Seeing Double: ASASSN-18bt Exhibits a Two-component Rise in the Early-time K2 Light Curve
B. J. ShappeeInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; [email protected]T. W. S. HoloienThe Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101, USAM. R. DroutThe Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101, USAKatie AuchettlCenter for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University, 191 W. Woodruff Ave., Columbus, OH 43210, USAM. StritzingerDepartment of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, DenmarkC. S. KochanekCenter for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University, 191 W. Woodruff Ave., Columbus, OH 43210, USAK. Z. StanekCenter for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University, 191 W. Woodruff Ave., Columbus, OH 43210, USAE. ShayaAstronomy Department, University of Maryland, College Park, MD 20742-2421, USAGautham NarayanDepartment of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USAASAS-SNDepartment of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USAJ. S. BrownDepartment of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USAS. BoseKavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Road 5, Hai Dian District, Beijing 100871, People’s Republic of ChinaD. BersierAstrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UKJ. BrimacombeCoral Towers Observatory, Cairns, Queensland 4870, AustraliaPing ChenKavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Road 5, Hai Dian District, Beijing 100871, People’s Republic of ChinaSubo DongKavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Road 5, Hai Dian District, Beijing 100871, People’s Republic of ChinaS. HolmboDepartment of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, DenmarkBoaz KatzDepartment of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, IsraelJ. A. MuñozDepartamento de Astronomía y Astrofísica, Universidad de Valencia, E-46100 Burjassot, Valencia, SpainR. L. MutelDepartment of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USAR. S. PostPost Observatory, Lexington, MA 02421, USAJose L. PrietoMillennium Institute of Astrophysics, Santiago, ChileJ. ShieldsDepartment of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USAD. TallonDepartment of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USATodd A. ThompsonCenter for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University, 191 W. Woodruff Ave., Columbus, OH 43210, USAPatrick J. VallelyDepartment of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USASteven VillanuevaDepartment of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210, USAATLASInstitute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI 96822, USAL. DenneauInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; [email protected]H. FlewellingInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; [email protected]A. N. HeinzeInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; [email protected]K. SmithAstrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN, UKB. StalderLSST, 950 North Cherry Avenue, Tucson, AZ 85719, USAJ. TonryInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; [email protected]H. WeilandInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; [email protected]Kepler/K2NASA Ames Research Center, Moffett Field, CA 94035, USAThomas BarclayNASA Goddard Space Flight Center, 8800 Greenbelt Rd, Greenbelt, MD 20771, USAGeert BarentsenBay Area Environmental Research Institute, P.O. Box 25, Moffett Field, CA 94035, USAA. M. CodyBay Area Environmental Research Institute, P.O. Box 25, Moffett Field, CA 94035, USAJessie DotsonNASA Ames Research Center, Moffett Field, CA 94035, USAF. FoersterCenter for Mathematical Modeling, University of Chile, Santiago, ChileP. GarnavichDepartment of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN, 46556-5670, USAM. Gully-SantiagoBay Area Environmental Research Institute, P.O. Box 25, Moffett Field, CA 94035, USAChristina HedgesBay Area Environmental Research Institute, P.O. Box 25, Moffett Field, CA 94035, USASteve B. HowellNASA Ames Research Center, Moffett Field, CA 94035, USADaniel KasenDepartment of Astronomy, University of California, Berkeley, CA 94720-3411, USAS. MargheimGemini Observatory, La Serena, ChileR. F. MushotzkyAstronomy Department, University of Maryland, College Park, MD 20742-2421, USAA. RestDepartment of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USAC. TuckerNational Centre for the Public Awareness of Science, Australian National University, Canberra, ACT 2601, AustraliaA. VillarHarvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USAA. ZentenoCerro Tololo Inter-American Observatory, Casilla 603, La Serena, ChileKepler Spacecraft TeamNASA Ames Research Center, Moffett Field, CA 94035, USAG. BeermanLASP, University of Colorado at Boulder, Boulder, CO 80303, USAR. BjellaLASP, University of Colorado at Boulder, Boulder, CO 80303, USAG. A. Rodríguez CastilloLASP, University of Colorado at Boulder, Boulder, CO 80303, USAJeffrey L. CoughlinNASA Ames Research Center, Moffett Field, CA 94035, USAB. ElsaesserLASP, University of Colorado at Boulder, Boulder, CO 80303, USASierra FlynnLASP, University of Colorado at Boulder, Boulder, CO 80303, USAR. GangopadhyayLASP, University