A5057801572- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Pulsars and Gravitational Waves Research
- Astrophysics and Star Formation Studies
- Astrophysics and Cosmic Phenomena
- Astro and Planetary Science
- High-pressure geophysics and materials
- Particle Accelerators and Free-Electron Lasers
- Galaxies: Formation, Evolution, Phenomena
- History and Developments in Astronomy
- Scientific Measurement and Uncertainty Evaluation
- Calibration and Measurement Techniques
- Mechanics and Biomechanics Studies
- Spectroscopy and Laser Applications
- Solar and Space Plasma Dynamics
- X-ray Spectroscopy and Fluorescence Analysis
- Adaptive optics and wavefront sensing
- Atmospheric Ozone and Climate
- Particle accelerators and beam dynamics
- Photocathodes and Microchannel Plates
- SAS software applications and methods
- Advanced X-ray Imaging Techniques
Dartmouth College
2015-2024
Dartmouth Hospital
1998-2021
British Astronomical Association
2012
American Association of Variable Star Observers
2012
Universidad de La Laguna
2012
University of Warwick
2012
Naresuan University
2012
Thailand Center of Excellence in Physics
2012
Instituto de Astrofísica de Canarias
2012
University of Leicester
2010
We present ground-based and Swift photometric spectroscopic observations of the candidate tidal disruption event (TDE) ASASSN-14li, found at center PGC 043234 ($d\simeq90$ Mpc) by All-Sky Automated Survey for SuperNovae (ASAS-SN). The source had a peak bolometric luminosity $L\simeq10^{44}$ ergs s$^{-1}$ total integrated energy $E\simeq7\times10^{50}$ radiated over $\sim6$ months presented. UV/optical emission is well-fit blackbody with roughly constant temperature $T\sim35,000$ K, while...
We discuss the properties of 137 cataclysmic variables (CVs) which are included in Sloan Digital Sky Survey (SDSS) spectroscopic data base, and for accurate orbital periods have been measured. 92 these systems new discoveries from SDSS were followed-up more detail over past few years. 45 previously identified as CVs because detection optical outbursts and/or X-ray emission, subsequently re-identified spectroscopy. The period distribution differs dramatically that all known CVs, particular it...
Optical photometry is presented for the quadruple gravitational lens PG1115+080. A preliminary reduction of data taken from November 1995 to June 1996 gives component ``C'' leading ``B'' by 23.7+/-3.4 days and components ``A1'' ``A2'' 9.4 days. range models has been fit image positions, none which an adequate fit. The best fitting most physically plausible these, taking lensing galaxy associated group galaxies be singular isothermal spheres, a Hubble constant 42 km/s/Mpc Omega=1, with...
Optical light curves and spectra of the Type Ia supernova 1986G in NGC 5128 (Centaurus A) are presented. Although spectral evolution closely resembled that more common "slower" photometric classes supernovae, subtle differences maximum-light were detected. The expansion velocity photosphere SN decreased rapidly at early phases. appears to have been heavily obscured by dust lane 5128. This circumstances accounts for strong interstellar-absorption lines Ca II H K Na I D observed as well...
ABSTRACT We present a kinematic analysis of 152 low surface gravity M7-L8 dwarfs by adding 18 new parallaxes (including 10 for comparative field objects), 38 radial velocities, and 19 proper motions. also add low- or moderate-resolution near-infrared spectra 43 sources confirming their features. Among the full sample, we find 39 objects to be high-likelihood bona fide members nearby moving groups, 92 ambiguous 21 that are non-members. Using this age-calibrated investigate trends in...
ABSTRACT We present a catalogue of 507 cataclysmic variables (CVs) observed in SDSS I to IV including 70 new classifications collated from multiple archival data sets. This represents the largest sample CVs with high-quality and homogeneous optical spectroscopy. have used this derive unbiased space densities period distributions for major sub-types CVs. also report on some peculiar CVs, bouncers exhibiting large changes accretion rates. 59 periods, 178 unpublished spectra, 262 or updated...
SN 1997ef has been recognized as a peculiar supernova from its light curve and spectral properties. The object was classified Type Ic (SN Ic) because spectra were dominated by broad absorption lines of oxygen iron, lacking any clear signs hydrogen or helium line features. is very different that previously known SNe Ic, showing peak slow tail. strikingly features in the 1997ef, which also seen hypernova 1998bw, suggest interesting possibility may be hypernova. modeled first with standard...
