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2361. SN 2020cxd multi-photometry
ID:
ivo://CDS.VizieR/J/A+A/655/A90
Title:
SN 2020cxd multi-photometry
Short Name:
J/A+A/655/A90
Date:
22 Feb 2022
Publisher:
CDS
Description:
We present observations and analysis of SN 2020cxd, a low-luminosity (LL), long-lived Type IIP supernova (SN). This object was a clear outlier in the magnitude-limited SN sample recently presented by the Zwicky Transient Facility (ZTF) Bright Transient Survey. We demonstrate that SN 2020cxd is an additional member of the group of LL SNe, and discuss the rarity of LL SNe in the context of the ZTF survey, and how further studies of these faintest members of the core-collapse (CC) SN family might help understand the underlying initial mass function for stars that explode. We present optical light curves (LCs) from the ZTF in the $gri$ bands and several epochs of ultra-violet data from the Neil Gehrels Swift Observatory as well as a sequence of optical spectra. We construct colour curves, a bolometric LC, compare ejecta-velocity and black-body temperature evolutions for LL SNe, as well as for typical Type II SNe. Furthermore, we adopt a Monte Carlo code that fits semi-analytic models to the LC of SN 2020cxd, which allows the estimation of physical parameters. Using our late-time nebular spectra, we also compare against SN II spectral synthesis models from the literature to constrain the progenitor properties of SN 2020cxd. The LCs of SN 2020cxd show great similarity with those of LL SNe IIP, in luminosity, timescale and colours. Also the spectral evolution of SN 2020cxd is that of a Type IIP SN. The spectra show prominent and narrow P-Cygni lines, indicating low expansion velocities. This is one of the faintest LL SNe observed, with an absolute plateau magnitude of M_r_=-14.5mag, and also one with the longest plateau lengths, with a duration of 118 days. Finally, the velocities measured from the nebular emission lines are among the lowest ever seen in a SN, with intrinsic Full Width at Half Maximum of 478km/s. The underluminous late-time exponential LC tail indicates that the mass of ^56^Ni ejected during the explosion is much smaller than the average of normal SNe IIP, we estimate M_^56^Ni_=0.003M+{sun+_. The Monte Carlo fitting of the bolometric LC suggests that the progenitor of SN 2020cxd had a radius of R_0_=1.3x10^13^cm, kinetic energy of E_kin_=4.3x10^50^erg, and ejecta mass M_ej_=9.5M_{sun}_. From the bolometric LC, we estimate the total radiated energy E_rad_=1.52x10^48^erg. Using our late-time nebular spectra, we compare against SN II spectral synthesis models to constrain the progenitor Zero-age Main-sequence mass and found it likely to be <~15M_{sun}+. SN 2020cxd is a LL Type IIP SN. The inferred progenitor parameters and the features observed in the nebular spectrum favour a low-energy, Ni-poor, iron CC SN from a low mass ~12M_{sun}_ red supergiant.
2362. SNe Ia spectra from SNLS
ID:
ivo://CDS.VizieR/J/A+A/614/A134
Title:
SNe Ia spectra from SNLS
Short Name:
J/A+A/614/A134
Date:
21 Oct 2021
Publisher:
CDS
Description:
We aim to present 70 spectra of 68 new high-redshift type Ia supernovae (SNe Ia) measured at ESO's VLT during the final two years of operation (2006-2008) of the Supernova Legacy Survey (SNLS). This new sample complements the VLT three year spectral set. Altogether, these two data sets form the five year sample of SNLS SN Ia spectra measured at the VLT on which the final SNLS cosmological analysis will partly be based. In the redshift range considered, this sample is unique in terms of homogeneity and number of spectra. We use it to investigate the possibility of a spectral evolution of SNe Ia populations with redshift as well as SNe Ia spectral properties as a function of lightcurve fit parameters and the mass of the host-galaxy. Reduction and extraction are based on both IRAF standard tasks and our own reduction pipeline. Redshifts are estimated from host-galaxy lines whenever possible or alternatively from supernova features. We used the spectro-photometric SN Ia model SALT2 combined with a set of galaxy templates that model the host-galaxy contamination to assess the type Ia nature of the candidates. We identify 68 new SNe Ia with redshift ranging from z=0.207 to z=0.98 for an average redshift of z=0.62. Each spectrum is presented individually along with its best-fit SALT2 model. Adding this new sample to the three year VLT sample of SNLS, the final dataset contains 209 spectra corresponding to 192 SNe Ia identified at the VLT. We also publish the redshifts of other candidates (host galaxies or other transients) whose spectra were obtained at the same time as the spectra of live SNe Ia. This list provides a new redshift catalog useful for upcoming galaxy surveys. Using the full VLT SNe Ia sample, we build composite spectra around maximum light with cuts in color, the lightcurve shape parameter ("stretch"), host-galaxy mass and redshift. We find that high-z SNe Ia are bluer, brighter and have weaker intermediate mass element absorption lines than their low-z counterparts at a level consistent with what is expected from selection effects. We also find a flux excess in the range [3000-3400]{AA} for SNe Ia in low mass host-galaxies (M<10^10^M_{sun}_) or with locally blue U-V colors, and suggest that the UV flux (or local color) may be used in future cosmological studies as a third standardization parameter in addition to stretch and color.