of Colorado at Boulder, Boulder, CO 80303, USAK. GriestLASP, University of Colorado at Boulder, Boulder, CO 80303, USAM. HanleyLASP, University of Colorado at Boulder, Boulder, CO 80303, USAJennifer KampmeierLASP, University of Colorado at Boulder, Boulder, CO 80303, USAR. KloetzelLASP, University of Colorado at Boulder, Boulder, CO 80303, USAL. KohnertLASP, University of Colorado at Boulder, Boulder, CO 80303, USAC. LabondeLASP, University of Colorado at Boulder, Boulder, CO 80303, USAR. LarsenLASP, University of Colorado at Boulder, Boulder, CO 80303, USAK. A. LarsonBall Aerospace and Technologies Corp., Boulder, Colorado, 80301, USAK. M. McCalmont-EvertonBall Aerospace and Technologies Corp., Boulder, Colorado, 80301, USAChris McGinnLASP, University of Colorado at Boulder, Boulder, CO 80303, USAL. MiglioriniLASP, University of Colorado at Boulder, Boulder, CO 80303, USAJ. MoffattLASP, University of Colorado at Boulder, Boulder, CO 80303, USAM. MuszynskiLASP, University of Colorado at Boulder, Boulder, CO 80303, USAV. NystromLASP, University of Colorado at Boulder, Boulder, CO 80303, USADarren OsborneLASP, University of Colorado at Boulder, Boulder, CO 80303, USAM. PackardLASP, University of Colorado at Boulder, Boulder, CO 80303, USAC. PetersonBall Aerospace and Technologies Corp., Boulder, Colorado, 80301, USAM. RedickLASP, University of Colorado at Boulder, Boulder, CO 80303, USALee ReedyLASP, University of Colorado at Boulder, Boulder, CO 80303, USAS. RossBall Aerospace and Technologies Corp., Boulder, Colorado, 80301, USABrittany SpencerLASP, University of Colorado at Boulder, Boulder, CO 80303, USAK. StewardLASP, University of Colorado at Boulder, Boulder, CO 80303, USAJeffrey E. Van CleveNASA Ames Research Center, Moffett Field, CA 94035, USAJosé Vinícius de Miranda CardosoNASA Ames Research Center, Moffett Field, CA 94035, USAT. WeschlerLASP, University of Colorado at Boulder, Boulder, CO 80303, USAA. WheatonLASP, University of Colorado at Boulder, Boulder, CO 80303, USAPan-STARRSInstitute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI 96822, USAJ. BulgerInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; [email protected]K. C. ChambersInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; [email protected]M. E. HuberInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; [email protected]T. LoweInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; [email protected]E. A. MagnierInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; [email protected]A. S. B. SchultzInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; [email protected]C. WatersInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; [email protected]M. WillmanInstitute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA; [email protected]PTSS/TNTSPhysics Department and Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing, 100084, People's Republic of ChinaE. BaronHomer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK, USAZhihao ChenPhysics Department and Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing, 100084, People’s Republic of ChinaJames M. DerKacyHomer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK, USA
2018en
ABI
Annotatsiya
Abstract On 2018 February 4.41, the All-Sky Automated Survey for SuperNovae (ASAS-SN) discovered ASASSN-18bt in the K2 Campaign 16 field. With a redshift of z = 0.01098 and a peak apparent magnitude of B max = 14.31, ASASSN-18bt is the nearest and brightest SNe Ia yet observed by the Kepler spacecraft. Here we present the discovery of ASASSN-18bt, the K2 light curve, and prediscovery data from ASAS-SN and the Asteroid Terrestrial-impact Last Alert System. The K2 early-time light curve has an unprecedented 30-minute cadence and photometric precision for an SN Ia light curve, and it unambiguously shows a ∼4 day nearly linear phase followed by a steeper rise. Thus, ASASSN-18bt joins a growing list of SNe Ia whose early light curves are not well described by a single power law. We show that a double-power-law model fits the data reasonably well, hinting that two physical processes must be responsible for the observed rise. However, we find that current models of the interaction with a nondegenerate companion predict an abrupt rise and cannot adequately explain the initial, slower linear phase. Instead, we find that existing published models with shallow 56 Ni are able to span the observed behavior and, with tuning, may be able to reproduce the ASASSN-18bt light curve. Regardless, more theoretical work is needed to satisfactorily model this and other early-time SNe Ia light curves. Finally, we use Swift X-ray nondetections to constrain the presence of circumstellar material (CSM) at much larger distances and lower densities than possible with the optical light curve. For a constant-density CSM, these nondetections constrain ρ < 4.5 × 10 5 cm −3 at a radius of 4 × 10 15 cm from the progenitor star. Assuming a wind-like environment, we place mass loss limits of for v w = 100 km s −1 , ruling out some symbiotic progenitor systems. This work highlights the power of well-sampled early-time data and the need for immediate multiband, high-cadence follow-up for progress in understanding SNe Ia.
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