10 research outputs found
Observational studies of supernovae and intermediate luminosity optical transients
Thanks to modern all-sky surveys, thousands of astronomical transient events are discovered annually. Although many of these, such as regular supernovae (SNe), are fairly well understood, new rarer classes of transients have been discovered since the late 20th century. These include SNe interacting with dense circumstellar matter (CSM) and intermediate luminosity optical transients (ILOTs a.k.a. gap transients). Because of the limited number of facilities available, only a small fraction of all transients are spectroscopically classified.
As a part of international collaborations, I have participated in the acquisition and processing of data for classification and follow-up of a variety of transient events. The main telescopes used were the Nordic Optical Telescope and the European Southern ObservatoryâsNewTechnology Telescope. Thewavelength regions observed span from the optical to the near-infrared.
A total of 111 spectroscopic classifications and five selected follow-up papers that I have contributed to are discussed in this work. Two of the events, SNe 2015bh and 2016bdu are possibly produced by SNe interacting with CSM although other interpretations cannot be completely ruled out. The other three objects are ILOTs. SNhunt248 was likely produced either by an outburst from a yellow hypergiant star (SN impostor) or a binary merger (luminous red nova, LRN). The LRN M101OT2015-1was probably produced by a merger. A sub-energetic SN explosion in a dusty environment is favoured as the origin for the intermediate luminosity red transient (ILRT) AT 2017be.
Even though ILOTs share many common observable similarities, such as their early spectral features and maximum luminosities, there are distinguishable characteristics to each subclass. SN impostors exhibit strong variability prior to their outbursts. The progenitors of ILRTs are low mass stars (compared to other SN progenitors, that is) surrounded by dusty CSM. LRNe are produced by binary merger and they tend to develop molecular spectral lines during the later stages of their evolution.
In the case of so-called SN 2009ip -like transients (such as SNe 2015bh and 2016bdu), more data are required to fully understand these events. Although their photometric and spectral evolution is conspicuously similar, it is still not clear whether or not they are produced by a terminal SN explosion or, for instance, some erratic progenitor activity.discovered annually. Although many of these, such as regular supernovae (SNe), are fairly well understood, new rarer classes of transients have been discovered since the late 20th century. These include SNe interacting with dense circumstellar matter (CSM) and intermediate luminosity optical transients (ILOTs a.k.a. gap transients). Because of the limited number of facilities available, only a small fraction of all transients are spectroscopically classified.
As a part of international collaborations, I have participated in the acquisition and processing of data for classification and follow-up of a variety of transient events. The main telescopes used were the Nordic Optical Telescope and the European Southern ObservatoryâsNewTechnology Telescope. Thewavelength regions observed span from the optical to the near-infrared.
A total of 111 spectroscopic classifications and five selected follow-up papers that I have contributed to are discussed in this work. Two of the events, SNe 2015bh and 2016bdu are possibly produced by SNe interacting with CSM although other interpretations cannot be completely ruled out. The other three objects are ILOTs. SNhunt248 was likely produced either by an outburst from a yellow hypergiant star (SN impostor) or a binary merger (luminous red nova, LRN). The LRN M101OT2015-1was probably produced by a merger. A sub-energetic SN explosion in a dusty environment is favoured as the origin for the intermediate luminosity red transient (ILRT) AT 2017be.
Even though ILOTs share many common observable similarities, such as their early spectral features and maximum luminosities, there are distinguishable characteristics to each subclass. SN impostors exhibit strong variability prior to their outbursts. The progenitors of ILRTs are low mass stars (compared to other SN progenitors, that is) surrounded by dusty CSM. LRNe are produced by binary merger and they tend to develop molecular spectral lines during the later stages of their evolution.
In the case of so-called SN 2009ip -like transients (such as SNe 2015bh and 2016bdu), more data are required to fully understand these events. Although their photometric and spectral evolution is conspicuously similar, it is still not clear whether or not they are produced by a terminal SN explosion or, for instance, some erratic progenitor activity.