2363. SNe II light curves & spectra from the CfA
ID:
ivo://CDS.VizieR/J/ApJS/233/6
Title:
SNe II light curves & spectra from the CfA
Short Name:
J/ApJS/233/6
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present multiband photometry of 60 spectroscopically confirmed supernovae (SNe): 39 SNe II/IIP, 19 IIn, 1 IIb, and 1 that was originally classified as a IIn but later as a Ibn. Of these, 46 have only optical photometry, 6 have only near-infrared (NIR) photometry, and 8 have both optical and NIR. The median redshift of the sample is 0.016. We also present 195 optical spectra for 48 of the 60 SN. There are 26 optical and 2 NIR light curves of SNe II/IIP with redshifts z>0.01, some of which may give rise to useful distances for cosmological applications. All photometry was obtained between 2000 and 2011 at the Fred Lawrence Whipple Observatory (FLWO), via the 1.2m and 1.3m PAIRITEL telescopes for the optical and NIR, respectively. Each SN was observed in a subset of the u'UBVRIr'i'JHK_s_ bands. There are a total of 2932 optical and 816 NIR light curve points. Optical spectra were obtained using the FLWO 1.5m Tillinghast telescope with the FAST spectrograph and the MMT Telescope with the Blue Channel Spectrograph. Our photometry is in reasonable agreement with select samples from the literature: two-thirds of our star sequences have average V offsets within +/-0.02mag and roughly three-quarters of our light curves have average differences within +/-0.04mag. The data from this work and the literature will provide insight into SN II explosions, help with developing methods for photometric SN classification, and contribute to their use as cosmological distance indicators.
2364. SN 2020faa multiphotometry and spectra
ID:
ivo://CDS.VizieR/J/A+A/646/A22
Title:
SN 2020faa multiphotometry and spectra
Short Name:
J/A+A/646/A22
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present observations of SN 2020faa. This Type II supernova displays a luminous lightcurve that started to rebrighten from an initial decline. We investigate this in relation to the famous supernova iPTF14hls, which received a great deal of attention and multiple interpretations in the literature, but whose nature and source of energy still remain unknown. We demonstrate the great similarity between SN 2020faa and iPTF14hls during the first 6 months, and use this comparison to forecast the evolution of SN 2020faa and to reflect on the less well observed early evolution of iPTF14hls. We present and analyse our observational data, consisting mainly of optical lightcurves from the Zwicky Transient Facility in the gri bands and of a sequence of optical spectra. We construct colour curves and a bolometric lightcurve, and we compare ejecta-velocity and black-body radius evolutions for the two supernovae and for more typical Type II supernovae. The lightcurves show a great similarity with those of iPTF14hls over the first 6 months in luminosity, timescale, and colour. In addition, the spectral evolution of SN 2020faa is that of a Type II supernova, although it probes earlier epochs than those available for iPTF14hls. The similar lightcurve behaviour is suggestive of SN 2020faa being a new iPTF14hls. We present these observations now to advocate follow-up observations, since most of the more striking evolution of supernova iPTF14hls came later, with lightcurve undulations and a spectacular longevity. On the other hand, for SN 2020faa we have better constraints on the explosion epoch than we had for iPTF14hls, and we have been able to spectroscopically monitor it from earlier phases than was done for the more famous sibling.
