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3411. Speckle observations TESS exoplanet host stars. II.
ID:
ivo://CDS.VizieR/J/AJ/162/75
Title:
Speckle observations TESS exoplanet host stars. II.
Short Name:
J/AJ/162/75
Date:
18 Mar 2022 09:30:45
Publisher:
CDS
Description:
We present high-angular-resolution imaging observations of 517 host stars of TESS exoplanet candidates using the 'Alopeke and Zorro speckle cameras at Gemini North and South. The sample consists mainly of bright F, G, K stars at distances of less than 500pc. Our speckle observations span angular resolutions of ~20mas out to 1.2", yielding spatial resolutions of <10-500au for most stars, and our contrast limits can detect companion stars 5-9mag fainter than the primary at optical wavelengths. We detect 102 close stellar companions and determine the separation, magnitude difference, mass ratio, and estimated orbital period for each system. Our observations of exoplanet host star binaries reveal that they have wider separations than field binaries, with a mean orbital semimajor axis near 100 au. Other imaging studies have suggested this dearth of very closely separated binaries in systems which host exoplanets, but incompleteness at small separations makes it difficult to disentangle unobserved companions from a true lack of companions. With our improved angular resolution and sensitivity, we confirm that this lack of close exoplanet host binaries is indeed real. We also search for a correlation between planetary orbital radii versus binary star separation; but, given the very short orbital periods of the TESS planets, we do not find any clear trend. We do note that in exoplanet systems containing binary host stars, there is an observational bias against detecting Earth-size planet transits due to transit depth dilution caused by the companion star.
3412. Spectra & HST obs. of gal. in 1ES1553+113 field
ID:
ivo://CDS.VizieR/J/ApJ/884/L31
Title:
Spectra & HST obs. of gal. in 1ES1553+113 field
Short Name:
J/ApJ/884/L31
Date:
21 Oct 2021
Publisher:
CDS
Description:
The relationship between galaxies and the state/chemical enrichment of the warm-hot intergalactic medium (WHIM) expected to dominate the baryon budget at low-z provides sensitive constraints on structure formation and galaxy evolution models. We present a deep redshift survey in the field of 1ES1553+113, a blazar with a unique combination of ultraviolet (UV)+X-ray spectra for surveys of the circumgalactic/intergalactic medium (CGM/IGM). Nicastro+ (2018Natur.558..406N) reported the detection of two OVII WHIM absorbers at z=0.4339 and 0.3551 in its spectrum, suggesting that the WHIM is metal rich and sufficient to close the missing baryons problem. Our survey indicates that the blazar is a member of a z=0.433 group and that the higher-z OVII candidate arises from its intragroup medium. The resulting bias precludes its use in baryon censuses. The z=0.3551 candidate occurs in an isolated environment 630kpc from the nearest galaxy (with stellar mass logM_*_/M_{sun}_~9.7), which we show is unexpected for the WHIM. Finally, we characterize the galactic environments of broad HI Ly{alpha} absorbers (Doppler widths of b=40-80km/s; T<~4x10^5^K) that provide metallicity-independent WHIM probes. On average, broad Ly{alpha} absorbers are ~2x closer to the nearest luminous (L>0.25L*) galaxy (700kpc) than narrow (b<30km/s; T<~4x10^5^K) ones (1300kpc) but ~2x further than OVI absorbers (350kpc). These observations suggest that gravitational collapse heats portions of the IGM to form the WHIM, but with feedback that does not enrich the IGM far beyond galaxy/group halos to levels currently observable in UV/X-ray metal lines.
3413. Spectral analysis of 100 evolved PNe from SPM
ID:
ivo://CDS.VizieR/J/ApJ/771/114
Title:
Spectral analysis of 100 evolved PNe from SPM
Short Name:
J/ApJ/771/114
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have selected a group of 100 evolved planetary nebulae (PNe) and study their kinematics based upon spatially-resolved, long-slit, echelle spectroscopy. The data have been drawn from the San Pedro Martir Kinematic Catalogue of PNe (SPM Catalogue). The aim is to characterize in detail the global kinematics of PNe at advanced stages of evolution with the largest sample of homogenous data used to date for this purpose. The results reveal two groups that share kinematics, morphology, and photo-ionization characteristics of the nebular shell and central star luminosities at the different late stages under study. The typical flow velocities we measure are usually larger than seen in earlier evolutionary stages, with the largest velocities occurring in objects with very weak or absent [NII]{lambda}6584 line emission, by all indications the least evolved objects in our sample. The most evolved objects expand more slowly. This apparent deceleration during the final stage of PNe evolution is predicted by hydrodynamical models, but other explanations are also possible. These results provide a template for comparison with the predictions of theoretical models.
