1. SN 2012fr: Ultraviolet, Optical, and Near-infrared Light Curves of a Type Ia Supernova Observed within a Day of Explosion* * This paper includes data gathered with the 6.5 m Magellan Baade Telescope, located at Las Campanas Observatory, Chile.
- Author
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Contreras, Carlos, Phillips, MM, Burns, Christopher R, Piro, Anthony L, Shappee, BJ, Stritzinger, Maximilian D, Baltay, C, Brown, Peter J, Conseil, Emmanuel, Klotz, Alain, Nugent, Peter E, Turpin, Damien, Parker, Stu, Rabinowitz, D, Hsiao, Eric Y, Morrell, Nidia, Campillay, Abdo, Castellón, Sergio, Corco, Carlos, González, Consuelo, Krisciunas, Kevin, Serón, Jacqueline, Tucker, Brad E, Walker, ES, Baron, E, Cain, C, Childress, Michael J, Folatelli, Gastón, Freedman, Wendy L, Hamuy, Mario, Hoeflich, P, Persson, SE, Scalzo, Richard, Schmidt, Brian, and Suntzeff, Nicholas B
- Subjects
Astronomical Sciences ,Physical Sciences ,supernovae: general ,supernovae: individual ,astro-ph.HE ,Astronomical and Space Sciences ,Atomic ,Molecular ,Nuclear ,Particle and Plasma Physics ,Physical Chemistry (incl. Structural) ,Astronomy & Astrophysics ,Astronomical sciences ,Particle and high energy physics ,Space sciences - Abstract
We present detailed ultraviolet, optical, and near-infrared light curves of the Type Ia supernova (SN) 2012fr, which exploded in the Fornax cluster member NGC 1365. These precise high-cadence light curves provide a dense coverage of the flux evolution from -12 to +140 days with respect to the epoch of B-band maximum (). Supplementary imaging at the earliest epochs reveals an initial slow and nearly linear rise in luminosity with a duration of ∼2.5 days, followed by a faster rising phase that is well reproduced by an explosion model with a moderate amount of 56Ni mixing in the ejecta. From our analysis of the light curves, we conclude that: (i) the explosion occurred 1800) luminosity was 16.5 ±0.6 days, (iii) the supernova suffered little or no host-galaxy dust reddening, (iv) the peak luminosity in both the optical and near-infrared was consistent with the bright end of normal Type Ia diversity, and (v) 0.60 ±0.15 M o of 56Ni was synthesized in the explosion. Despite its normal luminosity, SN 2012fr displayed unusually prevalent high-velocity Ca ii and Si ii absorption features, and a nearly constant photospheric velocity of the Si ii λ6355 line at ∼12,000 that began ∼5 days before . We also highlight some of the other peculiarities in the early phase photometry and the spectral evolution. SN 2012fr also adds to a growing number of Type Ia supernovae that are hosted by galaxies with direct Cepheid distance measurements.
- Published
- 2018
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V = 19.5, i.e., a heliocentric distance of ~50 kpc for RR Lyrae stars. The survey reveals 2016 RR Lyrae candidates. Follow-up photometric monitoring of a subset of these candidates shows ~24% contamination by non-RR Lyrae variables. We derive a map of overdensity of RR Lyrae stars in the halo that reveals a series of structures coincident with the leading and trailing arms of debris from the Sagittarius dwarf galaxy. One of the regions of overdensity is found on the trailing arm, 200deg from the main body of the Sagittarius dwarf at a distance of ~45 kpc. This distant detection of the stellar population of the outer trailing arm of Sagittarius offers a tight constraint on the motion of the dwarf galaxy. A distinctly separate region of overdensity is seen toward the Virgo overdensity.