This paper reports extensive optical observations on the PG0027 + 260 binary, carried out August 1984 with 1.3 McGraw-Hill telescope and Mark II spectrometer at Michigan-Dartmouth-MIT Observatory Kitt Peak. It is shown that this object an eclipsing novalike variable orbital period of 3.51 hr. The displays several unexplained phenomena which are remarkably similar to those SW Sex, DW UMa, V1315 Aql, stars periods between 3 4 hrs. eclipse modeled, it that, while mean light curve easy match,...
We present proper motions for 21 bright main shell and 17 faint, higher velocity, outer ejecta knots in the Cas A supernova remnant use them to derive new estimates remnant's expansion center age. Our study included 1951–1976 Palomar 5 m prime focus plates, 1988–1999 CCD images from KPNO 4 MDM 2.4 telescopes, 1999 HST WFPC2 images. Measurable positions covered a 23 41 yr time span most knots, with few followed almost 48 yr. an of α(J2000) = 23h23m2777 ± 005, δ(J2000) 58°48'494 04 (ICRS),...
We report the imaging and spectroscopic localization of GRB 060218 to a low-metallicity dwarf starburst galaxy at z = 0.03345 ± 0.00006. In addition making it second nearest gamma-ray burst known, optical spectroscopy reveals earliest detection weak, supernova-like Si II near 5720 Å (~0.1c), starting 1.95 days after trigger. UBVRI photometry obtained between 1 26 postburst confirms early rise supernova light, suggests short time delay onset SN 2006aj if appearance soft component in X-ray...
view Abstract Citations (194) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS X-Ray and Optical Observations of the Ultrashort Period Dwarf Nova SW Ursae Majoris: A Likely New DQ Herculis Star Shafter, A. W. ; Szkody, P. Thorstensen, J. R. photometric spectroscopic X-ray observations dwarf nova UMa are presented. Moderate resolution data have established an orbital period 81.8 min revealed that Balmer emission lines a multiple structure....
We report on the discovery and observations of extremely luminous optical transient CSS100217:102913+404220 (CSS100217 hereafter). Spectroscopic show this was coincident with a galaxy at redshift z=0.147, reached an apparent magnitude V ~ 16.3. After correcting for foreground Galactic extinction we determine absolute to be M_V =-22.7 approximately 45 days after maximum light. Based our unfiltered photometry peak emission L = 1.3 x 10^45 erg s^-1, over period 287 rest-frame had integrated...
Subluminous Type Ia supernovae, such as the Iax class prototype SN 2002cx, are described by a variety of models failed detonation and partial deflagration an accreting carbon-oxygen white dwarf star, or explosion accreting, hybrid carbon-oxygen-neon core. These predict that bound remnants survive events with, according to some simulations, high kick velocity. We report discovery proper motion, low-mass (LP 40-365) travels at velocity greater than Galactic escape whose peculiar atmosphere is...
I used the 2.4 m Hiltner Telescope at MDM Observatory in an attempt to measure trigonometric parallaxes for 14 cataclysmic variable stars. Techniques are described detail. In best cases parallax uncertainties below 1 mas, and significant found most of program A Bayesian method that combines together with proper motions absolute magnitude constraints is developed derive distance estimates confidence intervals. The precise derived here WZ Sge, which find 43.3 pc. Six Luyten Half-Second stars...
We report detailed follow-up observations of the cataclysmic variable HS 2331+3905, identified as an emission-line object in Hamburg Quasar Survey. An orbital period 81.08 min is unambiguously determined from detection eclipses light curves 2331+3905. A second photometric consistently detected at min, ∼2.8% longer than Porb, which we tentatively relate to presence permanent superhumps. High time resolution photometry exhibits short-timescale variability on scales 5-6 interpret non-radial...
The Sloan Digital Sky Survey (SDSS) source J102347.6+003841 was recently revealed to be a binary 1.69 millisecond radio pulsar with 4.75 hr orbital period and ~0.2 M_sun companion. Here we analyze the SDSS spectrum of in detail. taken on 2001 February 1, when bright state showed broad, double-peaked hydrogen helium lines -- dramatically different from G-type absorption seen 2003 onward. are consistent emission disk around compact primary. We derive properties by fitting continuum simple...
