- ID:
- ivo://CDS.VizieR/J/A+A/622/A75
- Title:
- MWC 480 ALMA image
- Short Name:
- J/A+A/622/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Gap-like structures in protoplanetary disks are likely related to planet formation processes. In this work, we present and analyze high-resolution 1.3mm ALMA continuum observations of the protoplanetary disk around the Herbig Ae star MWC 480. Our observations show for the first time a gap centered at ~74AU with a width of ~23AU, surrounded by a bright ring centered at ~98AU from the central star. Detailed radiative transfer modeling of the ALMA image and the broadband spectral energy distribution is used to constrain the surface density profile and structural parameters of the disk. If the width of the gap corresponds to 4-8 times the Hill radius of a single forming planet, then the putative planet would have a mass of 0.4~3M_J_. We test this prediction by performing global three-dimensional smoothed particle hydrodynamic gas/dust simulations of disks hosting a migrating and accreting planet. We find that the dust emission across the disk is consistent with the presence of an embedded planet with a mass of ~2.3M_J_ at an orbital radius of ~78AU. Given the surface density of the best-fit radiative transfer model, the amount of depleted mass in the gap is higher than the mass of the putative planet, which satisfies the basic condition for the formation of such a planet.
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- ID:
- ivo://CDS.VizieR/J/A+AS/131/469
- Title:
- MWC 314 spectroscopy
- Short Name:
- J/A+AS/131/469
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of high-resolution optical spectroscopy obtained for a recently suggested LBV (luminous blue variable) candidate, MWC 314, are presented. Photospheric lines mostly of N II and S II have been found for the first time with a resolution of 0.4-0.8{AA}. They imply a N/O overabundance previously reported for AG and HR Car since no O II absorptions were detected. Nearly 400 emission lines have been identified in the spectrum between 4190 and 8864{AA} many of which appear double-peaked. No significant P Cygni type absorption components have been found for the optically thick Balmer lines. This suggests that the stellar wind of MWC 314 is non-spherical and the circumstellar envelope is viewed not edge on. The systemic velocity measured using the emission lines of ionized metals turned out to be 55km/s, which corresponds to a distance towards the object of 3.0+/-0.2kpc, according to the galactic rotation curve. Our analysis of the characteristics of both photospheric and wind lines resulted in an estimate of the object's T_eff_ of nearly 25000K, which, however, needs further improvement. The other stellar parameters were found to be as follows: Log(L_bol_/L_{sun}_)=6.1+/-0.3, R_star_=60^+30^_=10_R_{sun}_. Our study confirms that MWC 314 is one of the most luminous stars in the Milky Way.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A69
- Title:
- MWC 922 XSHOOTER spectra
- Short Name:
- J/A+A/601/A69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Medium-resolution echelle spectra of the Red Square Nebula surrounding the star MWC 922 are presented. The spectra have been obtained in 2010 and 2012 using the XSHOOTER spectrograph mounted on the Very Large Telescope (VLT) in Paranal, Chile. The spectrum covers a wavelength range between 300nm-2.5um and shows that the nebula is rich in emission lines. We aim to identify the emission lines and use them as a tool to determine the physical and chemical characteristics of the nebula. The emission lines are also used to put constraints on the structure of the nebula and on the nature of the central stars. We analyzed and identified emission lines that indicated that the Red Square Nebula consists of a low density bipolar outflow, eminent in the broad emission component seen in [FeII], as well as in P Cygni line profiles indicative of fast outflowing material. The narrow component in the [FeII] lines is most likely formed in the photosphere of a surrounding disk. Some of the emission lines show a pronounced double peaked profile, such as CaII, indicating an accretion disk in Keplerian rotation around the central star. [OI] emission lines are formed in the neutral atomic zone separating the ionized disk photosphere from the molecular gas in the interior of the disk, which is prominent in molecular CO emission in the near-IR. [NII] and [SII] emission clearly originates in a low density but fairly hot (7000-10000K) nebular environment. HI recombination lines trace the extended nebula as well as the photosphere of the disk.
- ID:
- ivo://CDS.VizieR/J/other/Ap/57.500
- Title:
- New H{alpha} emission stars in Cep OB3
- Short Name:
- J/other/Ap/57.50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A search of emission stars has been done on the basis of digitized photographic plates received with the 40" Schmidt telescope of Byurakan Observatory equipped with a 4{deg} objective prism. Forty-six new emission stars are found in a small area around the known FU Ori type variable V733 Cep. Emission stars on the J-H - H-K diagram are situated on or in the neighborhood of T Tau locus. V, R, I photometry for some of the emission stars is performed as well. Three new variable stars are found in the region. A rapid brightness variation is detected on V733 Cep.