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Jatkuvasti taivasta kartoittavien havainto-ohjelmien ansiosta tuhansia lyhytikĂ€isiĂ€ tĂ€htitieteellisiĂ€ kohteita löydetÀÀn vuosittain. Tavallisimmat nĂ€istĂ€ kohteista â kuten supernovat â ovat varsin hyvin ymmĂ€rrettyjĂ€. Harvinaisemmille kohteille tĂ€mĂ€ ei pĂ€de. Harvinaisiksi lasketaan muun muassa viime vuosituhannen loppupuolelta alkaen löydetyt uudet kohteet, joihin kuuluvat esimerkiksi tiheĂ€n tĂ€hteĂ€ ympĂ€röivĂ€n aineen kanssa vuorovaikuttavat supernovat ja keskikirkkaat lyhytikĂ€iset optiset kohteet (ILOT-kohteet). Havaintolaitteiden mÀÀrĂ€n rajallisuudesta johtuen uusista kohteista luokitellaan kuitenkin vain pieni murtoosa.
Olen ollut mukana suurissa kansainvÀlisissÀ hankkeissa havaitsemassa ja kÀsittelemÀssÀ aineistoa monelle eri havaintokohteelle. KeskeisimmÀt kÀytössÀ olleet kaukoputket ovat Nordic Optical Telescope ja Euroopan etelÀisen obsevatorion New Technology Telescope. Havainnot painottuivat nÀkyvÀn valon ja lÀhi-infrapunan alueille.
TÀssÀ työssÀ esitellÀÀn 111 kohteen spektroskoopiset luokitukset ja viisi valittua artikkelia, joihin olen kerÀnnyt ja kÀsitellyt havaintoaineistoa. Kaksi kohteista, SN 2015bh ja SN2016bdu, ovat todennÀköisesti seurausta tÀhteÀ ympÀröivÀn aineen kanssa vuorovaikuttavasta supernovasta, joskaan muita tulkintoja ei voi tÀysin sulkea pois. Kohteen SNhunt248 kirkastumiselle on esitetty kaksi mahdollista tulkintaa: keltaisen ylijÀttilÀistÀhden purkaus tai kaksoistÀhtijÀrjestelmÀn yhteensulautuminen. Kohteelle M101 OT2015-1 on myös esitetty jÀlkimmÀistÀ tulkintaa. PölyisessÀ ympÀristössÀ rÀjÀhtÀnyt matalaenergeettinen supernova on puolestaan todennÀköisin selitys kohteelle AT 2017be.
Vaikkakin ILOT-kohteilla on yhtenevÀisiÀ havaittuja piirteitÀ, kuten spektrin yksityiskohtien kehitys ja kirkkauden maksimi, on jokaisella kohteella myös omat tunnusomaiset piirteensÀ. Esimerkiksi suuren tÀhden massiivista purkausta edeltÀÀ usein epÀstabiilisuus vuosien aikaskaalalla.
Niin kutsutuille SN 2009ip -tyyppisille kohteille â joita myös kohteet SN 2015bh ja SN2016bdu edustavat â lisĂ€havainnot ovat tarpeen. Vaikkakin havaitut ominaisuudet ovat suurilta osin samat, ei vielĂ€ tiedetĂ€, ettĂ€ ovatko nĂ€mĂ€ kohteet seurausta supernovarĂ€jĂ€hdyksestĂ€ vai esimerkiksi tĂ€hden epĂ€stabiilisuudesta, joka tuottaa supernovaa muistuttavia havaittavia piirteitĂ€
TakapyörÀkonekylvön vaikutus satoon helposti liettyvillÀ mailla
ViimevuosikymmeninĂ€ muokkaus- ja kylvökalusto ovat kehittyneet tehokkaimmiksi ja työvaiheet ovat vĂ€hentyneet. ValtamenetelmĂ€ksi on noussut kylvölannoitus takapyörĂ€koneella, jolla kylvettĂ€essĂ€ siemenrivin tiivistĂ€minen tapahtuu suuren osan koneen massasta kantavilla takapyörillĂ€. Halusimme selvittÀÀ, lisÀÀkö kylvötapa liettymis- ja kuorettumariskiĂ€. Maassamme on runsaasti helposti liettyviĂ€ ja kuorettuvia maita, joissa savespitoisuus on 15â40 %. Kyseiset maat ovat ruotsalaisluokittelun mukaan kevyt- ja keskisavia. Suomalaisen luokituksen mukaan kyseiset maalajit ovat lĂ€hinnĂ€: Hs, He, HHt, HsS, HeS ja HtS maita. Ilmajoella suoritettiin kesinĂ€ 2013 ja 2014 kylvötapakoe. Maalaji oli suhteellisen helposti liettyvĂ€ mHHt, jossa on 27 % Hs ja 12 % S. Kokeessa selvitettiin eri vaiheessa tehdyn jyrĂ€yksen merkitystĂ€ ohrasadon mÀÀrÀÀn ja laatuun. JyrĂ€ys tehtiin Junkkarin Superseed takapyörĂ€kylvökoneella sĂ€iliöt puolillaan. Varsinainen kylvö tehtiin sivupyörĂ€koneella, jossa oli kylvörivin tiivistĂ€vĂ€ kapea jyrĂ€kiekko Kokeessa oli molempina vuosina kolme koejĂ€sentĂ€, neljĂ€ kerrannetta jolloin tuli kaksitoista 0,125 ha ruutua. Kuhunkin ruutuun arvottiin