Browsing by Subject "spectrophotometric standards"
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Item The Broad-Lined Type Ic SN 2012ap And The Nature Of Relativistic Supernovae Lacking A Gamma-Ray Burst Detection(2015-01) Milisavljevic, Dan; Margutti, R.; Parrent, Jerod T.; Soderberg, Alicia M.; Fesen, Robert A.; Mazzali, P.; Maeda, K.; Sanders, N. E.; Cenko, S. Bradley; Silverman, Jeffrey M.; Filippenko, Alexei V.; Kamble, A.; Chakraborti, S.; Drout, M. R.; Kirshner, Robert P.; Pickering, T. E.; Kawabata, K.; Hattori, T.; Hsiao, Eric Y.; Stritzinger, Maximillian D.; Marion, G. H.; Vinko, Jozsef; Wheeler, J. Craig; Silverman, Jeffrey M.; Marion, G. H.; Vinko, Jozsef; Wheeler, J. CraigWe present ultraviolet, optical, and near-infrared observations of SN 2012ap, a broad-lined Type Ic supernova in the galaxy NGC 1729 that produced a relativistic and rapidly decelerating outflow without a gamma-ray burst signature. Photometry and spectroscopy follow the flux evolution from -13 to +272 days past the B-band maximum of -17.4 +/- 0.5mag. The spectra are dominated by Fe II, OI, and Ca II absorption lines at ejecta velocities of nu approximate to 20,000 km s(-1) that change slowly over time. Other spectral absorption lines are consistent with contributions from photospheric He I, and hydrogen may also be present at higher velocities (nu greater than or similar to 27,000 km s(-1)). We use these observations to estimate explosion properties and derive a total ejecta mass of similar to 2.7 M-circle dot, a kinetic energy of similar to 1.0 x 10(52) erg, and a Ni-56 mass of 0.1-0.2 M-circle dot. Nebular spectra (t > 200 days) exhibit an asymmetric double-peaked [O I] lambda lambda 6300, 6364 emission profile that we associate with absorption in the supernova interior, although toroidal ejecta geometry is an alternative explanation. SN 2012ap joins SN2009bb as another exceptional supernova that shows evidence for a central engine (e. g., black hole accretion or magnetar) capable of launching a non-negligible portion of ejecta to relativistic velocities without a coincident gamma-ray burst detection. Defining attributes of their progenitor systems may be related to notable observed properties including environmental metallicities of Z greater than or similar to Z(circle dot), moderate to high levels of host galaxy extinction (E(B - V) > 0.4mag), detection of high-velocity helium at early epochs, and a high relative flux ratio of [Ca II]/[O I] > 1 at nebular epochs. These events support the notion that jet activity at various energy scales may be present in a wide range of supernovae.Item M Dwarf Metallicities And Giant Planet Occurrence: Ironing Out Uncertainties And Systematics(2014-08) Gaidos, Eric; Mann, Andrew W.; Mann, Andrew W.Comparisons between the planet populations around solar-type stars and those orbiting M dwarfs shed light on the possible dependence of planet formation and evolution on stellar mass. However, such analyses must control for other factors, i.e., metallicity, a stellar parameter that strongly influences the occurrence of gas giant planets. We obtained infrared spectra of 121 M dwarfs stars monitored by the California Planet Search and determined metallicities with an accuracy of 0.08 dex. The mean and standard deviation of the sample are -0.05 and 0.20 dex, respectively. We parameterized the metallicity dependence of the occurrence of giant planets on orbits with a period less than two years around solar-type stars and applied this to our M dwarf sample to estimate the expected number of giant planets. The number of detected planets (3) is lower than the predicted number (6.4), but the difference is not very significant (12% probability of finding as many or fewer planets). The three M dwarf planet hosts are not especially metal rich and the most likely value of the power-law index relating planet occurrence to metallicity is 1.06 dex per dex for M dwarfs compared to 1.80 for solar-type stars; this difference, however, is comparable to uncertainties. Giant planet occurrence around both types of stars allows, but does not necessarily require, a mass dependence of similar to 1 dex per dex. The actual planet-mass-metallicity relation may be complex, and elucidating it will require larger surveys like those to be conducted by ground-based infrared spectrographs and the Gaia space astrometry mission.Item Spectro-Thermometry Of M Dwarfs And Their Candidate Planets: Too Hot, Too Cool, Or Just Right?(2013-12) Mann, Andrew W.; Gaidos, Eric; Ansdell, Megan; Mann, Andrew W.We use moderate-resolution spectra of nearby late K and M dwarf stars with parallaxes and interferometrically determined radii to refine their effective temperatures, luminosities, and metallicities. We use these revised values to calibrate spectroscopic techniques to infer the fundamental parameters of more distant late-type dwarf stars. We demonstrate that, after masking out poorly modeled regions, the newest version of the PHOENIX atmosphere models accurately reproduce temperatures derived bolometrically. We apply methods to late-type hosts of transiting planet candidates in the Kepler field, and calculate effective temperature, radius, mass, and luminosity with typical errors of 57 K, 7%, 11%, and 13%, respectively. We find systematic offsets between our values and those from previous analyses of the same stars, which we attribute to differences in atmospheric models utilized for each study. We investigate which of the planets in this sample are likely to orbit in the circumstellar habitable zone. We determine that four candidate planets (KOI 854.01, 1298.02, 1686.01, and 2992.01) are inside of or within 1 sigma of a conservative definition of the habitable zone, but that several planets identified by previous analyses are not (e.g., KOI 1422.02 and KOI 2626.01). Only one of the four habitable-zone planets is Earth sized, suggesting a downward revision in the occurrence of such planets around M dwarfs. These findings highlight the importance of measuring accurate stellar parameters when deriving parameters of their orbiting planets.