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2491. Spectra of two mid-L subdwarfs
ID:
ivo://CDS.VizieR/J/A+A/579/A58
Title:
Spectra of two mid-L subdwarfs
Short Name:
J/A+A/579/A58
Date:
21 Oct 2021
Publisher:
CDS
Description:
We obtained low- to intermediate-resolution (R~2500-9000) optical (~560-770nm) spectra of two mid-L subdwarfs, SDSS J125637.13-022452.4 (SDSS1256; sdL3.5) and 2MASS J162620.14+392519.5 (2MASS1626; sdL4). We report the presence of a feature at the nominal position of the lithium absorption doublet at 6707.8{AA} in the spectrum of SDSS1256, with an equivalent width of 66+/-27{AA} at 2.4{sigma}, which we identify as arising from a CaH molecular transition based on atmosphere models. We do not see any feature at the position of the lithium feature in the spectrum of 2MASS1626. The existence of overlapping molecular absorption sets a confusion detection limit of [Li/H]=-3 for equivalently-typed L subdwarfs. We provided improved radial velocity measurements of -126+/-10km/s and -239+/-12km/s for SDSS1256 and 2MASS1626, respectively, as well as revised Galactic orbits. We implemented adjusting factors for the CaH molecule in combination with the NextGen atmosphere models to fit the optical spectrum of SDSS1256 in the 6200-7300{AA} range. We also estimate the expected Li abundance from interstellar accretion ([Li/H]=-5), place limits on circumstellar accretion (10^9^g/yr), and discuss the prospects of Li searches in cooler L and T subdwarfs.
2492. Spectra of 5 Type II supernovae
ID:
ivo://CDS.VizieR/J/A+A/555/A142
Title:
Spectra of 5 Type II supernovae
Short Name:
J/A+A/555/A142
Date:
21 Oct 2021
Publisher:
CDS
Description:
Core-collapse Supernovae (CC-SNe) descend from progenitors more massive than about 8M_{sun}_. Because of the young age of the progenitors, the ejecta may eventually interact with the circumstellar medium (CSM) via highly energetic processes detectable in the radio, X-ray, ultraviolet (UV) and, sometimes, in the optical domains. In this paper we present ultraviolet, optical and near infrared observations of five type II SNe, namely SNe 2009dd, 2007pk, 2010aj, 1995ad, and 1996W. Together with few other SNe they form a group of moderately luminous type II events. We investigate the photometric similarities and differences among these bright objects. We also attempt to characterise them by analysing the spectral evolutions, in order to find some traces of CSM-ejecta interaction. We collected photometry and spectroscopy with several telescopes in order to construct well-sampled light curves and spectral evolutions from the photospheric to the nebular phases. Both photometry and spectroscopy indicate a degree of heterogeneity in this sample. Modelling the data of SNe 2009dd, 2010aj and 1995ad allows us to constrain the explosion parameters and the properties of the progenitor stars. The light curves have luminous peak magnitudes (-16.95<M_B}_-18.70). The ejected masses of ^56^Ni for three SNe span a wide range of values (2.8x10^-2^M_{sun}<M(^56^Ni)<1.4x10^-1^M_{sun}_), while for a fourth (SN2010aj) we could determine a stringent upper limit (7x10^-3^M_{sun}_). Clues of interaction, such as the presence of high velocity (HV) features of the Balmer lines, are visible in the photospheric spectra of SNe 2009dd and 1996W. For SN2007pk we observe a spectral transition from a type IIn to a standard type II SN. Modelling the observations of SNe 2009dd, 2010aj and 1995ad with radiation hydrodynamics codes, we infer kinetic plus thermal energies of about 0.2-0.5 foe, initial radii of 2-5x10^13^cm and ejected masses of ~5.0-9.5M_{sun}_. These values suggest moderate-mass, super-asymptotic giant branch (SAGB) or red super-giants (RSG) stars as SN precursors, in analogy with other luminous type IIP SNe 2007od and 2009bw.