kylvötavat, joita olivat: kylvö sivupyörĂ€koneella, kylvö sivupyörĂ€koneella + jyrĂ€ys sekĂ€ kolmantena jyrĂ€ys + kylvö. Koealat muokattiin joustopiikkiĂ€keellĂ€ 2-3 kertaa hienorakeiseksi. KesĂ€kuussa 2013 satoi reilut 90 mmja maa liettyi voimakkaasti, mutta kuorettunut maa pysyi lĂ€pĂ€isevĂ€nĂ€. Kasvusto orastui tasaisesti (kylvö 23.5) ja satoerot olivat vĂ€hĂ€isiĂ€, keskisato oli 5 612 kg/ha. Vuonna 2014 vĂ€hennettiin Ă€estystĂ€, koeruutujen etuosa Ă€estettiin kuitenkin hienommaksi (koejĂ€sen 13). KevÀÀllĂ€ 2014, (kylvö 23.5.) kesĂ€kuun alun 8 mm sade lietti eniten jyrĂ€pyörĂ€n jĂ€ljille jÀÀnyttĂ€ koejĂ€sentĂ€ joka kuorettui kuivuessaan eniten. KesĂ€kuu jĂ€i kuivaksi (sademÀÀrĂ€ 22 mm). HeinĂ€kuun lopun sateissa vilja lakoutui. JyrĂ€tyillĂ€ mailla versoutuminen oli heikompaa kuin jyrÀÀmĂ€ttömĂ€llĂ€ ja kahteen kertaa Ă€estetyllĂ€ osuudella heikointa. Kerran Ă€estetyllĂ€ versojen lukumÀÀrĂ€ oli suurin sivupyörĂ€konekylvöllĂ€ 587 kpl/mÂČ ja pienin kylvön jĂ€lkeen jyrĂ€tyllĂ€ 552 Kpl/mÂČ. Kahteen kertaan Ă€estetyillĂ€ vastaavat lukemat olivat 740 ja 487 kpl/mÂČ. SivupyörĂ€kylvölle kertaalleen Ă€estetty oli ollut liian vĂ€hĂ€n, mutta jyrĂ€tyille sopivasti. Kaikkien kertaalleen Ă€estettyjen lohkojen keskisadoksi tuli 4965 kg/ha (14 % kosteana). Hienommaksi Ă€estetty koejĂ€sen 13 antoi satoa 4677 kg/ha. Paras hehtaarisato ja hehtolitrapaino saatiin, kun pelkĂ€stÀÀn kylvettiin ilman jyrĂ€ystĂ€ 5215 kg/ha, jyrĂ€ys ennen kylvöÀ tuotti 4869 kg/ha ja kylvön jĂ€lkeen tehty jyrĂ€ys 4812 kg/ha. Vuonna 2014 vilja lakoontui heinĂ€kuun rankkojen vesisateiden johdosta. Ilman lakoutumista satoerot olisivat todennĂ€köisesti olleet vielĂ€kin suuremmat. Hienoksi muokatun alueen sato jĂ€i 583 kg/ha pienemmĂ€ksi kuin kapeilla jyrĂ€kiekoilla varustetulla koneella kylvössĂ€. Helposti liettyvillĂ€ mailla takapyörĂ€koneella kylvön yhteydessĂ€ on syytĂ€ vĂ€lttÀÀ liiallista muokkausta, koska jyrĂ€pyörĂ€t lisÀÀvĂ€t liettymĂ€riskiĂ€ rikkoessaan heikkorakenteisia muruja. JĂ€lkiharalla voitaneen vĂ€hentÀÀ liettymisriski
A dust-enshrouded tidal disruption event with a resolved radio jet in a galaxy merger
Tidal disruption events (TDEs) are transient flares produced when a star is ripped apart by the gravitational field of a supermassive black hole (SMBH). We have observed a transient source in the western nucleus of the merging galaxy pair Arp 299 that radiated >1.5 à 10 erg at infrared and radio wavelengths but was not luminous at optical or x-ray wavelengths. We interpret this as a TDE with much of its emission reradiated at infrared wavelengths by dust. Efficient reprocessing by dense gas and dust may explain the difference between theoretical predictions and observed luminosities of TDEs. The radio observations resolve an expanding and decelerating jet, probing the jet formation and evolution around a SMBH. Copyright © 2018, American Association for the Advancement of ScienceS.M. acknowledges financial support from the Academy of Finland (pmject 8120503). The research leading to these mats has received funding from the European.. Commission Seventh Framework Programme (FP/2007-2013) under grant agreement number & 227290, 283393 (RadioNc-t) and 60725 (HELP). AA., M.P.-T., N.R.-O. and R.H.T. acknowledge support from the Spanish MINECO through grants AYA2012-38491-002-02 and AYA2015 63939 C2 1 P. P.G.J. acknowledges support from European Research Council Consolidator Grant 647208. C.R.