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1261. Optical Spectroscopy of WIYN Hydra FLS sources
ID:
ivo://CDS.VizieR/J/ApJ/663/218
Title:
Optical Spectroscopy of WIYN Hydra FLS sources
Short Name:
J/ApJ/663/218
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an optical spectroscopic survey of 24um and 1.4GHz sources, detected in the Spitzer extragalactic First Look Survey (FLS), using the multifiber spectrograph, Hydra, on the WIYN telescope. We have obtained spectra for 772 sources, with flux densities above 0.15mJy in the infrared and 0.09mJy in the radio. The redshifts measured in this survey are mostly in the range 0<z<0.4, with a distribution peaking at z~0.2.
1262. Optical spectroscopy of young {alpha}-rich stars
ID:
ivo://CDS.VizieR/J/ApJ/860/49
Title:
Optical spectroscopy of young {alpha}-rich stars
Short Name:
J/ApJ/860/49
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report chemical abundances of 14 young {alpha}-rich stars including neutron-capture elements based on high-quality optical spectra from HIRES/Keck I and differential line-by-line analysis. From a comparison of the abundance patterns of young {alpha}-rich stars to those of nearby bright red giants with a similar metallicity range (-0.7<[Fe/H]{<}-0.2), we confirm their high {alpha}-element abundances reported by previous studies based on near-infrared spectroscopy. We reveal for the first time low abundances of s-process elements and high abundances of r-process elements. All the abundances are consistent with those seen in the typical {alpha}-rich population of the Galactic disk, and no abundance anomalies are found except for Li-enhancement in one object previously reported and mild enhancement of Na in two stars. In particular, the lack of s-process enhancement excludes the hypothesis that mass transfer from asymptotic giant branch stars plays an important role in the formation of young {alpha}-rich stars. The high frequency of radial velocity variation (more than 50%) is also confirmed. We argue that mass transfer from low-mass red giants is the likely dominant formation mechanism for young {alpha}-rich stars.
1263. Optical spectroscopy toward Orion B fields
ID:
ivo://CDS.VizieR/J/ApJ/844/138
Title:
Optical spectroscopy toward Orion B fields
Short Name:
J/ApJ/844/138
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from high-resolution optical spectra toward 66 young stars in the Orion B molecular cloud to study their kinematics and other properties. Observations of the H{alpha} and Li I 6707{AA} lines are used to check membership and accretion properties. While the stellar radial velocities of NGC 2068 and L1622 are in good agreement with that of the molecular gas, many of the stars in NGC 2024 show a considerable offset. This could be a signature of either the expansion of the cluster, the high degree of the ejection of the stars from the cluster through dynamical interaction, or the acceleration of the gas due to stellar feedback.
1264. Optimizing exoplanet transit searches
ID:
ivo://CDS.VizieR/J/A+A/537/A147
Title:
Optimizing exoplanet transit searches
Short Name:
J/A+A/537/A147
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate a method to increase the efficiency of a targeted exoplanet search with the transit technique by preselecting a subset of candidates from large catalogs of stars. Assuming spin-orbit alignment, this can be achieved by considering stars that have a higher probability to be oriented nearly equator-on (inclination close to 90{deg}).
