Browsing by Author "Strader, J."

Now showing 1 - 6 of 6
  • Thumbnail Image
    Item
    An AO-assisted variability study of four globular clusters
    (2016) Salinas, R.; Contreras Ramos, Rodrigo Andrés; Strader, J.; Hakala, P.; Catelan, Márcio; Peacock, M. B.; Simunovic , M.
  • No Thumbnail Available
    Item
    Mapping Milky Way And Local Volume Structure With LSST
    (2011) Geha, Marla C.; Willman, B.; Bochanski, J.; Bullock, J.; Catelan, Márcio; Debattista, V.; Grillmair, C.; Jordan, A.; Juric, M.; Kalirai, J.; Kallivayalil, N.; McGehee, P.; Minniti, D.; Munoz, R.; Roskar, R.; Sarajedini, A.; Simon, J.; Strader, J.
    The LSST will yield revolutionary, multi-dimensional maps of the Milky Way (MW) galaxy and its neighbors. With its planned 1000 epochs over 6 bands and a final limiting magnitude of r=27.5 (AB mag; 5-sigma), it will provide an excellent resource for mapping the structure and accretion history of the MW and beyond in a way that the present generation of surveys can only hint at. LSST is expected to catalog 10 billion stars, including photometric metallicities for the 200 million F/G stars within 100 kpc and map the tangential velocity field of stars bright than r=24 mag to at least 10 kpc (at 10 km/s precision) and as far as 25 kpc (at 60 km/s precision). Specific related science to be enabled by LSST includes: mapping the 3D distribution of dust in the MW's disk, including variations in RV; understanding the smooth distribution of stars in the MW and other nearby galaxies; understanding large-scale chemical gradients in the MW; discovering lumps and streams in metallicity and phase-space; inferring the mass distribution in the MW; discovering ultra-faint galaxies throughout the Local Volume....
  • No Thumbnail Available
    Item
    SOAR/Goodman Spectroscopic Assessment of Candidate Counterparts of the LIGO/Virgo Event GW190814*
    (2022) Tucker, D. L.; Wiesner, M. P.; Allam, S. S.; Soares-Santos, M.; Bom, C. R.; Butner, M.; Garcia, A.; Morgan, R.; Olivares E, F.; Palmese, A.; Santana-Silva, L.; Shrivastava, A.; Annis, J.; Garcia-Bellido, J.; Gill, M. S. S.; Herner, K.; Kilpatrick, C. D.; Makler, M.; Sherman, N.; Amara, A.; Lin, H.; Smith, M.; Swann, E.; Arcavi, I; Bachmann, T. G.; Bechtol, K.; Berlfein, F.; Briceno, C.; Brout, D.; Butler, R. E.; Cartier, R.; Casares, J.; Chen, H-Y; Conselice, C.; Contreras, C.; Cook, E.; Cooke, J.; Dage, K.; D'Andrea, C.; Davis, T. M.; de Carvalho, R.; Diehl, H. T.; Dietrich, J. P.; Doctor, Z.; Drlica-Wagner, A.; Drout, M.; Farr, B.; Finley, D. A.; Fishbach, M.; Foley, R. J.; Forster-Buron, F.; Fosalba, P.; Friedel, D.; Frieman, J.; Frohmaier, C.; Gruendl, R. A.; Hartley, W. G.; Hiramatsu, D.; Holz, D. E.; Howell, D. A.; Kawash, A.; Kessler, R.; Kuropatkin, N.; Lahav, O.; Lundgren, A.; Lundquist, M.; Malik, U.; Mann, A. W.; Marriner, J.; Marshall, J. L.; Martinez-Vazquez, C. E.; McCully, C.; Menanteau, F.; Meza, N.; Narayan, G.; Neilsen, E.; Nicolaou, C.; Nichol, R.; Paz-Chinchon, F.; Pereira, M. E. S.; Pineda, J.; Points, S.; Quirola-Vasquez, J.; Rembold, S.; Rest, A.; Rodriguez, O.; Romer, A. K.; Sako, M.; Salim, S.; Scolnic, D.; Smith, J. A.; Strader, J.; Sullivan, M.; Swanson, M. E. C.; Thomas, D.; Valenti, S.; Varga, T. N.; Walker, A. R.; Weller, J.; Wood, M. L.; Yanny, B.; Zenteno, A.; Aguena, M.; Andrade-Oliveira, F.; Bertin, E.; Brooks, D.; Burke, D. L.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Costanzi, M.; da Costa, L. N.; De Vicente, J.; Desai, S.; Everett, S.; Ferrero, I; Flaugher, B.; Gaztanaga, E.; Gerdes, D. W.; Gruen, D.; Gschwend, J.; Gutierrez, G.; Hinton, S. R.; Hollowood, D. L.; Honscheid, K.; James, D. J.; Kuehn, K.; Lima, M.; Maia, M. A. G.; Miquel, R.; Ogando, R. L. C.; Pieres, A.; Malagon, A. A. Plazas; Rodriguez-Monroy, M.; Sanchez, E.; Scarpine, V; Schubnell, M.; Serrano, S.; Sevilla-Noarbe, I; Suchyta, E.; Tarle, G.; To, C.; Zhang, Y.
