In this paper, we present the results of our adaptive optics fed three-dimensional imaging spectroscopy study of the FU Orionis binary system. If we assume coevality of the stellar components, we ...have thus placed an estimated age on the FU Ori system. Moreover, assuming the canonical model for the nature of FU Ori in that its optical and infrared absorption features arise primarily from the inner circumstellar disk around a ~0.3M| star, we find that the fainter FU Ori S component is actually the more massive star in the system. Future monitoring of FU Ori S to investigate flux variability and orbital motion should further clarify the nature of this curious young binary.
Abstract
The HH 24 complex harbors five collimated jets emanating from a small protostellar multiple system. We have carried out a multiwavelength study of the jets, their driving sources, and the ...cloud core hosting the embedded stellar system, based on data from the Hubble Space Telescope, Gemini, Subaru, Apache Point Observatory 3.5 m, Karl G. Jansky Very Large Array, and Atacama Large Millimeter/submillimeter Array (ALMA) telescopes. The data show that the multiple system, SSV 63, contains at least 7 sources, ranging in mass from the hydrogen-burning limit to proto-Herbig Ae stars. The stars are in an unstable nonhierarchical configuration, and one member, a borderline brown dwarf, is moving away from the protostellar system with 25 km s
−1
, after being ejected ∼5800 yr ago as an orphaned protostar. Five of the embedded sources are surrounded by small, possibly truncated, disks resolved at 1.3 mm with ALMA. Proper motions and radial velocities imply jet speeds of 200–300 km s
−1
. The two main HH 24 jets, E and C, form a bipolar jet system that traces the innermost portions of parsec-scale chains of Herbig–Haro and H
2
shocks with a total extent of at least 3 pc. H
2
CO and C
18
O observations show that the core has been churned and continuously fed by an infalling streamer.
13
CO and
12
CO trace compact, low-velocity, cavity walls carved by the jets and an ultracompact molecular outflow from the most embedded object. Chaotic
N
-body dynamics likely will eject several more of these objects. The ejection of stars from their feeding zones sets their masses. Dynamical decay of nonhierarchical systems can thus be a major contributor to establishing the initial mass function.
We present an optical/infrared study of the dense molecular cloud, L935, dubbed “The Gulf of Mexico”, which separates the North America and the Pelican nebulae, and we demonstrate that this area is a ...very active star forming region. A wide-field imaging study with interference filters has revealed 35 new Herbig-Haro objects in the Gulf of Mexico. A grism survey has identified 41 Hα emission-line stars, 30 of them new. A small cluster of partly embedded pre-main sequence stars is located around the known LkHα 185-189 group of stars, which includes the recently erupting FUor HBC 722.
A detailed imaging and spectroscopic analysis is presented of the little-studied T Tauri star PR Ori and its associated Herbig-Haro flow HH 305, located on the outskirts of the L1641-N cluster in ...Orion. PR Ori is shown to be a multiple system, where the A component is a close 0 077 binary, and the B component, at a distance of 3 50, is the driver of the large Herbig-Haro flow. A low-luminosity source, here called C, is located 9 3 to the southeast and is shown spectroscopically to be straddling the stellar/brown dwarf boundary. The corresponding separations in projection are 32, 1450, and 3900 au, respectively. Although PR Ori A is a weak-line T Tauri star, high-resolution optical spectra reveal high-velocity outflowing winds and, at the same time, material infalling with speeds up to 200 km s−1. PR Ori B shows a similar combination of outflow and infall but is a strong H emission star, with a major near-infrared excess that dominates the luminosity of the system at wavelengths longer than ∼5 m. HH 305 displays three pairs of knots symmetrically on either side of PR Ori, with higher velocities near the source and gradually decreasing velocities with increasing distance from the source. The innermost knots show bubble-like morphologies, very different from a collimated jet, with the northern lobe redshifted and the southern lobe blueshifted. The origin and nature of this unusual Herbig-Haro flow is discussed.