2365. SNF20080514-002 and LSQ12fxd spectra
ID:
ivo://CDS.VizieR/J/A+A/614/A71
Title:
SNF20080514-002 and LSQ12fxd spectra
Short Name:
J/A+A/614/A71
Date:
21 Oct 2021
Publisher:
CDS
Description:
Observations of Type Ia supernovae (SNe Ia) can be used to derive accurate cosmological distances through empirical standardization techniques. Despite this success neither the progenitors of SNe Ia nor the explosion process are fully understood. The U-band region has been less well observed for nearby SNe, due to technical challenges, but is the most readily accessible band for high-redshift SNe. Using spectrophotometry from the Nearby Supernova Factory, we study the origin and extent of U-band spectroscopic variations in SNe Ia and explore consequences for their standardization and the potential for providing new insights into the explosion process. We divide the U-band spectrum into four wavelength regions {lambda}(uNi), {lambda}(uTi), {lambda}(uSi) and {lambda}(uCa). Two of these span the Ca H&K {lambda}{lambda}3934,3969 complex. We employ spectral synthesis using SYNAPPS to associate the two bluer regions with Ni/Co and Ti. Results: (1) The flux of the uTi feature is an extremely sensitive temperature/luminosity indicator, standardizing the SN peak luminosity to 0.116+/-0.011mag RMS. A traditional SALT2.4 fit on the same sample yields a 0.135mag RMS. Standardization using uTi also reduces the difference in corrected magnitude between SNe originating from different host galaxy environments. (2) Early U-band spectra can be used to probe the Ni+Co distribution in the ejecta, thus offering a rare window into the source of lightcurve power. (3) The uCa flux further improves standardization, yielding a 0.086+/-0.010mag RMS without the need to include an additional intrinsic dispersion to reach chi^2^/dof~1. This reduction in RMS is partially driven by an improved standardization of Shallow Silicon and 91T-like SNe.
2366. SN2016hnk photometry and spectroscopy
ID:
ivo://CDS.VizieR/J/A+A/630/A76
Title:
SN2016hnk photometry and spectroscopy
Short Name:
J/A+A/630/A76
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a comprehensive dataset of optical and near-infrared photometry and spectroscopy of type Ia supernova (SN) 2016hnk, combined with integral field spectroscopy (IFS) of its host galaxy, MCG -01-06-070, and nearby environment. Our goal with this complete dataset is to understand the nature of this peculiar object. Methods: Properties of the SN local environment are characterized by means of single stellar population synthesis applied to IFS observations taken two years after the SN exploded. We performed detailed analyses of SN photometric data by studying its peculiar light and color curves. SN 2016hnk spectra were compared to other 1991bg-like SNe Ia, 2002es-like SNe Ia, and Ca-rich transients. In addition, we used abundance stratification modeling to identify the various spectral features in the early phase spectral sequence and also compared the dataset to a modified non-LTE model previously produced for the subluminous SN1999by. Results: SN 2016hnk is consistent with being a subluminous (MB=-16.7mag, sBV=0.43+/-0.03), highly reddened object. The IFS of its host galaxy reveals both a significant amount of dust at the SN location, residual star formation, and a high proportion of old stellar populations in the local environment compared to other locations in the galaxy, which favors an old progenitor for SN 2016hnk. Inspection of a nebular spectrum obtained one year after maximum contains two narrow emission lines attributed to the forbidden [CaII] {lambda}{lambda}7291,7324 doublet with a Doppler shift of 700km/s. Based on various observational diagnostics, we argue that the progenitor of SN 2016hnk was likely a near Chandrasekhar-mass (MCh) carbon-oxygen white dwarf that produced 0.108M_{sun}_ of 56 Ni. Our modeling suggests that the narrow [CaII] features observed in the nebular spectrum are associated with 48 Ca from electron capture during the explosion, which is expected to occur only in white dwarfs that explode near or at the MCh limit.