    On 2019 August 14 at 21:10:39 UTC, the LIGO/Virgo Collaboration (LVC) detected a possible neutron star-black hole merger (NSBH), the first ever identified. An extensive search for an optical counterpart of this event, designated GW190814, was undertaken using the Dark Energy Camera on the 4 m Victor M. Blanco Telescope at the Cerro Tololo Inter-American Observatory. Target of Opportunity interrupts were issued on eight separate nights to observe 11 candidates using the 4.1 m Southern Astrophysical Research (SOAR) telescope's Goodman High Throughput Spectrograph in order to assess whether any of these transients was likely to be an optical counterpart of the possible NSBH merger. Here, we describe the process of observing with SOAR, the analysis of our spectra, our spectroscopic typing methodology, and our resultant conclusion that none of the candidates corresponded to the gravitational wave merger event but were all instead other transients. Finally, we describe the lessons learned from this effort. Application of these lessons will be critical for a successful community spectroscopic follow-up program for LVC observing run 4 (O4) and beyond.
  • Thumbnail Image
    Item
    Stellar variability at the main-sequence turnoff of the intermediate-age LMC cluster NGC 1846
    (2018) Salinas, R.; Pajkos, M.A.; Vivas, A.K.; Strader, J.; Contreras Ramos, Rodrigo Andrés
  • No Thumbnail Available
    Item
    The ASAS-SN bright supernova catalogue - V. 2018-2020
    (2023) Neumann, K. D.; Holoien, T. W-S; Kochanek, C. S.; Stanek, K. Z.; Vallely, P. J.; Shappee, B. J.; Prieto, J. L.; Pessi, T.; Jayasinghe, T.; Brimacombe, J.; Bersier, D.; Aydi, E.; Basinger, C.; Beacom, J. F.; Bose, S.; Brown, J. S.; Chen, P.; Clocchiatti, A.; Desai, D. D.; Dong, Subo; Falco, E.; Holmbo, S.; Morrell, N.; Shields, J. V.; Sokolovsky, K. V.; Strader, J.; Stritzinger, M. D.; Swihart, S.; Thompson, T. A.; Way, Z.; Aslan, L.; Bishop, D. W.; Bock, G.; Bradshaw, J.; Cacella, P.; Castro-Morales, N.; Conseil, E.; Cornect, R.; Cruz, I.; Farfan, R. G.; Fernandez, J. M.; Gabuya, A.; Gonzalez-Carballo, J-L; Kendurkar, M. R.; Kiyota, S.; Koff, R. A.; Krannich, G.; Marples, P.; Masi, G.; Monard, L. A. G.; Munoz, J. A.; Nicholls, B.; Post, R. S.; Pujic, Z.; Stone, G.; Tomasella, L.; Trappett, D. L.; Wiethoff, W. S.
    We catalogue the 443 bright supernovae (SNe) discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN) in 2018-2020 along with the 519 SNe recovered by ASAS-SN and 516 additional m(peak) <= 18 mag SNe missed by ASAS-SN. Our statistical analysis focuses primarily on the 984 SNe discovered or recovered in ASAS-SN g-band observations. The complete sample of 2427 ASAS-SN SNe includes earlier V-band samples and unrecovered SNe. For each SN, we identify the host galaxy, its UV to mid-IR photometry, and the SN's offset from the centre of the host. Updated peak magnitudes, redshifts, spectral classifications, and host galaxy identifications supersede earlier results. With the increase of the limiting magnitude to g <= 18 mag, the ASAS-SN sample is nearly complete up to m(peak) = 16.7 mag and is 90 per cent complete for m(peak) <= 17.0 mag. This is an increase from the V-band sample, where it was roughly complete up to m(peak) = 16.2 mag and 70 per cent complete for m(peak) <= 17.0 mag.
  • No Thumbnail Available
    Item
    THE OVERLOOKED ROLE OF STELLAR VARIABILITY IN THE EXTENDED MAIN SEQUENCE OF LMC INTERMEDIATE-AGE CLUSTERS
    (2016) Salinas, R.; Pajkos, M. A.; Strader, J.; Vivas, A. K.; Ramos, R. Contreras
    Intermediate-age star clusters in the Large Magellanic Cloud show extended main sequence turnoffs (MSTOs) that are not consistent with a canonical single stellar population. These broad turnoffs have been interpreted as evidence for extended star formation and/or stellar rotation. Since most of these studies use single frames per filter to do the photometry, the presence of variable stars near the MSTO in these clusters has remained unnoticed and their impact has been totally ignored. We model the influence of Delta Scuti using synthetic CMDs, adding variable stars following different levels of incidence and amplitude distributions. We show that Delta Scuti observed at a single phase will produce a broadening of the MSTO without affecting other areas of a CMD such as the upper MS or the red clump; furthermore, the amount of spread introduced correlates with cluster age, as observed. This broadening is constrained to ages similar to 1-3 Gyr when the MSTO area crosses the instability strip, which is also consistent with observations. Variable stars cannot explain bifurcarted MSTOs or the extended MSTOs seen in some young clusters, but they can make an important contribution to the extended MSTOs in intermediate-age clusters.