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2121. Radial velocity measurements in LAMOST-II
ID:
ivo://CDS.VizieR/J/ApJS/244/27
Title:
Radial velocity measurements in LAMOST-II
Short Name:
J/ApJS/244/27
Date:
09 Dec 2021
Publisher:
CDS
Description:
The radial velocity (RV) is a basic physical quantity that can be determined through the Doppler shift of the spectrum of a star. The precision of the RV measurement depends on the resolution of the spectrum we used and the accuracy of wavelength calibration. In this work, radial velocities of the Large Sky Area Multi-Object Fibre Spectroscopic Telescope-II (LAMOST-II) medium-resolution (R~7500) spectra are measured for 1,594,956 spectra (each spectrum has two wavebands) through matching with templates. A set of RV standard stars are used to recalibrate the zero point of the measurement, and some reference sets with RVs derived from medium-/high-resolution observations are used to evaluate the accuracy of the measurement. By comparing with reference sets, the accuracy of our measurement can get 0.0277km/s with respect to radial velocities of standard stars. The intrinsic precision is estimated with the multiple observations of single stars, which can be achieved to 1.36km/s, 1.08km/s, and 0.91km/s for the spectra at signal-to-noise levels of 10, 20, and 50, respectively.
2122. Radial velocity measurements of 51 Peg
ID:
ivo://CDS.VizieR/J/A+A/646/A159
Title:
Radial velocity measurements of 51 Peg
Short Name:
J/A+A/646/A159
Date:
21 Oct 2021
Publisher:
CDS
Description:
The analysis of exoplanetary atmospheres by means of high-resolution spectroscopy is an expanding research field which provides information o n chemical composition, thermal structure, atmospheric dynamics and orbital velocity of exoplanets. In this work, we aim at the detection of the light reflected by the exoplanet 51 Peg b employing optical high-resolution spectroscopy. To detect the light reflected by the planetary dayside we use optical HARPS and HARPS-N spectra taken near the superior conjunction of the planet, when the flux contrast between the planet and the star is maximum. To search for the weak planetary signal, we cross-correlate the observed spectra with a high S/N stellar spectrum. We homogeneously analyze the available datasets and derive a 10^-5^ upper limit on the planet-to-star flux contrast in the optical. The upper limit on the planet-to-star flux contrast of 10^-5^ translates into a low albedo of the planetary atmosphere (A_g_~0.05-0.15 for an assumed planetary radius in the range 1.5-0.9R_Jup_, as estimated from the planet's mass).
2123. Radial velocity monitoring of TOI-421
ID:
ivo://CDS.VizieR/J/AJ/160/114
Title:
Radial velocity monitoring of TOI-421
Short Name:
J/AJ/160/114
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of a warm Neptune and a hot sub-Neptune transiting TOI-421 (BD-141137, TIC94986319), a bright (V=9.9) G9 dwarf star in a visual binary system observed by the Transiting Exoplanet Survey Satellite (TESS) space mission in Sectors 5 and 6. We performed ground-based follow-up observations-comprised of Las Cumbres Observatory Global Telescope transit photometry, NIRC2 adaptive optics imaging, and FIbre-fed Echelle Spectrograph, CORALIE, High Accuracy Radial velocity Planet Searcher, High Resolution Echelle Spectrometer, and Planet Finder Spectrograph high-precision Doppler measurements-and confirmed the planetary nature of the 16 day transiting candidate announced by the TESS team. We discovered an additional radial velocity signal with a period of five days induced by the presence of a second planet in the system, which we also found to transit its host star. We found that the inner mini-Neptune, TOI-421b, has an orbital period of Pb=5.19672{+/-}0.00049days, a mass of Mb=7.17{+/-}0.66M{Earth}, and a radius of Rb=2.68_-0.18_^+0.19^R{Earth}, whereas the outer warm Neptune, TOI-421c, has a period of Pc=16.06819{+/-}0.00035days, a mass of Mc=16.42_-1.04_^+1.06^M{Earth}, a radius of Rc=5.09_-0.15_^+0.16^R{Earth}, and a density of {rho}c=0.685_-0.072_^+0.080^g/cm^3^. With its characteristics, the outer planet ({rho}c=0.685_-0.072_^+0.080^g/cm^3^) is placed in the intriguing class of the super-puffy mini-Neptunes. TOI-421b and TOI-421c are found to be well-suited for atmospheric characterization. Our atmospheric simulations predict significant Ly{alpha} transit absorption, due to strong hydrogen escape in both planets, as well as the presence of detectable CH4 in the atmosphere of TOI-421c if equilibrium chemistry is assumed.
