A5028232023- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Calibration and Measurement Techniques
- Astronomical Observations and Instrumentation
- Geophysics and Sensor Technology
- Cosmology and Gravitation Theories
- Statistical and numerical algorithms
- Seismic Waves and Analysis
- Seismology and Earthquake Studies
- Astrophysics and Star Formation Studies
- Superconducting Materials and Applications
- Spacecraft and Cryogenic Technologies
- Atomic and Subatomic Physics Research
- Astro and Planetary Science
- Radio Astronomy Observations and Technology
- Advanced Frequency and Time Standards
- Infrared Target Detection Methodologies
- GNSS positioning and interference
- Advanced Thermodynamic Systems and Engines
Hayatabad Medical Complex
2023
University of Washington
2017-2019
Goddard Space Flight Center
2015-2017
The Ohio State University
2010-2015
Oak Ridge Associated Universities
2015
Columbia University
2007-2011
Cardiff University
2011
Carleton College
2011
California Institute of Technology
2011
Andrews University
2011
Using a sample of high-redshift lensed quasars from the CASTLES project with observed-frame ultraviolet or optical and near-infrared spectra, we have searched for possible biases between supermassive black hole (BH) mass estimates based on C iv, Hα, Hβ broad emission lines. Our is upon that Greene, Peng, & Ludwig, expanded new near-IR spectroscopic observations, consistently analyzed high signal-to-noise ratio (S/N) consistent continuum luminosity at 5100 Å. We find BH full width...
We use the progenitor of SN2012aw to illustrate consequences modeling circumstellar dust using Galactic (interstellar) extinction laws that (1) ignore emission in near-IR and beyond; (2) average over compositions, (3) mis-characterize optical/UV absorption by assuming scattered photons are lost observer. The primary for both luminosity significantly over-estimated. In particular, stellar is most likely range 10^4.8 < L/Lsun 10^5.0 star was not extremely massive a Type IIP progenitor, with M...
Abstract We present an ongoing, five-year systematic search for extragalactic infrared transients, dubbed SPIRITS—SPitzer InfraRed Intensive Transients Survey. In the first year, using Spitzer /IRAC, we searched 190 nearby galaxies with cadence baselines of one month and six months. discovered over 1958 variables 43 transients. Here, describe survey design highlight 14 unusual transients no optical counterparts to deep limits, which refer as SPRITEs (eSPecially Red Intermediate-luminosity...
We identify a pre-explosion counterpart to the nearby Type IIP supernova ASASSN-16fq (SN 2016cok) in archival Hubble Space Telescope (HST) data. The source appears be blend of several stars that prevents obtaining accurate photometry. However, with reasonable assumptions about stellar temperature and extinction, progenitor almost certainly had an initial mass M<17Msun, was most likely range 8-12Msun. Observations once has faded will have no difficulty accurately determining properties...
A new link in the causal mapping between massive stars and potentially fatal explosive transients opened with 2008 discovery of dust-obscured progenitors luminous outbursts NGC 6946 300. Here we carry out a systematic mid-IR photometric search for massive, luminous, self-obscured four nearby galaxies: M33, 300, M81, 6946. For detection, use only 3.6 micron 4.5 IRAC bands, as these can still be used multi-epoch Spitzer surveys galaxies (=<10 Mpc). We combine familiar PSF aperture-photometry...
Silence in the analytic situation is a recurrent and complex clinical phenomenon. Recently J. A. Arlow M. Zeligs have discussed exhaustively patient's silence as serving functions of discharge, defense communication situation. In this chapter, author tries to show communicative function his persistent He shows that primary was communicate through transference process very disturbed early childhood relationship mother which had brought about identity diffusion at adolescence. The author's...
We present multi-epoch mid-infrared (IR) photometry and the optical discovery observations of "impostor" supernova (SN) 2010da in NGC 300 using new archival Spitzer Space Telescope images ground-based observatories. The mid-IR counterpart SN was detected as SPIRITS 14bme SPitzer InfraRed Intensive Transient Survey (SPIRITS), an ongoing systematic search for IR transients. A sharp increase 3.6 $\mu$m flux followed by a rapid decrease measured ~150 d before ~80 after initial outburst,...
We present Spitzer IRAC $3.6-8$um and MIPS $24$um point-source catalogs for seven galaxies: NGC$6822$, M$33$, NGC$300$, NGC$2403$, M$81$, NGC$0247$, NGC$7793$. The contain a total of $\sim300,000$ sources were created by dual-band selection with $>3\sigma$ detections at both $3.6$um $4.5$um. source lists become significantly incomplete near $m_{3.6}=m_{4.5}\simeq18$. complement the $4.5$um fluxes $5.8$um, $8.0$um or $3\sigma$ upper limits using combination PSF aperture photometry. This...
We determine the ages of young, resolved stellar populations at locations 237 optically-identified supernova remnants in M83. These age distributions put constraints on progenitor masses supernovae that produced 199 remnants. The other 38 show no evidence for having a young and are therefore good Type Ia SNR candidates. Starting from Hubble Space Telescope broadband imaging, we measured photometry seven archival WFC3/UVIS fields F336W, F438W, F814W. generate color-magnitude diagrams stars...
We discuss the emerging trend that super-Chandrasekhar Type Ia Supernovae (SCSNe) with progenitor mass estimates significantly exceeding ∼1.4 M☉ tend to explode in metal-poor environments. While Taubenberger et al. noted some of SCSNe host galaxies are relatively metal-poor, we focus quantitatively on their locations hosts point out three four cases, explosions occurred outer edge disks hosts. It is therefore very likely progenitors had far lower metallicities than those implied by...
