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  • 1. Adams, S. M.
    et al.
    Blagorodnova, N.
    Kasliwal, M. M.
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Barlow, T.
    Bue, B.
    Bulla, Mattia
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Cao, Y.
    Cenko, S. B.
    Cook, D. O.
    Ferretti, Raphael
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fox, O. D.
    Fremling, Christoffer
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Gezari, S.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ho, A. Y. Q.
    Hung, Tiara
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Karamehmetoglu, Emir
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kulkarni, S. R.
    Kupfer, T.
    Laher, R. R.
    Masci, F. J.
    Miller, A. A.
    Neill, J. D.
    Nugent, P. E.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walters, R.
    iPTF Survey for Cool Transients2018In: Publications of the Astronomical Society of the Pacific, ISSN 0004-6280, E-ISSN 1538-3873, Vol. 130, no 985, article id 034202Article in journal (Refereed)
    Abstract [en]

    We performed a wide-area (2000 deg2) g and I band experiment as part of a two month extension to the Intermediate Palomar Transient Factory. We discovered 36 extragalactic transients including iPTF17lf, a highly reddened local SN Ia, iPTF17bkj, a new member of the rare class of transitional Ibn/IIn supernovae, and iPTF17be, a candidate luminous blue variable outburst. We do not detect any luminous red novae and place an upper limit on their rate. We show that adding a slow-cadence I band component to upcoming surveys such as the Zwicky Transient Facility will improve the photometric selection of cool and dusty transients.

  • 2. Ashcraft, Teresa A.
    et al.
    Windhorst, Rogier A.
    Jansen, Rolf A.
    Cohen, Seth H.
    Grazian, Andrea
    Paris, Diego
    Fontana, Adriano
    Giallongo, Emanuele
    Speziali, Roberto
    Testa, Vincenzo
    Boutsia, Konstantina
    O'Connell, Robert W.
    Rutkowski, Michael J.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ryan, Russell E.
    Scarlata, Claudia
    Weiner, Benjamin
    Ultra-deep Large Binocular Camera U-band Imaging of the GOODS-North Field: Depth Versus Resolution2018In: Publications of the Astronomical Society of the Pacific, ISSN 0004-6280, E-ISSN 1538-3873, Vol. 130, no 988, article id 064102Article in journal (Refereed)
    Abstract [en]

    We present a study of the trade-off between depth and resolution using a large number of U-band imaging observations in the GOODS-North field from the Large Binocular Camera (LBC) on the Large Binocular Telescope (LBT). Having acquired over 30 hr of data (315 images with 5-6 minutes exposures), we generated multiple image mosaics, starting with the best atmospheric seeing images (FWHM less than or similar to 0 ''.8), which constitute similar to 10% of the total data set. For subsequent mosaics, we added in data with larger seeing values until the final, deepest mosaic included all images with FWHM less than or similar to 1 ''.8 (similar to 94% of the total data set). From the mosaics, we made object catalogs to compare the optimal-resolution, yet shallower image to the lower-resolution but deeper image. We show that the number counts for both images are similar to 90% complete to U-AB less than or similar to 26 mag. Fainter than U-AB similar to 27 mag, the object counts from the optimal-resolution image start to drop-off dramatically (90% between U-AB = 27 and 28 mag), while the deepest image with better surface-brightness sensitivity (mu(AB)(U) less than or similar to 32 mag arcsec(-2)) show a more gradual drop (10% between U-AB similar or equal to 27 and 28 mag). For the brightest galaxies within the GOODS-N field, structure and clumpy features within the galaxies are more prominent in the optimal-resolution image compared to the deeper mosaics. We conclude that for studies of brighter galaxies and features within them, the optimal-resolution image should be used. However, to fully explore and understand the faintest objects, the deeper imaging with lower resolution are also required. Finally, we find-for 220 brighter galaxies with U-AB less than or similar to 23 mag-only marginal differences in total flux between the optimal-resolution and lower-resolution light-profiles to mu(AB)(U) less than or similar to 32 mag arcsec(-2). In only 10% of the cases are the total-flux differences larger than 0.5 mag. This helps constrain how much flux can be missed from galaxy outskirts, which is important for studies of the Extragalactic Background Light.

