Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/135/348
- Title:
- SDSS-II SNe survey: search and follow-up
- Short Name:
- J/AJ/135/348
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sloan Digital Sky Survey-II Supernova Survey has identified a large number of new transient sources in a 300deg^2^ region along the celestial equator during its first two seasons of a three-season campaign. Multi-band (ugriz) light curves were measured for most of the sources, which include solar system objects, galactic variable stars, active galactic nuclei, supernovae (SNe), and other astronomical transients. The imaging survey is augmented by an extensive spectroscopic follow-up program to identify SNe, measure their redshifts, and study the physical conditions of the explosions and their environment through spectroscopic diagnostics. During the survey, light curves are rapidly evaluated to provide an initial photometric type of the SNe, and a selected sample of sources are targeted for spectroscopic observations. In the first two seasons, 476 sources were selected for spectroscopic observations, of which 403 were identified as SNe. For the type Ia SNe, the main driver for the survey, our photometric typing and targeting efficiency is 90%. Only 6% of the photometric SN Ia candidates were spectroscopically classified as non-SN Ia instead, and the remaining 4% resulted in low signal-to-noise, unclassified spectra.
- ID:
- ivo://CDS.VizieR/J/ApJ/821/115
- Title:
- SDSS-II SN Survey: host-galaxy spectral data
- Short Name:
- J/ApJ/821/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the largest single-survey sample of Type Ia supernovae (SNe Ia) to date, we study the relationship between properties of SNe Ia and those of their host galaxies, focusing primarily on correlations with Hubble residuals (HRs). Our sample consists of 345 photometrically classified or spectroscopically confirmed SNe Ia discovered as part of the SDSS-II Supernova Survey (SDSS-SNS). This analysis utilizes host-galaxy spectroscopy obtained during the SDSS-I/II spectroscopic survey and from an ancillary program on the SDSS-III Baryon Oscillation Spectroscopic Survey that obtained spectra for nearly all host galaxies of SDSS-II SN candidates. In addition, we use photometric host-galaxy properties from the SDSS-SNS data release such as host stellar mass and star formation rate. We confirm the well-known relation between HR and host-galaxy mass and find a 3.6{sigma} significance of a nonzero linear slope. We also recover correlations between HR and host-galaxy gas-phase metallicity and specific star formation rate as they are reported in the literature. With our large data set, we examine correlations between HR and multiple host-galaxy properties simultaneously and find no evidence of a significant correlation. We also independently analyze our spectroscopically confirmed and photometrically classified SNe Ia and comment on the significance of similar combined data sets for future surveys.
- ID:
- ivo://CDS.VizieR/J/ApJ/708/661
- Title:
- SDSS-II SN Survey: SNe II-P standardization
- Short Name:
- J/ApJ/708/661
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We apply the Standardized Candle Method (SCM) for Type II Plateau supernovae (SNe II-P), which relates the velocity of the ejecta of a SN to its luminosity during the plateau, to 15 SNe II-P discovered over the three season run of the Sloan Digital Sky Survey-II Supernova Survey. The redshifts of these SNe - 0.027<z<0.144 - cover a range hitherto sparsely sampled in the literature; in particular, our SNe II-P sample contains nearly as many SNe in the Hubble flow (z>0.01) as all of the current literature on the SCM combined. We find that the SDSS SNe have a very small intrinsic I-band dispersion (0.22mag), which can be attributed to selection effects. When the SCM is applied to the combined SDSS-plus-literature set of SNe II-P, the dispersion increases to 0.29mag, larger than the scatter for either set of SNe separately. We show that the standardization cannot be further improved by eliminating SNe with positive plateau decline rates, as proposed in Poznanski et al. (2009ApJ...694.1067P). We thoroughly examine all potential systematic effects and conclude that for the SCM to be useful for cosmology, the methods currently used to determine the FeII velocity at day 50 must be improved, and spectral templates able to encompass the intrinsic variations of Type II-P SNe will be needed.
