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- ID:
- ivo://CDS.VizieR/J/AJ/157/85
- Title:
- The CIDA Variability Survey of Orion OB1. II.
- Short Name:
- J/AJ/157/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of our large-scale, optical, multi-epoch photometric survey across ~180 square degrees in the Orion OB1 association, complemented with extensive follow-up spectroscopy. Our focus is mapping and characterizing the off-cloud, low-mass, pre-main-sequence (PMS) populations. We report 2062 K- and M-type confirmed T Tauri members; 59% are located in the OB1a subassociation, 27% in the OB1b subassociation, and the remaining 14% in the A and B molecular clouds. We characterize two new clusterings of T Tauri stars, the HD 35762 and HR 1833 groups, both located in OB1a not far from the 25 Ori cluster. We also identify two stellar overdensities in OB1b, containing 231 PMS stars, and find that the OB1b region is composed of two populations at different distances, possibly due to the OB1a subassociation overlapping with the front of OB1b. A ~2 deg wide halo of young stars surrounds the Orion Nebula Cluster, corresponding in part to the low-mass populations of NGC 1977 and NGC 1980. We use the strength of H{alpha} in emission, combined with the IR excess and optical variability, to define a new type of T Tauri star, the C/W class, stars we propose may be nearing the end of their accretion phase, in an evolutionary state between classical and weak-lined T Tauri stars. The evolution of the ensemble-wide equivalent width of Li I{lambda}6707 indicates a Li depletion timescale of ~8.5 Myr. Disk accretion declines with an e-folding timescale of ~2 Myr, consistent with previous studies.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A127
- Title:
- The C^+^ ion photofragment spectra
- Short Name:
- J/A+A/647/A127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon monoxide (CO) is one of the most abundant molecular species in comets. Its photodissociation by the solar radiation in the vacuum ultraviolet (VUV) region produces excited atomic fragments C(^1^D), C(^1^S), and O(^1^D), which radiate at characteristic wavelengths when they decay to lower states. The fractional rate constants for generating these fragments from CO photodissociation under the entire range of the solar radiation field are key input values in modelling the observed atomic emission intensities from comets. In this study, the branching ratios of the four lowest dissociation channels C(^3^P)+O(^3^P), C(^1^D)+O(^3^P), C(^3^P)+O(^1^D), and C(^1^S)+O(^3^P) of the ^12^C^16^O photodissociation are measured in the VUV energy range between the threshold of producing the C(^1^S)+O(^3^P) channel (~110500cm^-1^) and the ionisation energy (IE) of ^12^C^16^O (~113045cm^-1^). We measured these ratios using the VUV time-slice velocity-map ion imaging apparatus. We observe a number of high Rydberg states in the aforementioned energy range, with most of them mainly producing ground C(^3^P) and O(^3^P) atomic fragments, and only a few of them producing a significant amount of excited C(^1^D) or O(^1^D) fragments. We also observe the excited C(^1^S) fragment from CO photodissociation and measured its branching ratio for the first time. Based on the photodissociation branching ratios measured in the current and previous studies, we are able to estimate the relative percentages of the excited atomic fragments C(^1^D), C(^1^S), and O(^1^D) from the solar photolysis of ^12^C^16^O below its IE. We discuss the implications for the photochemical modelling of the CO-dominated comet C/2016 R2 (Pan-STARRS).
21544. The CLASS blazar survey. I.
- ID:
- ivo://CDS.VizieR/J/MNRAS/326/1455
- Title:
- The CLASS blazar survey. I.
- Short Name:
- J/MNRAS/326/1455
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents a new complete and well-defined sample of flat-spectrum radio sources (FSRS) selected from the Cosmic Lens All-Sky Survey (CLASS), with the further constraint of a bright (mag<=17.5) optical counterpart. The sample has been designed to produce a large number of low-luminosity blazars in order to test the current unifying models in the low-luminosity regime. In this first paper the new sample is presented and the radio properties of the 325 sources contained therein are discussed.
21545. The CLASS blazar survey. II.
- ID:
- ivo://CDS.VizieR/J/MNRAS/329/877
- Title:
- The CLASS blazar survey. II.
- Short Name:
- J/MNRAS/329/877
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the optical properties of the objects selected in the CLASS blazar survey. Because an optical spectrum is now available for 70 per cent of the 325 sources present in the sample, a spectral classification, based on the appearance of the emission/absorption lines, is possible. A wide variety of optical spectral types is found. Besides `classical' BL Lacs (42), BL Lac candidates (5) and high-power (P_5GHz_>10^26^W/Hz) flat spectrum radio quasars (67), a significant number of `passive' elliptical galaxies (41) is also found. Moreover, 33 broad emission line objects with a low radio power (P(5GHz)>10^26^W/Hz) are discovered, suggesting that at least a fraction (~24-30 per cent) of low-power blazars have a broad line region. Finally, 34 objects showing only narrow emission lines, either as a result of some starburst activity in the host galaxy or as a result of the presence of an active galactic nucleus, appear in the sample.
- ID:
- ivo://CDS.VizieR/J/MNRAS/348/937
- Title:
- The CLASS blazar survey. III.
- Short Name:
- J/MNRAS/348/937
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the properties of the sources in the CLASS blazar survey, which aims at the selection of low radio power (P_5GHz_<10^25^W/Hz) blazars. We use Very Large Array (VLA) data from available catalogues and from our own observations to constrain the radio core-dominance of the sample which, together with the flat radio spectral index, is a signature of the blazar activity. X-ray data from the ROSAT All Sky Survey were also collected in order to constrain the radio-to-X-ray luminosity ratio of the sources.
