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Featured researches published by Helder Sebastião.


European Journal of Finance | 2010

The informational impact of electronic trading systems on the FTSE 100 stock index and its futures contracts

Helder Sebastião

This article examines the partial adjustment factors of Financial Times Stock Exchange (FTSE) 100 stock index and stock index futures. Using high frequency data from 15 January 1997 to 17 March 2000, it aims to assess the informational impact of the electronic trading systems implemented at the London Stock Exchange and London International Financial Futures Exchange (LIFFE). The results suggest that information runs mainly from the futures market to the spot market. We find that the introduction of stock exchange trading system, in October 1997, has increased the FTSE 100 indexs absolute efficiency; however, it reduced the informational feedback to the futures market. The implementation of LIFFE CONNECT at LIFFE, in May 1999, has reduced the absolute and relative efficiency of FTSE 100 futures. These findings seem to imply that during the period under scrutiny electronic trading increased the level of microstructural noise, probably due to the bid–ask bounce and order flow imbalances.


Scientific Annals of Economics and Business | 2018

Information Transmission Between Cryptocurrencies: Does Bitcoin Rule the Cryptocurrency World?

Pedro Bação; António Portugal Duarte; Helder Sebastião; Srdjan Redzepagic

Abstract This paper investigates the information transmission between the most important cryptocurrencies - Bitcoin, Litecoin, Ripple, Ethereum and Bitcoin Cash. We use a VAR modelling approach, upon which the Geweke’s feedback measures and generalized impulse response functions are computed. This methodology allows us to fully characterize the direction, intensity and persistence of information flows between cryptocurrencies. At this data granularity, most of information transmission is contemporaneous. However, it seems that there are some lagged feedback effects, mainly from other cryptocurrencies to Bitcoin. The generalized impulse-response functions confirm that there is a strong contemporaneous correlation and that there is not much evidence of lagged effects. The exception appears to be related to the overreaction of Bitcoin returns to contemporaneous shocks.


International Transactions in Operational Research | 2017

Portfolio Management With Higher Moments: The Cardinality Impact

Rui Pedro Brito; Helder Sebastião; Pedro Godinho


Journal of Asset Management | 2016

Efficient skewness/semivariance portfolios

Rui Pedro Brito; Helder Sebastião; Pedro Godinho


Archive | 2008

The partial adjustment factors of FTSE 100 stock index and stock index futures: The informational impact of electronic trading systems

Helder Sebastião


The Journal of Energy Markets | 2018

The Iberian electricity market: analysis of the risk premium in an illiquid market

Márcio Ferreira; Helder Sebastião


Social Science Research Network | 2017

The Iberian Electricity Market: Price Dynamics and Risk Premium in an Illiquid Market

Márcio Ferreira; Helder Sebastião


Portuguese Economic Journal | 2017

Portfolio choice with high frequency data: CRRA preferences and the liquidity effect

Rui Pedro Brito; Helder Sebastião; Pedro Godinho


Notas Económicas | 2017

Where is the information on USD/Bitcoin hourly prices?

Helder Sebastião; António Portugal Duarte; Gabriel Guerreiro


Archive | 2017

Where is the information on USD/Bitcoins hourly price movements?

Helder Sebastião; António Portugal Duarte; Gabriel Guerreiro

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Srdjan Redzepagic

Centre national de la recherche scientifique

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