- ID:
- ivo://CDS.VizieR/J/A+A/526/A28
- Title:
- SDSS-II supernovae NTT and NOT spectroscopy
- Short Name:
- J/A+A/526/A28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sloan Digital Sky Survey II (SDSS-II) Supernova Survey, conducted between 2005 and 2007, was designed to detect a large number of type Ia supernovae around z~0.2, the redshift "gap" between low-z and high-z supernova searches. The survey has provided multi-band (ugriz) photometric lightcurves for variable targets, and supernova candidates were scheduled for spectroscopic observations, primarily to provide supernova classification and accurate redshifts. We present supernova spectra obtained in 2006 and 2007 using the New Technology Telescope (NTT) and the Nordic Optical Telescope (NOT). We provide an atlas of supernova spectra in the range z=0.03-0.32 that complements the well-sampled lightcurves from SDSS-II in the forthcoming three-year SDSS supernova cosmology analysis. The sample can, for example, be used for spectral studies of type Ia supernovae, which are critical for understanding potential systematic effects when supernovae are used to determine cosmological distances. The spectra were reduced in a uniform manner, and special care was taken in estimating the uncertainties for the different processing steps. Host-galaxy light was subtracted when possible and the supernova type fitted using the SuperNova IDentification code (SNID). We also present comparisons between spectral and photometric dating using SALT lightcurve fits to the photometry from SDSS-II, as well as the global distribution of our sample in terms of the lightcurve parameters: stretch and colour.
- ID:
- ivo://CDS.VizieR/J/ApJ/674/668
- Title:
- SDSS J102839.11+450009.4 Fe II emission lines
- Short Name:
- J/ApJ/674/668
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report identification of SDSS J102839.11+450009.4 as a peculiarly interesting quasar. It shows very prominent narrow emission lines (NELs) in FeII that are remarkably different from the broad FeII multiplets commonly observed in quasars and Seyfert 1 galaxies. The FeII NEL spectrum is dominated in the UV by transitions to the low-lying ground levels with even parity, and by forbidden transitions in the optical, suggesting its formation in a warm collisionally ionized low density medium.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A102
- Title:
- SDSS J160429.12+100002.2 spectra
- Short Name:
- J/A+A/650/A102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the past, SDSS J160429.12+100002.2 was spectroscopically classified as a blue horizontal branch (BHB) star. Assuming a luminosity that is characteristic of BHB stars, the object's radial velocity and proper motions from Gaia Early Data Release 3 would imply that its Galactic rest-frame velocity exceeds its local escape velocity. Consequently, the object would be considered a hypervelocity star, which would prove particularly interesting because its Galactic trajectory points in our direction. However, based on the spectroscopic analysis of follow-up observations, we show that the object is actually a short-period (P~3.4h) single-lined spectroscopic binary system with a visible B-type star (effective temperature Teff=15840+/-160K and surface gravity log(g)=4.86+/-0.04) that is less luminous than typical BHB stars. Accordingly, the distance of the system is lower than originally thought, which renders its Galactic orbit bound to the Galaxy. Nevertheless, it is still an extreme halo object on a highly retrograde orbit. The abundances of He, C, N, O, Ne, Mg, Al, Si, S, and Ca are subsolar by factors from 3 to more than 100, while Fe is enriched by a factor of about 6. This peculiar chemical composition pattern is most likely caused by atomic diffusion processes. Combining constraints from astrometry, orbital motion, photometry, and spectroscopy, we conclude that the visible component is an unevolved proto-helium white dwarf with a thin hydrogen envelope that was stripped by a substellar companion through common-envelope ejection. Its unique configuration renders the binary system an interesting test bed for stellar binary evolution in general and common-envelope evolution in particular.