2124. Radial velocity of HR 7224
ID:
ivo://CDS.VizieR/J/A+A/457/1033
Title:
Radial velocity of HR 7224
Short Name:
J/A+A/457/1033
Date:
21 Oct 2021
Publisher:
CDS
Description:
HR 7224 is a rapidly rotating He-weak silicon star known as photometrically variable with a period of 1.123d. Drastic changes of photometric amplitude and period were reported in 2003. We investigate the star spectroscopically to determine the time scales of variability, to derive basic atmospheric parameters, and to give first estimates on possible surface structures. We investigate time series of more then 570 high-resolution spectra of HR 7224 for radial velocity and line profile variations. The rotation period is determined from period analysis of data. Comparing radial velocity and line profile variations we draw first conclusions on possible surface structures in terms of line strengths. From Balmer and metal lines we determine Teff, log(g), vsini and metal abundances depending on rotation phase. The star shows a remarkable half-amplitude of radial velocity variation of 6km/s. From this variation we deduce a rotation period of 1.12324d. The period and the double-wave shaped radial velocity curve are in agreement with earlier photometric findings. The observed radial velocity variations can be explained by the rotation period and its harmonics and no further periodic contributions were found in the residuals. HR 7224 has enhanced Si and Fe abundances whereas He is extremely depleted. The star shows line strength variations of all observed elements with the rotation period. Variations of radial velocity, line strength and line shape of silicon lines and their relationships can be explained by assuming two large spots on the stellar surface showing enhanced line strength. From Balmer lines we deduce different temperatures of the star for different rotation phases. The observed difference in amplitudes of the variation of Mg II and Si II lines supports the assumption of surface regions of different temperature on this presumably magnetic CP star. Synthetic uvby colors computed from adapted synthetic spectra confirm the high photometric amplitude reported for the 2003 light curves.
2125. Radial velocity of TOI-201
ID:
ivo://CDS.VizieR/J/AJ/161/235
Title:
Radial velocity of TOI-201
Short Name:
J/AJ/161/235
Date:
16 Mar 2022 11:46:40
Publisher:
CDS
Description:
We present the confirmation of the eccentric warm giant planet TOI-201b, first identified as a candidate in Transiting Exoplanet Survey Satellite photometry (Sectors 1-8, 10-13, and 27-28) and confirmed using ground-based photometry from Next Generation Transit Survey and radial velocities from FEROS, HARPS, CORALIE, and Minerva-Australis. TOI-201b orbits a young (0.87_-0.49_^+0.46^Gyr) and bright (V=9.07mag) F-type star with a 52.9781day period. The planet has a mass of 0.42_-0.03_^+0.05^M_J_, a radius of 1.008_-0.015_^+0.012^R_J_, and an orbital eccentricity of 0.28_-0.09_^+0.06^; it appears to still be undergoing fairly rapid cooling, as expected given the youth of the host star. The star also shows long-term variability in both the radial velocities and several activity indicators, which we attribute to stellar activity. The discovery and characterization of warm giant planets such as TOI-201b are important for constraining formation and evolution theories for giant planets.
2126. Radial velocity of 240 YSOs with MMT/Hectochelle
ID:
ivo://CDS.VizieR/J/AJ/162/56
Title:
Radial velocity of 240 YSOs with MMT/Hectochelle
Short Name:
J/AJ/162/56
Date:
14 Mar 2022 06:56:34
Publisher:
CDS
Description:
Stellar kinematics is a powerful tool for understanding the formation process of stellar associations. Here, we present a kinematic study of the young stellar population in the Rosette nebula using recent Gaia data and high-resolution spectra. We first isolate member candidates using the published mid-infrared photometric data and the list of X-ray sources. A total of 403 stars with similar parallaxes and proper motions are finally selected as members. The spatial distribution of the members shows that this star-forming region is highly substructured. The young open cluster NGC2244 in the center of the nebula has a pattern of radial expansion and rotation. We discuss its implication on the cluster formation, e.g., monolithic cold collapse or hierarchical assembly. On the other hand, we also investigate three groups located around the border of the HII bubble. The western group seems to be spatially correlated with the adjacent gas structure, but their kinematics is not associated with that of the gas. The southern group does not show any systematic motion relative to NGC2244. These two groups might be spontaneously formed in filaments of a turbulent cloud. The eastern group is spatially and kinematically associated with the gas pillar receding away from NGC2244. This group might be formed by feedback from massive stars in NGC2244. Our results suggest that the stellar population in the Rosette Nebula may form through three different processes: the expansion of stellar clusters, hierarchical star formation in turbulent clouds, and feedback-driven star formation.
