2,119 research outputs found

    Entrepreneurs’ Activities on Social Media and Venture Financing

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    Social media has been an incredible platform for startups to develop meaningful connections with stakeholders and customers. We investigate ways in which entrepreneurs use social media to drive both the level of engagement for their startup and the subsequent level of venture financing. Our empirical analysis demonstrates how differences in entrepreneurs’ tweets—i.e., differences in the level informativity, persuasiveness, and transformativity—is associated with different levels of startup engagement and venture financing. We show differences in entrepreneurs’ activity with the social media platform—i.e., the number of tweets, the number of mentions of other accounts, and the number of retweets—further drives engagement and venture financing. We test our model by collecting an extensive dataset of over 7,000,000 tweets from entrepreneurs and startups that have been through accelerators. Results indicate associates between the social media activities of entrepreneurs, startup engagement, and venture financing

    Statistics of X-ray flares of Sagittarius A*: evidence for solar-like self-organized criticality phenomenon

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    X-ray flares have routinely been observed from the supermassive black hole, Sagittarius A⋆^\star (Sgr A⋆^\star), at our Galactic center. The nature of these flares remains largely unclear, despite of many theoretical models. In this paper, we study the statistical properties of the Sgr A⋆^\star X-ray flares, by fitting the count rate (CR) distribution and the structure function (SF) of the light curve with a Markov Chain Monte Carlo (MCMC) method. With the 3 million second \textit{Chandra} observations accumulated in the Sgr A⋆^\star X-ray Visionary Project, we construct the theoretical light curves through Monte Carlo simulations. We find that the 2−82-8 keV X-ray light curve can be decomposed into a quiescent component with a constant count rate of ∌6×10−3 \sim6\times10^{-3}~count s−1^{-1} and a flare component with a power-law fluence distribution dN/dE∝E−αEdN/dE\propto E^{-\alpha_{\rm E}} with αE=1.65±0.17\alpha_{\rm E}=1.65\pm0.17. The duration-fluence correlation can also be modelled as a power-law T∝EαETT\propto E^{\alpha_{\rm ET}} with αET<0.55\alpha_{\rm ET} < 0.55 (95%95\% confidence). These statistical properties are consistent with the theoretical prediction of the self-organized criticality (SOC) system with the spatial dimension S=3S = 3. We suggest that the X-ray flares represent plasmoid ejections driven by magnetic reconnection (similar to solar flares) in the accretion flow onto the black hole.Comment: to appear in Ap
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