  • 3. Boldt, Luis N.
    et al.
    Stritzinger, Maximilian D.
    Burns, Chris
    Hsiao, Eric
    Phillips, M. M.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Marion, G. H.
    Stanishev, Vallery
    Near-Infrared K Corrections of Type Ia Supernovae and their Errors2014In: Publications of the Astronomical Society of the Pacific, ISSN 0004-6280, E-ISSN 1538-3873, Vol. 126, no 938, p. 324-337Article in journal (Refereed)
    Abstract [en]

    In this paper we use near-infrared (NIR) spectral observations of Type Ia supernovae (SNe Ia) to study the uncertainties inherent in NIR K corrections. To do so, 75 previously published NIR spectra of 33 SNe Ia are employed to determine K-correction uncertainties in the YJHK(s) passbands as a function of temporal phase and redshift. The resultant K corrections are then fed into an interpolation algorithm that provides mean K corrections as a function of temporal phase and robust estimates of the associated errors. These uncertainties are both statistical and intrinsic-i.e., due to the diversity of spectral features from object to object and must be included in the overall error budget of cosmological parameters constrained through the use of NIR observations of SNe Ia. Intrinsic variations are likely the dominant source of error for all four passbands at maximum light. Given the present data, the total Y-band K-correction uncertainties at maximum are smallest, amounting to +/- 0.04 mag at a redshift of z = 0.08. The J-band K-term errors are also reasonably small (+/- 0.06 mag), but intrinsic variations of spectral features and noise introduced by telluric corrections in the H-band currently limit its total K-correction errors at maximum to +/- 0.10 mag at z = 0.08. Finally, uncertainties in the K-s-band K terms at maximum amount to +/- 0.07 mag at this same redshift. These results are largely constrained by the small number of published NIR spectra of SNe Ia, which do not yet allow spectral templates to be constructed as a function of the light curve decline rate.

  • 4. Branch, David
    et al.
    Jeffery, David J.
    Parrent, Jerod
    Baron, E.
    Troxel, M. A.
    Stanishev, Vallery
    Stockholm University, Faculty of Science, Department of Physics.
    Keithley, Melissa
    Harrison, Joshua
    Bruner, Christopher
    Comparative direct analysis of type Ia supernova spectra. IV. Postmaximum2008In: Publications of the Astronomical Society of the Pacific, ISSN 0004-6280, E-ISSN 1538-3873, Vol. 120, no 864, p. 135-149Article in journal (Refereed)
    Abstract [en]

    A comparative study of optical spectra of Type Ia supernovae ( SNe Ia) obtained near 1 week, 3 weeks, and 3 months after maximum light is presented. Most members of the four groups that were defined on the basis of maximum light spectra in Paper II ( core normal, broad line, cool, and shallow silicon) develop highly homogeneous postmaximum spectra, although there are interesting exceptions. Comparisons with SYNOW synthetic spectra show that most of the spectral features can be accounted for in a plausible way. The fits show that 3 months after maximum light, when SN Ia spectra are often said to be in the nebular phase and to consist of forbidden emission lines, the spectra actually remain dominated by resonance- scattering features of permitted lines, primarily those of Fe II. Even in SN 1991bg, which is said to have made a very early transition to the nebular phase, there is no need to appeal to forbidden lines at 3 weeks postmaximum, and at 3 months postmaximum the only clear identification of a forbidden line is [Ca II]lambda lambda 7291, 7324. Recent studies of SN Ia rates indicate that most of the SNe Ia that have ever occurred have been "" prompt"" SNe Ia, produced by young (similar to 10(8) yr) stellar populations, while most of the SNe Ia that occur at low redshift today are "" tardy,"" produced by an older ( several Gyr) population. We suggest that the shallow silicon SNe Ia tend to be the prompt ones.

  • 5. Clocchiatti, Alejandro
    et al.
    Wheeler, J. Craig
    Kirshner, Robert P.
    Branch, David
    Challis, Peter
    Chevalier, Roger A.
    Filippenko, Alexei V.
    Fransson, Claes
    Stockholm University, Faculty of Science, Department of Astronomy.
    Garnavich, Peter
    Leibundgut, Bruno
    Panagia, Nino
    Phillips, Mark M.
    Suntzeff, Nicholas B.
    Hoeflich, Peter A.
    Gallardo, Jose
    Late-time HST photometry of SN1994I: Hints of positron annihilation energy deposition2008In: Publications of the Astronomical Society of the Pacific, ISSN 0004-6280, E-ISSN 1538-3873, Vol. 120, no 865, p. 290-300Article in journal (Refereed)
    Abstract [en]

    We present multicolor Hubble Space Telescope ( HST) WFPC2 broadband observations of the Type Ic SN 1994I obtained similar to 280 d after maximum light. We measure the brightness of the SN and, relying on the detailed spectroscopic database of SN 1994I, we transform the ground-based photometry obtained at early times to the HST photometric system, deriving light curves for the WFPC2 F439W, F555W, F675W, and F814W passbands that extend from 7 days before to 280 days after maximum. We use the multicolor photometry to build a quasi-bolometric light curve of SN 1994I, and compare it with similarly constructed light curves of other supernovae. In doing so, we propose and test a scaling in energy and time that allows for a more meaningful comparison of the exponential tails of different events. Through comparison with models, we find that the late-time light curve of SN 1994I is consistent with that of spherically symmetric ejecta in homologous expansion, for which the ability to trap the gamma-rays produced by the radioactive decay of Co-56 diminishes roughly as the inverse of time squared. We also find that by the time of the HST photometry, the light curve was significantly energized by the annihilation of positrons.

