THE YOUNG AND BRIGHT TYPE IA SUPERNOVA ASASSN-141p: DISCOVERY, EARLY-TIME OBSERVATIONS, FIRST-LIGHT TIME, DISTANCE TO NGC 4666, AND PROGENITOR CONSTRAINTS

On 2014 December 9.61, the All-sky Automated Survey for SuperNovae (ASAS-SN or "Assassin") discovered ASASSN-141p just similar to 2 days after first light using a global array of 14 cm diameter telescopes. ASASSN-141p went on to become a bright supernova (V = 11.94 mag), second only to SN 2014J for the year. We present prediscovery photometry (with a detection less than a day after first light) and ultraviolet through near-infrared photometric and spectroscopic data covering the rise and fall of ASASSN-141p for more than 100 days. We find that ASASSN-141p had a broad light curve (Delta m(15) (B) = 0.80 +/- 0.05), a B-band maximum at 2457015.82 +/- 0.03, a rise time of 16.941(-0.10)(+0.11) days, and moderate host-galaxy extinction (E (B - V)host = 0.33 +/- 0.06). Using ASASSN-141p, we derive a distance modulus for NGC 4666 of mu = 30.8 +/- 0.2, corresponding to a distance of 14.7 +/- 1.5 Mpc. However, adding ASASSN-141p to the calibrating sample of Type Ia supernovae still requires an independent distance to the host galaxy. Finally, using our early-time photometric and spectroscopic observations, we rule out red giant secondaries and, assuming a favorable viewing angle and explosion time, any nondegenerate companion larger than 0.34 RG(circle dot).NSF [AST-0908816, AST-1515876, AST-1515927, PHY-1404311, AST-0306969, AST-0607438, AST-1008343, AST-9987045]; CCAPP at the Ohio State University; Mt. Cuba Astronomical Foundation; Millennium Institute of Astrophysics (MAS) of the Millennium Science Initiative, Chilean Ministry of Economy [IC120009]; NASA through Hubble Fellowship - Space Telescope Science Institute [HF-51348.001]; Research in Astronomy, Inc., for NASA [NAS 5-26555]; DOE Computational Science Graduate Fellowship [DE-FG02-97ER25308]; FONDECYT [1151445]; Ministry of Economy, Development, and Tourism's Millennium Science Initiative [IC120009]; Strategic Priority Research Program-The Emergence of Cosmological Structures" of the Chinese Academy of Sciences [XDB09000000]; Danish Agency for Science and Technology and Innovation realized through a Sapere Aude Level 2 grant; Laboratory Directed Research and Development program at LANL; Smithsonian Astrophysical Observatory; UK Science and Technology Facilities Council; NSF Telescope System Instrumentation Program (TSIP); Ohio Board of Regents; Ohio State University Office of Research; Alfred P. Sloan Foundation; Participating Institutions; National Science Foundation; U.S. Department of Energy; National Aeronautics and Space Administration; Japanese Monbukagakusho; Max Planck Society; Higher Education Funding Council for England; Robert Martin Ayers Sciences FundSCI(E)ARTICLEbshappee@obs.carnegiescience.edu282