Browsing by Author "Kim, Sam"

Now showing 1 - 20 of 21
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    A comprehensive view of a strongly lensedplanck-associated submillimeter galaxy.
    (2012) Fu, Hai; Kim, Sam; Jullo, E.; Cooray, Asantha; Bussmann, R. S.; Ivison, R. J.; Pérez-Fournon, I.; Djorgovski, S. G.; Scoville, Nick Z.; Yan, L.; Riechers, D. A.
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    Cosmic evolution and metal aversion in superluminous supernova host galaxies
    (2018) Schulze, Steve; Krühler, T.; Leloudas, G.; Gorosabel, J.; Mehner, A.; Buchner, J.; Kim, Sam; Ibar, Edo; Amorín, Ricardo; Herrero Illana, Rubén; Anderson, Joseph; Bauer, Franz Erik
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    Delayed appearance and evolution of coronal lines in the TDE AT2019qiz
    (Oxford University Press, 2023) Short, P.; Lawrence, A.; Nicholl, M.; Ward, M.; Reynolds, T. M.; Mattila, S.; Yin, C.; Arcavi, I; Carnall, A.; Charalampopoulos, P.; Gromadzki, M.; Jonker, P. G.; Kim, Sam; Leloudas, G.; Mandel, I; Onori, F.; Pursiainen, M.; Schulze, S.; Villforth, C.; Wevers, T.
    Tidal disruption events (TDEs) occur when a star gets torn apart by a supermassive black hole as it crosses its tidal radius. We present late-time optical and X-ray observations of the nuclear transient AT2019qiz, which showed the typical signs of an optical-UV transient class commonly believed to be TDEs. Optical spectra were obtained 428, 481, and 828 rest-frame days after optical light-curve peak, and a UV/X-ray observation coincided with the later spectrum. The optical spectra show strong coronal emission lines, including [Fe vii], [Fe x], [Fe xi], and [Fe xiv]. The Fe lines rise and then fall, except [Fe xiv] that appears late and rises. We observe increasing flux of narrow H & alpha; and H & beta; and a decrease in broad H & alpha; flux. The coronal lines have full width at half-maximum ranging from & SIM;150-300 km s(-1), suggesting they originate from a region between the broad- and narrow-line emitting gas. Between the optical flare and late-time observation, the X-ray spectrum softens dramatically. The 0.3-1 keV X-ray flux increases by a factor of & SIM;50, while the hard X-ray flux decreases by a factor of & SIM;6. Wide-field Infrared Survey Explorer fluxes also rose over the same period, indicating the presence of an infrared echo. With AT2017gge, AT2019qiz is one of two examples of a spectroscopically confirmed optical-UV TDE showing delayed coronal line emission, supporting speculations that Extreme Coronal Line Emitters in quiescent galaxies can be echos of unobserved past TDEs. We argue that the coronal lines, narrow lines, and infrared emission arise from the illumination of pre-existing material likely related to either a previous TDE or active galactic nucleus activity.
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    Discovery of a Multiply-Lensed Submillimeter Galaxy in Early HerMES Herschel/SPIRE Data
    (2011) Conley, A.; Kim, Sam; Cooray, Asantha; Vieira, J. D.; González Solares, E. A.; Aguirre, J. E.; Amblard, A.; Auld, R.; Baker, A. J.; Beelen, A.; Blain, A.
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    Dynamical structure of the molecular interstellar medium in an extremely bright, multiply lensed z 3 submillimeter galaxy discovered with Herschel.
    (2011) Riechers, Dominik A.; Kim, Sam; Cooray, Asantha; Omont, A.; Neri, R.; Harris, A. I.; Baker, A. J.; Cox, P.; Frayer, D. T.; Carpenter, J. M.; Auld, R.
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    Herschel*-ATLAS : deep HST/WFC3 imaging of strongly lensed submillimetre galaxies.
    (2014) Negrello, Mattia; Kim, Sam; Hopwood, R.; Dye, S.; Cunha, E. da; Serjeant, S.; Fritz, J.; Rowlands, K.; Fleuren, S.; Bussmann, R. S.; Cooray, Asantha
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    Lens Models of Herschel-Selected Galaxies From High-Resolution Near-IR Observations.
    (2014) Calanog, J.; Kim, Sam; Fu, Hai; Cooray, Asantha; Wardlow, Julie L.; Ma, B.; Amber, S.; Baker, A. J.; Baes, M.; Bock, J.; Bourne, N.
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    Long-term x-ray variability of typical active galactic nuclei in the distant universe.
    (2016) Yang, G.; Kim, Sam; Brandt, W N.; Bauer, Franz Erik; Schulze, Steve.; Luo, B.; Xue, Y. Q.; Sun, M. Y.; Zheng, X. C.; Paolillo, M.; Shemmer, O.