  • 6. Kattner, ShiAnne
    et al.
    Leonard, Douglas C.
    Burns, Christopher R.
    Phillips, M. M.
    Folatelli, Gaston
    Morrell, Nidia
    Stritzinger, Maximilian
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hamuy, Mario
    Freedman, Wendy L.
    Persson, Sven E.
    Roth, Miguel
    Suntzeff, Nicholas B.
    The Standardizability of Type Ia Supernovae in the Near-Infrared: Evidence for a Peak-Luminosity Versus Decline-Rate Relation in the Near-Infrared2012In: Publications of the Astronomical Society of the Pacific, ISSN 0004-6280, E-ISSN 1538-3873, Vol. 124, no 912, p. 114-127Article in journal (Refereed)
    Abstract [en]

    We analyze the standardizability of Type Ia supernovae (SNe Ia) in the near-infrared (NIR) by investigating the correlation between observed peak NIR (Y JH) absolute magnitude and postmaximum B-band decline rate [Delta m(15)(B)]. A sample of 27 low-redshift SNe Ia with well-observed NIR light curves observed by the Carnegie Supernova Project (CSP) between 2004 and 2007 is used. All 27 objects have premaximum coverage in optical bands, with a subset of 13 having premaximum NIR observations as well; coverage of the other 14 begins shortly after NIR maximum brightness. We describe the methods used to derive light-curve parameters (absolute peak magnitudes and decline rates) from both spline-and template-fitting procedures, and we confirm prior findings that fitting templates to SNe Ia light curves in the NIR is problematic due to the diversity of postmaximum behavior of objects that are characterized by similar Delta m(15)(B) values, especially at high decline rates. Nevertheless, we show that NIR light curves can be reasonably fit with a template, especially if the observations begin within 5 days after NIR maximum. SNe Ia appear to be better standardizable candles in the NIR bands than in the optical bands. For the subset of 13 objects in our data set that excludes the highly reddened and fast-declining SNe Ia and includes only those objects for which NIR observations began prior to 5 days after maximum light, we find modest (1.7 sigma) evidence for a peak-luminosity versus decline-rate relation in Y, and stronger evidence (2.8 sigma) in J and H. Using R-V values differing from the canonical value (R-V = 3.1) is shown to have little effect on the results. A Hubble diagram is presented for the NIR bands and the B band. The resulting scatter for the combined NIR bands is 0.13 mag, while the B band produces a scatter of 0.22 mag. Finally, we find evidence for a bimodal distribution in the NIR absolute magnitudes of fast-declining SNe Ia [Delta m(15)(B) > 1.7]. These data suggest that applying a correction to SNe Ia peak luminosities for decline rate is likely to be beneficial in the J and H bands to make SNe Ia more precise distance indicators, but of only marginal importance in the Y band.

  • 7. Kessler, Richard
    et al.
    Bassett, Bruce
    Belov, Pavel
    Bhatnagar, Vasudha
    Campbell, Heather
    Conley, Alex
    Frieman, Joshua A.
    Glazov, Alexandre
    Gonzalez-Gaitan, Santiago
    Hlozek, Renee
    Jha, Saurabh
    Kuhlmann, Stephen
    Kunz, Martin
    Lampeitl, Hubert
    Mahabal, Ashish
    Newling, James
    Nichol, Robert C.
    Parkinson, David
    Philip, Ninan Sajeeth
    Poznanski, Dovi
    Richards, Joseph W.
    Rodney, Steven A.
    Sako, Masao
    Schneider, Donald P.
    Smith, Mathew
    Stritzinger, Maximilian
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Varughese, Melvin
    Results from the Supernova Photometric Classification Challenge2010In: Publications of the Astronomical Society of the Pacific, ISSN 0004-6280, E-ISSN 1538-3873, Vol. 122, no 898, p. 1415-1431Article in journal (Refereed)
    Abstract [en]

