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J/ApJ/789/10           M33 WR and Of-type Stars                 (Neugent+, 2014)

The close binary frequency of Wolf-Rayet stars as a function of metallicity in M31 and M33. Neugent K.F., Massey P. <Astrophys. J., 789, 10 (2014)> =2014ApJ...789...10N (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Stars, Wolf-Rayet ; Stars, double and multiple Equivalent widths ; Magnitudes Keywords: galaxies: individual: M31, M33 - galaxies: stellar content - Local Group - binaries: close - stars: Wolf-Rayet Abstract: Massive star evolutionary models generally predict the correct ratio of WC-type and WN-type Wolf-Rayet stars at low metallicities, but underestimate the ratio at higher (solar and above) metallicities. One possible explanation for this failure is perhaps single-star models are not sufficient and Roche-lobe overflow in close binaries is necessary to produce the "extra" WC stars at higher metallicities. However, this would require the frequency of close massive binaries to be metallicity dependent. Here we test this hypothesis by searching for close Wolf-Rayet binaries in the high metallicity environments of M31 and the center of M33 as well as in the lower metallicity environments of the middle and outer regions of M33. After identifying ∼100 Wolf-Rayet binaries based on radial velocity variations, we conclude that the close binary frequency of Wolf-Rayets is not metallicity dependent and thus other factors must be responsible for the overabundance of WC stars at high metallicities. However, our initial identifications and observations of these close binaries have already been put to good use as we are currently observing additional epochs for eventual orbit and mass determinations. Description: Our ability to undertake this project was in a large part due to the existence of the multi-object fiber-fed spectrograph Hectospec (Fabricant et al. 2005PASP..117.1411F) on the 6.5 m MMT. Its large field of view (1° in diameter) was well matched to our survey areas of M31 and M33. Hectospec's 300 fibers and their allowed close spacing (20'') let us observe a multitude of candidates using only four pointing configurations. We were assigned 2.5 nights of dark time in the Fall of 2012 through NOAO (2012B-0129). When designing the fiber configurations, we were able to assign 71% of our M31 WRs using two configurations and 77% of our M33 WRs using an additional two configurations, making a total of four configurations. We were able to observe five of the remaining M33 candidates as part of the present study, and recently obtained spectra of the sixth star as part of our follow-up study of the binaries we identify here. Objects: ---------------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------------- 00 42 44.33 +41 16 07.5 M31 = NAME Andromeda 01 33 50.90 +30 39 35.8 M33 = NAME Triangulum Galaxy ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table2.dat 77 6 Newly Found M33 WR and Of-type Stars table3.dat 34 250 E/I Values for the 250 observed candidates
See also: J/ApJ/505/793 : New WR star in M33 (Massey+, 1998) J/AJ/131/2478 : M31 and M33 UBVRI photometry (Massey+, 2006) J/AJ/133/2393 : UBVRI phot. in seven Local Group dwarfs galaxies (Massey+, 2007) J/ApJ/733/123 : The Wolf-Rayet content of M33 (NGC 598) (Neugent+, 2011) Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 19 A19 --- Star Star ([NM2011] in Simbad) 21- 24 F4.2 --- rho Distance from the center within the plane of M33 normalized to D25 (1) 26- 35 A10 --- Type Type of star 37- 39 F3.1 [0.1nm] log(-EW)HeII ?=- Log(-EW) of He II lambda4686 41- 42 I2 0.1nm FWHMHeII ?=- FWHM of He II lambda4686 44- 46 F3.1 [0.1nm] log(-EW)CIV ?=- Log(-EW) of C IV lambda5606 48- 49 I2 0.1nm FWHMCIV ?=- FWHM of C IV lambda5606 51- 55 F5.2 mag Vmag V-band magnitude (2) 57- 61 F5.2 mag m4750 lambda4750 Å AB magnitude (3) 63- 66 F4.1 mag VMag V-band Absolute magnitudes (4) 68- 71 F4.1 mag M4750 lambda4750 Å Absolute magnitudes (4) 73- 77 A5 --- OBassoc OB association (5)
Note (1): Distance from the center within the plane of M33, normalized to the D25 isophotal radius of 30.8' assuming α2000 = 01h33m50.89s, δ2000 = 30°39'36.8'', an inclination of 56°, and a position angle of the major axis of 23°, following Kwitter & Aller (1981MNRAS.195..939K) and Zaritsky et al. (1989AJ.....97...97Z). Note (2): From Massey et al. (2006, J/AJ/131/2478). Note (3): AB magnitude through CT filter centered at 4750 Å and calibrated using the values from Massey & Johnson (1998, J/ApJ/505/793). Note (4): Absolute magnitudes computed assuming a true distance modulus of 24.60 (830 Mpc) and adopting an average reddening of E(B - V) = 0.12 based on Massey et al. (2007, J/AJ/133/2393). Adopting RV = 3.1 leads to an AV = 0.37 mag and Am4750=0.45 mag. Note (5): OB association as defined by Humphreys & Sandage (1980ApJS...44..319H). Parenthesis means the star is just outside the boundaries of the association, while "Fld" implies it is a field star, not in a cataloged OB association.
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 17 A17 --- ID Star name ( 19- 22 I4 0.1nm Wave Wavelength; Angstroms 24- 27 F4.1 --- E/Ifxcor External scatter to internal error ratio from fxcor 29- 32 F4.1 --- E/Ihand External scatter to internal error ratio by hand 34 I1 --- Num Number of lines used
History: From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 14-Mar-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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