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    Measurements of co redshifts with Z-spec for lensed submillimeter galaxies discovered in the H-atlas survey.
    (2012) Lupu, R. E.; Kim, Sam; Scott, K. S.; Aguirre, J. E.; Aretxaga, I.; Auld, R.; Barton, E.; Beelen, A.; Bertoldi, F.; Bock, J. J.; Bonfield, D.
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    Multi-messenger Observations of a Binary Neutron Star Merger.
    (2017) Abbott, B. P.; Kim, Sam; Bauer, Franz Erik; González López, Jorge; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams Wrighton, Christopher William; Adams, T.; Addesso, P.; Abbott, B. P.; Kim, Sam; Bauer, Franz Erik; González López, Jorge; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams Wrighton, Christopher William; Adams, T.; Addesso, P.; Abbott, B. P.; Kim, Sam; Bauer, Franz Erik; González López, Jorge; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams Wrighton, Christopher William; Adams, T.; Addesso, P.; Abbott, B. P.; Kim, Sam; Bauer, Franz Erik; González López, Jorge; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams Wrighton, Christopher William; Adams, T.; Addesso, P.
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    Optical survey with kmtnet for dusty star-forming galaxies in the AKARI Deep Field South
    (2016) Jeong, Woong-Seob; Kim, Sam; Ko, Kyeongyeon; Kim, Minjin; Ko, Jongwan; Pyo, Jeonghyun; Kim, Seong Jin; Kim, Taehyun; Seo, Hyun Jong; Park, Won-Kee; Park, Sung-Joon
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    Radial Velocity Survey for Planets around Young stars (RVSPY) : Target characterisation and high-cadence survey
    (EDP Sciences, 2022) Zakhozhay, Olga V.; Launhardt, Ralf; Müller, Andre; Eigenthaler, Paul; Hempel, Angela; Hempel, Maren; Henning, Thomas; Kim, Sam; Kurster, Martin; Lachaume, Régis; Manerikar, Yashodham; Pavlov, Alexey; Trifonov, Trifonov; Brems, Stefan S.; Reffert, Sabine; Gennaro, Mario; Kennedy G.M.; Patel, Jayshil A.
    Context. The occurrence rate and period distribution of (giant) planets around young stars is still not as well constrained as for older main-sequence stars. This is mostly due to the intrinsic activity-related complications and the avoidance of young stars in many large planet search programmes. Yet, dynamical restructuring processes in planetary systems may last significantly longer than the actual planet formation phase and may well extend long into the debris disc phase, such that the planet populations around young stars may differ from those observed around main-sequence stars. Aims. We introduce our Radial Velocity Survey for Planets around Young stars (RVSPY), which is closely related to the NaCo-ISPY direct imaging survey, characterise our target stars, and search for substellar companions at orbital separations smaller than a few au from the host star. Methods. We used the FEROS spectrograph, mounted to the MPG/ESO 2.2 m telescope in Chile, to obtain high signal-to-noise spectra and time series of precise radial velocities (RVs) of 111 stars, most of which are surrounded by debris discs. Our target stars have spectral types between early F and late K, a median age of 400 Myr, and a median distance of 45 pc. During the initial reconnaissance phase of our survey, we determined stellar parameters and used high-cadence observations to characterise the intrinsic stellar activity, searched for hot companions with orbital periods of up to 10 days, and derived the detection thresholds for longer-period companions. In our analysis we, have included archival spectroscopic data, spectral energy distribution, and data for photometric time series from the TESS mission. Results. For all target stars we determined their basic stellar parameters and present the results of the high-cadence RV survey and activity characterisation. We have achieved a median single-measurement RV precision of 6 m s−1 and derived the short-term intrinsic RV scatter of our targets (median 23 m s−1), which is mostly caused by stellar activity and decays with an age from >100 m s−1 at <20 Myr to <20 m s−1 at >500 Myr. We analysed time series periodograms of the high-cadence RV data and the shape of the individual cross-correlation functions. We discovered six previously unknown close companions with orbital periods between 10 and 100 days, three of which are low-mass stars, and three are in the brown dwarf mass regime. We detected no hot companion with an orbital period <10 days down to a median mass limit of ~1 MJup for stars younger than 500 Myr, which is still compatible with the established occurrence rate of such companions around main-sequence stars. We found significant RV periodicities between 1.3 and 4.5 days for 14 stars, which are, however, all caused by rotational modulation due to starspots. We also analysed the data for TESS photometric time series and found significant periodicities for most of the stars. For 11 stars, the photometric periods are also clearly detected in the RV data. We also derived stellar rotation periods ranging from 1 to 10 days for 91 stars, mostly from the TESS data. From the intrinsic activity-related short-term RV jitter, we derived the expected mass-detection thresholds for longer-period companions, and selected 84 targets for the longer-term RV monitoring
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    Spatially resolved analysis of superluminous supernovae PTF 11hrq and PTF 12dam host galaxies.