    We report results from the Supernova Photometric Classification Challenge (SNPhotCC), a publicly released mix of simulated supernovae (SNe), with types (Ia, Ibc, and II) selected in proportion to their expected rates. The simulation was realized in the griz filters of the Dark Energy Survey (DES) with realistic observing conditions (sky noise, point-spread function, and atmospheric transparency) based on years of recorded conditions at the DES site. Simulations of non-Ia-type SNe are based on spectroscopically confirmed light curves that include unpublished non-Ia samples donated from the Carnegie Supernova Project (CSP), the Supernova Legacy Survey (SNLS), and the Sloan Digital Sky Survey-II (SDSS-II). A spectroscopically confirmed subset was provided for training. We challenged scientists to run their classification algorithms and report a type and photo-z for each SN. Participants from 10 groups contributed 13 entries for the sample that included a host-galaxy photo-z for each SN and nine entries for the sample that had no redshift information. Several different classification strategies resulted in similar performance, and for all entries the performance was significantly better for the training subset than for the unconfirmed sample. For the spectroscopically unconfirmed subset, the entry with the highest average figure of merit for classifying SNe Ia has an efficiency of 0.96 and an SN Ia purity of 0.79. As a public resource for the future development of photometric SN classification and photo-z estimators, we have released updated simulations with improvements based on our experience from the SNPhotCC, added samples corresponding to the Large Synoptic Survey Telescope (LSST) and the SDSS-II, and provided the answer keys so that developers can evaluate their own analysis.

  • 8. van Dishoeck, E. F.
    et al.
    Kristensen, L. E.
    Benz, A. O.
    Bergin, E. A.
    Caselli, P.
    Cernicharo, J.
    Herpin, F.
    Hogerheijde, M. R.
    Johnstone, D.
    Liseau, R.
    Nisini, B.
    Shipman, R.
    Tafalla, M.
    van der Tak, F.
    Wyrowski, F.
    Aikawa, Y.
    Bachiller, R.
    Baudry, A.
    Benedettini, M.
    Bjerkeli, P.
    Blake, G. A.
    Bontemps, S.
    Braine, J.
    Brinch, C.
    Bruderer, S.
    Chavarria, L.
    Codella, C.
    Daniel, F.
    de Graauw, Th.
    Deul, E.
    di Giorgio, A. M.
    Dominik, C.
    Doty, S. D.
    Dubernet, M. L.
    Encrenaz, P.
    Feuchtgruber, H.
    Fich, M.
    Frieswijk, W.
    Fuente, A.
    Giannini, T.
    Goicoechea, J. R.
    Helmich, F. P.
    Herczeg, G. J.
    Jacq, T.
    Jorgensen, J. K.
    Karska, A.
    Kaufman, M. J.
    Keto, E.
    Larsson, Bengt
    Stockholm University, Faculty of Science, Department of Astronomy.
    Lefloch, B.
    Lis, D.
    Marseille, M.
    McCoey, C.
    Melnick, G.
    Neufeld, D.
    Olberg, M.
    Pagani, L.
    Panic, O.
    Parise, B.
    Pearson, J. C.
    Plume, R.
    Risacher, C.
    Salter, D.
    Santiago-Garcia, J.
    Saraceno, P.
    Staeuber, P.
    van Kempen, T. A.
    Visser, R.
    Viti, S.
    Walmsley, M.
    Wampfler, S. F.
    Yildiz, U. A.
    Water in Star-forming Regions with the Herschel Space Observatory (WISH). I. Overview of Key Program and First Results2011In: Publications of the Astronomical Society of the Pacific, ISSN 0004-6280, E-ISSN 1538-3873, Vol. 123, no 900, p. 138-170Article in journal (Refereed)
    Abstract [en]

    Water In Star-forming regions with Herschel (WISH) is a key program on the Herschel Space Observatory designed to probe the physical and chemical structures of young stellar objects using water and related molecules and to follow the water abundance from collapsing clouds to planet-forming disks. About 80 sources are targeted, covering a wide ranee of luminosities-from low (< 1 L(circle dot)) to high (> 10(5) L(circle dot))-and a wide range of evolutionary stages-from cold prestellar cores to warm protostellar envelopes and outflows to disks around young stars. Both the HIFI and PACS instruments are used to observe a variety of lines of H(2)O, H(2)(18)O and chemically related species at the source position and in small maps around the protostars and selected outflow positions. In addition, high-frequency lines of CO, (13)CO, and C(18)O are obtained with Herschel and are complemented by ground-based observations of dust continuum, HDO, CO and its isotopologs, and other molecules to ensure a self-consistent data set for analysis. An overview of the scientific motivation and observational strategy of the program is given, together with the modeling approach and analysis tools that have been developed. Initial science results are presented. These include a lack of water in cold gas at abundances that are lower than most predictions, strong water emission from shocks in protostellar environments, the importance of UV radiation in heating the gas along outflow walls across the full range of luminosities, and surprisingly widespread detection of the chemically related hydrides OH(+) and H(2)O(+) in outflows and foreground gas. Quantitative estimates of the energy budget indicate that H(2)O is generally not the dominant coolant in the warm dense gas associated with protostars. Very deep limits on the cold gaseous water reservoir in the outer regions of protoplanetary disks are obtained that have profound implications for our understanding of grain growth and mixing in disks.

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