- ID:
- ivo://CDS.VizieR/J/ApJ/702/940
- Title:
- Radio and UV spectra of HVC toward the MC
- Short Name:
- J/ApJ/702/940
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the spectra of 139 early-type Large Magellanic Cloud (LMC) stars observed with Far Ultraviolet Spectroscopic Explorer and with deep radio Parkes HI 21cm observations along with those stars, we search for and analyze the absorption and emission from high-velocity gas at +90<={nu}_LSR_<=+175km/s. The HI column density of the high-velocity clouds (HVCs) along these sightlines ranges from <1018.4 to 1019.2cm^-2^. The incidence of the HVC metal absorption is 70%, significantly higher than the HI emission occurrence of 32%. We find that the mean metallicity of the HVC is [OI/HI]=-0.51+/-^0.12^_0.16_. This is the first example of a large (>10^6^M_{sun}_) HVC complex that is linked to stellar feedback occurring in a dwarf spiral galaxy.
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- ID:
- ivo://CDS.VizieR/J/A+A/281/161
- Title:
- Radio emission from stars at 250GHz
- Short Name:
- J/A+A/281/161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the IRAM 30 m-telescope together with the Max Planck Institute for Radio Astronomy (MPIfR) bolometer to survey nearly 270 stars of different types for 250GHz continuum emission. We compare these data with their low frequency (cm-range) properties. Early type stars show very often a deviation from the uniformly expanding wind model which we tentatively attribute to temperature and/or density fluctuations in their deeper atmospheric layers. For WR stars this deviation seems to depend on the effective temperature. Pre-main sequence stars usually seem to be surrounded by a shell of warm dust making a substantial contribution to the 250 GHz flux density value. We have found especially for nearby giants and supergiants that a layer at the transition from photosphere to chromosphere emits ample 250 GHz radiation. We show that the present data can still be explained by a simple uniformly illuminated disk model with the known stellar radius. Optically variable stars are not very strong emitters at 250 GHz. We preferentially detected the more exotic ones, a few Beta Lyr-type and symbiotic stars. Comments on many individual objects are given in the appropriate sections.
- ID:
- ivo://CDS.VizieR/J/A+A/572/A110
- Title:
- R-band light curve of MY Cam
- Short Name:
- J/A+A/572/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The early-type binary MY Cam belongs to the young open cluster Alicante 1, embedded in Cam OB3. MY Cam consists of two early-O type main-sequence stars and shows a photometric modulation suggesting an orbital period slightly above one day. We intend to confirm this orbital period and derive orbital and stellar parameters. Timing analysis of a very exhaustive (4607 points) light curve indicates a period of 1.1754514+/-0.0000015d. High-resolution spectra and the cross-correlation technique implemented in the TODCOR program were used to derive radial velocities and obtain the corresponding radial velocity curves for MY Cam. Modelling with the stellar atmosphere code FASTWIND was used to obtain stellar parameters and create templates for cross-correlation. Stellar and orbital parameters were derived using the Wilson-Devinney code, such that a complete solution to the binary system could be described. We determine masses of the primary and secondary stars in MY Cam are 37.7+/-1.6 and 31.6+/-1.4M_{sun}_ , respectively. The corresponding temperatures, derived from the model atmosphere fit, are 42000 and 39000K, with the more massive component being hotter. Both stars are overfilling their Roche lobes, sharing a common envelope. MY Cam contains the most massive dwarf O-type stars found so far in an eclipsing binary. Both components are still on the main sequence, and probably not far from the zero-age main sequence. The system is a likely merger progenitor, owing to its very short period.
- ID:
- ivo://CDS.VizieR/J/A+A/439/1107
- Title:
- R-band spectra for 13 early-type supergiants
- Short Name:
- J/A+A/439/1107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue contains R-band spectra for 13 early-type supergiants. Spectral types range from B0 to A6, all with luminosity classes Ia or Iab. Eight of the stars are classified as having emission. The wavelength range is 5846 to 7030{AA} at a spectral resolution of 1.2{AA}, and a signal-to-noise ratio of 400 or above. Identification of spectral lines in supergiant spectra can be found in Chentsov et al. (2003A&A...397.1035C). The reader should be aware of the blends of atmospheric telluric lines that contaminate the spectra in the ranges 5870-5995{AA}, 6270-6315{AA}, 6470-6500{AA}, and 6850{AA} onwards.
