- ID:
- ivo://CDS.VizieR/J/MNRAS/451/1973
- Title:
- Type Ia supernovae igh-velocity features
- Short Name:
- J/MNRAS/451/1973
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 'High-velocity features' (HVFs) are spectral features in Type Ia supernovae (SNe Ia) that have minima indicating significantly higher (by greater than about 6000km/s) velocities than typical 'photospheric-velocity features' (PVFs). The PVFs are absorption features with minima indicating typical photospheric (i.e. bulk ejecta) velocities (usually~9000-15000km/s near B-band maximum brightness). In this work, we undertake the most in-depth study of HVFs ever performed. The data set used herein consists of 445 low-resolution optical and near-infrared (NIR) spectra (at epochs up to 5d past maximum brightness) of 210 low-redshift SNe Ia that follow the 'Phillips relation'. A series of Gaussian functions is fit to the data in order to characterize possible HVFs of CaII H&K, SiII {lambda}6355, and the CaII NIR triplet. The temporal evolution of the velocities and strengths of the PVFs and HVFs of these three spectral features is investigated, as are possible correlations with other SN Ia observables. We find that while HVFs of CaII are regularly observed (except in underluminous SNe Ia, where they are never found), HVFs of Siii {lambda}6355 are significantly rarer, and they tend to exist at the earliest epochs and mostly in objects with large photospheric velocities. It is also shown that stronger HVFs of SiII {lambda}6355 are found in objects that lack CII absorption at early times and that have red ultraviolet/optical colours near maximum brightness. These results lead to a self-consistent connection between the presence and strength of HVFs of SiII {lambda}6355 and many other mutually correlated SN Ia observables, including photospheric velocity.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/146/61
- Title:
- Type II Cepheid candidates. IV. Objects from NSVS
- Short Name:
- J/AJ/146/61
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained VR photometry of 447 Cepheid variable star candidates with declinations north of -14{deg}30', most of which were identified using the Northern Sky Variability Survey (NSVS) data archive. Periods and other photometric properties were derived from the combination of our data with the NSVS data. Atmospheric parameters were determined for 81 of these stars from low-resolution spectra. The identification of type II Cepheids based on the data presented in all four papers in this series is discussed. On the basis of spectra, 30 type II Cepheids were identified while 53 variables were identified as cool, main sequence stars and 283 as red giants following the definitions in Paper III. An additional 30 type II Cepheids were identified on the basis of light curves. The present classifications are compared with those from the Machine-learned All Sky Automated Survey Classification Catalog for 174 stars in common.
- ID:
- ivo://CDS.VizieR/J/ApJ/799/208
- Title:
- Type IIP supernovae from Pan-STARRS1
- Short Name:
- J/ApJ/799/208
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In recent years, wide-field sky surveys providing deep multiband imaging have presented a new path for indirectly characterizing the progenitor populations of core-collapse supernovae (SNe): systematic light-curve studies. We assemble a set of 76 grizy-band Type IIP SN light curves from Pan-STARRS1, obtained over a constant survey program of 4yr and classified using both spectroscopy and machine-learning-based photometric techniques. We develop and apply a new Bayesian model for the full multiband evolution of each light curve in the sample. We find no evidence of a subpopulation of fast-declining explosions (historically referred to as "Type IIL" SNe). However, we identify a highly significant relation between the plateau phase decay rate and peak luminosity among our SNe IIP. These results argue in favor of a single parameter, likely determined by initial stellar mass, predominantly controlling the explosions of red supergiants. This relation could also be applied for SN cosmology, offering a standardizable candle good to an intrinsic scatter of <~0.2mag. We compare each light curve to physical models from hydrodynamic simulations to estimate progenitor initial masses and other properties of the Pan-STARRS1 Type IIP SN sample. We show that correction of systematic discrepancies between modeled and observed SN IIP light-curve properties and an expanded grid of progenitor properties are needed to enable robust progenitor inferences from multiband light-curve samples of this kind. This work will serve as a pathfinder for photometric studies of core-collapse SNe to be conducted through future wide-field transient searches.
- ID:
- ivo://CDS.VizieR/J/A+A/434/1107
- Title:
- UBV(RI)c photometry of stars around V838 Mon
- Short Name:
- J/A+A/434/1107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extensive optical and infrared photometry as well as low and high resolution spectroscopy are used as inputs in deriving robust estimates of the reddening, distance and nature of the progenitor of V838 Mon, the 2002 outbursting event that produced a most spectacular light-echo.
- ID:
- ivo://CDS.VizieR/J/ApJ/737/86
- Title:
- UCD galaxies in the Coma cluster
- Short Name:
- J/ApJ/737/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have undertaken a spectroscopic search for ultra-compact dwarf galaxies (UCDs) in the dense core of the dynamically evolved, massive Coma cluster as part of the Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) Coma Cluster Treasury Survey. UCD candidates were initially chosen based on color, magnitude, degree of resolution within the ACS images, and the known properties of Fornax and Virgo UCDs. Follow-up spectroscopy with Keck/Low-Resolution Imaging Spectrometer confirmed 27 candidates as members of the Coma cluster, a success rate >60% for targeted objects brighter than M_R_=-12. Another 14 candidates may also prove to be Coma members, but low signal-to-noise spectra prevent definitive conclusions.
