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2451. SN 2007on and SN 2011iv light curves
ID:
ivo://CDS.VizieR/J/A+A/611/A58
Title:
SN 2007on and SN 2011iv light curves
Short Name:
J/A+A/611/A58
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of ultraviolet (UV) to near-infrared observations of the fast-declining Type Ia supernovae (SNe Ia) 2007on and 2011iv, hosted by the Fornax cluster member NGC 1404. The B-band light curves of SN 2007on and SN 2011iv are characterised by {Delta}m15(B) decline-rate values of 1.96mag and 1.77mag, respectively. Although they have similar decline rates, their peak B- and H-band magnitudes differ by ~0.60mag and ~0.35mag, respectively. After correcting for the luminosity vs. decline rate and the luminosity vs. colour relations, the peak B-band and H-band light curves provide distances that differ by ~14% and ~9%, respectively. These findings serve as a cautionary tale for the use of transitional SNe Ia located in early-type hosts in the quest to measure cosmological parameters. Interestingly, even though SN 2011iv is brighter and bluer at early times, by three weeks past maximum and extending over several months, its B-V colour is 0.12mag redder than that of SN 2007on. To reconcile this unusual behaviour, we turn to guidance from a suite of spherical one-dimensional Chandrasekhar-mass delayed-detonation explosion models. In this context, ^56^Ni production depends on both the so-called transition density and the central density of the progenitor white dwarf. To first order, the transition density drives the luminosity-width relation, while the central density is an important second-order parameter. Within this context, the differences in the B-V colour evolution along the Lira regime suggest that the progenitor of SN 2011iv had a higher central density than SN 2007on.
2452. SNRs in M33 from optical and X-ray
ID:
ivo://CDS.VizieR/J/ApJS/187/495
Title:
SNRs in M33 from optical and X-ray
Short Name:
J/ApJS/187/495
Date:
21 Oct 2021
Publisher:
CDS
Description:
M33 contains a large number of emission nebulae identified as supernova remnants (SNRs) based on the high [SII]:H{alpha} ratios characteristic of shocked gas. Using Chandra data from the ChASeM33 survey with a 0.35-2keV sensitivity of ~2x10^34^erg/s, we have detected 82 of 137 SNR candidates, yielding confirmation of (or at least strongly support for) their SNR identifications. A spectral analysis of the seven X-ray brightest SNRs reveals that two, G98-31 and G98-35, have spectra that appear to indicate enrichment by ejecta from core-collapse supernova explosions. We have used a combination of new and archival optical and radio observations to attempt to better understand why some objects are detected as X-ray sources and others are not. We have also developed a morphological classification scheme for the optically identified SNRs and discussed the efficacy of this scheme as a predictor of X-ray detectability. Finally, we have compared the SNRs found in M33 to those that have been observed in the Galaxy and the Magellanic Clouds.
2453. 2019 SOAR speckle interferometry of binary stars
ID:
ivo://CDS.VizieR/J/AJ/160/7
Title:
2019 SOAR speckle interferometry of binary stars
Short Name:
J/AJ/160/7
Date:
09 Dec 2021
Publisher:
CDS
Description:
The results of speckle-interferometric observations at the 4.1m Southern Astrophysical Research Telescope in 2019 are given, totaling 2555 measurements of 1972 resolved pairs with separations from 15mas (median 0.21") and magnitude difference up to 6mag, and non-resolutions of 684 targets. We resolved for the first time 90 new pairs or subsystems in known binaries. This work continues our long-term speckle program. Its main goal is to monitor orbital motion of close binaries, including members of high-order hierarchies and Hipparcos pairs in the solar neighborhood. We give a list of 127 orbits computed using our latest measurements. Their quality varies from excellent (25 orbits of grades 1 and 2) to provisional (47 orbits of grades 4 and 5).
2454. Sodium excess objects. I. SDSS-DR7
ID:
ivo://CDS.VizieR/J/ApJS/208/7
Title:
Sodium excess objects. I. SDSS-DR7
Short Name:
J/ApJS/208/7
Date:
21 Oct 2021
Publisher:
CDS
Description:
Several studies have reported the presence of sodium excess objects having neutral atomic absorption lines at 5895{AA} (Na.D) and 8190{AA} that are deeper than expected based on stellar population models that match the stellar continuum. The origin of these lines is therefore hotly debated. van Dokkum & Conroy (2010Natur.468..940V) proposed that low-mass stars (<~0.3M_{sun}_) are more prevalent in massive early-type galaxies, which may lead to a strong Na I 8190 line strength. It is necessary to test this prediction, however, against other prominent optical line indices such as Na.D, Mg b, and Fe 5270, which can be measured with a significantly higher signal-to-noise ratio than Na I 8190. We identified a new sample of roughly 1000 Na.D excess objects (NEOs; ~8% of galaxies in the sample) based on Na.D line strength in the redshift range 0.00<=z<=0.08 from the Sloan Digital Sky Survey (SDSS) DR7 through detailed analysis of galaxy spectra. We explore the properties of these new objects here. The novelty of this work is that the galaxies were carefully identified through direct visual inspection of SDSS images, and we systematically compared the properties of NEOs and those of a control sample of galaxies with normal Na.D line strengths. We note that the majority of galaxies with high velocity dispersions ({sigma}_e_>250km/s) show Na.D excesses.
