Search

Start Over Subject spectroscopy Content Level Research
2911. Transit time of K2-146b and K2-146c with K2 and HPF
ID:
ivo://CDS.VizieR/J/AJ/159/120
Title:
Transit time of K2-146b and K2-146c with K2 and HPF
Short Name:
J/AJ/159/120
Date:
21 Oct 2021
Publisher:
CDS
Description:
K2-146 is a cool, 0.358M_{sun}_ dwarf that was found to host a mini-Neptune with a 2.67day period. The planet exhibited strong transit timing variations (TTVs) of greater than 30minutes, indicative of the presence of an additional object in the system. Here we report the discovery of the previously undetected outer planet in the system, K2-146c, using additional photometric data. K2-146c was found to have a grazing transit geometry and a 3.97day period. The outer planet was only significantly detected in the latter K2 campaigns presumably because of precession of its orbital plane. The TTVs of K2-146b and c were measured using observations spanning a baseline of almost 1200days. We found strong anti-correlation in the TTVs, suggesting the two planets are gravitationally interacting. Our TTV and transit model analyses revealed that K2-146b has a radius of 2.25{+/-}0.10R_{earth}_ and a mass of 5.6{+/-}0.7M_{earth}_, whereas K2-146c has a radius of 2.59_-0.39_^+1.81^R_{earth} and a mass of 7.1{+/-}0.9M_{earth}_. The inner and outer planets likely have moderate eccentricities of e=0.14{+/-}0.07 and 0.16{+/-}0.07, respectively. Long-term numerical integrations of the two-planet orbital solution show that it can be dynamically stable for at least 2Myr. We show that the resonance angles of the planet pair are librating, which may be an indication that K2-146b and c are in a 3:2 mean motion resonance. The orbital architecture of the system points to a possible convergent migration origin.
2912. Transmission Spectroscopy Metric of exoplanets
ID:
ivo://CDS.VizieR/J/AJ/159/239
Title:
Transmission Spectroscopy Metric of exoplanets
Short Name:
J/AJ/159/239
Date:
21 Oct 2021
Publisher:
CDS
Description:
Recent years have seen increasing interest in the characterization of sub-Neptune-sized planets because of their prevalence in the Galaxy, contrasted with their absence in our solar system. HD97658 is one of the brightest stars hosting a planet of this kind, and we present the transmission spectrum of this planet by combining four Hubble Space Telescope transits, 12 Spitzer/IRAC transits, and eight Microvariability and Oscillations of Stars Telescope (MOST) transits of this system. Our transmission spectrum has a higher signal-to-noise ratio than those from previous works, and the result suggests that the slight increase in transit depth from wavelength 1.1-1.7{mu}m reported in previous works on the transmission spectrum of this planet is likely systematic. Nonetheless, our atmospheric modeling results are inconclusive, as no model provides an excellent match to our data. Nonetheless, we find that atmospheres with high C/O ratios (C/O~>0.8) and metallicities of ~>100 solar metallicity are favored. We combine the mid-transit times from all of the new Spitzer and MOST observations and obtain an updated orbital period of P=9.489295{+/-}0.000005, with a best-fit transit time center at T0=2456361.80690{+/-}0.00038(BJD). No transit timing variations are found in this system. We also present new measurements of the stellar rotation period (34{+/-}2days) and stellar activity cycle (9.6yr) of the host star HD97658. Finally, we calculate and rank the Transmission Spectroscopy Metric of all confirmed planets cooler than 1000K and with sizes between 1R_{Earth}_ and 4R_{Earth}_. We find that at least a third of small planets cooler than 1000K can be well characterized using James Webb Space Telescope, and of those, HD97658b is ranked fifth, meaning that it remains a high-priority target for atmospheric characterization.
2913. Transmission spectrum of Venus
ID:
ivo://CDS.VizieR/J/A+A/537/L2
Title:
Transmission spectrum of Venus
Short Name:
J/A+A/537/L2
Date:
21 Oct 2021
Publisher:
CDS
Description:
On 5-6 June 2012, Venus will be transiting the Sun for the last time before 2117. This event is an unique opportunity to assess the feasibility of the atmospheric characterisation of Earth-size exoplanets near the habitable zone with the transmission spectroscopy technique and provide an invaluable proxy for the atmosphere of such a planet. In this letter, we provide a theoretical transmission spectrum of the atmosphere of Venus that could be tested with spectroscopic observations during the 2012 transit. This is done using radiative transfer across Venus' atmosphere, with inputs from in-situ missions such as Venus Express and theoretical models. The transmission spectrum covers a range of 0.1-5m and probes the limb between 70 and 150km in altitude. It is dominated in UV by carbon dioxide absorption producing a broad transit signal of ~20ppm as seen from Earth, and from 0.2 to 2.7m by Mie extinction (~5ppm at 0.8m) caused by droplets of sulfuric acid composing an upper haze layer above the main deck of clouds. These features are not expected for a terrestrial exoplanet and could help discriminating an Earth-like habitable world from a cytherean planet.