- ID:
- ivo://CDS.VizieR/J/ApJS/171/29
- Title:
- UCSD/Keck Damped Ly{alpha} Abundance Database
- Short Name:
- J/ApJS/171/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We publish the Keck/HIRES and Keck/ESI spectra that we have obtained during the first 10 years of Keck observatory operations. Our full sample includes 42 HIRES spectra and 39 ESI spectra along 65 unique sight lines providing abundance measurements on about 85 DLA systems. The normalized data can be downloaded from the journal or from our supporting Web site. The database includes all of the sight lines that have been included in our papers on the chemical abundances, kinematics, and metallicities of the damped Ly{alpha} systems. This data has also been used to argue for variations in the fine-structure constant. We present new chemical abundance measurements for 10 damped Ly{alpha} systems and a summary table of high-resolution metallicity measurements (including values from the literature) for 153 damped Ly{alpha} systems at z>1.6. We caution, however, that this metallicity sample (and all previous ones) is biased to higher N_HI_ values than a random sample.
1937. U Gem spectroscopy
- ID:
- ivo://CDS.VizieR/J/MNRAS/361/1091
- Title:
- U Gem spectroscopy
- Short Name:
- J/MNRAS/361/1091
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a phase-resolved spectroscopic study of the secondary star in the cataclysmic variable (CV) U Gem. We use our data to measure the radial velocity semi-amplitude, systemic velocity and rotational velocity of the secondary star. Combining this with literature data allows us to determine masses and radii for both the secondary star and white dwarf, which are independent of any assumptions about their structure. We use these to compare their properties to those of field stars and find that both components follow field mass-radius relationships. The secondary star has the mass, radius, luminosity and photometric temperature of an M2 star, but a spectroscopic temperature of M4. The latter may well be due to a high metallicity. There is a troubling inconsistency between the radius of the white dwarf inferred from its gravitational redshift and inclination and that inferred from its temperature, flux and astrometric distance.
- ID:
- ivo://CDS.VizieR/J/AJ/126/1720
- Title:
- ugriz and H{alpha} of double-peaked AGN
- Short Name:
- J/AJ/126/1720
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new sample of 116 double-peaked Balmer line active galactic nuclei (AGNs) selected from the Sloan Digital Sky Survey.
- ID:
- ivo://CDS.VizieR/J/AJ/136/1290
- Title:
- Ultracool dwarfs from the 2MASS
- Short Name:
- J/AJ/136/1290
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using data from the 2 Micron All Sky Survey All-Sky Point Source Catalogue, we have extended our census of nearby ultracool dwarfs to cover the full celestial sphere above Galactic latitude of 15{deg}. Starting with an initial catalog of 2139484 sources, we have winnowed the sample to 467 candidate late-type M or L dwarfs within 20pc of the Sun. Fifty-four of those sources already have spectroscopic observations confirming them as late-type dwarfs. We present optical spectroscopy of 376 of the remaining 413 sources, and identify 44 as ultracool dwarfs with spectroscopic distances less than 20pc. Twenty-five of the 37 sources that lack optical data have near-infrared spectroscopy. Combining the present sample with our previous results and data from the literature, we catalog 94 L dwarf systems within 2pc. We discuss the distribution of activity, as measured by H{alpha} emission, in this volume-limited sample. We have coupled the present ultracool catalog with data for stars in the northern 8pc sample and recent (incomplete) statistics for T dwarfs to provide a snapshot of the current 20pc census as a function of spectral type.
- ID:
- ivo://CDS.VizieR/J/AJ/160/19
- Title:
- 827 ultracool dwarfs with K2
- Short Name:
- J/AJ/160/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The occurrence of planets orbiting ultracool dwarfs is poorly constrained. We present results from a guest observer program on NASA's K2 spacecraft to search for transiting planets orbiting a sample of 827 ultracool dwarfs. Having found no transiting planets in our sample, we determined an upper limit on the occurrence of planets. We simulated planets orbiting our sample for a range of orbital periods and sizes. For the simulated planets that transit their host, we injected the transit light curve into the real K2 light curves, then attempted to recover the injected planets. For a given occurrence rate, we calculated the probability of seeing no planets, and use the results to place an upper limit on planet occurrence as a function of planet radius and orbital period. We find that short-period, mini-Neptune and Jupiter-sized planets are rare around ultracool dwarfs, consistent with results for early and mid-type M dwarf stars. We constrain the occurrence rate {eta} for planets between 0.5 and 10 R{earth} with orbital periods between 1 and 26.3days.
