Probing the luminous stellar cores of the giant H II regions 30 DOR in the LMC and NGC 3603 in the Galaxy

Moffat, A. F. J.; Seggewiß, W.; Shara, Michael M.

doi:10.1086/163356

Cited by 56 publications

(44 citation statements)

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“…Of particular note is that the photometric period found for star A1 (1.8867 days from source A and 1.8864 days from B, with a mean of 1.8865 adopted in Table 1) is exactly half (within the errors) of the previously published period [(3:7720 AE 0:0003)=2 ¼ 1:8860 days] found from radial velocity (RV) variations of the global emission-line spectrum of the unresolved central core of NGC 3603, obtained by Moffat & Niemela (1984) and confirmed from additional RV data by Moffat et al (1985). This would suggest that star A1 is in fact an eclipsing binary system, since its light curve shows two dips per orbit.…”

Section: Discussionsupporting

confidence: 80%

“…For the net He ii k4686 and N iv k4058 emission lines arising in the core, they find an RV amplitude of K obs ¼ 72 AE 5 km s À1 , confirmed later by Moffat et al (1985). Assuming the emission-line RV of star A1 to be diluted by the presence of WR stars B and C in the spectrograph slit according to their respective brightnesses, we can estimate the approximate K-value for the WR component of A1, assuming that WR stars B and C also contribute to the total emission-line flux ( but not to the 3.7720 days RV amplitude) according to their known equivalent widths (Drissen et al 1995):…”

Section: The Brig Ght Central Star A1mentioning

confidence: 62%

“…It is interesting to note that one of the four luminous WR stars in R136 must also be a short-period binary, given the 4.377 day cyclic behavior of the unresolved emission line of He ii k4686 discovered in the same way as for NGC 3603 by Moffat & Seggewiss (1983) and confirmed by Moffat et al (1985). Its RV amplitude is K obs ¼ 37 km s À1 ; this is significantly less than for NGC 3603 and possibly the result of more diluted emission lines than NGC 3603's WR spectrum and/or the result of a lower orbital inclination angle (the masses are also somewhat lower in R136; Crowther & Dessart 1998).…”

Section: Comparison With Other Luminous Wr Starsmentioning

confidence: 72%

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Hubble Space TelescopeNICMOS Variability Study of Massive Stars in the Young Dense Galactic Starburst NGC 3603

et al. 2004

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We have used the relatively long data string of the 1997-1999 NICMOS focus tests on NGC 3603 to extract $J-band light curves for several hundred stars in the cluster core. Given the relatively modest photometric precision [(J ) ! 0:05 mag], we were able to isolate only a half-dozen variable candidates with peak-to-valley amplitudes above $0.2 mag. One of the variables is one of the two outstandingly brightest cluster members, A1, located in the very dense cluster center. A1 shows double eclipses on each orbital cycle, with the same period (P ¼ 3:7724 days) as found previously and independently in unresolved ground-based radial velocity variations of the Wolf-Rayet (WR) emission component in the central core of NGC 3603. Very rough best estimates for the masses of the components of A1 are in the range 30-90 M for the brighter and more massive H-rich WR component (WN6ha) and 25-50 M for its assumed O star companion. A more detailed study is urgently needed, given the potential for this extremely luminous system to harbor the most massive main-sequence star ever ''weighed.'' Another variable, HST 12, escaped the original search, which was based on larger than average standard deviation. It is a probable field-star eclipsing variable with a moderately long period.

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Section: Discussionsupporting

confidence: 80%

Section: The Brig Ght Central Star A1mentioning

confidence: 62%

Section: Comparison With Other Luminous Wr Starsmentioning

confidence: 72%

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Hubble Space TelescopeNICMOS Variability Study of Massive Stars in the Young Dense Galactic Starburst NGC 3603

et al. 2004

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“…Based on 9 spectra for each object spread over 22 days using VLT/SINFONI in NIR/AO spectroscopic mode, they find that none of these stars shows RV variations above the σ ∼ 20 km/s level (worse for a5, which has weak lines). This is in contrast with the expectation of Moffat et al (1985) that one component in R136 revealed (heavily diluted) binary motion with P = 4.377d. This result, although subject to small numbers, is in stark contrast with the central WNL stars in NGC 3603, where 2/3 are short-period binaries, and the Carina Nebula, where 2/3 are moderately long-period binaries.…”

Section: Dor/outside R136contrasting

confidence: 99%

Massive Binaries

Moffat

2007

Proc. IAU

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Abstract.As with all binaries, those that contain massive stars reveal various degrees of interaction, depending mainly on orbital separation and age, although things happen much faster in massive binaries. Those massive binaries with initial periods exceeding ∼10 years generally only interact via wind-wind collisions, with little or no effect on their subsequent evolution (unless located in dense clusters). Shorter-period systems show even stronger wind-wind collisions as a rule, but also interact more directly via Roche Lobe Overflow or Common Envelope, with dramatic effects on their evolution. If we didn't have binaries among massive stars, we would be missing a whole host of interesting phenomena in the Universe, such as sources of enhanced stellar X-ray or non-thermal radio emission, WR dust-spirals, inverse mass-ratios, very rapid spin, rejuvenation and massive blue-stragglers, enhanced cluster dynamics, many runaways and possibly even SMBHs and GRBs! On the other hand, non(or little)-interacting massive binaries are also useful to provide information on Star-Formation processes and determination of stellar parameters (such as the mass) that would otherwise be difficult or impossible to obtain from single stars. In this review, I highlight some of the developments that have occurred during the past few years since the last IAU Symposium on Massive Stars in 2002.

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“…As in our Galaxy, the young clusters in these galaxies are less massive than the old ones, and only the oldest LMC clusters approach typical galactic globular clusters in size. The most luminous young cluster in the Local Group, located in the bright LMC HII region 30 Doradus, has a total luminosity of about 4 χ 10 7 suns (Jones et al 1986) and contains about three hundred 0 stars (Moffat et al 1985); with a conventional IMF, this implies a total stellar mass of about 10 gas in the 30 Dor region is about 5 χ 10 7 solar masses (Rohlfs et al 1984), also roughly a hundred times the total mass in the Orion region (Maddalena et al 1986) rather than the three orders of magnitude more that may be required to form a globular cluster.…”

Section: Clues To Cluster Formationmentioning

confidence: 99%

Galaxy Formation and Cluster Formation

Larson¹

1988

Symp. - Int. Astron. Union

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A primary motivation for studying globular clusters is that, as the oldest known galactic fossils, they trace the earliest stages of galactic evolution; indeed, they may hold the key to understanding galaxy formation. Thus it is clearly of great importance to learn how to read the fossil record. To do this, we need to understand something about how the globular clusters themselves formed. Were they the first bound objects to form, or did they form in larger pre-existing systems of which they are just small surviving fragments? If the latter, what were the prehistoric cluster-forming systems like? And how did they manage to produce objects like globular clusters?

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Probing the luminous stellar cores of the giant H II regions 30 DOR in the LMC and NGC 3603 in the Galaxy

Cited by 56 publications

References 0 publications

Hubble Space TelescopeNICMOS Variability Study of Massive Stars in the Young Dense Galactic Starburst NGC 3603

Hubble Space TelescopeNICMOS Variability Study of Massive Stars in the Young Dense Galactic Starburst NGC 3603

Massive Binaries

Galaxy Formation and Cluster Formation

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