- ID:
- ivo://CDS.VizieR/J/A+A/638/A21
- Title:
- New Herbig Ae/Be and classical Be stars catalog
- Short Name:
- J/A+A/638/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The intermediate-mass pre-main sequence (PMS) Herbig Ae/Be stars are key to understanding the differences in formation mechanisms between low- and high-mass stars. The study of the general properties of these objects is hampered by the lack of a well-defined, homogeneous sample, and because few and mostly serendipitously discovered sources are known. Our goal is to identify new Herbig Ae/Be candidates to create a homogeneous and well defined catalogue of these objects. We have applied machine learning techniques to 4150983 sources with data from Gaia DR2, 2MASS, WISE, and IPHAS or VPHAS+. Several observables were chosen to identify new Herbig Ae/Be candidates based on our current knowledge of this class, which is characterised by infrared excesses, photometric variabilities, and Halpha emission lines. Classical techniques are not efficient for identifying new Herbig Ae/Be stars mainly because of their similarity with classical Be stars (CBe), with which they share many characteristics. By focusing on disentangling these two types of objects, our algorithm has also identified new classical Be stars. We have obtained a large catalogue of 8470 new pre-main sequence candidates and another catalogue of 693 new classical Be candidates with a completeness of 78.8+/-1.4% and 85.5+/-1.2%, respectively. Of the catalogue of pre-main sequence candidates, at least 1361 sources are potentially new Herbig Ae/Be candidates according to their position in the Hertzsprung-Russell diagram. In this study we present the methodology used, evaluate the quality of the catalogues, and perform an analysis of their flaws and biases. For this assessment, we make use of observables that have not been accounted for by the algorithm and hence are selection-independent, such as coordinates and parallax based distances. The catalogue of new Herbig Ae/Be stars that we present here increases the number of known objects of the class by an order of magnitude.
- ID:
- ivo://CDS.VizieR/J/A+A/612/A48
- Title:
- 4 oxygen-rich evolved stars NH3 spectra
- Short Name:
- J/A+A/612/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The circumstellar ammonia (NH_3_) chemistry in evolved stars is poorly understood. Previous observations and modelling showed that NH_3_ abundance in oxygen-rich stars is several orders of magnitude above that predicted by equilibrium chemistry. We would like to characterise the spatial distribution and excitation of NH_3_ in the oxygen-rich circumstellar envelopes (CSEs) of four diverse targets: IK Tau, VY CMa, OH 231.8+4.2, and IRC +10420. We observed NH_3_ emission from the ground state in the inversion transitions near 1.3cm with the Very Large Array (VLA) and submillimetre rotational transitions with the Heterodyne Instrument for the Far-Infrared (HIFI) aboard Herschel Space Observatory from all four targets. For IK Tau and VY CMa, we observed NH_3_ rovibrational absorption lines in 2 band near 10.5um with the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility (IRTF).We also attempted to search for the rotational transition within the excited vibrational state (v_2_=1) near 2mm with the IRAM 30m Telescope. Non-LTE radiative transfer modelling, including radiative pumping to the vibrational state, was carried out to derive the radial distribution of NH_3_ in the CSEs of these targets. We detected NH_3_ inversion and rotational emission in all four targets. IK Tau and VY CMa show blueshifted absorption in the rovibrational spectra. We did not detect vibrationally excited rotational transition from IK Tau. Spatially resolved VLA images of IK Tau and IRC +10420 show clumpy emission structures; unresolved images of VY CMa and OH 231.8+4.2 indicate that the spatial-kinematic distribution of NH_3_ is similar to that of assorted molecules, such as SO and SO2, that exhibit localised and clumpy emission. Our modelling shows that the NH_3_ abundance relative to molecular hydrogen is generally of the order of 10^-7^, which is a few times lower than previous estimates that were made without considering radiative pumping and is at least ten times higher than that in the carbon-rich CSE of IRC +10216. NH_3_ in OH 231.8+4.2 and IRC +10420 is found to emit in gas denser than the ambient medium. Incidentally, we also derived a new period of IK Tau from its V-band light curve. NH_3_ is again detected in very high abundance in evolved stars, especially the oxygen-rich ones. Its emission mainly arises from localised spatial-kinematic structures that are probably denser than the ambient gas. Circumstellar shocks in the accelerated wind may contribute to the production of NH_3_. Future mid-infrared spectroscopy and radio imaging studies are necessary to constrain the radii and physical conditions of the formation regions of NH_3_.