2367. SN1993J spectra 100 to 500 days post-explosion
ID:
ivo://CDS.VizieR/J/A+A/573/A12
Title:
SN1993J spectra 100 to 500 days post-explosion
Short Name:
J/A+A/573/A12
Date:
21 Oct 2021
Publisher:
CDS
Description:
We investigate line formation processes in Type IIb supernovae (SNe) from 100 to 500 days post-explosion using spectral synthesis calculations. The modelling identifies the nuclear burning layers and physical mechanisms that produce the major emission lines, and the diagnostic potential of these. We compare the model calculations with data on the three best observed Type IIb SNe to-date - SN 1993J, SN 2008ax, and SN 2011dh.
2368. SNU bright quasar survey (SNUQSO)
ID:
ivo://CDS.VizieR/J/ApJS/175/116
Title:
SNU bright quasar survey (SNUQSO)
Short Name:
J/ApJS/175/116
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from the first phase of the Seoul National University Bright Quasar Survey in Optical (SNUQSO) as well as its basic observational setup. Previous and current large-area surveys have been successful in identifying many quasars, but they could have missed bright quasars due to their survey design. In order to help complete the census of bright quasars, we have performed spectroscopic observations of new bright quasar candidates selected from various methods based on optical colors, near-infrared colors, radio, and X-ray data. In 2005/2006, we observed 55 bright quasar candidates using the Bohyunsan Optical Echelle Spectrograph (BOES) on the 1.8m telescope at the Bohyunsan Optical Astronomy Observatory in Korea. We identify 14 quasars/Seyferts from our observation, including an optically bright quasar with i=14.98mag at z=0.092 (SDSS J003236.59-091026.2). Non-quasar/Seyfert objects are found to be mostly stars, among which there are five M-type stars and one cataclysmic variable. Our result shows that there still exist bright quasars to be discovered. However, at the same time, we conclude that finding new bright quasars in high Galactic latitude regions is very challenging and that the existing compilation of optically bright quasars is nearly complete in the northern hemisphere.
2369. SN 2012Z spectra
ID:
ivo://CDS.VizieR/J/A+A/573/A2
Title:
SN 2012Z spectra
Short Name:
J/A+A/573/A2
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 8 unpublished low-resolution visual-wavelength spectra of the Type Iax supernova 2012Z ranging from +1.8d to +248.1d relative to B-band maximum. In addition a high-resolution spectrum is presented obtained on -6.4d. Accompanying these data are 7 low-resolution spectra ranging from -9.2d to +33.8d, which were previously published by Foley et al. (2013ApJ...767...57F). The Foley et al. spectra were provided in normalized ascii format, which we have convert to fits format. Finally, we present the most comprehensive set of near-infrared spectra yet obtained for a Type Ia supernova. This includes 10 epochs ranging from -7.3d to +268.8d relative to B-band maximum. For spectra taken with ESO facilities a single fits file is present for each instrumental setup, i.e., each grating has its own fits file. For the FIRE spectra the one-dimensional spectra are stored in fits files as 2048x3 arrays, corresponding to the wavelength, flux and error values for each of the 2048 pixels across the detector. The wavelength and flux are as observed.
2370. SOAR spectra of the WD EPIC 228939929
ID:
ivo://CDS.VizieR/J/ApJ/894/19
Title:
SOAR spectra of the WD EPIC 228939929
Short Name:
J/ApJ/894/19
Date:
03 Dec 2021 00:38:57
Publisher:
CDS
Description:
We report the discovery of short-period photometric variability and modulated Zeeman-split hydrogen emission in SDSSJ125230.93-023417.72 (EPIC 228939929), a variable white dwarf star observed at long cadence in K2 Campaign 10. The behavior is associated with a magnetic (B=5.0MG) spot on the stellar surface, making the 317.278s period a direct measurement of the stellar rotation rate. This object is therefore the fastest-rotating, apparently isolated (without a stellar companion) white dwarf yet discovered and the second found to exhibit chromospheric Balmer emission after GD 356, in which the emission has been attributed to a unipolar inductor mechanism driven by a possible rocky planet. We explore the properties and behavior of this object, and consider whether its evolution may hold implications for white dwarf mergers and their remnants.

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