- ID:
- ivo://CDS.VizieR/J/AJ/158/167
- Title:
- Speckle observations & orbits of multiple stars
- Short Name:
- J/AJ/158/167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report results of speckle-interferometric monitoring of visual hierarchical systems using the newly commissioned instrument NN-EXPLORE Exoplanet and Stellar Speckle Imager at the 3.5 m WIYN telescope. During one year, 390 measurements of 129 resolved subsystems were made, while some targets were unresolved. Using our astrometry and archival data, we computed 36 orbits (27 for the first time). Spectro-interferometric orbits of seven pairs are determined by combining positional measurements with radial velocities measured, mostly, with the Center for Astrophysics digital speedometers. For the hierarchical systems HIP 65026 (periods 49 and 1.23 yr) and HIP 85209 (periods 34 and 1.23 yr) we determined both the inner and the outer orbits using astrometry and radial velocities and measured the mutual orbit inclinations of 11.3{deg}+/-1.0{deg} and 12.0{deg}+/-3.0{deg}, respectively. Four bright stars are resolved for the first time; two of those are triple systems. Several visual subsystems announced in the literature are shown to be spurious. We note that subsystems in compact hierarchies with outer separations less than 100 au tend to have less eccentric orbits compared to wider hierarchies.
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- 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.
- ID:
- ivo://CDS.VizieR/J/A+A/570/A2
- Title:
- Spectra and radial velocities of nuclear stars
- Short Name:
- J/A+A/570/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Within the central 10pc of our Galaxy lies a dense cluster of stars. This nuclear star cluster forms a distinct component of the Galaxy, and similar nuclear star clusters are found in most nearby spiral and elliptical galaxies. Studying the structure and kinematics of nuclear star clusters reveals the history of mass accretion and growth of galaxy nuclei and central massive black holes. Because the Milky Way nuclear star cluster is at a distance of only 8 kpc, we can spatially resolve the cluster on sub-parsec scales. This makes the Milky Way nuclear star cluster a reference object for understanding the formation of all nuclear star clusters.
- ID:
- ivo://CDS.VizieR/J/ApJS/151/299
- Title:
- Spectra classification from ISO PHT-S database
- Short Name:
- J/ApJS/151/299
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have classified over 1500 infrared spectra obtained with the PHT-S spectrometer aboard the Infrared Space Observatory according to the system developed for the Short Wavelength Spectrometer (SWS) spectra by Kraemer et al. (2002ApJS..140..389K). The majority of these spectra contribute to subclasses that are either under-represented in the SWS spectral database or contain sources that are too faint, such as M dwarfs, to have been observed by either the SWS or the Infrared Astronomical Satellite Low Resolution Spectrometer. There is strong overall agreement about the chemistry of objects observed with both instruments. Discrepancies can usually be traced to the different wavelength ranges and sensitivities of the instruments. Finally, a large subset of the observations (~250 spectra) exhibit a featureless, red continuum that is consistent with emission from zodiacal dust and suggest directions for further analysis of this serendipitous measurement of the zodiacal background.
- 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.
- 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.
17047. Spectral analysis of GRBs
- ID:
- ivo://CDS.VizieR/J/ApJ/720/1146
- Title:
- Spectral analysis of GRBs
- Short Name:
- J/ApJ/720/1146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A time-resolved spectral analysis for a sample of 22 intense, broad gamma-ray burst (GRB) pulses from the Compton Gamma Ray Observatory (CGRO)/BATSE GRB sample is presented. We fit the spectra with the Band function and investigate the correlation between the observed flux (F) and the peak energy (E_p_) of the {nu}f_{nu}_ spectrum in the rising and decaying phases of these pulses. Two kinds of E_p_ evolution trends, i.e., hard-to-soft (two-thirds of the pulses in our sample) and E_p_-tracing-F (one-third of the pulses in our sample), are observed in pulses from different GRBs and even from different pulses of the same burst. No dependence of spectral evolution feature on the pulse shape is found. A tight F-E_p_ positive correlation is observed in the decaying phases, with a power-law index ~2.2, which is much shallower than that expected from the curvature effect. In the rising phase, the observed F is either correlated or anti-correlated with E_p_, depending on the spectral evolution feature, and the power-law index of the correlation is dramatically different among pulses. More than 80% of the low-energy photon indices in the time-resolved spectra, whose E_p_'s are anti-correlated with F during the rising phase, violate the death line of the synchrotron radiation, disfavoring the synchrotron radiation model for these gamma rays. The F-E_p_ correlation, especially for those GRBs with E_p_-tracking-F spectral evolution, may be due to the viewing angle and jet structure effects. In this scenario, the observed F-E_p_ correlation in the rising phase may be due to the line of sight toward a structured jet (or jetter) moving from off-beam to on-beam, and both the on-beam emission and the delayed photons from high latitude of the GRB fireball contribute to the decaying phase, resulting in a shallower slope of the observed F-E_p_ correlation than that predicted by the pure curvature effect.