2914. TRAPPIST monitoring of comet C/2012 F6 (Lemmon)
ID:
ivo://CDS.VizieR/J/A+A/574/A38
Title:
TRAPPIST monitoring of comet C/2012 F6 (Lemmon)
Short Name:
J/A+A/574/A38
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the results of the long-term narrowband photometry and imaging monitoring of comet C/2012 F6 (Lemmon) with the robotic TRAPPIST telescope (La Silla observatory). Observations covered 52 nights pre- and post-perihelion between December 11, 2012 and June 11, 2013. We followed the evolution of the OH, NH, CN, C_3_ and C_2_ production rates computed with the Haser model as well as the evolution of the A({theta})f_{rho}_ parameter as a proxy for the dust production. All five gas species display similar slopes for the heliocentric dependence. An asymmetry about perihelion is observed, the rate of brightening being steeper than the rate of fading. The chemical composition of the comet's coma is changing slightly along the orbit: the relative abundance of C_2_ to CN is decreasing for heliocentric distances larger than 1.4AU while the C_3_ to CN ratio is constant during our observations. The behavior of the dust is different from that of the gas, the slope of the heliocentric dependence becoming steeper in early February, correlated to a change of the visual lightcurve slope. However, the dust color does not vary during the observations. The application of several enhancement techniques on the images revealed structures in the CN, C3 and C2 images. These features imply the existence of one or several active zone(s) on the comet nucleus. The shape of the structures is similar in those three filters and changes from a roughly hourglass shape in December and January to a corkscrew shape in February and March. The structures in the continuum filters (sampling the dust) are not correlated to those observed for the gas. During several full nights in February, we observed changes in the CN and C2 structures repeating periodically due to the nucleus rotation, our derived rotational period being of 9.52+/-0.05 hours.
2915. Triple system HD 28363; RVel and visual observations
ID:
ivo://CDS.VizieR/J/ApJ/885/9
Title:
Triple system HD 28363; RVel and visual observations
Short Name:
J/ApJ/885/9
Date:
15 Mar 2022 07:55:42
Publisher:
CDS
Description:
The star HD28363 in the Hyades cluster has been known for over a century as a visual binary with a period of 40yr. The secondary is, in turn, a single-lined spectroscopic binary with a 21day period. Here we report extensive spectroscopic monitoring of this hierarchical triple system that reveals the spectral lines of the third star for the first time. Combined with astrometric information, this makes it possible to determine the dynamical masses of all three stars. Only six other binaries in the Hyades have had their individual component masses determined dynamically. We infer the properties of the system by combining our radial-velocity measurements with visual observations, lunar occultation measurements, and with proper motions from the Hipparcos and Gaia missions that provide a constraint on the astrometric acceleration. We derive a mass of 1.341_-0.024_^+0.026^M{odot} for the visual primary, and 1.210{+/-}0.021 and 0.781{+/-}0.014 M{sun} for the other two stars. These measurements along with those for the other six systems establish an empirical mass-luminosity relation in the Hyades that is in broad agreement with current models of stellar evolution for the known age and chemical composition of the cluster.
2916. Trumpler 14 and 16 in the Carina nebula
ID:
ivo://CDS.VizieR/J/A+A/603/A81
Title:
Trumpler 14 and 16 in the Carina nebula
Short Name:
J/A+A/603/A81
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first extensive spectroscopic study of the global population in star clusters Trumpler 16, Trumpler 14, and Collinder 232 in the Carina nebula, using data from the Gaia-ESO Survey, down to solar-mass stars. In addition to the standard homogeneous survey data reduction, a special processing was applied here because of the bright nebulosity surrounding Carina stars. We find about 400 good candidate members ranging from OB types down to slightly subsolar masses. About 100 heavily reddened early-type Carina members found here were previously unrecognized or poorly classified, including two candidate O stars and several candidate Herbig Ae/Be stars. Their large brightness makes them useful tracers of the obscured Carina population. The spectroscopically derived temperatures for nearly 300 low-mass members enables the inference of individual extinction values and the study of the relative placement of stars along the line of sight. We find a complex spatial structure with definite clustering of low-mass members around the most massive stars and spatially variable extinction. By combining the new data with existing X-ray data, we obtain a more complete picture of the three-dimensional spatial structure of the Carina clusters and of their connection to bright and dark nebulosity and UV sources. The identification of tens of background giants also enables us to determine the total optical depth of the Carina nebula along many sightlines. We are also able to put constraints on the star formation history of the region with Trumpler 14 stars found to be systematically younger than stars in other subclusters. We find a large percentage of fast-rotating stars among Carina solar-mass members, which provide new constraints on the rotational evolution of pre-main-sequence stars in this mass range.