2455. Solar neighborhood. XXXIII. 45 M dwarfs
ID:
ivo://CDS.VizieR/J/AJ/147/85
Title:
Solar neighborhood. XXXIII. 45 M dwarfs
Short Name:
J/AJ/147/85
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present basic observational data and association membership analysis for 45 young and active low-mass stellar systems from the ongoing Research Consortium On Nearby Stars photometry and astrometry program at the Cerro Tololo Inter-American Observatory. Most of these systems have saturated X-ray emission (log(L_X_/L_bol_)>-3.5) based on X-ray fluxes from the ROSAT All-Sky Survey, and many are significantly more luminous than main-sequence stars of comparable color. We present parallaxes and proper motions, Johnson-Kron-Cousins VRI photometry, and multiplicity observations from the CTIOPI program on the CTIO 0.9m telescope. To this we add low-resolution optical spectroscopy and line measurements from the CTIO 1.5m telescope, and interferometric binary measurements from the Hubble Space Telescope Fine Guidance Sensors. We also incorporate data from published sources: JHK_S_ photometry from the Two Micron All Sky Survey point source catalog, X-ray data from the ROSAT All-Sky Survey, and radial velocities from literature sources. Within the sample of 45 systems, we identify 21 candidate low-mass pre-main-sequence members of nearby associations, including members of {beta} Pictoris, TW Hydrae, Argus, AB Doradus, two ambiguous {approx}30Myr old systems, and one object that may be a member of the Ursa Major moving group. Of the 21 candidate young systems, 14 are newly identified as a result of this work, and six of those are within 25pc of the Sun.
2456. Solar neighborhood. XXXII. L and M dwarfs
ID:
ivo://CDS.VizieR/J/AJ/147/94
Title:
Solar neighborhood. XXXII. L and M dwarfs
Short Name:
J/AJ/147/94
Date:
21 Oct 2021
Publisher:
CDS
Description:
We construct a Hertzsprung-Russell diagram for the stellar/substellar boundary based on a sample of 63 objects ranging in spectral type from M6V to L4. We report newly observed VRI photometry for all 63 objects and new trigonometric parallaxes for 37 objects. The remaining 26 objects have trigonometric parallaxes from the literature. We combine our optical photometry and trigonometric parallaxes with 2MASS and WISE photometry and employ a novel spectral energy distribution fitting algorithm to determine effective temperatures, bolometric luminosities, and radii. Our uncertainties range from ~20K to ~150K in temperature, ~0.01 to ~0.06 in log (L/L_{sun}_) and ~3% to ~10% in radius. We check our methodology by comparing our calculated radii to radii directly measured via long baseline optical interferometry. We find evidence for the local minimum in the radius-temperature and radius-luminosity trends that signals the end of the stellar main sequence and the start of the brown dwarf sequence at T_eff_~2075K, log(L/L_{sun}_)~-3.9, and (R/R_{sun}_)~0.086. The existence of this local minimum is predicted by evolutionary models, but at temperatures ~400K cooler. The minimum radius happens near the locus of 2MASS J0523-1403, an L2.5 dwarf with V-K=9.42. We make qualitative arguments as to why the effects of the recent revision in solar abundances accounts for the discrepancy between our findings and the evolutionary models. We also report new color-absolute magnitude relations for optical and infrared colors which are useful for estimating photometric distances. We study the optical variability of all 63 targets and find an overall variability fraction of 36_-7_^+9^% at a threshold of 15mmag in the I band, which is in agreement with previous studies.
2457. Solar neighborhood. XXXIX. Nearby white dwarfs
ID:
ivo://CDS.VizieR/J/AJ/154/32
Title:
Solar neighborhood. XXXIX. Nearby white dwarfs
Short Name:
J/AJ/154/32
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 114 trigonometric parallaxes for 107 nearby white dwarf (WD) systems from both the Cerro Tololo Inter-American Observatory Parallax Investigation (CTIOPI) and the U. S. Naval Observatory Flagstaff Station (NOFS) parallax programs. Of these, 76 parallaxes for 69 systems were measured by the CTIOPI program and 38 parallaxes for as many systems were measured by the NOFS program. A total of 50 systems are confirmed to be within the 25-pc horizon of interest. Coupled with a spectroscopic confirmation of a common proper-motion companion to a Hipparcos star within 25pc as well as confirmation parallax determinations for two WD systems included in the recently released Tycho Gaia Astrometric Solution catalog, we add 53 new systems to the 25-pc WD sample-a 42% increase. Our sample presented here includes four strong candidate halo systems, a new metal-rich DAZ WD, a confirmation of a recently discovered nearby short-period (P=2.85hr) double degenerate, a WD with a new astrometric perturbation (long period, unconstrained with our data), and a new triple system where the WD companion main-sequence star has an astrometric perturbation (P~1.6year).
