- ID:
- ivo://CDS.VizieR/J/ApJ/689/461
- Title:
- Circumstellar disk of {chi} Oph
- Short Name:
- J/ApJ/689/461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a numerical model describing a circularly symmetric gaseous disk around the Be star {chi} Ophiuchi. The model is constrained by long-baseline interferometric observations that are sensitive to the H{alpha} Balmer line emission from the disk. For the first time, our interferometric observations spatially resolve the inner region of the circumstellar disk around {chi} Oph, and we use these results to place a constraint on the physical extent of the H{alpha}-emitting region. We demonstrate how this in turn results in very specific constraints on the parameters that describe the variation of the gas density as a function of radial distance from the central star.
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- ID:
- ivo://CDS.VizieR/J/A+A/610/A70
- Title:
- 28 Cygni BRITE and SMEI satellite photometry
- Short Name:
- J/A+A/610/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The BRITE Constellation of nanosatellites obtained mmag photometry of 28 Cygni for 11 months in 2014-2016. Observations with the Solar Mass Ejection Imager in 2003-2010 and 118 H{alpha} line profiles were added. For decades, 28 Cyg has exhibited four large-amplitude frequencies: two closely spaced frequencies of spectroscopically confirmed g modes near 1.5c/d, one slightly lower exophotospheric (Stefl) frequency, and at 0.05c/d the difference frequency between the two g modes. This top-level framework is indistinguishable from eta Cen (Paper I), which is also very similar in spectral type, rotation rate, and viewing angle. The Stefl frequency is the only one that does not seem to be affected by the difference frequency. The amplitude of the latter undergoes large variations; around maximum the amount of near-circumstellar matter is increased, and the amplitude of the Stefl frequency grows by some factor. During such brightenings dozens of transient spikes appear in the frequency spectrum, concentrated in three groups. Only eleven frequencies were common to all years of BRITE observations. Be stars seem to be controlled by several coupled clocks, most of which are not very regular on timescales of weeks to months but function for decades. The combination of g modes to the low difference frequency and/or the atmospheric response to it appears significantly nonlinear. Like in eta Cen, the difference-frequency variability seems the main responsible for the modulation of the star-to-disc mass transfer in 28 Cyg. A hierarchical set of difference frequencies may reach the longest timescales known of the Be phenomenon.
- ID:
- ivo://CDS.VizieR/J/AJ/145/142
- Title:
- Differential BV photometry of {delta} Sco
- Short Name:
- J/AJ/145/142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We acquired Johnson BV photometry of the binary Be disk system {delta} Scorpii during its 2009, 2010, 2011, and 2012 observing seasons and used it to probe the innermost regions of the disk. We found that several disk building events have occurred during this time, resulting in an overall brightening in the V band and reddening of the system. In addition to these long-term trends, we found cyclical variability in each observing season on timescales between 60 and 100days. We were able to reproduce the changes in the magnitude and color of {delta} Sco using our theoretical models and found that variable mass-loss rates in the range 2.5-7.0*10^-9^M_{Sun}_/yr over ~35days can reproduce the observed increase in brightness.
- ID:
- ivo://CDS.VizieR/J/ApJ/686/1280
- Title:
- Discovery of hot subdwarf companion to FY CMa
- Short Name:
- J/ApJ/686/1280
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The rapid rotation of Be stars may be caused in some cases by past mass and angular momentum accretion in an interacting binary in which the mass donor is currently viewed as a small, hot subdwarf stripped of its outer envelope. Here we report on the spectroscopic detection of such a subdwarf in the Be binary system FY Canis Majoris from the analysis of data acquired by the IUE spacecraft and KPNO Coude Feed Telescope over the course of 16 and 21yr, respectively. We present a double-lined spectroscopic orbit for the binary based on radial velocities from the IUE spectra and use the orbital solutions with a Doppler tomography algorithm to reconstruct the components' UV spectra. The subdwarf is hot (T_eff_=45+/-5kK) and has a mass of about 1.3M_{sun}_ and a radius of about 0.6R_{sun}_. It contributes about 4% as much flux as the Be star does in the FUV. We also present observations of the H{alpha} and HeI{lambda}6678 emission features that are formed in the circumstellar disk of the Be star.
- ID:
- ivo://CDS.VizieR/J/A+A/309/787
- Title:
- DX Eri variability
- Short Name:
- J/A+A/309/787
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of nearly simultaneous monitoring of uvby light and HeI667.81nm line-profile variations of the equatorial Be star DX Eri in November 1991. They are analysed along with numerous uvby photometry in the period 1986-1995.
- ID:
- ivo://CDS.VizieR/III/17B
- Title:
- Early-Type Emission-Line Stars
- Short Name:
- III/17B
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog contains 5326 early-type emission-line stars. Of these, 1424 have no spectral classification but are assumed to be of early type. Some 71 percent of the stars listed here can also be found in the Mount Wilson and the Mount Wilson-Michigan survey catalogs. The catalog contains numerous cross identifications to other designations (name, HD, DM, LS, MWC, TON, HIL, WRA, HEN, etc.), spectroscopic type, magnitudes (visual and blue), equatorial (B1900 and B1950), and galactic coordinates.
