- ID:
- ivo://CDS.VizieR/J/MNRAS/465/1227
- Title:
- Nine WC 9 stars spectral variability
- Short Name:
- J/MNRAS/465/1227
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a spectroscopic monitoring campaign of nine presumably single Wolf-Rayet (WR) stars, eight of type WC 9 and one WC 8d. We characterize their variability and search for clues to the mechanism responsible for the formation of dust in their wind. For seven out of eight WC 9s, we find a large-scale line-flux variability level of {sigma}>5-8 per cent. The only WC 8d star is variable at a level more comparable with those associated with wind clumping, {sigma}=2.2 per cent. The changes take place on a time-scale of days but in many cases, observing over longer time spans resulted in higher line-flux variability levels. The width of the substructures ranges from ~150 to 300km/s, with the widest structures corresponding to stars with the highest variability amplitude. We searched for periodicities in integrated line quantities for CIII {lambda}5696. Radial velocity changes are typically ~20km/s but never exceed 40km/s and are anticorrelated with the skewness of the line, strongly suggesting that they do not correspond to a real movement of the star. No periodicity was found in these integrated quantities, except for WR 103. Therefore, a wind-wind collision in a close binary does not seem to be responsible for the short-term variability. We cannot, however, exclude that these stars are intermediate- to long-period binaries. We estimate that for periods up to a few years, the shock-cone resulting from wind collisions would be non-adiabatic and thus unstable. We suggest that this represents a viable mechanism to explain the spectroscopic variability.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/143/149
- Title:
- NIR spectroscopy of Galactic Wolf-Rayet stars. II.
- Short Name:
- J/AJ/143/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We are continuing a J, K and narrowband imaging survey of 300{deg}^2^ of the plane of the Galaxy, searching for new Wolf-Rayet (W-R) stars. Our survey spans 150{deg} in Galactic longitude and reaches 1{deg} above and below the Galactic plane. The survey has a useful limiting magnitude of K=15 over most of the observed Galactic plane, and K=14 (due to severe crowding) within a few degrees of the Galactic center. Thousands of emission-line candidates have been detected. In spectrographic follow-ups of 146 relatively bright W-R star candidates, we have re-examined 11 previously known WC and WN stars and discovered 71 new W-R stars, 17 of type WN and 54 of type WC. Our latest image analysis pipeline now picks out W-R stars with a 57% success rate. Star subtype assignments have been confirmed with the K-band spectra and distances approximated using the method of spectroscopic parallax. Some of the new W-R stars are among the most distant known in our Galaxy. The distribution of these new W-R stars is beginning to trace the locations of massive stars along the distant spiral arms of the Milky Way.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/2858
- Title:
- NIR spectroscopy of Galactic WR stars. III
- Short Name:
- J/MNRAS/452/2858
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new method of image subtraction is applied to images from a J, K, and narrow-band imaging survey of 300 deg2 of the plane of the Galaxy, searching for new Wolf-Rayet (WR) stars. Our survey spans 150{deg} in Galactic longitude and reaches b=+/-1{deg} with respect to the Galactic plane. The survey has a useful limiting magnitude of K=15 over most of the observed Galactic plane, and K=14 (due to severe crowding) within a few degrees of the Galactic Centre. The new image subtraction method described here (better than aperture or even point-spread-function photometry in very crowded fields) detected several thousand emission-line candidates. In 2011 and 2012 June and July, we spectroscopically followed up on 333 candidates with MDM-TIFKAM and Infrared Telescope Facility (IRTF)-SpeX, discovering 89 emission-line sources. These include 49 WR stars, 43 of them previously unidentified, including the most distant known Galactic WR stars, more than doubling the number on the far side of the Milky Way. We also demonstrate our survey's ability to detect very faint planetary nebulae and other NIR emission objects.
- ID:
- ivo://CDS.VizieR/III/136
- Title:
- Optical spectrophotometry of WR C and O Stars
- Short Name:
- III/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog contains a homogeneous set of optical spectrophotometric observations (3300-7300 angstroms) at moderate resolution (about 10 angstroms) of 86 Wolf-Rayet carbon and oxygen stars in this galaxy, the Large Magellanic Cloud, and the Small Magellanic Cloud. The observations were made with the Intensified Reticon Scanner on the white spectrograph of the 0.9 m telescope at Kitt Peak and with the SIT-Vidicon detector on the Cassegrain spectrograph of the 1.5-m telescope at Cerro Tololo Inter-American Observatory.
- ID:
- ivo://CDS.VizieR/J/other/ApSS/345.133
- Title:
- Photometric variability of WR 103
- Short Name:
- J/other/ApSS/345
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss a collection of archival multi-colour photometric data of the variable WC9-type Wolf-Rayet star WR103=HD164270 observed over a time interval of eleven years. The photometric systems used are Walraven VBLUW, Bessel UBV and Stromgren uvby. The purpose is to search for periodicity and to disentangle continuum and line emission variations.
