- ID:
- ivo://CDS.VizieR/J/ApJS/119/83
- Title:
- IUE sample of binaries with hot component
- Short Name:
- J/ApJS/119/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained or retrieved IUE spectra for over 100 middle- and late-type giant and supergiant stars whose spectra indicate the presence of a hot component earlier than type F2. The hot companions are classified accurately by temperature class from their far-UV spectra. The interstellar extinction of each system and the relative luminosities of the components are derived from analysis of the UV and optical fluxes, using a grid of UV intrinsic colors for hot dwarfs. We find that there is fair agreement in general between current UV spectral classification and ground-based hot component types, in spite of the difficulties of assigning the latter. There are a few cases in which the cool component optical classifications disagree considerably with the temperature classes inferred from our analysis of UV and optical photometry. The extinction parameter agrees moderately well with other determinations of B-V color excess. Many systems are worthy of further study especially to establish their spectroscopic orbits. Further work is planned to estimate luminosities of the cool components from the data herein; in many cases, these luminosities' accuracies should be comparable to or exceed those of the Hipparcos parallaxes.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/331/633
- Title:
- IUE spectra of lambda Boo stars
- Short Name:
- J/A+A/331/633
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An analysis of the stars included in the catalogue of {lambda} Bootis stars by Paunzen et al. (1997, Cat. <J/A+AS/123/93>) and which also have IUE observations is presented here. Population I A-F type stars as well as field horizontal branch stars were also included in the analysis. Using line-ratios of carbon to heavier elements (Al and Ni) allows us to establish unambiguous membership criteria for the {lambda} Bootis group.
1253. IUE spectra of WR stars
- ID:
- ivo://CDS.VizieR/J/A+AS/108/669
- Title:
- IUE spectra of WR stars
- Short Name:
- J/A+AS/108/669
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/A+A/417/515
- Title:
- I Zw 1 unusual emission line spectrum
- Short Name:
- J/A+A/417/515
- Date:
- 08 Mar 2022
- Publisher:
- CDS
- Description:
- Most Seyfert 1s show strong FeII lines in their spectrum having the velocity and width of the broad emission lines. To remove the FeII contribution in these objects, an accurate template is necessary. We used very high signal-to-noise, medium resolution archive optical spectra of I Zw 1 to build such a template. I Zw 1 is a bright narrow-line Seyfert 1 galaxy. As such it is well suited for a detailed analysis of its emission line spectrum. Furthermore it is known to have a very peculiar spectrum with, in addition to the usual broad and narrow line regions, two emission regions emitting broad and blue shifted [OIII] lines making it a peculiarly interesting object. While analysing the spectra, we found that the narrow-line region is, unlike the NLR of most Seyfert 1 galaxies, a very low excitation region dominated by both permitted and forbidden FeII lines. It is very similar to the emission spectrum of a blob in {eta} Carinae which is a low temperature (T~6500K), relatively high density (N_e_=10^6^cm^-3) cloud. The FeII lines in this cloud are mainly due to pumping via the stellar continuum radiation field (Verner et al., 2002ApJ...581.1154V). We did not succeed in modelling the spectrum of the broad-line region, and we suggest that a non radiative heating mechanism increases the temperature in the excited HI region, thus providing the necessary additional excitation of the FeII lines. For the low-excitation narrow-line region, we are able to settle boundaries to the physical conditions accounting for the forbidden and permitted FeII lines (10^6^<N_e_<10^7^cm^-3^; 10^-6^<U<10^-5^).
- ID:
- ivo://CDS.VizieR/J/A+A/648/A38
- Title:
- J1717-3342 and J1744-3116 CO spectra
- Short Name:
- J/A+A/648/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The chemistry of the diffuse interstellar medium is driven by the combined influences of cosmic rays, ultraviolet (UV) radiation, and turbulence. Previously detected at the outer edges of photodissociation regions (PDRs) and formed from the reaction of C^+^ and OH, CO^+^ is the main chemical precursor of HCO^+^ and CO in a thermal, cosmic-ray, and UV-driven chemistry. Our aim was to test whether the thermal cosmic-ray and UV-driven chemistry is producing CO in diffuse interstellar molecular gas through the intermediate formation of CO^+^ We searched for CO^+^ absorption with the Atacama Large Millimeter Array (ALMA) toward two quasars with known Galactic foreground absorption from diffuse interstellar gas, J1717-3342 and J1744-3116, targeting the two strongest hyperfine components of the J=2-1 transition near 236GHz. We could not detect CO^+^ but obtained sensitive upper limits toward both targets. The derived upper limits on the CO^+^ column densities represent about 4% of the HCO^+^ column densities. The corresponding upper limit on the CO^+^ abundance relative to H_2_ is <1.2x10^-10^. The non-detection of CO^+^ confirms that HCO^+^ is mainly produced in the reaction between oxygen and carbon hydrides, CH2^+^ or CH3^+^, induced by suprathermal processes, while CO^+^ and HOC^+^ result from reactions of C^+^ with OH and H_2_O. The densities r equired to form CO molecules at low extinction are consistent with this scheme.
