NGC 3603-A1
File:NGC3603 core.jpg A1 is the brightest (and top right) of the three barely-resolved stars at the centre in this HST image of the central region of HD 97950. Credit: NASA, ESA and Wolfgang Brandner (MPIA), Boyke Rochau (MPIA) and Andrea Stolte (University of Cologne) | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Carina[1] |
| Right ascension | Template:RA[2] |
| Declination | Template:Dec[2] |
| Apparent magnitude (V) | 11.18[2] |
| Characteristics | |
| Spectral type | WN6h+WN6h[3] |
| B−V Template:Engvar | 1.03[2] |
| Variable type | EA[4] |
| Astrometry | |
| Radial velocity (Rv) | Script error: No such module "val".[5] km/s |
| Proper motion (μ) | RA: +2.4[6] mas/yr Dec.: +2.8[6] mas/yr |
| Distance | 7,600[3] pc |
| Absolute magnitude (MV) | −7.3[5] |
| Orbit[5] | |
| Primary | A1a |
| Companion | A1b |
| Period (P) | Script error: No such module "val". days |
| Eccentricity (e) | 0 (fixed) |
| Inclination (i) | Script error: No such module "val".° |
| Semi-amplitude (K1) (primary) | Script error: No such module "val". km/s |
| Semi-amplitude (K2) (secondary) | Script error: No such module "val". km/s |
| Details | |
| A1a | |
| Mass | Script error: No such module "val".[5] Template:Solar mass |
| Radius | 22.6[5] Template:Solar radius |
| Luminosity | 2,500,000[3] Template:Solar luminosity |
| Temperature | 37,000[5] K |
| Rotational velocity (v sin i) | Script error: No such module "val".[5] km/s |
| Age | 1.5[3] Myr |
| A1b | |
| Mass | Script error: No such module "val".[5] Template:Solar mass |
| Radius | 18.4[5] Template:Solar radius |
| Luminosity | 1,500,000[3] Template:Solar luminosity |
| Temperature | 42,000[5] K |
| Metallicity [Fe/H] | {{{metal_fe2}}} dex |
| Rotational velocity (v sin i) | Script error: No such module "val".[5] km/s |
| Age | 1.5[3] Myr |
| Other designations | |
| NGC 3603-A1, CD−60°3452A1, CPD−60°2732A1, HD 97950A1, HIP 54948A1, WR 43a, UCAC2 4794917, AAVSO 1110-60, NGC 3603 MDS 30 | |
| Database references | |
| SIMBAD | data |
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NGC 3603-A1 (HD 97950A1) is a double-eclipsing binary star system located at the centre of the HD 97950 cluster in the NGC 3603 star-forming region, about 25,000 light years from Earth. Both stars are of spectral type WN6h and among the most luminous and most massive known.
HD 97950 was catalogued as a star, but was known to be a dense cluster or close multiple star. In 1926, the six brightest members were given letters from A to F,[7] although several of them have since been resolved into more than one star.[8] Star A was first resolved into three components using speckle interferometry, although they can now be directly imaged using space-based or adaptive optics.[2] Component A1 was finally determined to be a spectroscopic binary.[9]
The two component stars of NGC 3603-A1 circle each other every 3.77 days, and show brightness variations of about 0.3 magnitudes due to eclipses. The stars orbit very close to each other, separated by barely their own diameters and at or near to filling their Roche lobes.[9]
The masses of A1a and A1b determined from the orbital parameters are Script error: No such module "val". and Script error: No such module "val".respectively. The sum of masses is the hightest among binary systems in the Milky Way with directly measured masses (i.e. masses measured by the binary's orbit).[5] The masses estimated from analysis of the physical properties are slightly higher at Template:Solar mass and Template:Solar mass.[3]
Each component is a Wolf-Rayet (WR) star, with spectra dominated by strong broadened emission lines. Type WN6 indicates that ionised nitrogen lines are strong in comparison to ionised carbon lines, and the suffix h indicates that hydrogen is also seen in the spectrum. This type of WR star is not the classical stripped helium-burning aged star, but a young highly luminous object with CNO cycle fusion products showing at the surface due to strong conventional and rotational mixing, and high mass loss rates from the atmosphere. The emission lines are generated in the stellar wind and the photosphere is completely hidden. The surface fraction of hydrogen is still estimated to be 60-70%.[3]
Although the stars are very young, around 1.5 million years old, they have already lost a considerable fraction of their initial masses. The initial masses are estimated to have been Template:Solar mass and Template:Solar mass, meaning they have lost Template:Solar mass and Template:Solar mass respectively.[3]
References
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- ↑ a b Script error: No such module "Citation/CS1".
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- ↑ a b c Script error: No such module "Citation/CS1".
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