- ID:
- ivo://CDS.VizieR/J/ApJ/711/138
- Title:
- Spectral analysis of HIP 60350 and 18 Peg
- Short Name:
- J/ApJ/711/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young, massive stars in the Galactic halo are widely supposed to be the result of an ejection event from the Galactic disk forcing some stars to leave their place of birth as so-called runaway stars. Here, we present a detailed spectroscopic and kinematic analysis of the runaway B star HIP 60350 to determine which runaway scenario -a supernova explosion disrupting a binary system or dynamical interaction in star clusters- may be responsible for HIP 60350's peculiar orbit. Based on a non-local thermodynamic equilibrium approach, a high-resolution optical echelle spectrum was examined to revise spectroscopic quantities and for the first time to perform a differential chemical abundance analysis with respect to the B-type star 18 Peg. The results together with proper motions from the Hipparcos Catalog further allowed the three-dimensional kinematics of the star to be studied numerically. The abundances derived for HIP 60350 are consistent with a slightly supersolar metallicity agreeing with the kinematically predicted place of birth ~6kpc away from the Galactic center. However, they do not exclude the possibility of an {alpha}-enhanced abundance pattern expected in the case of the supernova scenario. Its outstanding high Galactic rest-frame velocity of 530+/-35km/s is a consequence of ejection in the direction of Galactic rotation and slightly exceeds the local Galactic escape velocity in a standard Galactic potential. Hence, HIP 60350 may be unbound to the Galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/393/425
- Title:
- Spectral analysis of Lockman Hole
- Short Name:
- J/A+A/393/425
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the X-ray spectral analysis of the first deep X-ray survey with the XMM-Newton observatory during Performance Verification. The X-ray data of the Lockman Hole field and the derived cumulative source counts were reported by Hasinger et al. (2001A&A...365L..45H). We restrict the analysis to the sample of 98 sources with more than 70 net counts (flux limit in the [0.5-7]keV band of 1.6x10^-15^erg/cm^2^/s) of which 61 have redshift identification. We find no correlation between the spectral index and the intrinsic absorption column density NH and, for both the Type-1 and Type-2 AGN populations, we obtain <Gamma>~=2.
- ID:
- ivo://CDS.VizieR/J/ApJ/853/150
- Title:
- Spectral analysis of low-mass X-ray binaries
- Short Name:
- J/ApJ/853/150
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A recent study of a small sample of X-ray binaries (XRBs) suggests a significant softening of spectra of neutron star (NS) binaries as compared to black hole (BH) binaries in the luminosity range 10^34^-10^37^erg/s. This softening is quantified as an anticorrelation between the spectral index and the 0.5-10keV X-ray luminosity. We extend the study to significantly lower luminosities (i.e., ~a few x10^30^erg/s) for a larger sample of XRBs. We find evidence for a significant anticorrelation between the spectral index and the luminosity for a group of NS binaries in the luminosity range 10^32^-10^33^erg/s. Our analysis suggests a steep slope for the correlation i.e., -2.12+/-0.63. In contrast, BH binaries do not exhibit the same behavior. We examine the possible dichotomy between NS and BH binaries in terms of a Comptonization model that assumes a feedback mechanism between an optically thin hot corona and an optically thick cool source of soft photons. We gauge the NS-BH dichotomy by comparing the extracted corona temperatures, Compton-y parameters, and the Comptonization amplification factors: the mean temperature of the NS group is found to be significantly lower than the equivalent temperature for the BH group. The extracted Compton-y parameters and the amplification factors follow the theoretically predicted relation with the spectral index.