A High-Resolution Multiband Survey of Westerlund 2 With the Hubble Space Telescope. Ii. Mass Accretion in the Pre-Main-Sequence Population

Zeidler, Peter; Grebel, Eva K.; Nota, A.; Sabbi, E.; Pasquali, A.; Tosi, M.; Bonanos, A. Z.; Christian, C. A.

doi:10.3847/0004-6256/152/4/84

Cited by 16 publications

(14 citation statements)

References 72 publications

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“…It will also give insight into the evolution and distribution of disk-bearing objects throughout the cluster. Observations (e.g., De Marchi et al 2011;Zeidler et al 2016a) hint that the close proximity to the OB-star population accelerates mass accretion processes in protostellar disks, leading to a faster disk dispersal, and eventually hinders planet formation, confirming various theoretical studies (e.g., Clarke 2007;Anderson et al 2013;Winter et al 2020). JWST will also allow us to map the gradual evolution of the gas and dust within the star-forming region as a function of its ionising stellar population.…”

Section: Feedback Processes and Stellar And Gas Dynamicssupporting

confidence: 60%

“…While X-ray observations require space missions (e.g., Chandra or XMM-Newton), the optical and NIR observations can also be obtained from the ground, and with extreme AO even at similar spatial resolutions as HST provides. Combining these broad-band observations with narrow-band observations such as the Hα or Paβ filter allows to detect pre-main sequence stars with active mass accretion (e.g., De Marchi et al 2011;Beccari et al 2015;Zeidler et al 2016a;Kalari 2019) revealing protoplanetary disks. NUV and FUV photometry and spectroscopy from space is necessary to study and classify the most massive OB-stars.…”

Section: Observing Young Star-forming Regionsmentioning

confidence: 99%

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Star Clusters Near and Far

et al. 2020

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Star clusters are fundamental units of stellar feedback and unique tracers of their host galactic properties. In this review, we will first focus on their constituents, i.e. detailed insight into their stellar populations and their surrounding ionised, warm, neutral, and molecular gas. We, then, move beyond the Local Group to review star cluster populations at various evolutionary stages, and in diverse galactic environmental conditions accessible in the local Universe. At high redshift, where conditions for cluster formation and evolution are more extreme, we are only able to observe the integrated light of a handful of objects that we believe will become globular clusters. We therefore discuss how numerical and analytical methods, informed by the observed properties of cluster populations in the local Universe, are used to develop sophisticated simulations potentially capable of disentangling the genetic map of galaxy formation and assembly that is carried by globular cluster populations.

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Section: Feedback Processes and Stellar And Gas Dynamicssupporting

confidence: 60%

Section: Observing Young Star-forming Regionsmentioning

confidence: 99%

Star Clusters Near and Far

et al. 2020

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“…As a consequence of their large integrated masses, the rich stellar populations of Wd1 and the Arches and Quintuplet clusters provide a unique opportunity to study the post-main sequence evolution of stars with M init ∼ 20 M to 120 M in the ∼2−5 Myr window (Clark et al 2018b(Clark et al , 2019b. Inclusion of clusters such as NGC 3603 or Westerlund 2 would extend this investigation to relatively unevolved very massive stars (∼1 Myr and 80 M ; Melena et al 2008;Zeidler et al 2016;Bonanos et al 2004;Schnurr et al 2008). Conversely, older aggregates such as Berkeley 51 and 55 and the RSG dominated clusters at the base of the Scutum-Crux arm (∼10−50 Myr; Lohr et al 2018b;Davies et al 2007;Clark et al 2009) permit the lifecycle of stars of initial masses down to ∼8 M -delineating the onset of core-collapse -to be explored.…”