Context. Our general understanding of multiple star and planet formation is primarily based on observations of young multiple systems in low density regions like Tau-Aur and Oph. Since many, if not ...most, of the stars are born in clusters, observational constraints from young binaries in those environments are fundamental for understanding both the formation of multiple systems and planets in multiple systems throughout the Galaxy. Aims. We build upon the largest survey for young binaries in the Orion Nebula Cluster (ONC), which is based on Hubble Space Telescope observations to derive both stellar and circumstellar properties of newborn binary systems in this cluster environment. Methods. We present adaptive optics spatially-resolved JHKL′-band photometry and K-band R ~ 5000 spectra for a sample of eight ONC binary systems from this database. We characterize the stellar properties of binary components and obtain a census of protoplanetary disks through K − L′ color excess. For a combined sample of ONC binaries including 7 additional systems with NIR spectroscopy from the literature, we derive mass ratio and relative age distributions. We compare the stellar and circumstellar properties of binaries in ONC with those in Tau-Aur and Oph from samples of binaries with stellar properties derived for each component from spectra and/or visual photometry and with a disk census obtained through K − L color excess. Results. The mass ratio distribution of ONC binaries is found to be indistinguishable from that of Tau-Aur and, to some extent, to that of Oph in the separation range 85–560 AU and for primary mass in the range 0.15 to 0.8 M⊙. A trend toward a lower mass ratio with larger separation is suggested in ONC binaries, which is not seen in Tau-Aur binaries. The components of ONC binaries are found to be significantly more coeval than the overall ONC population and as coeval as components of binaries in Tau-Aur and Oph. There is a hint of a larger fraction of mixed pairs, i.e. systems with a disk around only one component, in wide ONC binaries in comparison to wide binaries in Tau-Aur and Oph within the same primary mass range that could be caused by hierarchical triples. The mass ratio distributions of mixed and unmixed pairs in the overall population of T Tauri binaries are shown to be different. Some of these trends require confirmation with observations of a larger sample of binary systems.
From the early days of the HIV epidemic, Indigenous peoples were identified as a population group that experiences social and economic determinants—including colonialism and racism—that increase ...exposure to HIV. There are now substantial disparities in HIV rates between Indigenous and non-Indigenous peoples in some countries. We conducted a comprehensive literature review to assess the evidence on HIV-related behaviors and determinants in four countries—Australia, Canada, New Zealand and the United States—in which Indigenous peoples share important features of colonization and marginalization. We identified 107 articles over more than 20 years. The review highlights the determinants of HIV-related behaviors including domestic violence, stigma and discrimination, and injecting drug use. Many of the factors associated with HIV risk also contribute to mistrust of health services, which in turn contributes to poor HIV and health outcomes among Indigenous peoples.
Context. Outflows and jets are the first signposts of ongoing star formation processes in any molecular cloud, yet their study in optical bands provides limited results due to the large extinction ...present. Near-infrared unbiased wide-field observations in the H2 1−0 S(1) line at 2.122 μm alleviates the problem, enabling us to detect more outflows and trace them closer to their driving sources. Aims. As part of a large-scale multi-waveband study of ongoing star formation in the Braid Nebula star formation region, we focus on a one square degree region that includes Lynds Dark Nebula 1003 and 1004. Our goal is to find all of the near-infrared outflows, uncover their driving sources and estimate their evolutionary phase. Methods. We use near-infrared wide-field observations obtained with WFCAM on UKIRT, in conjunction with previously-published optical and archival MM data, to search for outflows and identify their driving sources; we subsequently use colour − colour analysis to determine the evolutionary phase of each source. Results. Within a one square degree field we have identified 37 complex MHOs, most of which are new. After combining our findings with other wide-field, multi-waveband observations of the same region we were able to discern 28 outflows and at least 18 protostars. Our analysis suggests that these protostars are younger and/or more energetic than those of the Taurus-Auriga region. The outflow data enable us to suggest connection between outflow ejection and repetitive FU Ori outburst events. We also find that star formation progresses from W to E across the investigated region.
Aboriginal and Torres Strait Islander people with chronic illness confront multiple challenges that contribute to their poor health outcomes, and to the health disparities that exist in Australian ...society. This study aimed to identify barriers and facilitators to care and support for Aboriginal and Torres Strait Islander people with chronic illness.