1265. Opt. & NIR spectral atlas of 16 2MASS NIR-red AGNs
ID:
ivo://CDS.VizieR/J/ApJS/238/37
Title:
Opt. & NIR spectral atlas of 16 2MASS NIR-red AGNs
Short Name:
J/ApJS/238/37
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present medium-resolution spectra (R~2000-4000) at 0.4-1.0{mu}m and 0.7-2.5{mu}m of 16 active galactic nuclei (AGNs) selected with red color in the near-infrared (NIR) of J-K>2.0mag at z~0.3. We fit the H{beta}, H{alpha}, P{beta}, and P{alpha} lines from these spectra to obtain their luminosities and line widths. We derive the E(B-V) color excess values of the NIR-red AGNs using two methods, one based on the line-luminosity ratios and another based on the continuum slopes. The two E(B-V) values agree with each other at rms dispersion ~0.249. About half of the NIR-red AGNs have g'-K<5 magnitude, and we find that these NIR-red, but blue in optical-NIR AGNs, have E(B-V)~0, suggesting that a significant fraction of the NIR color-selected red AGNs are unobscured or only mildly obscured. After correcting for the dust extinction, we estimate the black hole (BH) masses and the bolometric luminosities of the NIR-red AGNs using the Paschen lines to calculate their Eddington ratios ({lambda}Edd). The median Eddington ratios of nine NIR-red AGNs (log({lambda}_Edd_~-0.654+/-0.176) are only mildly higher than those of unobscured type 1 AGNs (log({lambda}_Edd_~-0.961+/-0.008). Moreover, we find that the MBH-{sigma}* relation for three NIR-red AGNs is consistent with that of unobscured type 1 AGNs at similar redshift. These results suggest that the NIR-red color selection alone is not effective at picking up dusty, intermediate-stage AGNs.
1266. Opt. spectroscopy of redback ms pulsar binaries
ID:
ivo://CDS.VizieR/J/ApJ/872/42
Title:
Opt. spectroscopy of redback ms pulsar binaries
Short Name:
J/ApJ/872/42
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first optical spectroscopy of five confirmed (or strong candidate) redback millisecond pulsar binaries, obtaining complete radial velocity curves for each companion star. The properties of these millisecond pulsar binaries with low-mass, hydrogen-rich companions are discussed in the context of the 14 confirmed and 10 candidate field redbacks. We find that the neutron stars in redbacks have a median mass of 1.78+/-0.09M_{sun}_ with a dispersion of {sigma}=0.21+/-0.09. Neutron stars with masses in excess of 2M_{sun}_ are consistent with, but not firmly demanded by, current observations. Redback companions have median masses of 0.36+/-0.04M_{sun}_ with a scatter of {sigma}=0.15+/-0.04M_{sun}_, and a tail possibly extending up to 0.7-0.9M_{sun}_. Candidate redbacks tend to have higher companion masses than confirmed redbacks, suggesting a possible selection bias against the detection of radio pulsations in these more massive candidate systems. The distribution of companion masses between redbacks and the less massive black widows continues to be strongly bimodal, which is an important constraint on evolutionary models for these systems. Among redbacks, the median efficiency of converting the pulsar spin-down energy to {gamma}-ray luminosity is ~10%.
1267. Orbits of spectro. binaries with CHARA Array. III.
ID:
ivo://CDS.VizieR/J/AJ/160/58
Title:
Orbits of spectro. binaries with CHARA Array. III.
Short Name:
J/AJ/160/58
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the visual orbits of two long-period spectroscopic binary stars, HD8374 and HD24546, using interferometric observations acquired with the Center for High Angular Resolution Astronomy (CHARA) Array and the Palomar Testbed Interferometer. We also obtained new radial velocities from echelle spectra using the APO 3.5m and Fairborn 2.0 telescopes. By combining the visual and spectroscopic observations, we solve for the full, three-dimensional orbits and determine the stellar masses and distances to within 3% uncertainty. We then estimate the effective temperature and radius of each component star through Doppler tomography and spectral energy distribution analyses, in order to compare the observed stellar parameters to the predictions of stellar evolution models. For HD8374, we find masses of M1=1.636{+/-}0.050M{sun} and M2=1.587{+/-}0.049M{sun}, radii of R1=1.84{+/-}0.05R{sun} and R2=1.66{+/-}0.12R{sun}, temperatures of Teff_1_=7280{+/-}110K and Teff-2-=7280{+/-}120K, and an estimated age of 1.0Gyr. For HD24546, we find masses of M1=1.434{+/-}0.014M{sun} and M2=1.409{+/-}0.014M{sun}, radii of R_1_=1.67{+/-}0.06R{sun} and R_2_=1.60{+/-}0.10R{sun}, temperatures of Teff_1_=6790{+/-}120K and Teff_2_=6770{+/-}90K, and an estimated age of 1.4Gyr. HD24546 is therefore too old to be a member of the Hyades cluster, despite its physical proximity to the group.
