Examinando por Autor "Phillips, Mark M."

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    Characterizing the v-band light-curves of hydrogen-rich type ii supernovae
    (Institute of Physics Publishing, 2014-05) Anderson, Joseph P.; González-Gaitán, Santiago; Hamuy, Mario; Gutiérrez, Claudia P.; Stritzinger, Maximilian D.; Olivares E., Felipe; Phillips, Mark M.; Schulze, Steve; Antezana, Roberto; Bolt, Luis; Campillay, Abdo; Castellón, Sergio; Contreras, Carlos; De Jaeger, Thomas; Folatelli, Gastón; Förster, Francisco; Freedman, Wendy L.; González, Luis; Hsiao, Eric; Krzemiński, Wojtek; Krisciunas, Kevin; Maza, José; McCarthy, Patrick; Morrell, Nidia I.; Persson, Sven E.; Roth, Miguel; Salgado, Francisco; Suntzeff, Nicholas B.; Thomas-Osip, Joanna
    We present an analysis of the diversity of V-band light-curves of hydrogen-rich type II supernovae. Analyzing a sample of 116 supernovae, several magnitude measurements are defined, together with decline rates at different epochs, and time durations of different phases. It is found that magnitudes measured at maximum light correlate more strongly with decline rates than those measured at other epochs: brighter supernovae at maximum generally have faster declining light-curves at all epochs. We find a relation between the decline rate during the “plateau” phase and peak magnitudes, which has a dispersion of 0.56 mag, offering the prospect of using type II supernovae as purely photometric distance indicators. Our analysis suggests that the type II population spans a continuum from low-luminosity events which have flat light-curves during the “plateau” stage, through to the brightest events which decline much faster. A large range in optically thick phase durations is observed, implying a range in progenitor envelope masses at the epoch of explosion. During the radioactive tails, we find many supernovae with faster declining light-curves than expected from full trapping of radioactive emission, implying low mass ejecta. It is suggested that the main driver of light-curve diversity is the extent of hydrogen envelopes retained before explosion. Finally, a new classification scheme is introduced where hydrogen-rich events are typed as simply “SN II” with an “s2” value giving the decline rate during the “plateau” phase, indicating its morphological type.
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    On the progenitor and supernova of the sn 2002cx-like supernova 2008ge
    (2010) Foley, Ryan J.; Rest, Armin; Stritzinger, Maximilian; Pignata, Giuliano; Anderson, Joseph P.; Hamuy, Mario; Morrell, Nidia I.; Phillips, Mark M.; Salgado, Francisco
    We present observations of supernova (SN) 2008ge, which is spectroscopically similar to the peculiar SN 2002cx, and its pre-explosion site that indicate that its progenitor was probably a white dwarf. NGC 1527, the host galaxy of SN 2008ge, is an S0 galaxy with no evidence of star formation or massive stars. Astrometrically matching late-time imaging of SN 2008ge to pre-explosion HST imaging, we constrain the luminosity of the progenitor star. Since SN 2008ge has no indication of hydrogen or helium in its spectrum, its progenitor must have lost its outer layers before exploding, requiring that it be a white dwarf, a Wolf-Rayet star, or a lower-mass star in a binary system. Observations of the host galaxy show no signs of individual massive stars, star clusters, or H II regions at the SN position or anywhere else, making a Wolf-Rayet progenitor unlikely. Late-time spectroscopy of SN 2008ge show strong [Fe II] lines with large velocity widths compared to other members of this class at similar epochs. These previously unseen features indicate that a significant amount of the SN ejecta is Fe (presumably the result of radioactive decay of 56Ni generated in the SN), further supporting a thermonuclear explosion. Placing the observations of SN 2008ge in the context of observations of other objects in the class of SN, we suggest that the progenitor was most likely a white dwarf.
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    Persistent C II absorption in the normal type Ia supernova 2002fk
    (Institute of Physics Publishing, 2014-07) Cartier, Régis; Hamuy, Mario; Pignata, Giuliano; Förster, Francisco; Förster, Francisco; Folatelli, Gaston; Phillips, Mark M.; Morrell, Nidia; Krisciunas, Kevin; Suntzeff, Nicholas B.; Clocchiatti, Alejandro; Coppi, Paolo; Contreras, Carlos; Roth, Miguel; Koviak, Kathleen; Koviak, Kathleen; González, Luis; González, Sergio; Huerta, Leonor
    We present well-sampled UBVRIJHK photometry of SN 2002fk starting 12 days before maximum light through 122 days after peak brightness, along with a series of 15 optical spectra from −4 to +95 days since maximum. Our observations show the presence of C ii lines in the early-time spectra of SN 2002fk, expanding at 11,000 km s−1 and persisting until 8 days past maximum light with a velocity of ∼9000 km s−1. SN 2002fk is characterized by a small velocity gradient of v˙Si ii = 26 km s−1 day−1, possibly caused by an off-center explosion with the ignition region oriented toward the observer. The connection between the viewing angle of an off-center explosion and the presence of C ii in the early-time spectrum suggests that the observation of Cii could be also due to a viewing angle effect. Adopting the Cepheid distance to NGC 1309 we provide the first H0 value based on near infrared (near-IR) measurements of a Type Ia supernova (SN) between 63.0 ± 0.8 (±3.4 systematic) and 66.7 ± 1.0 (±3.5 systematic) km s−1 Mpc−1, depending on the absolute magnitude/decline rate relationship adopted. It appears that the near-IR yields somewhat lower (6%–9%) H0 values than the optical. It is essential to further examine this issue by (1) expanding the sample of high-quality near-IR light curves of SNe in the Hubble flow, and (2) increasing the number of nearby SNe with near-IR SN light curves and precise Cepheid distances, which affords the promise to deliver a more precise determination of H0.