3414. Spectral and timing results of 1ES 1959+650
ID:
ivo://CDS.VizieR/J/ApJS/238/13
Title:
Spectral and timing results of 1ES 1959+650
Short Name:
J/ApJS/238/13
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the detailed timing and spectral results obtained during the Swift observations of the TeV-detected blazar 1ES 1959+650 in 2016 August-2017 November. The source continued its trend of gradually enhancing X-ray flaring activity in the 0.3-10keV energy range, starting in 2015 August, and a new highest historical brightness state was recorded twice. A long-term high state was superimposed by both weak and strong flares, and we detected 32 instances of intraday X-ray flux variability, including several occasions of extremely fast fluctuations with fractional amplitudes of 5.4%-7.5% within 1ks exposures. The 0.3-10keV spectra generally showed a best fit with the log-parabolic model, yielding a very wide range of the curvature parameter b and the photon index at 1keV. The position of the synchrotron SED peak Ep showed an extreme variability on various timescales between energies less than 0.1keV and 7.7+/-0.7keV, with 25% of the spectra peaking at hard X-rays. In 2017 May-November, the source mostly showed lower spectral curvature and an anticorrelation b-Ep, expected in the case of efficient stochastic acceleration of X-ray-emitting electrons. The 0.3-100GeV and optical-UV fluxes also attained their highest historical values in this period, although the latter showed an anticorrelation with the 0.3-10keV emission, which is explained by the stochastic acceleration of electrons with a narrow initial energy distribution, having an average energy significantly higher than the equilibrium energy.
3415. Spectral and UBV analysis of {epsilon} Aur
ID:
ivo://CDS.VizieR/J/A+A/530/A146
Title:
Spectral and UBV analysis of {epsilon} Aur
Short Name:
J/A+A/530/A146
Date:
21 Oct 2021
Publisher:
CDS
Description:
A series of 353 red electronic spectra (from three observatories, mostly from 6300 to 6700{AA}) obtained between 1994 and 2010, and of 171 UBV photometric observations (from two observatories) of the 2010 eclipse, were analyzed in an effort to better understand epsilon Aur, the well-known, but still enigmatic eclipsing binary with the longest known orbital period (~27yrs).
3416. Spectral classification for 631 {rho}Puppis stars
ID:
ivo://CDS.VizieR/J/AJ/160/52
Title:
Spectral classification for 631 {rho}Puppis stars
Short Name:
J/AJ/160/52
Date:
09 Mar 2022
Publisher:
CDS
Description:
The {rho}Puppis stars are mid-F-type stars that show peculiar chemical-abundance patterns similar to those of the Am stars. Typically they exhibit overabundances of iron-peak elements such as Fe and Ni and s- and r-process elements such as Sr and Eu, and underabundances of certain other elements including He, Ca, and Sc. It has been proposed that these stars are evolving Am stars passing through the short-lived phase that occurs between the re-establishment of convection and the consequent erasure of their chemical peculiarities. In this paper we suggest a second hypothesis: these stars may have acquired their peculiar abundance patterns in a fashion similar to the Barium stars, i.e., they may have gained the s-process element enhancements via mass transfer from a once asymptotic giant-branch companion star, now turned white dwarf. This study will detail our efforts to investigate the {rho}Puppis stars with regard to these two hypotheses, with a view to understanding these stars and their significance in terms of stellar evolution. We have performed a spectral classification survey, and a detailed chemical-abundance analysis of selected {rho}Puppis stars. This paper gives an overview of the {rho}Puppis stars and describes the spectral classification survey which has increased the number of {rho}Puppis stars currently known from 6 to 49. A future paper will describe the chemical-abundance analysis which should provide insight into the nature of these stars.