- ID:
- ivo://CDS.VizieR/J/A+A/611/A22
- Title:
- Jekyll & Hyde galaxies ALMA cube & spectrum
- Short Name:
- J/A+A/611/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained ALMA spectroscopy and deep imaging to investigate the origin of the unexpected sub-millimeter emission toward the most distant quiescent galaxy known to date, ZF-COSMOS-20115 at z=3.717. We show here that this sub-millimeter emission is produced by another massive (M*~10^11^M_{sun}_), compact (r_1/2_=0.67+/-0.14kpc) and extremely obscured galaxy (A_V_~3.5), located only 0.4300 (3.1kpc) away from the quiescent galaxy. We dub the quiescent and dusty galaxies Jekyll and Hyde, respectively. No dust emission is detected at the location of the quiescent galaxy, implying SFR<13M_{sun}_/yr which is the most stringent upper limit ever obtained for a quiescent galaxy at these redshifts. The two sources are spectroscopically confirmed to lie at the same redshift thanks to the detection of [CII]158 in Hyde (z=3.709), which provides one the few robust redshifts for a highly-obscured "H-dropout" galax (H-[4.5]=5.1+/-0.8). The [CII] line shows a clear rotating-disk velocity profile which is blueshifted compared to the Balmer lines of Jekyll by 549+/-60km/s, demonstrating that it is produced by another galaxy. Careful de-blending of the Spitzer imaging confirms the existence of this new massive galaxy, and its non-detection in the Hubble images requires extremely red colors and strong attenuation by dust. Full modeling of the UV-to-far-IR emission of both galaxies shows that Jekyll has fully quenched at least 200Myr prior to observation and still presents a challenge for models, while Hyde only harbors moderate star-formation with SFR<~120M_{sun}/yr, and is located at least a factor 1.4 below the z~4 main sequence. Hyde could also have stopped forming stars less than 200Myr before being observed; this interpretation is also suggested by its compactness comparable to that of z~4 quiescent galaxies and its low [CII]/FIR ratio, but significant on-going star-formation cannot be ruled out. Lastly, we find that despite its moderate SFR, Hyde hosts a dense reservoir of gas comparable to that of the most extreme starbursts. This suggests that whatever mechanism has stopped or reduced its star-formation must have done so without expelling the gas outside of the galaxy. Because of their surprisingly similar mass, compactness, environment and star-formation history, we argue that Jekyll and Hyde can be seen as two stages of the same quenching process, and provide a unique laboratory to study this poorly understood phenomenon.
- ID:
- ivo://CDS.VizieR/J/AJ/127/3553
- Title:
- JHK photometry and spectroscopy for L and T dwarfs
- Short Name:
- J/AJ/127/3553
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new JHK photometry on the MKO-NIR (Mauna Kea Observatories Near-Infrared) system and JHK spectroscopy for a large sample of L and T dwarfs. Photometry has been obtained for 71 dwarfs, and spectroscopy for 56. The sample comprises newly identified very red objects from the Sloan Digital Sky Survey (SDSS, http://www.sdss.org/) and known dwarfs from the SDSS and the Two Micron All Sky Survey (2MASS, Cat. <II/246>). Spectral classification has been carried out using four previously defined indices from Geballe et al. (2002ApJ...564..466G) that measure the strengths of the near infrared water and methane bands.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A71
- Title:
- J,H,K spectroscopy of HD 106906 b
- Short Name:
- J/A+A/608/A71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Directly imaged planets are ideal candidates for spectroscopic characterization of their atmospheres. The angular separations that are typically close to their host stars, however, reduce the achievable contrast and thus signal-to-noise ratios (S/N). We spectroscopically characterize the atmosphere of HD 106906 b, which is a young low-mass companion near the deuterium burning limit. The wide separation from its host star of 7.1" makes it an ideal candidate for high S/N and high-resolution spectroscopy. We aim to derive new constraints on the spectral type, effective temperature, and luminosity of HD 106906 b and also to provide a high S/N template spectrum for future characterization of extrasolar planets. We obtained 1.1-2.5um integral field spectroscopy with the VLT/SINFONI instrument with a spectral resolution of R~=2000-4000. New estimates of the parameters of HD 106906 b are derived by analyzing spectral features, comparing the extracted spectra to spectral catalogs of other low-mass objects, and fitting with theoretical isochrones.