- ID:
- ivo://CDS.VizieR/J/AJ/162/150
- Title:
- Resolving circumstellar environment of MWC137 .II.
- Short Name:
- J/AJ/162/150
- Date:
- 14 Mar 2022 06:35:34
- Publisher:
- CDS
- Description:
- The Galactic B[e] supergiant MWC137 is surrounded by a large-scale optical nebula. To shed light on the physical conditions and kinematics of the nebula, we analyze the optical forbidden emission lines [NII] {lambda}{lambda}6548,6583 and [SII] {lambda}{lambda}6716,6731 in long-slit spectra taken with ALFOSC at the Nordic Optical Telescope. The radial velocities display a complex behavior but, in general, the northern nebular features are predominantly approaching while the southern ones are mostly receding. The electron density shows strong variations across the nebula with values spreading from about zero to ~800cm^-3^. Higher densities are found closer to MWC137 and in regions of intense emission, whereas in regions with high radial velocities the density decreases significantly. We also observe the entire nebula in the two [SII] lines with the scanning Fabry-Perot interferometer attached to the 6m telescope of the Special Astrophysical Observatory. These data reveal a new bow-shaped feature at PA=225{deg}-245{deg} and a distance 80" from MWC137. A new H{alpha} image has been taken with the Danish 1.54m telescope on La Silla. No expansion or changes in the nebular morphology appear within 18.1yr. We derive a mass of 37_-5_^+9^M{sun} and an age of 4.7{+/-}0.8Myr for MWC137. Furthermore, we detect a period of 1.93d in the time series photometry collected with the TESS satellite, which could suggest stellar pulsations. Other, low-frequency variability is seen as well. Whether these signals are caused by internal gravity waves in the early-type star or by variability in the wind and circumstellar matter currently cannot be distinguished.
- ID:
- ivo://CDS.VizieR/J/AJ/160/111
- Title:
- RI light curve of KELT-25 and KELT-26
- Short Name:
- J/AJ/160/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discoveries of KELT-25b (TIC 65412605, TOI-626.01) and KELT-26b (TIC 160708862, TOI-1337.01), two transiting companions orbiting relatively bright, early A stars. The transit signals were initially detected by the KELT survey and subsequently confirmed by Transiting Exoplanet Survey Satellite (TESS) photometry. KELT-25b is on a 4.40day orbit around the V=9.66 star CD-245016 (Teff=8280_-180_^+440^K, M{star}=2.18_-0.11_^+0.12^M{sun}), while KELT-26b is on a 3.34day orbit around the V=9.95 star HD134004 (Teff=8640_-240_^+500^K, M{star}=1.93_-0.16_^+0.14^M{sun}), which is likely an Am star. We have confirmed the substellar nature of both companions through detailed characterization of each system using ground-based and TESS photometry, radial velocity measurements, Doppler tomography, and high-resolution imaging. For KELT-25, we determine a companion radius of RP=1.64_-0.043_^+0.039^RJ and a 3{sigma} upper limit on the companion's mass of ~64MJ. For KELT-26b, we infer a planetary mass and radius of MP=1.41_-0.51_^+0.43^M_J_ and RP=1.94_-0.058_^+0.060^RJ. From Doppler tomographic observations, we find KELT-26b to reside in a highly misaligned orbit. This conclusion is weakly corroborated by a subtle asymmetry in the transit light curve from the TESS data. KELT-25b appears to be in a well-aligned, prograde orbit, and the system is likely a member of the cluster Theia449.