On 2014 Dec. 9.61, the All-Sky Automated Survey for SuperNovae (ASAS-SN or "Assassin") discovered ASASSN-14lp just $\sim2$ days after first light using a global array of 14-cm diameter telescopes. went on to become bright supernova ($V = 11.94$ mag), second only SN 2014J year. We present prediscovery photometry (with detection less than day light) and ultraviolet through near-infrared photometric spectroscopic data covering rise fall more 100 days. find that had broad curve ($\Delta...
The radio source FIRST J102347.6+003841 was presented as the first radio-selected cataclysmic. In discovery paper, Bond et al. (2002) show a spectrum consistent with magnetic AM Her-type system and light curve rapid, irregular flickering. contrast, Woudt, Warner, Pretorius (2004) found smoothly-varying period near 4.75 h one minimum per orbit, indicating dramatic change. We present time-resolved spectra showing superficially normal, mid-G type photosphere, no detectable emission lines....
The optical light curve of the energetic γ-ray burst GRB 991216 is consistent with jetlike behavior in which a power-law decay steepens from t-1.22±0.04 at early times to t-1.53±0.05 gradual transition around 2 days. derivation late-time slope takes into account constant contribution host or intervening galaxy, was measured 110 days after event R = 24.56 ± 0.14, although deviates single power law whether not term included. early-time spectral energy distribution afterglow can be described as...
We report photometry and spectroscopy of the dwarf nova EG Cancri in its 1996/1997 episode eruptions. The main eruption was clearly a superoutburst featuring common superhumps with period 0.06036(2) days, establishing star as new member SU UMa class novae. At end eruption, were replaced by another wave slightly longer (0.06045 days), which endured for at least 90 days. properties latter suggest identification "late superhump." recurrence time superoutbursts is long, probably range 7–20 yr....
We present optical spectroscopy and photometry IUE of the counterpart extremely powerful LMC recurrent X-ray transient A0538 – 66. During one 16.6 day outburst cycle at end 1980 December spectra show steadily increasing Balmer He I emission (indicative an expanding envelope) superposed on a B2 III–IV spectrum. There is substantial brightness increase 2 mag peak, accompanied by sudden turn-on IIλ 4686. These other significant radial velocity changes but we can find no clear correlation with...
The quasar 3C 279 was the target of an extensive multiwavelength monitoring campaign from 2006 January through April. An optical-IR-radio by Whole Earth Blazar Telescope (WEBT) collaboration organized around target-of-opportunity X-ray and soft γ-ray observations with Chandra INTEGRAL in mid-January, additional coverage RXTE Swift XRT. In this paper we focus on results WEBT campaign. source exhibited substantial variability optical flux spectral shape, a characteristic timescale few days....
We have derived an X-ray luminosity function using parallax-based distance measurements of a set 12 dwarf novae, consisting Suzaku, XMM–Newton and ASCA observations. The shape the obtained is most accurate to date, luminosities our sample are concentrated between ∼1030 1031 erg s−1, lower than previous functions novae. Based on integrated function, becomes more incomplete below ∼3 × 1030 s−1 it above this limit, dominated by bright total within radius 200 pc 1.48 1032 over range 1 1028...
We present astrometric parallaxes for 18 suspected nearby stars selected from the LSPM-north proper motion catalog. 16 objects are confirmed to be main-sequence M dwarfs within pc of Sun, including three (LSPM J0011+5908, LSPM J0330+5413, and J0510+2714) which lie just 10 horizon. Two other targets J1817+1328, J2325+1403) white at distances 14 22 pc, respectively. One our targets, common pair J0405+7116E + J0405+7116W, is revealed a triple system, with western component resolved into 16th...
ABSTRACT SDSS-V is carrying out a dedicated survey for white dwarfs, single, and in binaries, we report the analysis of spectroscopy 118 cataclysmic variables (CVs) CV candidates obtained during final plug plate observations SDSS. We identify eight new CVs, spectroscopically confirm 53 refute 11 published candidates, 21 or improved orbital periods. The period distribution CVs does not clearly exhibit gap. In common with previous studies, shows that identified have larger proportion...