The Standardized Candle Method for Type II Plateau Supernovae

Artículo de publicación ISIIn this paper we study the “standardized candle method” using a sample of 37 nearby (redshift z < 0.06) Type II plateau supernovae having BV RI photometry and optical spectroscopy. An analytic procedure is implemented to fit light curves, color curves, and velocity curves. We find that the V − I color toward the end of the plateau can be used to estimate the host-galaxy reddening with a precision of (AV ) = 0.2 mag. The correlation between plateau luminosity and expansion velocity previously reported in the literature is recovered. Using this relation and assuming a standard reddening law (RV = 3.1), we obtain Hubble diagrams in the BV I bands with dispersions of 0.4 mag. Allowing RV to vary and minimizing the spread in the Hubble diagrams, we obtain a dispersion range of 0.25–0.30 mag, which implies that these objects can deliver relative distances with precisions of 12–14%. The resulting best-fit value of RV is 1.4 ± 0.1

Type II supernovae as distance indicators at near-IR wavelengths

Motivated by the advantages of observing at near-IR wavelengths, we investigate Type II supernovae (SNe II) as distance indicators at those wavelengths through the Photospheric Magnitude Method (PMM). For the analysis, we use BVIJH photometry and optical spectroscopy of 24 SNe II during the photospheric phase. To correct photometry for extinction and redshift effects, we compute total-to-selective broad-band extinction ratios and K-corrections up to z = 0.032. To estimate host galaxy colour excesses, we use the colour-colour curve method with the V-I versus B-V as colour combination. We calibrate the PMM using four SNe II in galaxies having Tip of the Red Giant Branch distances. Among our 24 SNe II, nine are at cz &gt; 2000 km s -1, which we use to construct Hubble diagrams (HDs). To further explore the PMM distance precision, we include into HDs the four SNe used for calibration and oth

The high cadence transient survey (HITS). Compilation and characterization of light–curve catalogs

The High Cadence Transient Survey (HiTS) aims to discover and study transient objects with characteristic timescales between hours and days, such as pulsating, eclipsing and exploding stars. This survey represents a unique laboratory to explore large etendue observations from cadences of about 0.1 days and to test new computational tools for the analysis of large data. This work follows a fully Data Science approach: from the raw data to the analysis and classification of variable sources. We compile a catalog of ∼15 million object detections and a catalog of ∼2.5 million light–curves classified by variability. The typical depth of the survey is 24.2, 24.3, 24.1 and 23.8 in u, g, r and i bands, respectively. We classified all point–like non–moving sources by first extracting features from their light–curves and then applying a Random Forest classifier. For the classification, we used a training set constructed using a combination of cross-matched catalogs, visual inspection, transfer/active learning and data augmentation. The classification model consists of several Random Forest classifiers organized in a hierarchical scheme. The classifier accuracy estimated on a test set is approximately 97%. In the unlabeled data, 3 485 sources were classified as variables, of which 1 321 were classified as periodic. Among the periodic classes we discovered with high confidence, 1 δ–scutti, 39 eclipsing binaries, 48 rotational variables and 90 RR–Lyrae and for the non–periodic classes we discovered 1 cataclysmic variables, 630 QSO, and 1 supernova candidates. The first data release can be accessed in the project archive of HiTSa