- ID:
- ivo://CDS.VizieR/J/AJ/127/1117
- Title:
- Halpha emission-line stars in NGC2264
- Short Name:
- J/AJ/127/1117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a deep survey of H{alpha} emission-line stars in the NGC 2264 region using wide-field objective prism films. We find 357 H{alpha} emission-line stars, of which 113 were previously detected, within an area of 3{deg}x3{deg} centered on the Cone Nebula, with a majority of stars being concentrated in a dense cluster at the center of the region. We present a large-scale CO map of NGC 2264 and find a strong correlation between the cluster of H{alpha} emission-line stars and the most massive core in the cloud complex. A more extended halo of stars poorly correlated with the gas may represent stars that have drifted away from their birth place, suggesting that star formation has taken place in NGC 2264 for several million years.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/613/L5
- Title:
- H{alpha} emitting sources around MWC758
- Short Name:
- J/A+A/613/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- MWC758 is a young star surrounded by a transitional disk. The disk shows an inner cavity and spiral arms that could be caused by the presence of protoplanets. Recently, a protoplanet candidate has been detected around MWC758 through high-resolution L'-band observations. The candidate is located inside the disk cavity at a separation of 111 mas from the central star, and at an average position angle of 165.5{deg}. We aim at detecting accreting protoplanet candidates within the disk of MWC758 through spectral angular differential imaging observations in the optical regime. In particular, we explore the emission at the position of the detected planet candidate. We have performed simultaneous adaptive optics observations in the H{alpha} line and the adjacent continuum using SPHERE/ZIMPOL at the Very Large Telescope (VLT). The data analysis does not reveal any H{alpha} signal around the target. The derived contrast curve in the B_Ha filter allows us to derive a 5{sigma} upper limit of 7.6mag at 111mas, the separation of the previously detected planet candidate. This contrast translates into a H{alpha} line luminosity of LH{alpha}<~5*10^-5^L_{sun}_ at 111mas. Assuming that LH{alpha} scales with Lacc as in Classical T Tauri stars as a first approximation, we can estimate an accretion luminosity of Lacc<3.7*10^-4^L_{sun}_ for the protoplanet candidate. For the predicted mass range of MWC758b, 0.5-5M_Jup_, this implies accretion rates smaller than dM/dt<3.4*(10^-8^-10^-9^)M_[sun}_/yr, for an average planet radius of 1.1 RJup. Therefore, our estimates are consistent with the predictions of accreting circumplanetary accretion models for R_in_=1R_Jup_. The ZIMPOL line luminosity is consistent with the H{alpha} upper limit predicted by these models for truncation radii <~3.2R_Jup_. The non-detection of any H{alpha}emitting source in the ZIMPOL images does not allow us to unveil the nature of the L' detected source. Either it is a protoplanet candidate or a disk asymmetry.
- ID:
- ivo://CDS.VizieR/J/ApJ/814/159
- Title:
- H{alpha} interferometric visibilities of o Aqr
- Short Name:
- J/ApJ/814/159
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Omicron Aquarii is a late-type, Be shell star with a stable and nearly symmetric H{alpha} emission line. We combine H{alpha} interferometric observations obtained with the Navy Precision Optical Interferometer covering 2007 through 2014 with H{alpha} spectroscopic observations over the same period and a 2008 observation of the system's near-infrared spectral energy distribution to constrain the properties of o Aqr's circumstellar disk. All observations are consistent with a circumstellar disk seen at an inclination of 75{deg}+/-3{deg} with a position angle on the sky of 110{deg}+/-8{deg} measured East from North. From the best-fit disk density model, we find that 90% of the H{alpha} emission arises from within 9.5 stellar radii, and the mass associated with this H{alpha} disk is ~1.8x10^-10^ of the stellar mass, and that the associated angular momentum, assuming Keplerian rotation for the disk, is ~1.6x10^-8^ of the total stellar angular momentum. The occurrence of a central quasi-emission feature in Mg II {lambda}4481 is also predicted by this best-fit disk model and the computed profile compares successfully with observations from 1999. To obtain consistency between the H{alpha} line profile modeling and the other constraints, it was necessary in the profile fitting to weight the line core (emission peaks and central depression) more heavily than the line wings, which were not well reproduced by our models. This may reflect the limitation of assuming a single power law for the disk's variation in equatorial density. The best-fit disk density model for o Aqr predicts that H{alpha} is near its maximum strength as a function of disk density, and hence the H{alpha} equivalent width and line profile change only weakly in response to large (factor of ~5) changes in the disk density. This may in part explain the remarkable observed stability of o Aqr's H{alpha} emission line profile.
