arXiv subjects

Nadia Murillo

Publications and source records attributed to Nadia Murillo.

5 recordsLinked to original sources

arXiv2026

Protostellar Outflows Shed Light on the Dominant Close Companion Star Formation Pathways

Understanding the formation pathway for close-companion protostars is central to unraveling the processes that govern stellar multiplicity and very early star formation. We analyze a large sample of 51 Class 0/I close-companion protostellar systems, of which 38 show detectable outflows, yielding 42 measured outflows used in our analysis. We use ALMA observations of 11 systems in Perseus and 40 systems in Orion. These companions formed either directly at these small scales ($\lesssim 500$ au separations) via disk fragmentation or at larger scales ($> 1000$ au separations) via turbulent fragmentation followed by inward migration. Because of differences in formation mechanism, the former is expected to have preferentially aligned disks and outflows, whereas the latter is expected to show no preferred alignment. The relative prevalence of these formation pathways remains uncertain, yet it is critical to forming a comprehensive picture of star formation. We examine the distribution of position angles of companion protostars relative to the position angles of their molecular outflows. The outflow, as traced by $^{12}$CO ($J=2\rightarrow1$), is a useful proxy for the angular momentum of the system, expected to be orthogonal to the binary orbital plane. We use a simple model to account for random sampling of inclination and orbital phase in each system, finding that the observations are consistent with a distribution in which the outflows are preferentially orthogonal to the companions. Based on this analysis, we suggest disk fragmentation is the dominant formation pathway for close-companion protostellar systems.

astro-ph.SR↗

arXiv2020

Missing water in Class I protostellar disks

Water is a key volatile that provides insights into the initial stages of planet formation. The low water abundances inferred from water observations toward low-mass protostellar objects may point to a rapid locking of water as ice by large dust grains during star and planet formation. However, little is known about the water vapor abundance in newly formed planet-forming disks. We aim to determine the water abundance in embedded Keplerian disks through spatially-resolved observations of H$_2^{18}$O lines to understand the evolution of water during star and planet formation. We present H$_2^{18}$O line observations with ALMA and NOEMA millimeter interferometers toward five young stellar objects. NOEMA observed the 3$_{1,3}$ - $2_{2,0}$ line (E$_{\rm up}$ = 203.7 K) while ALMA targeted the $4_{1,4}$ - $3_{2,1}$ line (E$_{\rm up}$ = 322.0 K). Water column densities are derived considering optically thin and thermalized emission. Our observations are sensitive to the emission from the known Keplerian disks around three out of the five Class I objects in the sample. No H$_2^{18}$O emission is detected toward any of our five Class I disks. We report upper limits to the integrated line intensities. The inferred water column densities in Class I disks are N < 10$^{15}$ cm$^{-2}$ on 100 au scales which include both disk and envelope. The upper limits imply a disk-averaged water abundance of $\lesssim 10^{-6}$ with respect to H$_2$ for Class I objects. After taking into account the physical structure of the disk, the upper limit to the water abundance averaged over the inner warm disk with $T>$ 100 K is between 10$^{-7}$ up to 10$^{-5}$. Water vapor is not abundant in warm protostellar envelopes around Class I protostars. Upper limits to the water vapor column densities in Class I disks are at least two orders magnitude lower than values found in Class 0 disk-like structures.

astro-ph.SR↗

arXiv2019

Fault-Tolerant Nanosatellite Computing on a Budget

Micro- and nanosatellites have become popular platforms for a variety of commercial and scientific applications, but today are considered suitable mainly for short and low-priority space missions due to their low reliability. In part, this can be attributed to their reliance upon cheap, low-feature size, COTS components originally designed for embedded and mobile-market applications, for which traditional hardware-voting concepts are ineffective. Software-fault-tolerance concepts have been shown effective for such systems, but have largely been ignored by the space industry due to low maturity, as most have only been researched in theory. In practice, designers of payload instruments and miniaturized satellites are usually forced to sacrifice reliability in favor deliver the level of performance necessary for cutting-edge science and innovative commercial applications. Thus, we developed a software-fault-tolerance-approach based upon thread-level coarse-grain lockstep, which was validated using fault-injection. To offer strong long-term fault coverage, our architecture is implemented as tiled MPSoC on an FPGA, utilizing partial reconfiguration, as well as mixed criticality. This architecture can satisfy the high performance requirements of current and future scientific and commercial space missions at very low cost, while offering the strong fault-coverage guarantees necessary for platform control even for missions with a long duration. This architecture was developed for a 4-year ESA project. Together with two industrial partners, we are developing a prototype to then undergo radiation testing.

cs.AR↗

arXiv2017

Bringing Fault-Tolerant GigaHertz-Computing to Space: A Multi-Stage Software-Side Fault-Tolerance Approach for Miniaturized Spacecraft

Modern embedded technology is a driving factor in satellite miniaturization, contributing to a massive boom in satellite launches and a rapidly evolving new space industry. Miniaturized satellites, however, suffer from low reliability, as traditional hardware-based fault-tolerance (FT) concepts are ineffective for on-board computers (OBCs) utilizing modern systems-on-a-chip (SoC). Therefore, larger satellites continue to rely on proven processors with large feature sizes. Software-based concepts have largely been ignored by the space industry as they were researched only in theory, and have not yet reached the level of maturity necessary for implementation. We present the first integral, real-world solution to enable fault-tolerant general-purpose computing with modern multiprocessor-SoCs (MPSoCs) for spaceflight, thereby enabling their use in future high-priority space missions. The presented multi-stage approach consists of three FT stages, combining coarse-grained thread-level distributed self-validation, FPGA reconfiguration, and mixed criticality to assure long-term FT and excellent scalability for both resource constrained and critical high-priority space missions. Early benchmark results indicate a drastic performance increase over state-of-the-art radiation-hard OBC designs and considerably lower software- and hardware development costs. This approach was developed for a 4-year European Space Agency (ESA) project, and we are implementing a tiled MPSoC prototype jointly with two industrial partners.

cs.DC↗

arXiv2017

Preliminary Performance Estimations and Benchmark Results for a Software-based Fault-Tolerance Approach aboard Miniaturized Satellite Computers

Modern embedded technology is a driving factor in satellite miniaturization, contributing to a massive boom in satellite launches and a rapidly evolving new space industry. Miniaturized satellites however suffer from low reliability, as traditional hardware-based fault-tolerance (FT) concepts are ineffective for on-board computers (OBCs) utilizing modern systems-on-a-chip (SoC). Larger satellites therefore continue to rely on proven processors with large feature sizes. Software-based concepts have largely been ignored by the space industry as they were researched only in theory, and have not yet reached the level of maturity necessary for implementation. In related work, we presented the first integral, real-world solution to enable fault-tolerant general-purpose computing with modern multiprocessor-SoCs (MPSoCs) for spaceflight, thereby enabling their use in future high-priority space missions. The presented multi-stage approach consists of three FT stages, combining coarse-grained thread-level distributed self-validation, FPGA reconfiguration, and mixed criticality to assure long-term FT and excellent scalability for both resource constrained and critical high-priority space missions. As part of the ongoing implementation effort towards a hardware prototype, several software implementations were achieved and tested. This document contains an outline of the conducted tests, performance evaluation results, and supplementary information not included in the actual paper. It is being continuously expanded and updated.

cs.DC↗