2127. Radial velocity variable stars from LAMOST DR4
ID:
ivo://CDS.VizieR/J/ApJS/249/22
Title:
Radial velocity variable stars from LAMOST DR4
Short Name:
J/ApJS/249/22
Date:
25 Oct 2021 00:46:50
Publisher:
CDS
Description:
Radial velocity (RV) variable stars are important in astrophysics. The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) spectroscopic survey has provided ~6.5 million stellar spectra in its Data Release 4 (DR4). During the survey ~4.7 million unique sources were targeted and ~1 million stars observed repeatedly. The probabilities of stars being RV variables are estimated by comparing the observed RV variations with simulated ones. We build a catalog of 80702 RV variable candidates with probability greater than 0.60 by analyzing the multi-epoch sources covered by LAMOST DR4. Simulations and cross-identifications show that the purity of the catalog is higher than 80%. The catalog consists of 77% binary systems and 7% pulsating stars as well as 16% pollution by single stars. 3138 RV variables are classified through cross-identifications with published results in literatures. By using the 3138 sources common in both LAMOST and a collection of published RV variable catalogs, we are able to analyze LAMOST's RV variable detection rate. The efficiency of the method adopted in this work relies not only on the sampling frequency of observations but also periods and amplitudes of RV variables. With the progress of LAMOST, Gaia, and other surveys, more and more RV variables will be confirmed and classified.
2128. Radiative contribution from stripped stars
ID:
ivo://CDS.VizieR/J/A+A/629/A134
Title:
Radiative contribution from stripped stars
Short Name:
J/A+A/629/A134
Date:
21 Oct 2021
Publisher:
CDS
Description:
Stars stripped of their envelopes from interaction with a binary companion emit a significant fraction of their radiation as ionizing photons. They are potentially important stellar sources of ionizing radiation, however, they are still often neglected in spectral synthesis simulations or simulations of stellar feedback. In anticipating the large datasets of galaxy spectra from the upcoming James Webb Space Telescope, we modeled the radiative contribution from stripped stars by using detailed evolutionary and spectral models. We estimated their impact on the integrated spectra and specifically on the emission rates of HI-, HeI-, and HeII-ionizing photons from stellar populations. We find that stripped stars have the largest impact on the ionizing spectrum of a population in which star formation halted several Myr ago. In such stellar populations, stripped stars dominate the emission of ionizing photons, mimicking a younger stellar population in which massive stars are still present. Our models also suggest that stripped stars have harder ionizing spectra than massive stars. The additional ionizing radiation, with which stripped stars contribute affects observable properties that are related to the emission of ionizing photons from stellar populations. In co-eval stellar populations, the ionizing radiation from stripped stars increases the ionization parameter and the production efficiency of hydrogen ionizing photons. They also cause high values for these parameters for about ten times longer than what is predicted for massive stars. The effect on properties related to non-ionizing wavelengths is less pronounced, such as on the ultraviolet continuum slope or stellar contribution to emission lines. However, the hard ionizing radiation from stripped stars likely introduces a characteristic ionization structure of the nebula, which leads to the emission of highly ionized elements such as O^2+^ and C^3+^. We, therefore, expect that the presence of stripped stars affects the location in the BPT diagram and the diagnostic ratio of OIII to OII nebular emission lines. Our models are publicly available through CDS database and on the STARBURST99 website.
2129. Radio and UV spectra of HVC toward the MC
ID:
ivo://CDS.VizieR/J/ApJ/702/940
Title:
Radio and UV spectra of HVC toward the MC
Short Name:
J/ApJ/702/940
Date:
21 Oct 2021
Publisher:
CDS
Description:
In the spectra of 139 early-type Large Magellanic Cloud (LMC) stars observed with Far Ultraviolet Spectroscopic Explorer and with deep radio Parkes HI 21cm observations along with those stars, we search for and analyze the absorption and emission from high-velocity gas at +90<={nu}_LSR_<=+175km/s. The HI column density of the high-velocity clouds (HVCs) along these sightlines ranges from <1018.4 to 1019.2cm^-2^. The incidence of the HVC metal absorption is 70%, significantly higher than the HI emission occurrence of 32%. We find that the mean metallicity of the HVC is [OI/HI]=-0.51+/-^0.12^_0.16_. This is the first example of a large (>10^6^M_{sun}_) HVC complex that is linked to stellar feedback occurring in a dwarf spiral galaxy.
2130. Radio galaxies in the 2dFGRS
ID:
ivo://CDS.VizieR/J/MNRAS/333/100
Title:
Radio galaxies in the 2dFGRS
Short Name:
J/MNRAS/333/100
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use redshift determinations and spectral analysis of galaxies in the 2dF Galaxy Redshift Survey (<VII/226>) to study the properties of local radio sources with S>=1mJy. 557 objects (hereafter called the spectroscopic sample) drawn from the FIRST survey(<VIII/71>) , corresponding to 2.3 per cent of the total radio sample, are found in the 2dFGRS catalogue within the area 9h 48min<=RA<=14h 32min and -2.77{deg}<=DE<=2.25{deg} (2000), down to a magnitude limit b_J_=19.45. The excellent quality of 2dF spectra allows us to divide these sources into classes, according to their optical spectra.

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