- ID:
- ivo://CDS.VizieR/J/A+A/649/A167
- Title:
- Hubble spectroscopy of LB-1 (LS V +22 25)
- Short Name:
- J/A+A/649/A167
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- LB-1 has variously been proposed as either an X-ray dim B-type star plus black hole (B+BH) binary, or a Be star plus an inflated stripped star (Be+Bstr) binary. The Space Telescope Imaging Spectrograph (STIS) on board HST was used to obtain a flux-calibrated spectrum that is compared with non-LTE spectral energy distributions (SED) and line profiles for the proposed models. The Hubble data, together with the Gaia EDR3 parallax, provide tight constraints on the properties and stellar luminosities of the system. In the case of the Be+Bstr model we adopt the published flux ratio for the Be and Bstr stars, re-determine the Teff of the Bstr using the silicon ionization balance, and infer Teff for the Be star from the fit to the SED. We derive stellar parameters consistent with previous results, but with greater precision enabled by the Hubble SED. While the Be+Bstr model is a better fit to the HeI lines and cores of the Balmer lines in the optical, the B+BH model provides a better fit to the SiIV resonance lines in the UV. The analysis also implies that the Bstr star has roughly twice solar silicon abundance, which is difficult to reconcile with a stripped star origin. The Be star on the other hand has a rather low luminosity, and a spectroscopic mass inconsistent with its possible dynamical mass. The fit to the UV can be significantly improved by reducing the Teff and radius of the Be star, though at the expense of leading to a different mass ratio. In the B+BH model, the single B-type spectrum is a good match to the UV spectrum. Adopting a mass ratio of 5.1+/-0.1 (Liu et al., 2020ApJ...900...42L) implies a BH mass of 21^+9^_-8_ solar masses.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/297/617
- Title:
- Hydra/Antlia extension redshifts
- Short Name:
- J/A+A/297/617
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopic observations have been carried out for galaxies in the Milky Way with the 1.9m telescope of the South African Astronomical Observatory (SAAO). The galaxies were selected from a deep optical galaxy search covering 266deg<~l<~296deg, |b|<~10deg (Kraan-Korteweg 1994). This is in the extension of the Hydra and Antlia clusters and in the approximate direction of the dipole anisotropy in the Cosmic Microwave Background radiation.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A2
- Title:
- Hydrogen in diffuse molecular clouds
- Short Name:
- J/A+A/600/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent sub-millimeter and far-infrared wavelength observations of absorption in the rotational ground state lines of various simple molecules against distant Galactic continuum sources have opened the possibility to study the chemistry of diffuse molecular clouds Milky Way-wide. In order to calculate abundances the column densities of molecular and atomic hydrogen, HI, must be known. We aim at determining the atomic hydrogen column densities for diffuse clouds located on the sight lines toward a sample of prominent high mass star forming regions that were intensely studied with the HIFI instrument onboard Herschel. Based on Jansky Very Large Array data, we employ the 21-cm HI absorption-line technique to construct profiles of the HI opacity versus radial velocity toward our target sources. These profiles are combined with lower resolution archival data of extended HI emission to calculate the HI column densities of the individual clouds along the sight lines. We employ Bayesian inference to estimate the uncertainties of the derived quantities. Our study delivers reliable estimates of the atomic hydrogen column density for a large number of diffuse molecular clouds at various Galactocentric distances. Together with column densities of molecular hydrogen derived from its surrogates observed with HIFI, the measurements can be used to characterize the clouds and, e.g., investigate the dependence of their chemistry on the molecular fraction.
- ID:
- ivo://CDS.VizieR/J/MNRAS/448/2332
- Title:
- Hydrogen Lyman and Balmer line profiles
- Short Name:
- J/MNRAS/448/2332
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new calculations of unified line profiles for hydrogen perturbed by collisions with protons. We report on new calculations of the potential energies and dipole moments which allow the evaluation of profiles for the lines of the Lyman series up to Lyman {delta} and the Balmer series up to Balmer 10. Unified calculations only existed for the lines Lyman {alpha} to Lyman {gamma} and Balmer {alpha} including the H_2_^+^ quasi-molecule. These data are available as online material accompanying this paper and should be included in atmosphere models, in place of the Stark effect of protons, since the quasi-molecular contributions cause not only satellites, but large asymmetries that are unaccounted for in models that assume that Stark broadening of electrons and that of protons are equal.