3417. Spectral classification of close binaries
ID:
ivo://CDS.VizieR/J/ApJS/143/513
Title:
Spectral classification of close binaries
Short Name:
J/ApJS/143/513
Date:
21 Oct 2021
Publisher:
CDS
Description:
A sample of 135 stars with composite spectra has been observed in the near-UV spectral region with the Aurelie spectrograph at the Observatoire de Haute-Provence. Using the spectral classifications of the cool components previously determined with near infrared spectra, we obtained reliable spectral types of the hot components of the sample systems. The hot components were isolated by the subtraction method using MK standards as surrogates of the cool components. We also derived the visual magnitude differences between the components using Willstrop's normalized stellar flux ratios. We propose a photometric model for each of these systems on the basis of our spectroscopic data and the Hipparcos data.
3418. Spectral classification of stars in NGC 6530
ID:
ivo://CDS.VizieR/J/A+A/546/A9
Title:
Spectral classification of stars in NGC 6530
Short Name:
J/A+A/546/A9
Date:
21 Oct 2021
Publisher:
CDS
Description:
Mechanisms involved in the star formation process and in particular the duration of the different phases of the cloud contraction are not yet fully understood. Photometric data alone suggest that objects coexist in the young cluster NGC 6530 with ages from ~1Myr up to 10Myrs. We want to derive accurate stellar parameters and, in particular, stellar ages to be able to constrain a possible age spread in the star-forming region NGC6530.
3419. Spectral distances to DA white dwarfs
ID:
ivo://CDS.VizieR/J/AJ/135/1239
Title:
Spectral distances to DA white dwarfs
Short Name:
J/AJ/135/1239
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using recent photometric calibrations, we develop greatly improved distance estimates for DA white dwarfs using multi-band synthetic photometry based on spectroscopic temperatures and gravities. Very good correlations are shown to exist between our spectroscopically based photometric distance estimates and those derived from trigonometric parallaxes. We investigate the uncertainties involved in our distance estimates, as well as discuss the circumstances where such techniques are most likely to fail. We apply our techniques to the large sample of Sloan Digital Sky Survey DA white dwarfs where automated fitting of HI Balmer profiles yields spectrometric temperatures and gravities. We determine simple empirical corrections to these temperatures and gravities with respect to published slit spectroscopy. After applying these T_eff_-logg corrections as well as appropriate interstellar extinction corrections, where necessary, we derive spectroscopically based photometric distances for 7062 DA stars from this sample.
3420. Spectral & environment properties of z~2 QSO pairs
ID:
ivo://CDS.VizieR/J/ApJ/860/41
Title:
Spectral & environment properties of z~2 QSO pairs
Short Name:
J/ApJ/860/41
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first results from our survey of intervening and proximate Lyman limit systems (LLSs) at z~2.0-2.5 using the Wide Field Camera 3 on board the Hubble Space Telescope. The quasars in our sample are projected pairs with proper transverse separations R_{perp}_<=150kpc and line-of- sight velocity separations <~11000km/s. We construct a stacked ultraviolet (rest-frame wavelengths 700-2000{AA}) spectrum of pairs corrected for the intervening Lyman forest and Lyman continuum absorption. The observed spectral composite presents a moderate flux excess for the most prominent broad emission lines, a ~30% decrease in flux at {lambda}=800-900{AA} compared to a stack of brighter quasars not in pairs at similar redshifts, and lower values of the mean free path of the HI ionizing radiation for pairs ({lambda}_mfp_^912^=140.7+/-20.2h_70_^-1^Mpc) compared to single quasars ({lambda}_mfp_^912^=213.8+/-28h_70_^-1^Mpc) at the average redshift z~2.44. From the modeling of LLS absorption in these pairs, we find a higher (~20%) incidence of proximate LLSs with logN_HI_>=17.2 at {delta}v<5000km/s compared to single quasars (~6%). These two rates are different at the 5{sigma} level. Moreover, we find that optically thick absorbers are equally shared between foreground and background quasars. Based on these pieces of evidence, we conclude that there is a moderate excess of gas-absorbing Lyman continuum photons in our closely projected quasar pairs compared to single quasars. We argue that this gas arises mostly within large-scale structures or partially neutral regions inside the dark matter halos where these close pairs reside.