2493. Spectra of unusual optical transient SCP 06F6
ID:
ivo://CDS.VizieR/J/ApJ/690/1358
Title:
Spectra of unusual optical transient SCP 06F6
Short Name:
J/ApJ/690/1358
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present observations of SCP 06F6, an unusual optical transient discovered during the Hubble Space Telescope Cluster Supernova Survey. The transient brightened over a period of ~100 days, reached a peak magnitude of ~21.0 in both i_775_ and z_850_, and then declined over a similar timescale. There is no host galaxy or progenitor star detected at the location of the transient to a 3{sigma} upper limit of i_775_>=26.4 and z_850_>=26.1, giving a corresponding lower limit on the flux increase of a factor of ~120. Multiple spectra show five broad absorption bands between 4100{AA} and 6500{AA}, and a mostly featureless continuum longward of 6500{AA}. The shape of the light curve is inconsistent with microlensing. The transient's spectrum, in addition to being inconsistent with all known supernova types, does not match any spectrum in the Sloan Digital Sky Survey database. We suggest that the transient may be one of a new class.
2494. Spectra of wide companions to planet-host stars
ID:
ivo://CDS.VizieR/J/A+A/569/A120
Title:
Spectra of wide companions to planet-host stars
Short Name:
J/A+A/569/A120
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a search for wide companions to planet-host stars to improve our knowledge on their multiplicity at wide physical separations. We cross-matched approximately 6200 square degree area of the Southern sky imaged by the Visible Infrared Survey Telescope for Astronomy (VISTA) Hemisphere Survey (VHS) with the Two Micron All Sky Survey (2MASS) to look for wide common proper motion companions to known planet-host stars. We complemented our astrometric search with photometric criteria. We confirmed spectroscopically the co-moving nature of seven sources out of 16 companion candidates and discarded eight, while the remaining one stays as a candidate. Among these new wide companions to planet-host stars, we discovered a T4.5 dwarf companion at 6.3-arcmin (~9000AU) from HIP70849, a K7V star which hosts a 9 Jupiter mass planet with an eccentric orbit. We also report two new stellar M dwarf companions to one G and one metal-rich K star. We infer stellar and substellar binary frequencies for our complete sample of 37 targets of 5.4+/-3.8% and 2.7+/-2.7% (1 sigma confidence level), respectively, for projected physical separations larger than ~60-160AU assuming the range of distances of planet-host stars (24-75pc). These values are comparable to the frequencies of non planet-host stars. We find that the period-eccentricity trend holds with a lack of multiple systems with planets at large eccentricities (e>0.2) for periods less than 40-days. However, the lack of planets more massive than 2.5 Jupiter masses and short periods (<40-days) orbiting single stars is not so obvious due to recent discoveries by ground-based transit surveys and space missions.
2495. Spectra of W49 massives young stars
ID:
ivo://CDS.VizieR/J/A+A/589/A16
Title:
Spectra of W49 massives young stars
Short Name:
J/A+A/589/A16
Date:
21 Oct 2021
Publisher:
CDS
Description:
Massive stars form on different scales ranging from large, dispersed OB associations to compact, dense starburst clusters. The complex structure of regions of massive star formation, and the involved short timescales provide a challenge for our understanding of their birth and early evolution. As one of the most massive and luminous star- forming region in our Galaxy, W49 is the ideal place to study the formation of the most massive stars. By classifying the massive young stars deeply embedded into the molecular cloud of W49, we aim to investigate and trace the star formation history of this region. We analyse near-infrared K-band spectroscopic observations of W49 from LBT/LUCI combined with JHK images obtained with NTT/SOFI and LBT/LUCI. Based on JHK -band photometry and K-band spectroscopy the massive stars are placed in a Hertzsprung Russell diagram. By comparison with evolutionary models, their age and hence the star formation history of W49 can be investigated.
2496. Spectra of young nearby stars
ID:
ivo://CDS.VizieR/J/AJ/133/2524
Title:
Spectra of young nearby stars
Short Name:
J/AJ/133/2524
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present high-dispersion (R~16000) optical (3900-8700{AA}) spectra of 390 stars obtained with the Palomar 60inch telescope. The majority of stars observed are part of the Spitzer Legacy Science Program "The Formation and Evolution of Planetary Systems." Through detailed analysis we determine stellar properties for this sample, including radial and rotational velocities, LiI{lambda}6708 and H{alpha} equivalent widths, the chromospheric activity index R'_HK_, and temperature- and gravity-sensitive line ratios. Several spectroscopic binaries are also identified. From our tabulations, we illustrate basic age- and rotation-related correlations among measured indices. One novel result is that CaII chromospheric emission appears to saturate at vsini values above ~30km/s, similar to the well-established saturation of X-rays that originate in the spatially separate coronal region.