- ID:
- ivo://CDS.VizieR/J/ApJ/817/113
- Title:
- RIOTS4: spectroscopic survey of SMC field OB stars
- Short Name:
- J/ApJ/817/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Runaways and Isolated O-Type Star Spectroscopic Survey of the SMC (RIOTS4), a spatially complete survey of uniformly selected field OB stars that covers the entire star-forming body of the Small Magellanic Cloud (SMC). Using the IMACS (Inamori-Magellan Areal Camera and Spectrograph) multislit spectrograph and MIKE (Magellan Inamori Kyocera Echelle) echelle spectrograph on the Magellan telescopes, we obtained spectra of 374 early-type field stars that are at least 28pc from any other OB candidates. We also obtained spectra of an additional 23 field stars in the SMC bar identified from slightly different photometric criteria. Here, we present the observational catalog of stars in the RIOTS4 survey, including spectral classifications and radial velocities. For three multi-slit fields covering 8% of our sample, we carried out monitoring observations over 9-16 epochs to study binarity, finding a spectroscopic, massive binary frequency of at least ~60% in this subsample. Classical Oe/Be stars represent a large fraction of RIOTS4 (42%), occurring at much higher frequency than in the Galaxy, consistent with expectation at low metallicity. RIOTS4 confirmed a steep upper initial mass function in the field, apparently caused by the inability of the most massive stars to form in the smallest clusters. Our survey also yields evidence for in situ field OB star formation, and properties of field emission-line star populations, including sgB[e] stars and classical Oe/Be stars. We also discuss the radial velocity distribution and its relation to SMC kinematics and runaway stars. RIOTS4 presents a first quantitative characterization of field OB stars in an external galaxy, including the contributions of sparse, but normal, star formation; runaway stars; and candidate isolated star formation.
- ID:
- ivo://CDS.VizieR/J/A+A/381/105
- Title:
- Rotational velocities of A-type stars. I.
- Short Name:
- J/A+A/381/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Within the scope of a Key Programme determining fundamental parameters of stars observed by HIPPARCOS, spectra of 525 B8 to F2-type stars brighter than V=8 have been collected at ESO. Fourier transforms of several line profiles in the range 4200-4500{AA} are used to derive vsini from the frequency of the first zero. Statistical analysis of the sample indicates that measurement error is a function of vsini and this relative error of the rotational velocity is found to be about 6% on average. The results obtained are compared with data from the literature. There is a systematic shift from standard values from Slk_7_5, which are 10 to 12% lower than our findings. Comparisons with other independent vsini values tend to prove that those from Slettebak et al. (1975ApJS...29..137S) are underestimated. This effect is attributed to the presence of binaries in the standard sample of Slettebak et al. (1975ApJS...29..137S), and to the model atmosphere they used.
- ID:
- ivo://CDS.VizieR/J/A+A/393/897
- Title:
- Rotational velocities of A-type stars II.
- Short Name:
- J/A+A/393/897
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This work is the second part of the set of measurements of vsini for A-type stars, begun by Royer et al. (2002, Cat. <J/A+A/381/105>). Spectra of 249 B8 to F2-type stars brighter than V=7 have been collected at Observatoire de Haute- Provence (OHP). Fourier transforms of several line profiles in the range 4200-4600 A are used to derive vsini from the frequency of the first zero. Statistical analysis of the sample indicates that measurement error mainly depends on vsini and this relative error of the rotational velocity is found to be about 5% on average. The systematic shift with respect to standard values from Slettebak et al. (1975ApJS...29..137S), previously found in the first paper, is here confirmed. Comparisons with data from the literature agree with our findings: vsini values from Slettebak et al. are underestimated and the relation between both scales follows a linear law vsini(new)=1.03*vsini(old)+7.7. Finally, these data are combined with those from the previous paper (Royer et al., 2002, Cat. <J/A+A/381/105>), together with the catalogue of Abt & Morrell (1995ApJS...99..135A). The resulting sample includes some 2150 stars with homogenized rotational velocities.
- ID:
- ivo://CDS.VizieR/J/AJ/150/41
- Title:
- Rotational velocities of 136 B stars from ALS
- Short Name:
- J/AJ/150/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have determined projected rotational velocities, vsini, from Magellan/MIKE echelle spectra for a sample of 136 early B-type stars having large Galactocentric distances. The target selection was done independently of their possible membership in clusters, associations or field stars. We subsequently examined the literature and assigned each star as Field, Association, or Cluster. Our vsini results are consistent with a difference in aggregate vsini with stellar density. We fit bimodal Maxwellian distributions to the Field, Association, and Cluster subsamples representing sharp-lined and broad-lined components. The first two distributions, in particular, for the Field and Association are consistent with strong bimodality in vsini. Radial velocities are also presented, which are useful for further studies of binarity in B-type stars, and we also identify a sample of possible new double-lined spectroscopic binaries. In addition, we find 18 candidate Be stars showing emission at H{alpha}.