    (2017) Cikota, Aleksandar; Kim, Sam; Cia, Annalisa De; Schulze, Steve; Vreeswijk, Paul M.; Leloudas, Giorgos; Gal-Yam, Avishay; Perley, Daniel A.; Cikota, Stefan; Patat, Ferdinando; Lunnan, Ragnhild
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    Spitzer imaging of Herschel-atlas gravitationally lensed submillimeter sources.
    (2011) Hopwood, R.; Kim, Sam; Wardlow, Julie L.; Cooray, Asantha; Khostovan, A. A.; Negrello, Mattia; Cunha, E. da; Burgarella, D.; Aretxaga, I.; Auld, R.; Baes, M.
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    Spitzer-irac identification of Herschel-atlas spire sources.
    (2012) Kim, Sam; Wardlow, Julie L.; Cooray, Asantha; Fleuren, S.; Sutherland, W.; Khostovan, A. A.; Auld, R.; Baes, M.; Bussmann, R. S.; Buttiglione, S.; Cava, A.
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    The ALMA Frontier Fields Survey. II. Multiwavelength Photometric analysis of 1.1 mm continuum sources in Abell 2744, MACSJ0416.1-2403 and MACSJ1149.5+2223.
    (2017) Laporte, Nicolás; Treister, Ezequiel; Bauer, Franz Erik; Troncoso Iribarren, Paulina Alejandra; Huang, X.; González López, Jorge; Kim, Sam; Anguita A., Timo; Aravena, M.; Barrientos, Luis Felipe; Bouwens, R.; Laporte, Nicolás; Treister, Ezequiel; Bauer, Franz Erik; Troncoso Iribarren, Paulina Alejandra; Huang, X.; González López, Jorge; Kim, Sam; Anguita A., Timo; Aravena, M.; Barrientos, Luis Felipe; Bouwens, R.
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    The high optical brightness of the BlueWalker 3 satellite
    (2023) Nandakumar, Sangeetha; Eggl, Siegfried; Tregloan-Reed, Jeremy; Adam, Christian; Anderson-Baldwin, Jasmine; Bannister, Michele T.; Battle, Adam; Benkhaldoun, Zouhair; Campbell, Tanner; Colque, J. P.; Damke, Guillermo; Plauchu Frayn, Ilse; Ghachoui, Mourad; Guillén, Pedro F.; Kaeouach, Aziz Ettahar; Krantz, Harrison R.; Langbroek, Marco; Rattenbury, Nicholas; Reddy, Vishnu; Kim, Sam
    Large constellations of bright artificial satellites in low Earth orbit pose significant challenges to ground-based astronomy1. Current orbiting constellation satellites have brightnesses between apparent magnitudes 4 and 6, whereas in the near-infrared Ks band, they can reach magnitude 2 (ref. 2). Satellite operators, astronomers and other users of the night sky are working on brightness mitigation strategies3,4. Radio emissions induce further potential risk to ground-based radio telescopes that also need to be evaluated. Here we report the outcome of an international optical observation campaign of a prototype constellation satellite, AST SpaceMobile’s BlueWalker 3. BlueWalker 3 features a 64.3 m2 phased-array antenna as well as a launch vehicle adaptor (LVA)5. The peak brightness of the satellite reached an apparent magnitude of 0.4. This made the new satellite one of the brightest objects in the night sky. Additionally, the LVA reached an apparent V-band magnitude of 5.5, four times brighter than the current International Astronomical Union recommendation of magnitude 7 (refs. 3,6); it jettisoned on 10 November 2022 (Universal Time), and its orbital ephemeris was not publicly released until 4 days later. The expected build-out of constellations with hundreds of thousands of new bright objects1 will make active satellite tracking and avoidance strategies a necessity for ground-based telescopes.
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    The superluminous transient ASASSN-15lh as a tidal disruption event from a Kerr black hole.
    (2016) Leloudas, G.; Kim, Sam; Fraser, M.; Stone, N. C.; Velzen, S. van; Jonker, P. G.; Arcavi, I.; Fremling, C.; Maund, J. R.; Smartt, S. J.; Krühler, Thomas
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    The supermassive black hole coincident with the luminous transient ASASSN-15lh.
    (2017) Krühler, Thomas; Kim, Sam; Fraser, M.; Leloudas, G.; Schulze, Steve; Stone, N. C.; Velzen, S. van; Amorin, R.; Hjorth, J.; Jonker, P. G.; Kann, D. A.
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    X-shooter and ALMA spectroscopy of GRB 161023A.
    (2018) Ugarte Postigo, A. de; Kim, Sam; Thöne, Christina C.; Bolmer, J.; Schulze, Steve.; Martín, S.; Kann, D. A.; D’Elia, V.; Selsing, J.; Martin-Carrillo, A.; Perley, Daniel A.