Orbits of Four Very Massive Binaries in the R136 Cluster

Massey, Philip; Penny, Laura R.; Vukovich, Julia

doi:10.1086/324783

Cited by 69 publications

(86 citation statements)

References 33 publications

(48 reference statements)

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“…Rotating stars are dimmer because of the reduced internal pressure. Mass loss and rotation also alter the MLR for intermediate and especially high-mass stars (16). The IMF follows by correcting the observed number of main sequence stars for the number of stars that have evolved off the main sequence.…”

Section: The Form Of the Imfmentioning

confidence: 99%

The Initial Mass Function of Stars: Evidence for Uniformity in Variable Systems

Kroupa

2002

Science

1,646

117

1,893

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The distribution of stellar masses that form in one star-formation event in a given volume of space is called the initial mass function (IMF). The IMF has been estimated from low-mass brown dwarfs to very massive stars. Combining IMF estimates for different populations in which the stars can be observed individually unveils an extraordinary uniformity of the IMF. This general insight appears to hold for populations including present-day star formation in small molecular clouds, rich and dense massive star-clusters forming in giant clouds, through to ancient and metal-poor exotic stellar populations that may be dominated by dark matter. This apparent universality of the IMF is a challenge for star formation theory because elementary considerations suggest that the IMF ought to systematically vary with star-forming conditions.The physics of star formation determines the conversion of gas to stars. The outcome of star formation are stars with a range of masses. Astrophysicists refer to the distribution of stellar masses as the stellar initial mass function. Together with the time-modulation of the star-formation rate, the IMF dictates the evolution and fate of galaxies and star clusters. The evolution of a stellar system is driven by the relative initial numbers of brown dwarfs (BDs, < ∼ 0.072 M ) that do not fuse H to He, very low-mass stars (0.072 − 0.5 M ), low-mass stars (0.5−1 M ), intermediate-mass stars (1−8 M ) and massive stars (m > 8 M ). Non-luminous BDs through to dim low-mass stars remove gas from the interstellar medium (ISM), lockingup an increasing amount of the mass of galaxies over cosmological time scales. Intermediate and luminous but short-lived massive stars expel a large fraction of their mass when they die and thereby enrich the ISM with elements heavier than H and He. They heat the ISM through radiation, outflows, winds and supernovae (1, 2). It is therefore of much importance to quantify the relative numbers of stars in different mass ranges and to find systematic variations of the 1

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Section: The Form Of the Imfmentioning

confidence: 99%

The Initial Mass Function of Stars: Evidence for Uniformity in Variable Systems

Kroupa

2002

Science

1,646

117

1,893

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“…They obtained FOS spectroscopy of all the bright point sources in the core and combined it with PC (WFPC2) photometry to derive a color-magnitude diagram of the massive stars. In a follow-up paper, Massey et al (2002) observed four spectroscopic eclipsing binaries and measured their masses. They also detected another five eclipsing binaries, indicating that massive binaries are also common in R136.…”

Section: R136mentioning

confidence: 99%

Biases on Initial Mass Function Determinations. II. Real Multiple Systems and Chance Superpositions1

Apellániz

2008

ApJ

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When calculating stellar initial mass functions (IMFs) for young clusters, one has to take into account that (1) most massive stars are born in multiple systems, (2) most IMFs are derived from data that cannot resolve such systems, and (3) multiple chance superpositions between members are expected to happen if the cluster is too distant. In this article I use numerical experiments to model the consequences of those phenomena on the observed color-magnitude diagrams and the IMFs derived from them. Real multiple systems affect the observed or apparent massive-star MF slope little but can create a significant population of apparently ultramassive stars. Chance superpositions produce only small biases when the number of superimposed stars is low but, once a certain number threshold is reached, they can affect both the observed slope and the apparent stellar upper mass limit. I apply these experiments to two well known massive young clusters in the Local Group, NGC 3603 and R136. In both cases I show that the observed population of stars with masses above 120 M can be explained by the effects of unresolved objects, mostly real multiple systems for NGC 3603 and a combination of real and chance-alignment multiple systems for R136. Therefore, the case for the reality of a stellar upper mass limit at solar or near-solar metallicities is strengthened, with a possible value even lower than 150 M . An IMF slope somewhat flatter than Salpeter or Kroupa with between À1.6 and À2.0 is derived for the central region of NGC 3603, with a significant contribution to the uncertainty arising from the imprecise knowledge of the distance to the cluster. The IMF at the very center of R136 cannot be measured with the currently available data but the situation could change with new HST observations.

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“…HST observations of Mk 34 show photometric variability of a few tenths of a magnitude over a period of 20 days (Massey et al 2002). Mk 34 was known to be X-ray bright from ROSAT data ( Wang 1995).…”

Section: Melnick 34 and Other Wn5h Starsmentioning

confidence: 99%

AChandraACIS Study of 30 Doradus. II. X-Ray Point Sources in the Massive Star Cluster R136 and Beyond

Townsley¹,

Broos²,

Feigelson³

et al. 2006

118

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We have studied the X-ray point-source population of the 30 Doradus (30 Dor) star-forming complex in the Large Magellanic Cloud using high spatial resolution X-ray images and spatially resolved spectra obtained with the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-Ray Observatory. Here we describe the X-ray sources in a 17 0 ; 17 0 field centered on R136, the massive star cluster at the center of the main 30 Dor nebula. We detect 20 of the 32 Wolf-Rayet stars in the ACIS field. The cluster R136 is resolved at the subarcsecond level into almost 100 X-ray sources, including many typical O3-O5 stars, as well as a few bright X-ray sources previously reported. Over 2 orders of magnitude of scatter in L X is seen among R136 O stars, suggesting that X-ray emission in the most massive stars depends critically on the details of wind properties and the binarity of each system, rather than reflecting the widely reported characteristic value L X /L bol ' 10 À7 . Such a canonical ratio may exist for single massive stars in R136, but our data are too shallow to confirm this relationship. Through this and future X-ray studies of 30 Dor, the complete life cycle of a massive stellar cluster can be revealed.

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Orbits of Four Very Massive Binaries in the R136 Cluster

Cited by 69 publications

References 33 publications

The Initial Mass Function of Stars: Evidence for Uniformity in Variable Systems

The Initial Mass Function of Stars: Evidence for Uniformity in Variable Systems

Biases on Initial Mass Function Determinations. II. Real Multiple Systems and Chance Superpositions1

AChandraACIS Study of 30 Doradus. II. X-Ray Point Sources in the Massive Star Cluster R136 and Beyond

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