-C. acknowledges support by the Ministry of Economy, Development and Tourism's Millennium Science Initiative through grant 10120009, awarded to The Millennium. Institute of Astrophysics, MAS Chile, and from CONICYT through FONDECYT grant 3150238 and China-CON1CYT fund CAS160313. P.M. and M.A.A. acknowledge support from the ERC research grant CAMAP-250276, and partial support from the Spanish MINECO grant AYA2015-66889C2-1P Lard the local Valencia government ghat PROMETE0-11-2014069. FIE. acknowledges support from a Science Foundation Ireland-Royal Society University Research Fellowship. D.L.C. acknowledges support from grants ST/0001901/4 ST/J001368/1, ST/ K001051/1, and st/N0001138/1. P.V. acknowledges support from the National Research Foundation of South Africa.. J.H. acknowledges financial support tom the Finis h ChAth ral Fouridation and the Virile), YIP and Kahle Vais8I8 Foundation. J.K. acknowledges financial support from the Academy of Finland (grant 311138)
The Eruption of the Candidate Young Star ASASSN-15qi
Outbursts on young stars are usually interpreted as accretion bursts caused by instabilities in the disk or the star-disk connection. However, some protostellar outbursts may not fit into this framework. In this paper, we analyze optical and near-infrared spectra and photometry to characterize the 2015 outburst of the probable young star ASASSN-15qi. The mag brightening in the band was sudden, with an unresolved rise time of less than one day. The outburst decayed exponentially by 1 mag for 6 days and then gradually back to the pre-outburst level after 200 days. The outburst is dominated by emission from K gas. An explosive release of energy accelerated matter from the star in all directions, seen in a spectacular cool, spherical wind with a maximum velocity of 1000 km/s. The wind and hot gas both disappeared as the outburst faded and the source the source returned to its quiescent F-star spectrum. Nebulosity near the star brightened with a delay of 10-20 days. Fluorescent excitation of H is detected in emission from vibrational levels as high as , also with a possible time delay in flux increase. The mid-infrared spectral energy distribution does not indicate the presence of warm dust emission, although the optical photospheric absorption and CO overtone emission could be related to a gaseous disk. Archival photometry reveals a prior outburst in 1976. Although we speculate about possible causes for this outburst, none of the explanations are compelling
The Palomar Transient Factory Core-Collapse Supernova Host-Galaxy Sample. I. Host-Galaxy Distribution Functions and Environment-Dependence of CCSNe
Kuminan viljely penkissÀ
Kuminan rikkakasvitorjunta on mahdollista hoitaa kokonaan tai osittain mekaanisesti viljelemÀllÀ kuminaa penkissÀ. Penkkiin kylvetty kumina kestÀÀ hyvin mekaanisen rikkatorjunnan haraamalla. PelkÀstÀÀn mekaanisella torjunnalla voidaan saavuttaa hyvÀ rikkakasvien torjuntatulos. Paras tulos saadaan yhdistÀmÀllÀ mekaanista ja kemiallista torjuntaa. Kuminan penkkiviljelyÀ tutkittiin SeinÀjoen ammattikorkeakoulun ja MTT:n vuonna 2009 alkaneessa projektissa. Tavoitteena oli hakea uusia, mekaanisia vaihtoehtoja kuminan rikkatorjuntaan. Samalla haluttiin selvittÀÀ, nopeuttaako penkin myötÀ parantuva maan lÀmpötalous kuminan kasvua ja sadonmuodostusta. Myös penkin vaikutukset kuminan talvehtimiseen haluttiin selvittÀÀ. Penkkiviljelykokeessa verrattiin kolmea erilaista viljelytapaa. Tavanomainen viljely kylvettiin normaalilla 12,5 cm rivivÀlillÀ. Rikkakasvien torjunta hoidettiin kemiallisesti. Penkkiviljely-koejÀsenet kylvettiin pneumaattisella kylvökoneella, joka muotoili noin kaksikymmentÀ senttiÀ korkean penkin. Penkkien vÀli oli 75 cm. Penkin pÀÀlle tuli kaksi noin 7 cm levyistÀ kylvöriviÀ noin kymmenen sentin etÀisyydelle toisistaan. Penkkiin kylvetyssÀ kuminassa rikkakasvien torjunta hoidettiin joko kokonaan mekaanisesti haraamalla tai yhdistÀen mekaaninen ja kemiallinen torjunta. Kokeita perustettiin vuonna 2009 kaksi ja edelleen vuonna 2010 kaksi. Satoa korjataan kahtena satovuonna. Kokeet kylvettiin ensimmÀisenÀ perustamisvuonna 2.6. 