- ID:
- ivo://CDS.VizieR/J/other/NatAs/2.778
- Title:
- Hyperfine rotational transitions of 26Al19F
- Short Name:
- J/other/NatAs/2.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Decades ago, {gamma}-ray observatories identified diffuse Galactic emission at 1.809MeV originating from {beta}^+^ decays of an isotope of aluminium, ^26^Al, that has a mean lifetime of 1.04 million years. Objects responsible for the production of this radioactive isotope have never been directly identified owing to insufficient angular resolutions and sensitivities of the {gamma}-ray observatories. Here, we report observations of millimetre-wave rotational lines of the isotopologue of aluminium monofluoride that contains the radioactive isotope (^26^AlF). The emission is observed towards CK Vul, which is thought to be a remnant of a stellar merger. Our constraints on the production of ^26^Al, combined with the estimates on the merger rate, make it unlikely that objects similar to CK Vul are major producers of Galactic ^26^Al. However, the observation may be a stepping stone for unambiguous identification of other Galactic sources of ^26^Al. Moreover, a high content of ^26^Al in the remnant indicates that, before the merger, the CK Vul system contained at least one solar-mass star that evolved to the red giant branch.
1126. IC 4665
- ID:
- ivo://CDS.VizieR/J/AJ/105/1441
- Title:
- IC 4665
- Short Name:
- J/AJ/105/1441
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a combined astrometric, photometric, and spectroscopic program to identify members of the open cluster IC 4665 are presented. Numerous new proper motion/photometric candidate members and at least 23 M dwarfs with H-alpha emission have been identified. A reanalysis of IC 4665's age using different methods yields conflicting results ranging from approx. 3x10^7^ yr to the age of the Pleiades. This study provides a list of candidate cluster members in the intermediate and low-mass regime of this cluster. Future spectroscopic observations of these candidates should eventually identify true cluster members. The results of new echelle observations of some candidates and the photometric monitoring of one apparent cluster member are given in an appendix.
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/1744
- Title:
- Identification of nitride dust
- Short Name:
- J/MNRAS/371/1744
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Nitride dust is predicted to form in small amounts around carbon stars, but the most likely candidate species such as aluminium nitride (AlN) have not yet been detected. Recently, {alpha}-Si_3_N_4_ was inferred to be the main carrier of the 8.5-12.5um absorption band(s) of an extreme carbon star (AFGL 5625), based on comparison with laboratory KBr dispersion spectra. However, this absorption band has also been attributed to silicon carbide (SiC) and C_3_. To investigate whether or not nitride dust has truly been detected and if it is present in other extreme carbon stars, we (i) gathered new laboratory infrared (IR) absorbance spectra from a suite of nitride compounds, including Si_3_N_4_, using the thin film technique which provides correct relative intensities of weak and strong peaks, and (ii) compared these data to Infrared Space Observatory Short Wavelength Spectrometer (ISO SWS) spectra of seven different extreme carbon stars which also show broad absorption features around ~11m.
- ID:
- ivo://CDS.VizieR/J/ApJS/254/26
- Title:
- Identifying 3FHL. V. CTIO-COSMOS spectra
- Short Name:
- J/ApJS/254/26
- Date:
- 19 Jan 2022 00:35:09
- Publisher:
- CDS
- Description:
- As a follow-up to the optical spectroscopic campaign aimed at achieving completeness in the Third Catalog of Hard Fermi-LAT Sources (3FHL), we present here the results of a sample of 28 blazars of an uncertain type observed using the 4m telescope at Cerro Tololo Inter-American Observatory in Chile. Out of these 28 sources, we find that 25 are BL Lacertae objects (BL Lacs) and 3 are flat-spectrum radio quasars (FSRQs). We measure redshifts or lower limits for 16 of these blazars, and it is observed that the 12 remaining blazars have featureless optical spectra. These results are part of a more extended optical spectroscopy follow-up campaign for 3FHL blazars, where, until now, 51 blazars of an uncertain type have been classified into BL Lac and FSRQ categories. Furthermore, this campaign has resulted in redshift measurements and lower limits for 15 of these sources. Our results contribute toward attaining a complete sample of blazars above 10 GeV, which then will be crucial in extending our knowledge on blazar emission mechanisms and the extragalactic background light.
- ID:
- ivo://CDS.VizieR/J/A+A/581/A65
- Title:
- IFU observations of NGC 4191
- Short Name:
- J/A+A/581/A65
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We here distinguish two counter-rotating stellar components in NGC 4191 and characterize their physical properties such as kinematics, size, morphology, age, metallicity. We obtained integral field spectroscopic observations with VIRUS-W and used a spectroscopic decomposition technique to separate the contribution of two stellar components to the observed galaxy spectrum. We also performed a photometric decomposition, modeling the galaxy with a Sersic bulge and two exponential disks of different scale length, with the aim of associating these structural components with the kinematic components. We then measured the equivalent width of the absorption line indices on the best-fit models that represent the kinematic components and compared our measurements to the predictions of stellar population models that also account for the variable abundance ratio of {alpha} elements.
- ID:
- ivo://CDS.VizieR/J/ApJS/164/1
- Title:
- IGM absorbers toward HE 0226-4110
- Short Name:
- J/ApJS/164/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the FUSE (Far Ultraviolet Spectroscopic Explorer) and HST (Hubble Space Telescope) STIS E140M spectra of HE 0226-4110 (z=0.495). We detect 56 Lyman absorbers and five OVI absorbers.