Face-to-face in-depth interviews were conducted with Aboriginal and Torres Strait Islander people with diabetes, chronic heart failure or chronic obstructive pulmonary disease (n-16) and family carers (n = 3). Interviews were transcribed verbatim and the transcripts were analysed using content analysis. Recurrent themes were identified and these were used to inform the key findings of the study.
Participants reported both negative and positive influences that affected their health and well-being. Among the negative influences, they identified poor access to culturally appropriate health services, dislocation from cultural support systems, exposure to racism, poor communication with health care professionals and economic hardship. As a counter to these, participants pointed to cultural and traditional knowledge as well as insights from their own experiences. Participants said that while they often felt overwhelmed and confused by the burden of chronic illness, they drew strength from being part of an Aboriginal community, having regular and ongoing access to primary health care, and being well-connected to a supportive family network. Within this context, elders played an important role in increasing people's awareness of the impact of chronic illness on people and communities.
Our study indicated that non-Indigenous health services struggled to meet the needs of Aboriginal and Torres Strait Islander people with chronic illness. To address their complex needs, health services could gain considerably by recognising that Aboriginal and Torres Strait Islander patients have a wealth of cultural knowledge at their disposal. Strategies to ensure that this knowledge is integrated into care and support programs for Aboriginal and Torres Strait Islander people with chronic illness should achieve major improvements.
Context.To follow the early evolution of stars we need to understand how young stars accrete and eject mass. It is generally assumed that the FU Orionis phenomenon is related to the variations in the ...disk accretion, but many questions remain still open, in particular because of the rarity of FU Ori type stars. Aims.We explore here the characteristics of the outburst and of the environment of one new object, discovered recently in the active star formation region containing RNO 127, within the Cygnus OB7 dark cloud complex. Methods.We present an extensive optical and near-infrared study of a new candidate of FU Orionis object, including its direct imaging, spectroscopy and scanning Fabry-Pérot interferometry. Results.The source, associated with the variable reflection nebula, underwent prodigious outburst. The “Braid” nebula, which appeared in 2000, as is indicated by its name, consists of two intertwined features, illuminated by the outburst. Subsequent NIR observations revealed the bright source, which was not visible on 2MASS images, and its estimated brightening was more than 4 mag. Optical and infrared spectral data show features, which are necessary for the system to be referred to as a FUor object. The bipolar optical flow directed by the axis of nebula also was found. Various estimates give the November/December 1999 as the most probable date for the eruption.
We have performed an optical CCD imaging survey of star-forming regions identified through compact reflection nebulae and/or embedded IRAS sources in order to search for new Herbig-Haro (HH) flows. ...Here we present the discovery of hitherto unknown HH objects in seven of these regions. A bright bow shock, HH 461, is found along the axis defined by the previously known HH 164 jet from the luminous young A star LkHα 198. The little-known cometary nebula PP 11, illuminated by the partly embedded IRAS source 03507+3801 in the Perseus clouds, contains an HH object HH 462, found along the symmetry axis of the nebula. A small jet, HH 463, emanates from the recently identified FU Orionis candidate PP 13S, while another HH flow, HH 464/HH 465, appears to originate from the nearby T Tauri star PP 13N. A group of HH objects, HH 466–468, are located around the nebulous young T Tauri binary GK Tau. A well-collimated HH jet and an associated bow shock, HH 470, are found extending from the young nebulous T Tauri star Haro 4-255 in Orion, and a tiny reflection nebula and associated HH object, HH 469, are located close by the deeply embedded Class I source Haro 4-255 FIR. In light of these new HH flows in Haro 4-255, we re-interpret existing 12CO data on this source in terms of two overlapping molecular outflows. The young star LkHα 316 and the nearby IRAS source 05451+0037 in Orion are found to be associated with a cluster of HH objects, HH 471–474. It is likely that a nearby and previously identified HH object, HH 71, also originates in this region. Finally, a chain of HH objects, HH 475, is found near the little-studied compact bipolar reflection nebula PP 95 in the Cygnus clouds. The origin of this HH chain remains unclear, and HH 475 may equally well be driven by one of several luminous massive young stars in the region.
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