Section: Concluding Remarks and Future Prospectsmentioning

confidence: 97%

A VLT/FLAMES survey for massive binaries in Westerlund 1

Clark

Ritchie

Negueruela

2020

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Context. The formation, properties, and evolution of massive stars remain subject to considerable theoretical and observational uncertainty. This impacts on fields as diverse as galactic feedback, the production of cosmic rays, and the nature of the progenitors of both electromagnetic and gravitational wave transients. Aims. The young massive clusters many such stars reside within provide a unique laboratory for addressing these issues. In this work we provide a comprehensive stellar census of Westerlund 1 in order to to underpin such efforts. Methods. We employed optical spectroscopy of a large sample of early-type stars to determine cluster membership for photometrically-identified candidates, characterise their spectral type, and identify new candidate spectroscopic binaries. Results. Sixty nine new members of Westerlund 1 are identified via I-band spectroscopy. Together with previous observations, they illustrate a smooth and continuous morphological sequence from late-O giant through to OB supergiant. Subsequently, the progression bifurcates, with one branch yielding mid-B to late-F hypergiants, and cool supergiants, and the other massive blue stragglers prior to a diverse population of H-depleted WRs. We identify a substantial population of O-type stars with very broad Paschen series lines, a morphology that is directly comparable to known binaries in the cluster. In a few cases additional low-resolution R-band spectroscopy is available, revealing double-lined He I profiles and confirming binarity for these objects; suggesting a correspondingly high binary fraction amongst relatively unevolved cluster members. Conclusions. Our current census remains incomplete, but indicates that Westerlund 1 contains at least 166 stars with initial masses estimated to lie between ∼25 M⊙ and ∼50 M⊙, with more massive stars already lost to supernova. Our data is consistent with the cluster being co-eval, although binary interaction is clearly required to yield the observed stellar population, which is characterised by a uniquely rich cohort of hypergiants ranging from spectral type O to F, with both mass-stripped primaries and rejuvenated secondaries or merger products present. Future observations of Wd1 and similar stellar aggregates hold out the prospect of characterising both single- and binary- evolutionary channels for massive stars and determining their relative contributions. This in turn will permit the physical properties of such objects at the point of core-collapse to be predicted, which is of direct relevance for understanding the formation of relativistic remnants such as the magnetars associated with Wd1 and other young massive clusters.

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“…Using the HST Advanced Camera for Surveys (ACS; filters F555W, F658N and F814W) and the Wide Field Camera (WFC3) IR channel (filters F125W, F128N, and F160W, PI Nota, GO-13038) we found that the cluster consists of two nearly coeval clumps (Zeidler et al 2015), and that is mass segregated (Zeidler et al 2017). Following the same approach described in De Marchi et al (2010), we identified a rich population of PMS stars with Hα excess, that are likely still accreting material from their circumestellar disks (Zeidler et al 2016) The paper is organized as follows. In Section 2 we present the data, describe how we created the reference frame and performed the photometric reduction.…”

Section: Introductionmentioning

confidence: 59%

Time-domain Study of the Young Massive Cluster Westerlund 2 with the Hubble Space Telescope. I

Sabbi

Gennaro

Anderson

et al. 2020

ApJ

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Time-domain studies of pre-main sequence stars have long been used to investigate star properties during their early evolutionary phases and to trace the evolution of circumstellar environments. Historically these studies have been confined to the nearest, low-density, star forming regions. We used the Wide Field Camera 3 on board of the Hubble Space Telescope to extend, for the first time, the study of pre-main sequence variability to one of the few young massive clusters in the Milky Way, Westerlund 2. Our analysis reveals that at least 1/3 of the intermediate and low-mass pre-main sequence stars in Westerlund 2 are variable. Based on the characteristics of their light curves, we classified ∼ 11% of the variable stars as weak-line T-Tauri candidates, ∼ 52% as classical T-Tauri candidates, ∼ 5% as dippers and ∼ 26% as bursters. In addition, we found that 2% of the stars below 6 M (∼ 6% of the variables) are eclipsing binaries, with orbital periods shorter than 80 days. The spatial distribution of the different populations of variable pre-main sequence stars suggests that stellar feedback and UVradiation from massive stars play an important role on the evolution of circumstellar and planetary disks.

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A High-Resolution Multiband Survey of Westerlund 2 With the Hubble Space Telescope. Ii. Mass Accretion in the Pre-Main-Sequence Population

Cited by 16 publications

References 72 publications

Star Clusters Near and Far

Star Clusters Near and Far

A VLT/FLAMES survey for massive binaries in Westerlund 1

Time-domain Study of the Young Massive Cluster Westerlund 2 with the Hubble Space Telescope. I

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