1268. Orbits of subsystems in six multiple stars. III.
ID:
ivo://CDS.VizieR/J/AJ/156/48
Title:
Orbits of subsystems in six multiple stars. III.
Short Name:
J/AJ/156/48
Date:
21 Oct 2021
Publisher:
CDS
Description:
Spectroscopic orbits are computed for inner pairs in six nearby hierarchical multiple systems (HIP 35733, 95106/95110, 105441, 105585/105569, 105947, and 109951). Radial velocities and resolved measurements, when available, are used to derive combined sets of outer orbital elements for three systems. Each multiple system is discussed individually. Additionally, HIP 115087 is a simple 7.9-day single-lined binary. Although the minimum companion mass is substellar (in the brown dwarf desert regime), it appears to be a 0.2 solar-mass star in a low-inclination orbit.
1269. Origins of post-starburst galaxies at z<0.05
ID:
ivo://CDS.VizieR/J/MNRAS/477/1708
Title:
Origins of post-starburst galaxies at z<0.05
Short Name:
J/MNRAS/477/1708
Date:
21 Oct 2021
Publisher:
CDS
Description:
Post-starburst galaxies can be identified via the presence of prominent Hydrogen Balmer absorption lines in their spectra. We present a comprehensive study of the origin of strong Balmer lines in a volume-limited sample of 189 galaxies with 0.01<z<0.05, log(M*/M_{sun}_)>9.5 and projected axial ratio b/a>0.32. We explore their structural properties, environments, emission lines, and star formation histories, and compare them to control samples of star-forming and quiescent galaxies, and simulated galaxy mergers. Excluding contaminants, in which the strong Balmer lines are most likely caused by dust-star geometry, we find evidence for three different pathways through the post-starburst phase, with most events occurring in intermediate-density environments: (1) a significant disruptive event, such as a gas-rich major merger, causing a starburst and growth of a spheroidal component, followed by quenching of the star formation (70 per cent of post-starburst galaxies at 9.5<log(M*/M_{sun}_)<10.5 and 60 per cent at log(M*/M_{sun}_)>10.5); (2) at 9.5<log(M*/M_{sun}_)<10.5, stochastic star formation in blue-sequence galaxies, causing a weak burst and subsequent return to the blue sequence (30 per cent); (3) at log(M*/M_{sun}_)>10.5, cyclic evolution of quiescent galaxies which gradually move towards the high-mass end of the red sequence through weak starbursts, possibly as a result of a merger with a smaller gas-rich companion (40 per cent). Our analysis suggests that active galactic nuclei (AGNs) are 'on' for 50 per cent of the duration of the post-starburst phase, meaning that traditional samples of post-starburst galaxies with strict emission-line cuts will be at least 50 per cent incomplete due to the exclusion of narrow-line AGNs.
1270. Ori OB1 CP stars magnetic fields. III.
ID:
ivo://CDS.VizieR/J/other/AstBu/74.55
Title:
Ori OB1 CP stars magnetic fields. III.
Short Name:
J/other/AstBu/74
Date:
21 Oct 2021
Publisher:
CDS
Description:
The paper presents results of magnetic field measurements of 10 chemically peculiar stars of subgroup (a) in the Orion OB1 association: HD33917, HD34859, HD35008, HD35039, HD35177, HD35575, HD35730, HD36549, HD38912, and HD294046. Observations were carried out with the circular polarization analyzer at the Main Stellar Spectrograph at the 6-m SAO RAS telescope.Magnetic fields were detected in four stars, six stars have magnetic fields below the detection threshold.