We present photometric and spectroscopic observations of the Type Ia supernova SN 2009nr in UGC 8255 (z=0.0122). Following discovery announcement at what turned out to be ten days after peak, we detected it V ~15.7 mag data collected by All Sky Automated Survey (ASAS) North telescope 2 weeks prior then followed up with telescopes ranging aperture from 10-cm 6.5-m. Using early available only ASAS, find that is similar over-luminous 1991T, a peak Mv=-19.6 mag, slow decline rate Dm_15(B)=0.95...
We discuss the nature of brightest mid-IR point source (which we dub Object X) in nearby galaxy M33. Although multi-wavelength data on this object have existed literature for some time, it had not previously been recognized as most luminous M33 because is entirely unremarkable both optical and near-IR light. In Local Group Galaxies Survey, X a faint red visible VRI Hα but U or B. It was easily seen at JHKs Two Micron All Sky Survey. all four Spitzer IRAC bands also MIPS 24 μm band. Its...
The late-stage evolution of the most massive stars such as {\eta} Carinae is controlled by effects mass loss, which may be dominated poorly understood eruptive ejections. Understanding this population challenging because no true analogs Car have been clearly identified in Milky Way or other galaxies. We utilize Spitzer IRAC images 7 nearby (=<4 Mpc) galaxies to search for analogs. find 34 candidates with a flat rising mid-IR spectral energy distributions towards longer mid-infrared...
ABSTRACT We present Spitzer IRAC 3.6–8 μ m and Multiband Imaging Photometer 24 point-source catalogs for M31 15 other mostly large, star-forming galaxies at distances ∼3.5–14 Mpc, including M51, M83, M101, NGC 6946. These contain ∼1 million sources ∼859,000 in ∼116,000 the galaxies. They were created following procedures described Khan et al. through a combination of point-spread function (PSF) fitting aperture photometry. data products constitute resource to improve our understanding...
Understanding the late-stage evolution of most massive stars such as $\eta$ Carinae is challenging because no true analogs Car have been clearly identified in Milky Way or other galaxies. In Khan et. al. (2013), we utilized Spitzer IRAC images $7$ nearby ($\lesssim4$ Mpc) galaxies to search for analogs, and found $34$ candidates with flat red mid-IR spectral energy distributions. Here, Paper II, present our characterization these using multi-wavelength data from optical through far-IR. Our...
We describe a method for searching transient gravitational waves associated with soft gamma-ray repeater (SGR) flares or other burst-like events using data collected by interferometric wave detectors. The can be used to analyze from either single detector two detectors coherently. excess power-type algorithm creates event sets conditioned which may compared signal simulations of known strength based on plausible waveform classes. Estimated search sensitivities obtained performing...
We have performed an in-depth concept study of a gravitational wave data analysis method which targets repeated long quasimonochromatic transients (triggers) from cosmic sources. The algorithm can be applied to multitrigger sets in the detector-source orientation and statistical properties stream change with time, does not require assumption that is Gaussian. Reconstructing or limiting energetics potential emissions associated quasiperiodic oscillations observed x-ray lightcurve tails soft...
We discuss the technical challenges we faced and techniques used to overcome them when reducing PHAT photometric data set on Amazon Elastic Compute Cloud (EC2). first describe architecture of our photometry pipeline, which found particularly efficient for in multiple ways different purposes. then features EC2 that make this both use challenging implement. adopted process data, suggest these may be improved those interested trying such reductions future. Finally, summarize output products,...
The luminosity, light curve, post-maximum spectrum, and lack of a progenitor on deep pre-outburst images suggest that SN 2010U was luminous, fast nova. Its outburst magnitude is consistent with for nova using the maximum magnitude–rate decline relationship classical novae.
One class of gravitational wave signals LIGO is searching for consists short duration bursts unknown waveforms. Potential sources include core collapse supernovae, gamma ray burst progenitors and mergers binary black holes or neutron stars. We present a density-based clustering algorithm to improve the performance time–frequency searches such gravitational-wave when they are extended in time and/or frequency, not sufficiently well known permit matched filtering. have implemented this as an...
Abstract The failed supernova N6946-BH1 likely formed a black hole (BH); we age-date the surrounding population and infer an age initial mass for progenitor of this BH formation candidate. First, use archival Hubble Space Telescope imaging to extract broadband photometry resolved stellar populations event. Using photometry, fit evolution models color–magnitude diagrams measure recent star history (SFH). Modeling requires accurate distance; therefore, tip red giant branch distance modulus...
The late-stage evolution of very massive stars such as $\eta$ Carinae may be dominated by episodic mass ejections which later lead to Type II superluminous supernova (SLSN-II; e.g., SN 2006gy). However, long Car is one a kind, it nearly impossible quantitatively evaluate these possibilities. Here we announce the discovery five objects in nearby ($\sim4-8$ Mpc) star-forming galaxies M51, M83, M101 and NGC6946 that have optical through mid-IR photometric properties consistent with hitherto...
The morphology of thin stellar streams can be used to test the nature dark matter. It is therefore crucial extend searches for globular cluster other galaxies than Milky Way. In this paper, we investigate current and future prospects detecting in external resolved stars (e.g. with WFIRST) using integrated light HSC, LSST Euclid). particular, inject mock-streams data from PAndAS M31 survey, produce simulated backgrounds mimicking what WFIRST will observe M31. Additionally, estimate distance...