2917. 33 T Tauri stars in Taurus Halpha measurements
ID:
ivo://CDS.VizieR/J/MNRAS/469/1783
Title:
33 T Tauri stars in Taurus Halpha measurements
Short Name:
J/MNRAS/469/1783
Date:
21 Oct 2021
Publisher:
CDS
Description:
We conducted a 12-month monitoring campaign of 33 T Tauri stars (TTS) in Taurus. Our goal was to monitor objects that possess a disc but have a weak H{alpha} line, a common accretion tracer for young stars, in order to determine whether they host a passive circumstellar disc. We used medium-resolution optical spectroscopy to assess the accretion status of the objects and to measure the H{alpha} line. We found no convincing examples of passive discs: only transition disc and debris disc systems in our sample are non-accreting. Among accretors, we found no example of flickering accretion, leading to an upper limit of 2.2 per cent on the duty cycle of accretion gaps, assuming that all accreting TTS experience such events. When combining literature results with our observations, we found that the reliability of traditional H{alpha}-based criteria to test for accretion is high but imperfect, particularly for low-mass TTS. We found a significant correlation between stellar mass and the full width at 10 per cent of the peak (W_10_) of the H{alpha} line that does not seem to be related to variations in free-fall velocity. Finally, our data revealed a positive correlation between the H{alpha} equivalent width and its W_10_, indicative of a systematic modulation in the line profile whereby the high-velocity wings of the line are proportionally more enhanced than its core when the line luminosity increases. We argue that this supports the hypothesis that the mass accretion rate on the central star is correlated with the H{alpha} W_10_ through a common physical mechanism.
2918. Tubingen Ultraviolet Echelle Spectrometer
ID:
ivo://CDS.VizieR/VI/107
Title:
Tubingen Ultraviolet Echelle Spectrometer
Short Name:
VI/107
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Tubingen Echelle Spectrograph (TUES), designed and managed at the University of Tubingen, flew on the Orbiting and Retrievable Far and Extreme Ultraviolet Spectrograph (ORFEUS)-SPAS II space shuttle mission in 1996, returning spectra in the 900 Angstrom to 1400 Angstrom wavelength range. The instrument was designed to achieve a spectral resolution of 10000 when used with an entrance aperture of 10" diameter. During the 17.7 day flight, TUES returned 239 spectra of 62 targets.
2919. TW Hya CO (2-1), CN (2-1) and CS (5-4) data cubes
ID:
ivo://CDS.VizieR/J/A+A/592/A49
Title:
TW Hya CO (2-1), CN (2-1) and CS (5-4) data cubes
Short Name:
J/A+A/592/A49
Date:
21 Oct 2021
Publisher:
CDS
Description:
We aim to obtain a spatially resolved measurement of velocity dispersions in the disk of TW Hya. We obtained images with high spatial and spectral resolution of the CO J=2-1, CN N=2-1 and CS J=5-4 emission with ALMA in Cycle 2. The radial distribution of the turbulent broadening was derived with two direct methods and one modelling approach. The first method requires a single transition and derives T_ex_ directly from the line profile, yielding a v_turb_. The second method assumes that two different molecules are co-spatial, which allows using their relative line widths for calculating T_kin_ and v_turb_. Finally we fitted a parametric disk model in which the physical properties of the disk are described by power laws, to compare our direct methods with previous values.
2920. TW Hydrae association with X-shooter
ID:
ivo://CDS.VizieR/J/A+A/632/A46
Title:
TW Hydrae association with X-shooter
Short Name:
J/A+A/632/A46
Date:
21 Oct 2021
Publisher:
CDS
Description:
Measurements of the protoplanetary disk frequency in young star clusters of different ages indicate disk lifetimes <10Myr. However, our current knowledge of how mass accretion in young stars evolves over the lifespans of disks is subject to many uncertainties, especially at the lower stellar masses. In this study, we investigate ongoing accretion activity in the TW Hydrae association (TWA), the closest association of pre-main sequence stars with active disks. The age (8-10Myr) and the proximity of the TWA render it an ideal target to probe the final stages of disk accretion down to brown dwarf masses. The study is based on homogeneous spectroscopic data from 300nm to 2500nm, obtained synoptically with X-shooter, which allows simultaneous derivation of individual extinction, stellar parameters, and accretion parameters for each star. The continuum excess emission diagnostics is used to estimate the accretion luminosities and mass accretion rates of our disk-bearing targets, and the shape and intensity of permitted and forbidden emission lines are analyzed to probe the physics of the star-disk interaction environment.

Limit your search

more »

more »

more »

more »