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2581. Spectroscopy of active galaxies in nearby clusters
ID:
ivo://CDS.VizieR/J/AJ/124/2453
Title:
Spectroscopy of active galaxies in nearby clusters
Short Name:
J/AJ/124/2453
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used optical spectroscopy to investigate the active galaxy populations in a sample of 20 nearby Abell clusters. The targets were identified on the basis of 1.4GHz radio emission, which identifies them as either active galactic nuclei (AGNs) or galaxies forming stars at rates comparable to or greater than that of the Milky Way. The spectra were used to characterize the galaxies via their emission and absorption features.
2582. Spectroscopy of AE Circinus
ID:
ivo://CDS.VizieR/J/MNRAS/383/845
Title:
Spectroscopy of AE Circinus
Short Name:
J/MNRAS/383/845
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new optical spectroscopy and photometry, Two-Micron All-Sky Survey (2MASS) infrared observations and 24yr of combined American Association of Variable Star Observers (AAVSO) and Association Francaise des Observateurs d'Etoiles Variables (AFOEV) photometry of the symbiotic star candidate AE Cir. The long-term light curve is characterized by outbursts lasting several years and having a slow decline of ~2x10^-4^mag/d. The whole range of variability of the star in the V band is about 4mag. The periodogram of the photometric data reveals strong signals at ~342 and 171d. The presence of the emission feature at {lambda}6830{AA} at minimum and the detection of absorption lines of a ~K5 type star confirm the symbiotic classification and suggest that AE Cir is a new member of the small group of s-type yellow symbiotic stars. We estimate a distance of 9.4kpc. Our spectrum taken at the high state shows a much flatter spectral energy distribution, the disappearance of the {lambda}6830{AA} emission feature and the weakness of the HeII 4686 emission relative to the Balmer emission lines. Our observations indicate the presence of emission-line flickering in time-scales of minutes in 2001. The peculiar character of AE Cir is revealed in the visibility of the secondary star at the high and low state, the light curve resembling a dwarf nova superoutburst and the relatively short low states. The data are hard to reconciliate with standard models for symbiotic star outbursts.
2583. Spectroscopy of Alpha Cen
ID:
ivo://CDS.VizieR/J/A+A/328/261
Title:
Spectroscopy of Alpha Cen
Short Name:
J/A+A/328/261
Date:
21 Oct 2021
Publisher:
CDS
Description:
This table presents the results of a spectroscopic analysis (differentially to the Sun) of the two components of the binary system Alpha Centauri. This analysis has been carried out on the basis of extensive high resolution and high signal-to-noise spectra taken at the European Southern Observatory (La Silla, Chile).
2584. Spectroscopy of Be stars
ID:
ivo://CDS.VizieR/J/A+A/378/861
Title:
Spectroscopy of Be stars
Short Name:
J/A+A/378/861
Date:
21 Oct 2021
Publisher:
CDS
Description:
The 270 spectra enclosed are those used in the atlas and are described in the Table 1 of the paper: stars with magnitudes and spectral types, dates of observations and other data. All are normalized and corrected from the radial velocity due to Earth movement, but not corrected from the radial velocity of the star itself. The heliocentric Julian day of the mid-exposure appears in the header with a comment keyword. Very often it cannot be derived by a simple formula from the beginning and the time exposure, when the spectrum is the result of the sum of several successive ones, or when clouds have obliged to interrupt the exposure. For this reason, it is always indicated. The HD number of the star appears always in the name of the file, with additional letters to distinguish the different spectra of a same star. The tracings of the atlas (72 FITS files) are described in the subsection 2.4 of the paper and available with the electronic version.
2585. Spectroscopy of Be stars in open clusters
ID:
ivo://CDS.VizieR/J/ApJ/700/1216
Title:
Spectroscopy of Be stars in open clusters
Short Name:
J/ApJ/700/1216
Date:
21 Oct 2021
Publisher:
CDS
Description:
We recently discovered a large number of highly active Be stars in the open cluster NGC 3766, making it an excellent location to study the formation mechanism of Be star disks. To explore whether similar disk appearances and/or disappearances are common among the Be stars in other open clusters, we present here multiple epochs of H{alpha} spectroscopy for 296 stars in eight open clusters. We identify 12 new transient Be stars and confirm 17 additional Be stars with relatively stable disks. By comparing the H{alpha} equivalent widths to the photometric y-H{alpha} colors, we present a method to estimate the strength of the H{alpha} emission when spectroscopy is not available. For a subset of 128 stars in four open clusters, we also use blue optical spectroscopy and available Stromgren photometry to measure their projected rotational velocities, effective temperatures, and polar surface gravities. We combine our Be star detections from these four clusters to investigate physical differences between the transient Be stars, stable Be stars, and normal B-type stars with no line emission. Both types of Be stars are faster rotating populations than normal B-type stars, and we find no significant physical differences between the transient and stable Be stars in our sample.
