67 research outputs found
Surfing through the GFC : systemic risk in Australia
We provide empirical evidence on the degree of systemic risk in Australia before,
during and after the Global Financial Crisis. We calculate a daily index of systemic
risk from 2004 to 2013 in order to understand how real economy firms influence the
outcomes for the rest of the economy. This is done via a mapping of the interconnectedness
of the financial and non-financial sectors. The financial sector is in general the
home to the most consistently systemically risky firms in the economy. The mining
sector becomes occasionally as systemically risky as the financial sector, reflecting the
importance of understanding the interrelationships between the financial sector and
the real economy in monitoring systemic risks
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Common Short Selling and Excess Comovement
We show that common short sold capital can explain future four-factor excess return correlation one month ahead, controlling for many pair characteristics, including similarities in size, book-to-market, and momentum. We explore the possible explanations that could give rise to this result. Contrary to the predictions of price pressure, we find that the relationship weakens significantly with stock illiquidity. Instead, consistent with the informed trading hypothesis, the relationship is stronger when short positions originate from hedge funds, from active investors, and from short sellers with high past performance. Stocks connected by common short sellers are associated with non-transitory negative cumulative abnormal returns. Finally, we show that our results can be used to obtain diversifications benefits
Venture capital, credit, and FinTech start-up formation: A cross-country study
This is the author accepted manuscript. The final version is available from SAGE Publications via the DOI in this recordGrowing FinTech entrepreneurship is a recent global phenomenon. Drawing on the national
innovation systems framework, we examine how countriesâ venture capital (VC) and credit
markets differently affect FinTech entrepreneurship across countries. We argue that with their
established and globally diffused norms and practices, VC investorsâbut not banksârequire a
critical mass of FinTech entrepreneurship in a country to more positively influence FinTech
entrepreneurship. Moreover, we argue that VC and credit markets are substitutes, especially in
countries with more FinTech entrepreneurship. Using quantile regressions on data from 53
countries, we find support for our hypotheses
Impact of network structure and cellular response on spike time correlations
Novel experimental techniques reveal the simultaneous activity of larger and
larger numbers of neurons. As a result there is increasing interest in the
structure of cooperative -- or correlated -- activity in neural populations,
and in the possible impact of such correlations on the neural code. A
fundamental theoretical challenge is to understand how the architecture of
network connectivity along with the dynamical properties of single cells shape
the magnitude and timescale of correlations. We provide a general approach to
this problem by extending prior techniques based on linear response theory. We
consider networks of general integrate-and-fire cells with arbitrary
architecture, and provide explicit expressions for the approximate
cross-correlation between constituent cells. These correlations depend strongly
on the operating point (input mean and variance) of the neurons, even when
connectivity is fixed. Moreover, the approximations admit an expansion in
powers of the matrices that describe the network architecture. This expansion
can be readily interpreted in terms of paths between different cells. We apply
our results to large excitatory-inhibitory networks, and demonstrate first how
precise balance --- or lack thereof --- between the strengths and timescales of
excitatory and inhibitory synapses is reflected in the overall correlation
structure of the network. We then derive explicit expressions for the average
correlation structure in randomly connected networks. These expressions help to
identify the important factors that shape coordinated neural activity in such
networks
The CARMENES search for exoplanets around M dwarfs. Two temperate Earth-mass planet candidates around Teegardenâs Star