2497. Spectra of young planetary nebulae
ID:
ivo://CDS.VizieR/J/A+A/573/A65
Title:
Spectra of young planetary nebulae
Short Name:
J/A+A/573/A65
Date:
21 Oct 2021
Publisher:
CDS
Description:
The evolution of central stars of planetary nebulae was so far documented in just a few cases. However, spectra collected a few decades ago may provide a good reference for studying the evolution of central stars using the emission line fluxes of their nebulae. We investigated evolutionary changes of the [OIII] 5007{AA} line flux in the spectra of planetary nebulae. We compared nebular fluxes collected during a decade or longer. We used literature data and newly obtained spectra. A grid of Cloudy models was computed using existing evolutionary models, and the models were compared with the observations. An increase of the [OIII] 5007{AA} line flux is frequently observed in young planetary nebulae hosting H-rich central stars. The increasing nebular excitation is the response to the increasing temperature and hardening radiation of the central stars. We did not observe any changes in the nebular fluxes in the planetary nebulae hosting late-type Wolf-Rayet (WR) central stars. This may indicate a slower temperature evolution (which may stem from a different evolutionary status) of late-[WR] stars. In young planetary nebulae with H-rich central stars, the evolution can be followed using optical spectra collected during a decade or longer. The observed evolution of H-rich central stars is consistent with the predictions of the evolutionary models provided in the literature. Late-[WR] stars possibly follow a different evolutionary path.
2498. Spectrocopy of hot stars in galactic halo
ID:
ivo://CDS.VizieR/J/AJ/103/267
Title:
Spectrocopy of hot stars in galactic halo
Short Name:
J/AJ/103/267
Date:
21 Oct 2021
Publisher:
CDS
Description:
The paper presents spectroscopy for 769 hot stars from the HK objective-prism/interference-filter survey of Beers et al. (1985), 193 of which have also available broadband UBV colors. When available, photometric information is used to obtain estimates of the surface temperature for degenerates and for O- and B-type subdwarfs, based on previously derived calibrations. Several extremely hot (T(eff) greater than 50,000 K) He-rich sdO stars are identified. Out of 769 stars in this sample, 551 are clearly identified on the basis of their Balmer line profiles as field horizontal-branch (FHB) or mid-to late-type A stars. The A stars exhibit rotation and line-of-sight dispersion consistent with membership in the galactic thick disk. The FHB stars exhibit kinematic properties which suggest a transition from thick disk to halo.
2499. Spectrographic study of Kiso UV-excess galaxies
ID:
ivo://CDS.VizieR/J/A+A/285/1
Title:
Spectrographic study of Kiso UV-excess galaxies
Short Name:
J/A+A/285/1
Date:
21 Oct 2021
Publisher:
CDS
Description:
(no description available)
2500. Spectrophotometric Atlas of Galaxies
ID:
ivo://CDS.VizieR/VII/141
Title:
Spectrophotometric Atlas of Galaxies
Short Name:
VII/141
Date:
21 Oct 2021
Publisher:
CDS
Description:
This catalog contains 56 spectra: 55 galaxy spectra, and one night sky spectrum, which is included for users wishing to check for low-level spurious features in the galaxy spectra. The file "spectra.dat" contains a summary of the spectra. The user should consult the paper for details of the observations and a discussion of the limitations of the spectrophotometry. The spectra are integrated measurements made with apertures comparable to the diameters of the galaxies. The original spectra have been combined, rebinned to a common wavelength scale, and normalized in flux to unity at a reference wavelength of 555nm. An atmospheric extinction correction has been applied to the data, but otherwise they are not corrected for reddening, redshift, etc. The spectral range covered is 365-710 nm and the resolution is 5-8{AA}. Each spectrum consists in 1726 normalized flux values spaced each 2{AA}, stored as a file in the subdirectory "sp". Tests show that the spectrophotometry is accurate to the few percent level over small wavelength regions, and at the 10% level over the entire wavelength range. Although the data are useful for a variety of applications, the user should be forewarned that they may not be suitable for applications requiring precision colors over a long wavelength baseline (e.g., computation of K-corrections, some spectral synthesis applications).

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