2586. Spectroscopy of 341 bright A- and B-type stars
ID:
ivo://CDS.VizieR/J/AJ/152/40
Title:
Spectroscopy of 341 bright A- and B-type stars
Short Name:
J/AJ/152/40
Date:
21 Oct 2021
Publisher:
CDS
Description:
Binary stars and higher-order multiple systems are a ubiquitous outcome of star formation, especially as the system mass increases. The companion mass-ratio distribution is a unique probe into the conditions of the collapsing cloud core and circumstellar disk(s) of the binary fragments. Inside a~1000AU the disks from the two forming stars can interact, and additionally companions can form directly through disk fragmentation. We should, therefore, expect the mass-ratio distribution of close companions (a<~100AU) to differ from that of wide companions. This prediction is difficult to test using traditional methods, in particular, with intermediate-mass primary stars, for a variety of observational reasons. We present the results of a survey searching for companions to A- and B-type stars using the direct spectral detection method, which is sensitive to late-type companions within ~1'' of the primary and which has no inner working angle. We estimate the temperatures and surface gravity of most of the 341 sample stars and derive their masses and ages. We additionally estimate the temperatures and masses of the 64 companions we find, 23 of which are new detections. We find that the mass-ratio distribution for our sample has a maximum near q~0.3. Our mass-ratio distribution has a very different form than in previous works, where it is usually well-described by a power law, and indicates that close companions to intermediate-mass stars experience significantly different accretion histories or formation mechanisms than wide companions.
2587. Spectroscopy of bright M dwarfs in the northern sky
ID:
ivo://CDS.VizieR/J/AJ/145/102
Title:
Spectroscopy of bright M dwarfs in the northern sky
Short Name:
J/AJ/145/102
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a spectroscopic catalog of the 1564 brightest (J<9) M dwarf candidates in the northern sky, as selected from the SUPERBLINK proper motion catalog. Observations confirm 1408 of the candidates to be late-K and M dwarfs with spectral subtypes K7-M6. From the low ({mu}>40mas/yr) proper motion limit and high level of completeness of the SUPERBLINK catalog in that magnitude range, we estimate that our spectroscopic census most likely includes >90% of all existing, northern-sky M dwarfs with apparent magnitude J<9. Only 682 stars in our sample are listed in the Third Catalog of Nearby Stars (CNS3); most others are relative unknowns and have spectroscopic data presented here for the first time. Spectral subtypes are assigned based on spectral index measurements of CaH and TiO molecular bands; a comparison of spectra from the same stars obtained at different observatories, however, reveals that spectral band index measurements are dependent on spectral resolution, spectrophotometric calibration, and other instrumental factors. As a result, we find that a consistent classification scheme requires that spectral indices be calibrated and corrected for each observatory/instrument used. After systematic corrections and a recalibration of the subtype-index relationships for the CaH2, CaH3, TiO5, and TiO6 spectral indices, we find that we can consistently and reliably classify all our stars to a half-subtype precision. The use of corrected spectral indices further requires us to recalibrate the {zeta} parameter, a metallicity indicator based on the ratio of TiO and CaH optical bandheads. However, we find that our {zeta} values are not sensitive enough to diagnose metallicity variations in dwarfs of subtypes M2 and earlier (+/-0.5dex accuracy) and are only marginally useful at later M3-M5 subtypes (+/-0.2dex accuracy). Fits of our spectra to the Phoenix atmospheric model grid are used to estimate effective temperatures. These suggest the existence of a plateau in the M1-M3 subtype range, in agreement with model fits of infrared spectra but at odds with photometric determinations of T_eff_. Existing geometric parallax measurements are extracted from the literature for 624 stars, and are used to determine spectroscopic and photometric distances for all the other stars. Active dwarfs are identified from measurements of H{alpha} equivalent widths, and we find a strong correlation between H{alpha} emission in M dwarfs and detected X-ray emission from ROSAT and/or a large UV excess in the GALEX point source catalog. We combine proper motion data and photometric distances to evaluate the (U, V, W) distribution in velocity space, which is found to correlate tightly with the velocity distribution of G dwarfs in the solar neighborhood. However, active stars show a smaller dispersion in their space velocities, which is consistent with those stars being younger on average. Our catalog will be most useful to guide the selection of the best M dwarf targets for exoplanet searches, in particular those using high-precision radial velocity measurements.