21547. The CLASS BL Lac sample
- ID:
- ivo://CDS.VizieR/J/MNRAS/430/2464
- Title:
- The CLASS BL Lac sample
- Short Name:
- J/MNRAS/430/2464
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents a new sample of BL Lac objects selected from a deep (30mJy) radio survey of flat spectrum radio sources (the CLASS blazar survey). The sample is one of the largest well-defined samples in the low-power regime with a total of 130 sources of which 55 satisfy the 'classical' optical BL Lac selection criteria, and the rest have indistinguishable radio properties. The primary goal of this study is to establish the radio luminosity function (RLF) on firm statistical ground at low radio luminosities where previous samples have not been able to investigate. The gain of taking a peek at lower powers is the possibility to search for the flattening of the luminosity function which is a feature predicted by the beaming model but which has remained elusive to observational confirmation. In this study, we extend for the first time the BL Lac RLF down to very low radio powers ~10^22^W/Hz, i.e. two orders of magnitude below the RLF currently available in the literature. In the process, we confirm the importance of adopting a broader, and more physically meaningful set of classification criteria to avoid the systematic missing of low-luminosity BL Lacs. Thanks to the good statistics we confirm the existence of weak but significant positive cosmological evolution for the BL Lac population, and we detect, for the first time the flattening of the RLF at L~10^25^W/Hz in agreement with the predictions of the beaming model.
- ID:
- ivo://CDS.VizieR/J/AJ/143/101
- Title:
- The classification of Kepler B-star variables
- Short Name:
- J/AJ/143/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The light curves of 252 B-star candidates in the Kepler database are analyzed in a similar fashion to that done by Balona et al. (2011MNRAS.413.2403B) to further characterize B-star variability, increase the sample of variable B stars for future study, and to identify stars whose power spectra include particularly interesting features such as frequency groupings. Stars are classified as either constant light emitters, {beta} Cep stars, slowly pulsating B stars (SPBs), hybrid pulsators, binaries or stars whose light curves are dominated by rotation (Bin/Rot), hot subdwarfs, or white dwarfs. One-hundred stars in our sample were found to be either light constants or to be variable at a level of less than 0.02mmag. We increase the number of candidate B-star variables found in the Kepler database by Balona et al. (2011MNRAS.413.2403B) in the following fashion: {beta} Cep stars from 0 to 10, SPBs from eight to 54, hybrid pulsators from seven to 21, and Bin/Rot stars from 23 to 82. For comparison purposes, approximately 51 SPBs and six hybrids had been known prior to 2007. The number of {beta} Cep stars known prior to 2004 was 93. A secondary result of this study is the identification of an additional 11 pulsating white dwarf candidates, four of which possess frequency groupings.
- ID:
- ivo://CDS.VizieR/J/A+A/440/249
- Title:
- The close binary system epsilon Lupi
- Short Name:
- J/A+A/440/249
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We subjected 106 new high-resolution spectra of the double-lined spectroscopic close binary epsilon Lupi, obtained in a time-span of 17 days from two different observatories, to a detailed study of orbital and intrinsic variations. We derived accurate values of the orbital parameters. We refined the sidereal orbital period to 4.55970 days and the eccentricity to e=0.277. By adding old radial velocities, we discovered the presence of apsidal motion, with a period of the rotation of apses of about 430 years. Such a value is in agreement with theoretical expectations. Additional data is needed to confirm and refine this value. Our dataset did not allow to derive the orbit of the third body, which is known to orbit the close system in approximately 64 years. We present the secondary of epsilon Lupi as a new beta Cephei variable, while the primary is a beta Cephei suspect. A first detailed analysis of line-profile variations of both primary and secondary led to the detection of one pulsation frequency near 10.36c/d in the variability of the secondary, while no clear periodicity was found in the primary, although low-amplitude periodicities are suspected. The limited accuracy and extent of our dataset did not allow any further analysis, such as mode-identification.
- ID:
- ivo://CDS.VizieR/J/ApJ/702/506
- Title:
- The Clowes-Campusano LQG Survey. I.
- Short Name:
- J/ApJ/702/506
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The nature of galaxy structures on large scales is a key observational prediction for current models of galaxy formation. The Sloan Digital Sky Survey (SDSS) and the 2dF galaxy survey have revealed a number of structures on 40-150h<SUP>–1</SUP>Mpc scales at low redshifts, and some even larger ones. To constrain galaxy number densities, luminosities, and stellar populations in large structures at higher redshift, we have investigated two sheet-like structures of galaxies at z=0.8 and 1.3 spanning 150h<SUP>–1</SUP> comoving Mpc embedded in large quasar groups (LQGs) extending over at least 200h<SUP>–1</SUP>Mpc. We present first results of an analysis of these sheet-like structures using two contiguous 1° Galaxy Evolution Explorer (GALEX) fields (FUV and NUV) cross-correlated with optical data from the SDSS. We derive a sample of 462 Lyman break galaxy (LBG) candidates coincident with the sheets. Using the GALEX and SDSS data, we show that the overall average spectral energy distribution of a LBG galaxy at z∼1 is flat (in f<SUB>λ</SUB>) in the rest-frame wavelength range from 1500Å to 4000Å, implying evolved populations of stars in the LBGs. From the luminosity functions we get indications for overdensities in the two LQGs compared to their foreground regions.