- ID:
- ivo://CDS.VizieR/J/A+A/506/95
- Title:
- Fourier analysis of HD 49330 CoRoT light curve
- Short Name:
- J/A+A/506/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Be stars undergo outbursts producing a circumstellar disk from the ejected material. The beating of non-radial pulsations has been put forward as a possible mechanism of ejection. We analyze the pulsational behavior of the early B0.5IVe star HD 49330 observed during the first CoRoT long run towards the Galactical anticenter (LRA1). This Be star is located close to the lower edge of the {beta} Cephei instability strip in the HR diagram and showed a 0.03mag outburst during the CoRoT observations. It is thus an ideal case for testing the aforementioned hypothesis.
- ID:
- ivo://CDS.VizieR/J/A+A/451/1053
- Title:
- Fundamental parameters of Be stars
- Short Name:
- J/A+A/451/1053
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In preparation for the COROT space mission, we determined the fundamental parameters (spectral type, temperature, gravity, vsini) of the Be stars observable by COROT in its seismology fields (64 Be stars). We applied a careful and detailed modeling of the stellar spectra, taking into account the veiling caused by the envelope, as well as the gravitational darkening and stellar flattening due to rapid rotation. Evolutionary tracks for fast rotators were used to derive stellar masses and ages. The derived parameters will be used to select Be stars as secondary targets (i.e. observed for 5 consecutive months) and short-run targets of the COROT mission. Furthermore, we note that the main part of our stellar sample is falling in the second half of the main sequence life time, and that in most cases the luminosity class of Be stars is inaccurate in characterizing their evolutionary status.
- ID:
- ivo://CDS.VizieR/J/ApJ/765/2
- Title:
- FUV radial velocities of 59 Cyg
- Short Name:
- J/ApJ/765/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the detection of a hot subdwarf component in the Be binary system, 59 Cygni. The spectral signature is found in cross-correlation functions of photospheric model spectra with far-ultraviolet spectra obtained by the International Ultraviolet Explorer Satellite, and we used radial velocities from the cross-correlation functions to determine a double-lined spectroscopic orbit. The individual spectra of the binary components were extracted using a Doppler tomography algorithm. The flux of the system is dominated by the rapidly rotating Be star. However, the subdwarf contributes approximately 4% of the UV flux, and its spectrum bears a strong resemblance to that of the hot sdO star BD +75{deg}325. Based on the appearance of the UV spectrum and the orbital elements, we present estimates for the stellar masses, radii, and temperatures. The presence of the hot companion causes excess emission from the outer part of the Be disk facing the companion. We present a set of red spectra that show the orbital phase variations of the He I {lambda}6678 emission formed in the heated region of the disk, which probably occurs near the disk outer boundary. 59 Cygni, FY Canis Majoris, and {phi} Persei comprise the known set of Be binaries with detected hot evolved companions, which are the stripped down remains of mass transfer. Their properties demonstrate that some fraction of Be stars were spun up through angular momentum transfer by Roche lobe overflow.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A128
- Title:
- Gaia DR2 study of Herbig Ae/Be stars
- Short Name:
- J/A+A/620/A128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Gaia Data Release 2 (DR2, Cat. I/345) to place 252 Herbig Ae/Be stars in the HR diagram and investigate their characteristics and properties. For all known Herbig Ae/Be stars with parallaxes in Gaia DR2, we collected their atmospheric parameters and photometric and extinction values from the literature. To these data we added near- and mid-infrared photometry, collected Halpha emission line properties such as equivalent widths and line profiles, and their binarity status. In addition, we developed a photometric variability indicator from Gaia's DR2 information. We provide masses, ages, luminosities, distances, photometric variabilities and infrared excesses homogeneously derived for the most complete sample of Herbig Ae/Be stars to date. We find that high mass stars have a much smaller infrared excess and have much lower optical variabilities compared to lower mass stars, with the break at around 7M_{sun}_. Halpha emission is generally correlated with infrared excess, with the correlation being stronger for infrared emission at wavelengths tracing the hot dust closest to the star. The variability indicator as developed by us shows that approximately 25% of all Herbig Ae/Be stars are strongly variable. We observe that the strongly variable objects display doubly peaked Halpha line profiles, indicating an edge-on disk. The fraction of strongly variable Herbig Ae stars is close to that found for A-type UX Ori stars. It had been suggested that this variability is in most cases due to asymmetric dusty disk structures seen edge-on. The observation here is in strong support of this hypothesis. Finally, the difference in dust properties occurs at 7M_{sun}_, while various properties traced at UV/optical wavelengths differ at a lower mass, 3M_{sun}_. The latter has been linked to different accretion mechanisms at work whereas the differing infrared properties and photometric variabilities are related to different or differently acting (dust-)disk dispersal mechanisms.