2238. SDSS J1004+4112 spectra
- ID:
- ivo://CDS.VizieR/J/A+A/634/A27
- Title:
- SDSS J1004+4112 spectra
- Short Name:
- J/A+A/634/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new spectroscopic and polarimetric observations of the gravitational lens SDSS J1004+4112 taken with the 6m telescope of the Special Astrophysical Observatory (SAO, Russia). In order to explain the variability that is observed only in the blue wing of the CIV emission line, corresponding to image A, we analyze the spectroscopy and polarimetry of the four images of the lensed system. Spectra of the four images were taken in 2007, 2008, and 2018, and polarization was measured in the period 2014-2017. Additionally, we modeled the microlensing effect in the polarized light, assuming that the source of polarization is the equatorial scattering in the inner part of the torus. We find that a blue enhancement in the CIV line wings affects component A in all three epochs. We also find that the UV continuum of component D was amplified in the period 2007-2008, and that the red wings of CIII] and CIV appear brighter in D than in the other three components. We report significant changes in the polarization parameters of image D, which can be explained by microlensing. Our simulations of microlensing of an equatorial scattering region in the dusty torus can qualitatively explain the observed changes in the polarization degree and angle of image D.We do not detect significant variability in the polarization parameters of the other images (A, B, and C), although the averaged values of the polarization degree and angle are different for the different images. Microlensing of a broad line region model including a compact outflowing component can qualitatively explain the CIV blue wing enhancement (and variation) in component A. However, to confirmed this hypothesis, we need additional spectroscopic observation in future.
- ID:
- ivo://CDS.VizieR/J/A+A/596/A77
- Title:
- SDSS J1339+1310 spectra and light curves
- Short Name:
- J/A+A/596/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We spectroscopically re-observed the gravitational lens system SDSS J1339+1310 using OSIRIS on the GTC. We also monitored the r-band variability of the two quasar images (A and B) with the LT over 143 epochs in the period 2009-2016. These new data in both the wavelength and time domains have confirmed that the system is an unusual microlensing factory. The CIV emission line is remarkably microlensed, since the microlensing magnification of B relative to that for A,{mu}_BA_, reaches a value of 1.4 (~0.4mag) for its core. Moreover, the B image shows a red wing enhancement of CIV flux (relative to A), and {mu}_BA_=2 (0.75mag) for the CIV broad-line emission. Regarding the nuclear continuum, we find a chromatic behaviour of {mu}_BA_, which roughly varies from ~5 (1.75mag) at 7000{AA} to ~6 (1.95mag) at 4000{AA}. We also detect significant microlensing variability in the r band, and this includes a number of microlensing events on timescales of 50-100d. Fortunately, the presence of an intrinsic 0.7 mag dip in the light curves of A and B, permitted us to measure the time delay between both quasar images. This delay is {Delta}t_AB_=47^+5^_-6_d (1{sigma} confidence interval; A is leading), in good agreement with predictions of lens models.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A77
- Title:
- SDSS J080434.20+510349.2 spectra and photometry
- Short Name:
- J/A+A/549/A77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This study of SDSS J080434.20+510349.2 (SDSS0804) is primarily concerned with the double-hump shape in the light curve and its connection with the accretion disk in this bounce-back system. Time-resolved photometric and spectroscopic observations were obtained to analyze the behavior of the system between superoutbursts. A qualitative geometric model of a binary system containing a disk with two outer annuli spiral density waves was applied to explain the light curve and the Doppler tomography. Observations were carried out during 2008-2009, after the object's magnitude decreased to V~17.7+/-0.1 from the March 2006 eruption. The light curve clearly shows a sinusoid-like variability with a 0.07mag amplitude and a 42.48min periodicity, which is half of the orbital period of the system. In September 2010, the system underwent yet another superoutburst and returned to its quiescent level by the beginning of 2012. This light curve once again showed a double-hump-shape, but with a significantly smaller (~0.01mag) amplitude. Other types of variability like a "mini-outburst" or SDSS1238-like features were not detected. Doppler tomograms, obtained from spectroscopic data during the same period of time, show a large accretion disk with uneven brightness, implying the presence of spiral waves. We constructed a geometric model of a bounce-back system containing two spiral density waves in the outer annuli of the disk to reproduce the observed light curves. The Doppler tomograms and the double-hump-shape light curves in quiescence can be explained by a model system containing a massive >=0.7M_{sun}_ white dwarf with a surface temperature of ~12000K, a late-type brown dwarf, and an accretion disk with two outer annuli spirals. According to this model, the accretion disk should be large, extending to the 2:1 resonance radius, and cool ~2500K. The inner parts of the disk should be optically thin in the continuum or totally void.
