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<jats:title>Abstract</jats:title> <jats:p>We report on the discovery of <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="object" xlink:href="SPLUS J210428.01−004934.2" xlink:type="simple">SPLUS J210428.01−004934.2</jats:named-content>, an ultra metal-poor (UMP) star first identified from the narrowband photometry of the Southern Photometric Local Universe Survey (S-PLUS) Data Release 1, in the SDSS Stripe 82 region. Follow-up medium- and high-resolution spectroscopy (with Gemini South and Magellan-Clay, respectively) confirmed the effectiveness of the search for low-metallicity stars using the S-PLUS narrowband photometry. At [Fe/H] = −4.03, <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="object" xlink:href="SPLUS J2104−0049" xlink:type="simple">SPLUS J2104−0049</jats:named-content> has the lowest <jats:italic>detected</jats:italic> carbon abundance, <jats:italic>A</jats:italic>(C) = +4.34, when compared to the 34 previously known UMP stars in the literature, which is an important constraint on its stellar progenitor and also on stellar evolution models at the lowest metallicities. Based on its chemical abundance pattern, we speculate that <jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="object" xlink:href="SPLUS J2104−0049" xlink:type="simple">SPLUS J2104−0049</jats:named-content> could be a bona fide second-generation star, formed from a gas cloud polluted by a single metal-free ∼ 30<jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> star. This discovery opens the possibility of finding additional UMP stars directly from narrowband photometric surveys, a potentially powerful method to help complete the inventory of such peculiar objects in our Galaxy.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Protostellar jets have a fundamental role at the earliest evolution of protostars of all masses. In the case of low-mass (≲8 <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>) protostars, strong observational evidence exists that the launching and collimation is due to the X- and/or disk-wind mechanisms. In these models, it is the protostar/disk system that creates all the necessary conditions to launch and collimate the jets near the protostar via strong magnetic fields. The origin of jets from more massive protostars has been investigated much less, in part because of the difficulty of resolving the collimation zone in these more distant objects. Here we present the highest angular resolution observations of a jet powered by a massive protostar, the Cep A HW2 radio jet. We imaged the radio emission at projected distances of only ∼20 au from the protostar, resolving the innermost 100 au of a massive protostellar jet for the first time. The morphology of the radio jet emission in this massive object is very different than what is usually observed in jets from low-mass protostars. We found that the outflowing material in HW2 has two components: a wide-angle wind launched from the protostar/disk system, and a highly collimated jet starting at 20–30 au from the protostar. We discuss two possible scenarios: an extension of the classical disk-wind to a massive protostar, or external collimation of a wide-angle wind. These results have important consequences for our understanding of how stars of different masses are formed.</jats:p>