experiment assessing the epidemiological impact of digital contact tracing

While Digital contact tracing (DCT) has been argued to be a valuable complement to manual tracing in the containment of COVID-19, no empirical evidence of its effectiveness is available to date. Here, we report the results of a 4-week population-based controlled experiment that took place in La Gomera (Canary Islands, Spain) between June and July 2020, where we assessed the epidemiological impact of the Spanish DCT app Radar Covid. After a substantial communication campaign, we estimate that at least 33% of the population adopted the technology and further showed relatively high adherence and compliance as well as a quick turnaround time. The app detects about 6.3 close-contacts per primary simulated infection, a significant percentage being contacts with strangers, although the spontaneous follow-up rate of these notified cases is low. Overall, these results provide experimental evidence of the potential usefulness of DCT during an epidemic outbreak in a real population

The 1989 and 2015 outbursts of V404 Cygni: A global study of wind-related optical features

The black hole transient V404 Cygni exhibited a bright outburst in June 2015 that was intensively followed over a wide range of wavelengths. Our team obtained high time resolution optical spectroscopy (~90 s), which included a detailed coverage of the most active phase of the event. We present a data base consisting of 651 optical spectra obtained during this event, that we combine with 58 spectra gathered during the fainter December 2015 sequel outburst, as well as with 57 spectra from the 1989 event.We previously reported the discovery of windrelated features (P-Cygni and broad-wing line profiles) during both 2015 outbursts. Here, we build diagnostic diagrams that enable us to study the evolution of typical emission line parameters, such as line fluxes and equivalent widths, and develop a technique to systematically detect outflow signatures. We find that these are present throughout the outburst, even at very low optical fluxes, and that both types of outflow features are observed simultaneously in some spectra, confirming the idea of a common origin. We also show that the nebular phases depict loop patterns in many diagnostic diagrams, while P-Cygni profiles are highly variable on time-scales of minutes. The comparison between the three outbursts reveals that the spectra obtained during June and December 2015 share many similarities, while those from 1989 exhibit narrower emission lines and lower wind terminal velocities. The diagnostic diagrams presented in this work have been produced using standard measurement techniques and thus may be applied to other active low-mass X-ray binaries. © 2018 The Author(s).DMS acknowledges Fundacion La Caixa for the financial support received in the form of a PhD contract. TMD acknowledges support via a Ramon y Cajal Fellowship (RYC-2015-18148) and the Spanish MINECO project AYA2017-83216-P. JC acknowledges financial support from the Spanish Ministry of Economy, Industry and Competitiveness (MINECO) under the 2015 Severo Ochoa Program MINECO SEV-2015-0548, and to the Leverhulme Trust through grant VP2-2015-046. PAC gratefully acknowledges the receipt of a Leverhulme Emeritus Fellowship from the Leverhulme Trust. MAP's research is funded under the Juan de la Cierva Fellowship Programme (IJCI-2016-30867) from MINECO. ML is supported by EU's Horizon 2020 programme through a Marie Sklodowska-Curie Fellowship (grant nr. 702638). MAPT acknowledges support via a Ramon y Cajal Fellowship (RYC-2015-17854). AWS is supported by an NSERC Discovery Grant and a Discovery Accelerator Supplement. AJCT acknowledges support from the Spanish Ministry MINECO Project AYA 2015-71718-R (including FEDER funds). We thank Javier Mendez (head of the ING Service Program), Chris Benn (head of Astronomy), Marc Balcells (director of ING) and all the ING SAs for their help in monitoring this unique event during ING Service and Discretionary time. We also thank Romano Corradi (director of GTC), Antonio Cabrera (head of science operations) and the GTC support team for the quick response during the multiples triggers of our program. This research has been carried out with telescope time awarded by the CCI International Time Programme at the Canary Islands observatories (program ITP13-8). We also thank the GTC DDT committee (coordinated by the IAC director, Rafael Rebolo) for the awarded time to our observing program. This paper is partially based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), and Poland, and with the participation of Russia and the USA. MOLLY software developed by T. R. Marsh is gratefully acknowledged

Effects of insularity on digestion: living on islands induces shifts in physiological and morphological traits in island reptiles

“The final publication is available at Springer via http://dx.DOI: 10.1007/s00114-015-1301-8