- ID:
- ivo://CDS.VizieR/J/AJ/160/12
- Title:
- J, Ks, NUV emission of 133 red giant stars
- Short Name:
- J/AJ/160/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Main-sequence stars exhibit a clear rotation-activity relationship, in which rapidly rotating stars drive strong chromospheric/coronal ultraviolet and X-ray emission. While the vast majority of red giant stars are inactive, a few percent exhibit strong ultraviolet emission. Here we use a sample of 133 red giant stars observed by Sloan Digital Sky Survey APOGEE and Galaxy Evolution Explorer to demonstrate an empirical relationship between near-UV (NUV) excess and rotational velocity (vsini). Beyond this simple relationship, we find that NUV excess also correlates with rotation period and with Rossby number in a manner that shares broadly similar trends to those found in M dwarfs, including activity saturation among rapid rotators. Our data also suggest that the most extremely rapidly rotating giants may exhibit so-called supersaturation, which could be caused by centrifugal stripping of these stars rotating at a high fraction of breakup speed. As an example application of our empirical rotation-activity relation, we demonstrate that the NUV emission observed from a recently reported system comprising a red giant with a black hole companion is fully consistent with arising from the rapidly rotating red giant in that system. Most fundamentally, our findings suggest a common origin of chromospheric activity in rotation and convection for cool stars from main sequence to red giant stages of evolution.
1260. Jurassic structure
- ID:
- ivo://CDS.VizieR/J/A+A/644/A83
- Title:
- Jurassic structure
- Short Name:
- J/A+A/644/A83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Detailed elemental-abundance patterns of giant stars in the Galactic halo measured by the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2) have revealed the existence of a unique and significant stellar subpopulation of silicon-enhanced ([Si/Fe]>+0.5) metal-poor stars, spanning a wide range of metallicities (-1.5<[Fe/H]<-0.8). Stars with over-abundances in [Si/Fe] are of great interest because these have very strong silicon (^28^Si) spectral features for stars of their metallicity and evolutionary stage, offering clues about rare nucleosynthetic pathways in globular clusters (GCs). Si-rich field stars have been conjectured to have been evaporated from GCs, however, the origin of their abundances remains unclear, and several scenarios have been offered to explain the anomalous abundance ratios. These include the hypothesis that some of them were born from a cloud of gas previously polluted by a progenitor that underwent a specific and peculiar nucleosynthesis event or, alternatively, that they were due to mass transfer from a previous evolved companion. However, those scenarios do not simultaneously explain the wide gamut of chemical species that are found in Si-rich stars. Instead, we show that the present inventory of such unusual stars, as well as their relation to known halo substructures (including the in situ halo, Gaia-Enceladus, the Helmi Stream(s), and Sequoia, among others), is still incomplete. We report the chemical abundances of the iron-peak (Fe), the light- (C and N), the alpha- (O and Mg), the odd-Z (Na and Al), and the s-process (Ce and Nd) elements of 55 newly identified Si-rich field stars (among more than ~600000 APOGEE-2 targets), which exhibit over-abundances of [Si/Fe] as extreme as those observed in some Galactic GCs, and they are relatively well distinguished from other stars in the [Si/Fe]-[Fe/H] plane. This new census confirms the presence of a statistically significant and chemically-anomalous structure in the inner halo: Jurassic. The chemo-dynamical properties of the Jurassic structure is consistent with it being the tidally disrupted remains of GCs, which are easily distinguished by an over-abundance of [Si/Fe] among Milky Way (MW) populations or satellites.