- ID:
- ivo://CDS.VizieR/J/ApJ/843/24
- Title:
- H{alpha} interferometry obs. of the Be star 48 Per
- Short Name:
- J/ApJ/843/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We utilize a multi-step modeling process to produce synthetic interferometric and spectroscopic observables, which are then compared to their observed counterparts. Our extensive set of interferometric observations of the Be star 48 Per, totaling 291 data points, were obtained at the Navy Precision Optical Interferometer from 2006 November 07 to 23. Our models were further constrained by comparison with contemporaneous H{alpha} line spectroscopy obtained at the John S. Hall Telescope at the Lowell Observatory on 2006 November 1. Theoretical spectral energy distributions, SEDs, for 48 Per were confirmed by comparison with observations over a wavelength regime of 0.4-60 {mu}m from Touhami+ (2010PASP..122..379T) and Vieira+ (2017MNRAS.464.3071V). Our best-fitting combined model from H{alpha} spectroscopy, H{alpha} interferometry, and SED fitting has a power-law density fall off, n, of 2.3 and an initial density at the stellar surface of {rho}_0_=1.0x10^-11^g/cm^-3^ with an inclination constrained by H{alpha} spectroscopy and interferometry of 45+/-5{deg}. The position angle for the system, measured east from north, is 114+/-18{deg}. Our best-fit model shows that the disk emission originates in a moderately large disk with a radius of 25 R*, which is consistent with a disk mass of approximately 5x10^24^g or 3x10^-10^M*. Finally, we compare our results with previous studies of 48 Per by Quirrenbach+ (1997ApJ...479..477Q) and find agreement, whereas our disk size does not agree with Delaa+ (2011A&A...529A..87D), based on a much smaller visibility set.
- ID:
- ivo://CDS.VizieR/J/ApJS/187/228
- Title:
- H{alpha} profiles of Be stars
- Short Name:
- J/ApJS/187/228
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a set of theoretical H{alpha} emission-line profiles of Be stars, created by systematically varying model input parameters over a wide range of accepted values. Models were generated with a non-LTE radiative transfer code that incorporates a non-isothermal disk structure and a solar-type chemical composition. The theoretical H{alpha} emission-line profiles were compared to a large set of Be star spectra with the aim of reproducing their global characteristics. We find that the observed profile shapes cannot be used to uniquely determine the inclination angle of Be star+disk systems. Drastically different profile shapes arise at a given inclination angle as a direct result of the state of the gas, and self-consistent disk physical conditions are therefore crucial for interpreting the observations.
- ID:
- ivo://CDS.VizieR/J/A+A/554/A143
- Title:
- H{alpha} spectra of MWC 342 spectra, 2004-2010
- Short Name:
- J/A+A/554/A143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalogue presents spectra of MWC 342 (V1972 Cyg) obtained during the period 2004 to 2010 with the Coude spectrograph at the 2m telescope in Ondrejov observatory, Czech Republic, using the SITe CCD (2030x800 pixels, 15um pixel size) in a camera with 700mm focus. The spectral interval along the H{alpha} line covers 6265 to 6765{AA}. The resolving power is this range is R~13000. The data reduction was performed using IRAF. After the bias subtraction, flat-field and overscan correction, the dcr program written by Pych (2004PASP..116..148P) was used for the cosmic ray removal. The spectra subtraction was done by IRAF apall task without using the optimal extraction . The background, together with the night sky lines, is eliminated during spectra subtraction by individual pixel columns. The remaining wavelength calibration, heliocentric correction, and the continuum fitting are also performed using IRAF. The heliocentric correction was applied on the data. Chebyshev polynomial of the third order is used for the spectra normalisation to fit the intervals, which apparently contain no spectral lines. Each continuum interval is split into sub-intervals of five pixels, where the median value is taken for the continuum evaluation. Possible remaining cosmic ray hits thus do not affect continuum normalisation.