- ID:
- ivo://CDS.VizieR/J/A+AS/108/561
- Title:
- P Cygni spectrum in 1985
- Short Name:
- J/A+AS/108/561
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/III/2
- Title:
- Preliminary Catalog Early-Type Emission Stars
- Short Name:
- III/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The present catalogue presents a list of 3216 stars mostly earlier than type F which have shown emission features and specifically one or more lines of the Balmer series in emission. It is a compilation and rearrangement of the following lists: * the Catalogue and Bibliography of Stars of Classes B and A whose spectra have bright H lines by P. Merrill and C. Burwell, * the lists of Haro and his associates at Tonantzintla, * the catalogues of Luminous Stars in the Northern Milky Way, Vols. I to VI published by the astronomers of the Hamburger Sternwarte and the Warner and Swasey Observatoryy (III/76) * shorter lists of emission stars published by Parenago, Bidelman and McCarthy and Treanor have also been included. The present catalogue has a simple aim: to assist the astronomer in finding from a vast array of articles in the literature whether the star under investigation has been known to show emission features in the earlier major surveys of emission stars of early type carried out at the Mount Wilson, Tonantzila, Hamburg and Warner-Swasey Observatories. The catalogue includes the star identification, Durchmusterung identification, source catalog, RA and Dec, Galactic latitude and longitude, apparent magnitude, spectral classification and remarks.
- ID:
- ivo://CDS.VizieR/J/A+A/624/A4
- Title:
- R CrA SPHERE and SINFONI images
- Short Name:
- J/A+A/624/A4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- R Coronae Australis (R CrA) is the brightest star of the Coronet nebula of the Corona Australis (CrA) star forming region. It has very red colors, probably due to dust absorption and it is strongly variable. High contrast instruments allow for an unprecedented direct exploration of the immediate circumstellar environment of this star. We observed R CrA with the near-IR channels (IFS and IRDIS) of SPHERE at VLT. In this paper, we used four different epochs, three of them from open time observations while one is from the SPHERE guaranteed time. The data were reduced using the DRH pipeline and the SPHERE Data Center. On the reduced data we implemented custom IDL routines with the aim to subtract the speckle halo.We have also obtained pupil-tracking H-band (1.45-1.85um) observations with the VLT/SINFONI near-infrared medium-resolution (R3000) spectrograph. A companion was found at a separation of 0.156" from the star in the first epoch and increasing to 0.184" in the final one. Furthermore, several extended structures were found around the star, the most noteworthy of which is a very bright jet-like structure North-East from the star. The astrometric measurements of the companion in the four epochs confirm that it is gravitationally bound to the star. The SPHERE photometry and the SINFONI spectrum, once corrected for extinction, point toward an early M spectral type object with a mass between 0.3 and 0.55M_{sun}_. The astrometric analysis provides constraints on the orbit paramenters: e~0.4, semi-major axis at 27-28au, inclination of ~70{deg} and a period larger than 30 years. We were also able to put constraints of few MJup on the mass of possible other companions down to separations of few tens of au.
- ID:
- ivo://CDS.VizieR/J/AJ/149/7
- Title:
- SDSS-III/APOGEE. I. Be stars
- Short Name:
- J/AJ/149/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Apache Point Observatory Galactic Evolution Experiment (APOGEE) has amassed the largest ever collection of multi-epoch, high-resolution (R~22500), H-band spectra for B-type emission line (Be) stars. These stars were targeted by APOGEE as telluric standard stars and subsequently identified via visual inspection as Be stars based on HI Brackett series emission or shell absorption in addition to otherwise smooth continua and occasionally non-hydrogen emission features. The 128/238 APOGEE Be stars for which emission had never previously been reported serve to increase the total number of known Be stars by ~6%. Because the H band is relatively unexplored compared to other wavelength regimes, we focus here on identification of the H-band lines and analysis of the emission peak velocity separations ({Delta}v_p_) and emission peak intensity ratios (V/R) of the usually double-peaked HI and non-hydrogen emission lines. HI Br11 emission is found to preferentially form in the circumstellar disks at an average distance of ~2.2 stellar radii. Increasing {Delta}v_p_ toward the weaker Br12-Br20 lines suggests these lines are formed interior to Br11. By contrast, the observed IR FeII emission lines present evidence of having significantly larger formation radii; distinctive phase lags between IR FeII and HI Brackett emission lines further supports that these species arise from different radii in Be disks. Several emission lines have been identified for the first time including CI 16895, a prominent feature in the spectra for almost a fifth of the sample and, as inferred from relatively large {Delta}v_p_ compared to the Br11-Br20, a tracer of the inner regions of Be disks. Emission lines at 15760{AA} and 16781{AA} remain unidentified, but usually appear along with and always have similar line profile morphology to FeII 16878. Unlike the typical metallic lines observed for Be stars in the optical, the H-band metallic lines, such as FeII 16878, never exhibit any evidence of shell absorption, even when the HI lines are clearly shell-dominated. The first known example of a quasi-triple-peaked Br11 line profile is reported for HD253659, one of several stars exhibiting intra- and/or extra-species V/R and radial velocity variation within individual spectra. Br11 profiles are presented for all discussed stars, as are full APOGEE spectra for a portion of the sample.