2009 ja toisena 22.6.2010. Kemiallinen rikkatorjunta tehtiin tavanomaisen viljelyn koejÀsenessÀ kolme kertaa. Fenix ja Goltix-seos ruiskutettiin ennen kuminan taimettumista, taimettumisen jÀlkeen ja sama seos pienellÀ annoksella vielÀ elokuussa. Mekaaninen rikkatorjunta hoidettiin perunan multaimella. Koneeseen lisÀtyillÀ joustavilla piikeillÀ harattiin rikkoja penkin pÀÀltÀ. Mekaaninen rikkatorjunta tehtiin kylvövuonna kolme kertaa. Satovuoden kevÀÀllÀ tehtiin tavanomaisen viljelyn koejÀsenessÀ yksi rikkakasviruiskutus kevÀÀllÀ (Afalon 1 l/ha). PenkkiviljelykoejÀsenissÀ tehtiin satovuonna yksi haraus toukokuun puolivÀlin jÀlkeen. Kumina kestÀÀ hyvin mekaanista rikkakasvien harausta penkissÀ. Mekaanisella torjunnalla rikkakasvit saadaan pysymÀÀn kurissa. Ongelmakohta on penkin ylin osa, kylvörivien vÀli, johon rikkoja jÀi jonkin verran. Paras rikkakasvien torjuntatulos saatiin mekaanisen ja kemiallisen torjunnan yhdistelmÀllÀ. TÀllöin on mahdollista sÀÀstÀÀ ainekustannuksissa suuntaamalla ruiskutus penkkien pÀÀllystÀÀn ja vÀhentÀmÀllÀ ruiskutuskertoja. Vaoissa haraus pitÀÀ rikat kurissa. Kuminan kehitys aikaistuu penkissÀ. TÀmÀ nÀkyy selvÀsti kukinnan alkaessa. Ero tavanomaiseen viljelyyn on muutamien pÀivien luokkaa. PenkkiviljelyssÀ kuminassa kukkivia yksilöitÀ oli ensimmÀisenÀ satovuonna vain noin kolmannes siitÀ, mitÀ tavanomaisesti viljelyssÀ. Toteutetuista neljÀstÀ kokeesta kolmessa penkkiviljelyn sadot jÀivÀt perinteistÀ viljelyÀ pienemmiksi ensimmÀisenÀ satovuonna. Toisena satovuonna penkkiviljely tuotti tasamaan kanssa kilpailukykyisen sadon
SN 2016gsd: An unusually luminous and linear Type II supernova with high velocities
We present observations of the unusually luminous Type II supernova (SN) 2016gsd. With a peak absolute magnitude of V = -19.95 ± 0.08, this object is one of the brightest Type II SNe, and lies in the gap of magnitudes between the majority of Type II SNe and the superluminous SNe. Its light curve shows little evidence of the expected drop from the optically thick phase to the radioactively powered tail. The velocities derived from the absorption in H α are also unusually high with the blue edge tracing the fastest moving gas initially at 20 000 km s-1, and then declining approximately linearly to 15 000 km s-1 over âŒ100 d. The dwarf host galaxy of the SN indicates a low-metallicity progenitor which may also contribute to the weakness of the metal lines in its spectra. We examine SN 2016gsd with reference to similarly luminous, linear Type II SNe such as SNe 1979C and 1998S, and discuss the interpretation of its observational characteristics. We compare the observations with a model produced by the jekyll code and find that a massive star with a depleted and inflated hydrogen envelope struggles to reproduce the high luminosity and extreme linearity of SN 2016gsd. Instead, we suggest that the influence of interaction between the SN ejecta and circumstellar material can explain the majority of the observed properties of the SN. The high velocities and strong H α absorption present throughout the evolution of the SN may imply a circumstellar medium configured in an asymmetric geometry.MF acknowledges the support of a Royal Society â Science Foundation Ireland University Research Fellowship. The JEKYLL simulations were