2588. Spectroscopy of CaII-H line at solar limb
ID:
ivo://CDS.VizieR/J/A+A/531/A173
Title:
Spectroscopy of CaII-H line at solar limb
Short Name:
J/A+A/531/A173
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present constraints on the thermodynamical structure of the chromosphere from ground-based observations of the CaII H line profile near and off the solar limb.
2589. Spectroscopy of candidate members in Taurus
ID:
ivo://CDS.VizieR/J/AJ/153/46
Title:
Spectroscopy of candidate members in Taurus
Short Name:
J/AJ/153/46
Date:
21 Oct 2021
Publisher:
CDS
Description:
Previous studies have found that ~1deg^2^ fields surrounding the stellar aggregates in the Taurus star-forming region exhibit a surplus of solar-mass stars relative to denser clusters like IC 348 and the Orion Nebula Cluster. To test whether this difference reflects mass segregation in Taurus or a variation in the initial mass function, we have performed a survey for members of Taurus across a large field (~40deg^2^) that was imaged by the Sloan Digital Sky Survey (SDSS). We obtained optical and near-infrared spectra of candidate members identified with those images and the Two Micron All Sky Survey, as well as miscellaneous candidates that were selected with several other diagnostics of membership. We have classified 22 of the candidates as new members of Taurus, which includes one of the coolest known members (M9.75). Our updated census of members within the SDSS field shows a surplus of solar-mass stars relative to clusters, although it is less pronounced than in the smaller fields toward the stellar aggregates that were surveyed for previously measured mass functions in Taurus. In addition to spectra of our new members, we include in our study near-IR spectra of roughly half of the known members of Taurus, which are used to refine their spectral types and extinctions. We also present an updated set of near-IR standard spectra for classifying young stars and brown dwarfs at M and L types.
2590. Spectroscopy of CD_3_OH
ID:
ivo://CDS.VizieR/J/A+A/658/A127
Title:
Spectroscopy of CD_3_OH
Short Name:
J/A+A/658/A127
Date:
20 Mar 2022 08:37:11
Publisher:
CDS
Description:
Solar-type protostars have been shown to harbor highly deuterated complex organics as for example witnessed by the high relative abundances of doubly and triply deuterated isotopologs. While this degree of deuteration may provide important clues to the formation of these species, spectroscopic information on multiply deuterated isotopologs is often insufficient. In particular, searches for triply deuterated methanol, CD_3_OH, are hampered to a large extent by the lack of intensity information from a spectroscopic model. The aim of the present study is to develop a spectroscopic model of CD_3_OH in low-lying torsional states sufficiently accurate to facilitate further searches for CD_3_OH in space. We have performed a new measurement campaign for CD_3_OH involving three spectroscopic laboratories which covers the 34GHz-1.1THz and the 20-900cm^-1^ ranges. The analysis was perfomed using the rho-axis-method torsion- rotation Hamiltonian model. We determined a model that describes the ground and first excited torsional states of CD_3_OH up to quantum numbers J<=55 and K<=23, and derived a line list for radio-astronomical observations. The resulting line list is accurate up to at least 1.1THz and should be sufficient for all types of radio-astronomical searches for this methanol isotopolog. This line list was used to search for CD_3_OH in data from the Protostellar Interferometric Line Survey of IRAS 16293-2422 using the Atacama Large Millimeter/submillimeter Array. CD_3_OH is securely detected in the data with a large number of clearly separated and well-reproduced lines. We detected not only lines belonging to the ground torsional state, but also several belonging to the first excited torsional state. The derived column density of CD_3_OH and abundance relative to non-deuterated isotopolog confirm the significant enhancement of this multiply deuterated variant. This is in line with other observations of multiply deuterated complex organic molecules and may serve as an important constraint on models for their formation.

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