Context.Teegardenâs Star is the brightest and one of the nearest ultra-cool dwarfs in the solar neighbourhood. For its late spectral type (M7.0 V),the star shows relatively little activity and is a prime target for near-infrared radial velocity surveys such as CARMENES.Aims.As part of the CARMENES search for exoplanets around M dwarfs, we obtained more than 200 radial-velocity measurements of TeegardenâsStar and analysed them for planetary signals.Methods.We find periodic variability in the radial velocities of Teegardenâs Star. We also studied photometric measurements to rule out stellarbrightness variations mimicking planetary signals.Results.We find evidence for two planet candidates, each with 1.1Mâminimum mass, orbiting at periods of 4.91 and 11.4 d, respectively. Noevidence for planetary transits could be found in archival and follow-up photometry. Small photometric variability is suggestive of slow rotationand old age.Conclusions.The two planets are among the lowest-mass planets discovered so far, and they are the first Earth-mass planets around an ultra-cooldwarf for which the masses have been determined using radial velocities.We thank the referee Rodrigo DĂaz for a careful review andhelpful comments. M.Z. acknowledges support from the Deutsche Forschungs-gemeinschaft under DFG RE 1664/12-1 and Research Unit FOR2544 âBluePlanets around Red Starsâ, project no. RE 1664/14-1. CARMENES isan instrument for the Centro AstronĂłmico Hispano-AlemĂĄn de Calar Alto(CAHA, AlmerĂa, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de InvestigacionesCientĂficas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut fĂŒr Astronomie, Instituto de AstrofĂsica de AndalucĂa, LandessternwarteKönigstuhl, Institut de CiĂšncies de lâEspai, Institut fĂŒr Astrophysik Göttingen,Universidad Complutense de Madrid, ThĂŒringer Landessternwarte Tautenburg,Instituto de AstrofĂsica de Canarias, Hamburger Sternwarte, Centro de Astro-biologĂa and Centro AstronĂłmico Hispano-AlemĂĄn), with additional contribu-tions by the Spanish Ministry of Economy, the German Science Foundationthrough the Major Research Instrumentation Programme and DFG ResearchUnit FOR2544 âBlue Planets around Red Starsâ, the Klaus Tschira Stiftung, thestates of Baden-WĂŒrttemberg and Niedersachsen, and by the Junta de AndalucĂa.Based on data from the CARMENES data archive at CAB (INTA-CSIC). Thisarticle is based on observations made with the MuSCAT2 instrument, devel-oped by ABC, at Telescopio Carlos SĂĄnchez operated on the island of Tener-ife by the IAC in the Spanish Observatorio del Teide. Data were partly col-lected with the 150-cm and 90-cm telescopes at the Sierra Nevada Observa-tory (SNO) operated by the Instituto de AstrofĂsica de AndalucĂa (IAA-CSIC).Data were partly obtained with the MONET/South telescope of the MOnitoringNEtwork of Telescopes, funded by the Alfried Krupp von Bohlen und HalbachFoundation, Essen, and operated by the Georg-August-UniversitĂ€t Göttingen,the McDonald Observatory of the University of Texas at Austin, and the SouthAfrican Astronomical Observatory. We acknowledge financial support from theSpanish Agencia Estatal de InvestigaciĂłn of the Ministerio de Ciencia, Inno-vaciĂłn y Universidades and the European FEDER/ERF funds through projectsAYA2015-69350-C3-2-P, AYA2016-79425-C3-1/2/3-P, AYA2018-84089, BES-2017-080769, BES-2017-082610, ESP2015-65712-C5-5-R, ESP2016-80435-C2-1/2-R, ESP2017-87143-R, ESP2017-87676-2-2, ESP2017-87676-C5-1/2/5-R, FPU15/01476, RYC-2012-09913, the Centre of Excellence âSevero Ochoaâand âMarĂa de Maeztuâ awards to the Instituto de AstrofĂsica de Canarias (SEV-2015-0548), Instituto de AstrofĂsica de AndalucĂa (SEV-2017-0709), and Cen-tro de AstrobiologĂa (MDM-2017-0737), the Generalitat de Catalunya throughCERCA programmeâ, the Deutsches Zentrum fĂŒr Luft- und Raumfahrt throughgrants 50OW0204 and 50OO1501, the European Research Council through grant694513, the Italian Ministero dellâinstruzione, dellâuniversitĂ de della ricerca andUniversitĂ degli Studi di Roma Tor Vergata through FFABR 2017 and âMis-sion: Sustainability 2016â, the UK Science and Technology Facilities Council through grant ST/P000592/1, the Israel Science Foundation through grant848/16, the Chilean CONICYT-FONDECYT through grant 3180405, the Mexi-can CONACYT through grant CVU 448248, the JSPS KAKENHI through grantsJP18H01265 and 18H05439, and the JST PRESTO through grant JPMJPR1775
The CARMENES search for exoplanets around M dwarfs High-resolution optical and near-infrared spectroscopy of 324 survey stars
The CARMENES radial velocity (RV) survey is observing 324 M dwarfs to search for any orbiting planets. In this paper, we present the survey sample by publishing one CARMENES spectrum for each M dwarf. These spectra cover the wavelength range 520â1710 nm at a resolution of at least R >80 000, and we measure its RV, Hα emission, and projected rotation velocity. We present an atlas of high-resolution M-dwarf spectra and compare the spectra to atmospheric models. To quantify the RV precision that can be achieved in low-mass stars over the CARMENES wavelength range, we analyze our empirical information on the RV precision from more than 6500 observations. We compare our high-resolution M-dwarf spectra to atmospheric models where we determine the spectroscopic RV information content, Q, and signal-to-noise