performed on resources provided by the Swedish National Infrastructure for Computing (SNIC) at Parallelldatorcentrum (PDC). PL acknowledges support from the Swedish Research Council. MS is supported by a generous grant (13261) from Villum Fonden and a project grant (8021-00170B) from the Independent Research Fund Denmark (IRFD). NUTS2 is funded in part by the Instrument Center for Danish Astronomy (IDA). This work is based (in part) on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile as part of PESSTO (the Public ESO Spectroscopic Survey for Transient Objects) ESO program 188.Dâ3003, 191.Dâ0935, more ESO acknowledgements. The Pan-STARRS1 Surveys (PS1) and the PS1 public science archive have been made possible through contributions by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, the Queenâs University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation Grant No. ASTâ1238877, the University of Maryland, Eotvos Lorand University (ELTE), the Los Alamos National Laboratory, and the Gordon and Betty Moore Foundation. The SCUSS is funded by the Main Direction Program of Knowledge Innovation of Chinese Academy of Sciences (No. KJCX2âEWâT06). It is also an international cooperative project between National Astronomical Observatories, Chinese Academy of Sciences, and Steward Observatory, University of Arizona, USA. Technical support and observational assistance from the Bok telescope are provided by Steward Observatory. The project is managed by the National Astronomical Observatory of China and Shanghai Astronomical Observatory. Data resources are supported by Chinese Astronomical Data Center (CAsDC). SD and PC acknowledge Project 11573003 supported by NSFC. This research uses data obtained through the Telescope Access Program (TAP), which has been funded by the National Astronomical Observatories of China, the Chinese Academy of Sciences, and the Special Fund for Astronomy from the Ministry of Finance. SJS acknowledges STFC grant ST/P000312/1. This work has made use of data from the Asteroid Terrestial-impact Last Alert System (ATLAS) Project. ATLAS is primarily funded to search for near earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; byproducts of the NEO search include images and catalogues from the survey area. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, the Queenâs Univeristy Belfast, the Space Telescope Science Institute, and the South African Astronomical Observatory. OR acknowledges support by projects IC120009 âMillennium Institute of Astrophysics (MAS)â of the Iniciativa CientĂfica Milenio del Ministerio de EconomĂa, Fomento y Turismo de Chile and CONICYT PAI/INDUSTRIA 79090016. JH acknowledges financial support from the Finnish Cultural Foundation. Some data were taken with the Las Cumbres Observatory Network. GH and DAH are supported by NSF grant AST-1313484. GH thanks the LSSTC Data Science Fellowship Program, which is funded by LSSTC, NSF Cybertraining Grant #1829740, the Brinson Foundation, and the Moore Foundation; his participation in the program has benefited this work. LG was funded by the European Unionâs Horizon 2020 research and innovation programme under the Marie SkĆodowska-Curie grant agreement No. 839090. This work also makes use of observations collected at the European Southern Observatory under ESO programme 0103.D-0338(A). CPG acknowledges support from EU/FP7-ERC grant no. [615929]
Evidence for a Chandrasekhar-mass explosion in the Ca-strong 1991bg-like type Ia supernova 2016hnk