2458. Solar neighborhood. XXXV. Distances to M dwarfs
ID:
ivo://CDS.VizieR/J/AJ/149/5
Title:
Solar neighborhood. XXXV. Distances to M dwarfs
Short Name:
J/AJ/149/5
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present trigonometric, photometric, and photographic distances to 1748 southern ({delta}{<=}O{deg}) M dwarf systems with {mu}>=0.18''/yr, of which 1404 are believed to lie within 25pc of the Sun. The stars have 6.67{<=}V_J_{<=}21.38 and 3.50{<=}(V_J_-K_S_){<=}9.27, covering the entire M dwarf spectral sequence from M0.0 V through M9.5 V. This sample therefore provides a comprehensive snapshot of our current knowledge of the southern sky for the nearest M dwarfs that dominate the stellar population of the Galaxy. Roughly one-third of the 1748 systems, each of which has an M dwarf primary, have published high quality parallaxes, including 179 from the REsearch Consortium On Nearby Stars astrometry program. For the remaining systems, we offer photometric distance estimates that have well-calibrated errors. The bulk of these (~700) are based on new V_J_R_KC_I_KC_ photometry acquired at the CTIO/SMARTS 0.9m telescope, while the remaining 500 primaries have photographic plate distance estimates calculated using SuperCOSMOS B_J_R_59F_I_IVN_ photometry. Confirmed and candidate subdwarfs in the sample have been identified, and a census of companions is included.
2459. Solar neighborhood XXXVIII. Nearby M dwarf systems
ID:
ivo://CDS.VizieR/J/AJ/153/14
Title:
Solar neighborhood XXXVIII. Nearby M dwarf systems
Short Name:
J/AJ/153/14
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 160 new trigonometric parallaxes for 151 M dwarf systems from the REsearch Consortium On Nearby Stars (RECONS) group's long-term astrometry/photometry program at the CTIO/SMARTS 0.9m telescope. Most systems (124 or 82%) are found to lie within 25pc. The stars have 119mas/yr{<=}{mu}{<=}828mas/yr and 3.85{<=}(V-K){<=}8.47. Among these are 58 systems from the SuperCOSMOS-RECONS search, discovered via our proper motion trawls of the SuperCOSMOS digitized archival photographic plates, while the remaining stars were suspected via photometric distance estimates to lie nearby. Sixteen systems were newly discovered via astrometric perturbations to be binaries, many of which are ideal for accurate mass determinations due to their proximity and orbital periods on the order of a decade. A variability analysis of the stars presented, two-thirds of which are new results, shows six of the stars to vary by more than 20mmag. This effort brings the total number of parallaxes for M dwarf systems measured by RECONS to nearly 500 and increases by 26% the number of southern M dwarf systems with accurate trigonometric parallaxes placing them within 25pc.
2460. Solar neighborhood. XXXVI. VRI variability of M dwarfs
ID:
ivo://CDS.VizieR/J/AJ/150/6
Title:
Solar neighborhood. XXXVI. VRI variability of M dwarfs
Short Name:
J/AJ/150/6
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of long-term photometric variability for nearby red dwarf stars at optical wavelengths. The sample consists of 264 M dwarfs south of decl.=+30 with V-K=3.96-9.16 and M_V_~~10-20, corresponding to spectral types M2V-M8V, most of which are within 25pc. The stars have been observed in the VRI filters for ~4-14yr at the CTIO/SMARTS 0.9m telescope. Of the 238 red dwarfs within 25pc, we find that only ~8% are photometrically variable by at least 20mmag (~2%) in the VRI bands. Only four stars have been found to vary by more than 50mmag, including GJ 1207 at 8.6pc, which experienced a single extraordinary flare, and GJ 2006 A, TWA 8 A, and TWA 8 B, which are all young stars beyond 25pc linked to moving groups. We find that high variability at optical wavelengths over the long term can in fact be used to identify young stars. Overall, however, the fluxes of most red dwarfs at optical wavelengths are steady to a few percent over the long term. The low overall rate of photometric variability for red dwarfs is consistent with results found in previous work on similar stars on shorter timescales, with the body of work indicating that most red dwarfs are only mildly variable. As expected, we find that the degree of photometric variability is greater in the V band than in the R or I bands, but we do not find any obvious trends in variability over the long term with red dwarf luminosity or temperature. We highlight 17 stars that show long-term changes in brightness, sometimes because of flaring activity or spots, and sometimes because of stellar cycles similar to our Sun's solar cycle. Remarkably, two targets show brightnesses that monotonically increase (G 169-029) or decrease (WT 460AB) by several percent over a decade. We also provide long-term variability measurements for seven M dwarfs within 25pc that host exoplanets, none of which vary by more than 20mmag. Both as a population, and for the specific red dwarfs with exoplanets observed here, photometric variability is therefore often not a concern for planetary environments, at least at the optical wavelengths where they emit much of their light.