ratio. We find that for all M-type dwarfs, the highest RV precision can be reached in the wavelength range 700â900 nm. Observations at longer wavelengths are equally precise only at the very latest spectral types (M8 and M9). We demonstrate that in this spectroscopic range, the large amount of absorption features compensates for the intrinsic faintness of an M7 star. To reach an RV precision of 1 m sâ1 in very low mass M dwarfs at longer wavelengths likely requires the use of a 10 m class telescope. For spectral types M6 and earlier, the combination of a red visual and a near-infrared spectrograph is ideal to search for low-mass planets and to distinguish between planets and stellar variability. At a 4 m class telescope, an instrument like CARMENES has the potential to push the RV precision well below the typical jitter level of 3â4 m sâ1
The CARMENES search for exoplanets around M dwarfs High-resolution optical and near-infrared spectroscopy of 324 survey stars
The CARMENES radial velocity (RV) survey is observing 324 M dwarfs to search for any orbiting planets. In this paper, we present the survey sample by publishing one CARMENES spectrum for each M dwarf. These spectra cover the wavelength range 520â1710 nm at a resolution of at least R >80 000, and we measure its RV, Hα emission, and projected rotation velocity. We present an atlas of high-resolution M-dwarf spectra and compare the spectra to atmospheric models. To quantify the RV precision that can be achieved in low-mass stars over the CARMENES wavelength range, we analyze our empirical information on the RV precision from more than 6500 observations. We compare our high-resolution M-dwarf spectra to atmospheric models where we determine the spectroscopic RV information content, Q, and signal-to-noise ratio. We find that for all M-type dwarfs, the highest RV precision can be reached in the wavelength range 700â900 nm. Observations at longer wavelengths are equally precise only at the very latest spectral types (M8 and M9). We demonstrate that in this spectroscopic range, the large amount of absorption features compensates for the intrinsic faintness of an M7 star. To reach an RV precision of 1 m sâ1 in very low mass M dwarfs at longer wavelengths likely requires the use of a 10 m class telescope. For spectral types M6 and earlier, the combination of a red visual and a near-infrared spectrograph is ideal to search for low-mass planets and to distinguish between planets and stellar variability. At a 4 m class telescope, an instrument like CARMENES has the potential to push the RV precision well below the typical jitter level of 3â4 m sâ1
The CARMENES search for exoplanets around M dwarfs HD147379 b: A nearby Neptune in the temperate zone of an early-M dwarf
We report on the first star discovered to host a planet detected by radial velocity (RV) observations obtained within the CARMENES survey for exoplanets around M dwarfs. HD 147379 (Vâ=â8.9 mag, Mâ=â0.58â±â0.08âMâ), a bright M0.0 V star at a distance of 10.7 pc, is found to undergo periodic RV variations with a semi-amplitude of Kâ=â5.1 ± 0.4 m sâ1 and a period of Pâ=â86.54 ± 0.06 d. The RV signal is found in our CARMENES data, which were taken between 2016 and 2017, and is supported by HIRES/Keck observations that were obtained since 2000. The RV variations are interpreted as resulting from a planet of minimum mass mPâsinâiâ=â25â±â2âMâ, 1.5 times the mass of Neptune, with an orbital semi-major axis aâ=â0.32 au and low eccentricity (e < 0.13). HD 147379 b is orbiting inside the temperate zone around the star, where water could exist in liquid form. The RV time-series and various spectroscopic indicators show additional hints of variations at an approximate period of 21.1 d (and its first harmonic), which we attribute to the rotation period of the star.FEDER/ERF FICTS-2011-02 fundsMajor Research Instrumentation Programme
and DFG Research Unit FOR2544 âBlue Planets around Red StarsEuropean Research Council (ERC-279347), Deutsche Forschungsgemeinschaft
(RE 1664/12-1, RE 2694/4-1), Bundesministerium fĂŒr Bildung
und Forschung (BMBF-05A14MG3, BMBF-05A17MG3), Spanish Ministry
of Economy and Competitiveness (MINECO, grants AYA2015-68012-C2-2-P,
AYA2016-79425-C3-1,2,3-P, AYA2015-69350-C3-2-P, AYA2014-54348-C03-
01, AYA2014-56359-P, AYA2014-54348-C3-2-R, AYA2016-79425-C3-3-P and
2013 RamĂČn y Cajal program RYC-2013-14875), Fondo Europeo de Desarrollo
Regional (FEDER, grant ESP2016-80435-C2-1-R, ESP2015-65712-C5-
5-R), Generalitat de Catalunya/CERCA programme, Spanish Ministerio de
EducaciĂłn, Cultura y Deporte, programa de FormaciĂłn de Profesorado Universitario
(grant FPU15/01476), Deutsches Zentrum fĂŒr Luft- und Raumfahrt
(grants 50OW0204 and 50OO1501), Office of Naval Research Global (award
no. N62909-15-1-2011), Mexican CONACyT grant CB-2012-183007
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