International audienceAims. We present a comprehensive dataset of optical and near-infrared photometry and spectroscopy of type Ia supernova (SN) 2016hnk, combined with integral field spectroscopy (IFS) of its host galaxy, MCG -01-06-070, and nearby environment. Our goal with this complete dataset is to understand the nature of this peculiar object.Methods. Properties of the SN local environment are characterized by means of single stellar population synthesis applied to IFS observations taken two years after the SN exploded. We performed detailed analyses of SN photometric data by studying its peculiar light and color curves. SN 2016hnk spectra were compared to other 1991bg-like SNe Ia, 2002es-like SNe Ia, and Ca-rich transients. In addition, we used abundance stratification modeling to identify the various spectral features in the early phase spectral sequence and also compared the dataset to a modified non-LTE model previously produced for the sublumnious SN 1999by.Results. SN 2016hnk is consistent with being a subluminous (MBâ=ââ16.7 mag, sBV=0.43 ± 0.03), highly reddened object. The IFS of its host galaxy reveals both a significant amount of dust at the SN location, residual star formation, and a high proportion of old stellar populations in the local environment compared to other locations in the galaxy, which favors an old progenitor for SN 2016hnk. Inspection of a nebular spectrum obtained one year after maximum contains two narrow emission lines attributed to the forbidden [CaâŻII] λλ7291,7324 doublet with a Doppler shift of 700 km sâ1. Based on various observational diagnostics, we argue that the progenitor of SN 2016hnk was likely a near Chandrasekhar-mass (MCh) carbon-oxygen white dwarf that produced 0.108 Mâ of 56Ni. Our modeling suggests that the narrow [CaâŻII] features observed in the nebular spectrum are associated with 48Ca from electron capture during the explosion, which is expected to occur only in white dwarfs that explode near or at the MCh limit.Key words: supernovae: general / supernovae: individual: SN 2016hnkâ Tables C.1âC.7 are also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/630/A76ââ Pappalardo fellow
The Palomar Transient Factory Core-Collapse Supernova Host-Galaxy Sample. I. Host-Galaxy Distribution Functions and Environment-Dependence of CCSNe
Several thousand core-collapse supernovae (CCSNe) of different flavors
have been discovered so far. However, identifying their progenitors has
remained an outstanding open question in astrophysics. Studies of SN
host galaxies have proven to be powerful in providing constraints on the
progenitor populations. In this paper, we present all CCSNe detected
between 2009 and 2017 by the Palomar Transient Factory. This sample
includes 888 SNe of 12 distinct classes out to redshift . We
present the photometric properties of their host galaxies from the
far-ultraviolet to the mid-infrared and model the host-galaxy spectral
energy distributions to derive physical properties. The galaxy mass
functions of Type Ic, Ib, IIb, II, and IIn SNe ranges from to
, probing the entire mass range of star-forming
galaxies down to the least-massive star-forming galaxies known.
Moreover, the galaxy mass distributions are consistent with models of
star-formation-weighted mass functions. Regular CCSNe are hence direct
tracers of star formation. Small but notable differences exist between
some of the SN classes. Type Ib/c SNe prefer galaxies with slightly
higher masses (i.e., higher metallicities) and star-formation rates than
Type IIb and II SNe. These differences are less pronounced than
previously thought. H-poor SLSNe and SNe~Ic-BL are scarce in galaxies
above . Their progenitors require environments with
metallicities of