- ID:
- ivo://CDS.VizieR/J/A+A/560/A30
- Title:
- H{alpha} spectra of {pi} Aqr
- Short Name:
- J/A+A/560/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The work is aimed at studying the circumstellar disk of the bright classical binary Be star pi Aqr. We analysed variations of a double-peaked profile of the Halpha emission line in the spectrum of pi Aqr that was observed in many phases during ~40 orbital cycles in 2004-2013. We applied the discrete Fourier transform (DFT) method to search for periodicity in the peak intensity ratio (V/R). Doppler tomography was used to study the structure of the disk around the primary. The dominant frequency in the power spectrum of the Halpha V/R ratio is 0.011873d^-1^, which corresponds to a period of 84.2(2) days and agrees with the earlier determined orbital period of the system P_orb_=84.1d. The V/R shows a sinusoidal variation that is phase-locked with the orbital period. Doppler maps of all our spectra show a non-uniform structure of the disk around the primary: a ring with the inner and outer radii at V_in_~450km/s and V_out_~200km/s, respectively, along with an extended stable region (spot) at V_x_~225km/s and Vy~100km/s. The disk radius of ~65R_{sun}_=0.33AU was estimated by assuming Keplerian motion of a particle on a circular orbit at the disk's outer edge.
- ID:
- ivo://CDS.VizieR/J/ApJ/890/86
- Title:
- H{alpha} spectra & V-band photometry of {delta} Sco
- Short Name:
- J/ApJ/890/86
- Date:
- 04 Dec 2021
- Publisher:
- CDS
- Description:
- We model the circumstellar disk of {delta} Sco using the three-dimensional Monte Carlo radiative transfer code HDUST in order to quantify the large-scale changes in the disk through the years 2000-2018, and to see if these changes can be attributed to the secondary star affecting the disk throughout its orbit. We determine our best-fitting models through matching simulated observations to actual H{alpha} spectroscopy and V-band photometric observations. Our modeling results confirm previous findings that the disk of {delta}Sco was forming early in the century. We also find a period of disk dissipation when the companion is at apastron, as well as a significant growth of the disk between 2009 and 2011, prior to the periastron of 2011. Due to the steady-state nature of the disk after 2011, it is difficult to say whether the variations seen are due to the effect of the close passage of the binary companion.
- ID:
- ivo://CDS.VizieR/J/AJ/122/248
- Title:
- h and chi Per UBVI,H{alpha} photometry
- Short Name:
- J/AJ/122/248
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- UBVI and H{alpha} photometry is presented for 17319 stars in vicinity of the young double cluster h and {chi} Persei. Our photometry extends over a 37'x1{deg} field centered on the association. We construct reddening contours within the imaged field. We find that the two clusters share a common distance modulus of 11.75+/-0.05 and ages of log[age(yr)]=7.1+/-0.1. From the V-H{alpha} color, a measure of the H{alpha} emission strength, we conduct a survey for emission line objects within the association. We detect a sample of 33 Be stars, eight of which are new detections. We present a scenario of evolutionary enhancement of the Be phenomenon to account for the peak in Be fraction toward the top of the main sequence in the population of h and {chi} Persei and similar young clusters. UBVI and H{alpha} photometry was performed on five nights between 1999 August 17 and 25 at the San Diego State University Mount Laguna Observatory with the 1m telescope and a Loral 2048x2048 CCD.
- ID:
- ivo://CDS.VizieR/J/A+A/567/A28
- Title:
- HARPSpol magnetic massive stars
- Short Name:
- J/A+A/567/A28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Magnetism in Massive Stars (MiMeS) project aims at understanding the origin of the magnetic fields in massive stars as well as their impact on stellar internal structure, evolution, and circumstellar environment. One of the objectives of the MiMeS project is to provide stringent observational constraints on the magnetic fields of massive stars; however, identification of magnetic massive stars is challenging, as only a few percent of high-mass stars host strong fields detectable with the current instrumentation. Hence, one of the first objectives of the MiMeS project was to search for magnetic objects among a large sample of massive stars, and to build a sub-sample for in-depth follow-up studies required to test the models and theories of fossil field origins, magnetic wind confinement and magnetospheric properties, and magnetic star evolution. We obtained high-resolution spectropolarimetric observations of a large number of OB stars thanks to three large programs (LP) of observations that have been allocated on the high-resolution spectropolarimeters ESPaDOnS, Narval, and the polarimetric module HARPSpol of the HARPS spectrograph.