- ID:
- ivo://CDS.VizieR/J/AJ/119/2214
- Title:
- Photometry of Magellanic OB associations
- Short Name:
- J/AJ/119/2214
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine new CCD UBV photometry and spectroscopy with those from the literature to investigate 19 Magellanic Cloud OB associations that contain Wolf-Rayet (W-R) and other types of evolved, massive stars. Our spectroscopy reveals a wealth of newly identified interesting objects, including early O-type supergiants, a high-mass, double-lined binary in the SMC, and, in the LMC, a newly confirmed luminous blue variable (LBV; R85), a newly discovered W-R star (Sk -69^deg^ 194), and a newly found luminous B[e] star (LH 85-10). We use these data to provide precise reddening determinations and construct physical H-R diagrams for the associations.
- ID:
- ivo://CDS.VizieR/J/AJ/109/817
- Title:
- Photometry of WN8 Stars
- Short Name:
- J/AJ/109/817
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of an extensive photometric study of the most intrinsically variable Wolf-Rayet stars: the WN8 subclass. Some 375 individual differential observations of WR16 and WR40 were obtained over a contiguous interval of ~3 months in a narrow visual continuum bandpass. Over the same interval, we obtained roughly 200 broadband V observations of the fainter WN8 stars WR66 and WR82. All four WN8 stars show significant random variability on time scales of hours to ~a day -- probably related to the stochastic formation, propagation, and decay of emitting/scattering inhomogeneities in the winds. Unlike for WR66 and WR82, the photometric behaviour of WR16 and WR40 is more deterministic with ~two possible periods in the range ~2-30 days -- possibly related to some kind of LBV, binary, or rotation phenomenon. In addition, WR82 shows a possible secular decline during the 3 months and WR66 reveals a clear periodicity of 3.51 h. This short period may be related to nonradial pulsations or a spiral-in binary process invoking a low-mass, compact companion as seen in the massive x-ray binary Cyg X-3, a WN7 + c system of period 4.8 h.
- ID:
- ivo://CDS.VizieR/J/A+A/303/893
- Title:
- Planetary nebulae with WR-type nuclei
- Short Name:
- J/A+A/303/893
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A recent systematic search of Wolf-Rayet features in the spectra of Galactic planetary nebulae has increased the list of objects that are known to have WR-type nuclei to about 50. We have compared their nebular properties with those of the other planetary nebulae in the Galaxy.
- ID:
- ivo://CDS.VizieR/J/MNRAS/455/1275
- Title:
- Radial velocities of WR21a
- Short Name:
- J/MNRAS/455/1275
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-epoch spectroscopic observations of the massive binary system WR21a, which include the 2011 January periastron passage. Our spectra reveal multiple SB2 lines and facilitate an accurate determination of the orbit and the spectral types of the components. We obtain minimum masses of 64.4+/-4.8M_{sun} and 36.3+/-1.7M_{sun} for the two components of WR21a. Using disentangled spectra of the individual components, we derive spectral types of O3/WN5ha and O3Vz ((f*)) for the primary and secondary, respectively. Using the spectral type of the secondary as an indication for its mass, we estimate an orbital inclination of i=58.8+/-2.5{deg} and absolute masses of 103.6+/-10.2M_{sun} and 58.3+/-3.7M_{sun}_, in agreement with the luminosity of the system. The spectral types of the WR21a components indicate that the stars are very young (1-2Myr), similar to the age of the nearby Westerlund 2 cluster. We use evolutionary tracks to determine the mass-luminosity relation for the total system mass. We find that for a distance of 8kpc and an age of 1.5Myr, the derived absolute masses are in good agreement with those from evolutionary predictions.
- ID:
- ivo://CDS.VizieR/J/AJ/120/2101
- Title:
- Radial Velocity and Photometry of HD 104994
- Short Name:
- J/AJ/120/2101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Intense coordinated spectroscopic and photometric monitoring of the suspected Wolf-Rayet binary WR 46 in 1999 reveals clear periodic variations, P=0.329+/-0.013 days, in the radial velocities of the emission lines of highest ionization potential, O VI and N V, found deepest in the Wolf-Rayet wind and thus least likely to be perturbed by a companion. These are accompanied by coherent variability in the profiles of lines with lower ionization/excitation potential and in the continuum flux. Most probably originating from orbital motion of the Wolf-Rayet component of the binary, this periodic radial velocity signal disappears from time to time, thus creating a puzzle yet to be solved. We show that the entangled patterns of the line profile variability are mainly governed by transitions between high and low states of the system's continuum flux. Based in part on observations obtained at the European Southern Observatory, La Silla, Chile (ESO program 62.H-0110).
