A Major X-ray Outburst from an Ultraluminous X-Ray Source in M82 (2008)
Kaaret, Philip, Feng, Hua, Gorski, Mark
We detected a major X-ray outburst from M82 with a duration of 79 days, an average flux of 5E-11 erg cm^-2 s^-1 in the 2-10 keV band, and strong variability. The X-ray spectrum remained hard...
Relativistic Iron Line Emission from the Neutron Star Low-mass X-ray Binary 4U 1636-536 (2008)
Pandel, Dirk, Kaaret, Philip, Corbel, Stephane
We present an analysis of XMM-Newton and RXTE data from three observations of the neutron star LMXB 4U 1636-536. The X-ray spectra show clear evidence of a broad, asymmetric iron emission line...
Chandra Localizations and Spectra of INTEGRAL Sources in the Galactic Plane (2008)
Tomsick, John A., Chaty, Sylvain, Rodriguez, Jerome, Walter, Roland, Kaaret, Philip
We report on the results of observations of hard X-ray sources in the Galactic plane with the Chandra X-ray Observatory. The hard X-ray IGR sources were discovered by the INTEGRAL satellite, and the...
X-Ray Sources in the Star Forming Galaxies NGC 4194 and NGC 7541 (2008)
Kaaret, Philip, Alonso-Herrero, Almudena
We examine the X-ray point source population and 2-10 keV luminosity for two galaxies with high star formation rates (SFRs), NGC 4194 and NGC 7541. The X-ray point source luminosity function (XLF)...
Tomsick, John A., Kalemci, Emrah, Kaaret, Philip, Markoff, Sera, Corbel, Stephane, Migliari, Simone, ...
A major question in the study of black hole binaries involves our understanding of the accretion geometry when the sources are in the hard state. In this state, the X-ray energy spectrum is dominated...
Optical Counterpart of the Ultraluminous X-ray Source IC 342 X-1 (2007)
We present Chandra and HST observations of the ultraluminous X-ray source (ULX) IC 342 X-1. The Chandra and HST images are aligned using two X-ray emitting foreground stars. The astrometry corrected...
Confirmation of the 62 Day X-Ray Periodicity from M82 (2007)
Using 400 days of new X-ray monitoring of M82, we confirm the 62 day periodicity previously reported. In the full data set spanning 1124 days, we find a period of 62.0 +/- 0.3 days and a coherence, Q...
The starburst galaxy M82 contains two ultraluminous X-ray sources (ULXs), CXOM82 J095550.2+694047 (=X41.4+60) and CXOM82 J095551.1+694045 (=X42.3+59), which are unresolved by XMM-Newton. We revisited...
A Radio Nebula Surrounding the Ultra-luminous X-ray Source in NGC 5408 (2007)
Lang, Cornelia C., Kaaret, Philip, Corbel, Stephane, Mercer, Allison
New radio observations of the counterpart of the ultraluminous X-ray source in NGC 5408 show for the first time that the radio emission is resolved with an angular size of 1.5 to 2.0 arcseconds. This...
Optical studies of the ultraluminous X-ray source NGC1313 X-2 (2007)
Liu, Jifeng, Bregman, Joel, Miller, Jon, Kaaret, Philip
NGC1313 X-2 was among the first ultraluminous X-ray sources discovered, and has been a frequent target of X-ray and optical observations. Using the HST/ACS multi-band observations, this source is...
Spectral Evolution of NGC 1313 X-2: Evidence Against The Cool Disk Model (2007)
The presence of a cool multicolor disk component with an inner disk temperature kT=0.1~0.3 keV at a luminosity L>10^40 erg/s has been interpreted as evidence that the ultraluminous X-ray source NGC...
Tomsick, John A., Gelino, Dawn M., Kaaret, Philip
The X-ray transient, 4U 1730-22, has not been detected in outburst since 1972, when a single outburst was detected by the Uhuru satellite. This neutron star or black hole X-ray binary is presumably...
Intermittent pulsations in an accretion-powered millisecond pulsar (2006)
Galloway, Duncan K., Morgan, Edward H., Krauss, Miriam I., Kaaret, Philip, Chakrabarty, Deepto
We describe observations of the seventh accretion-powered millisecond pulsar, HETE J1900.1-2455 made with the Rossi X-ray Timing Explorer during the year of activity that followed its discovery in...
Spectral State Transitions of the Ultraluminous X-ray Sources X-1 and X-2 in NGC 1313 (2006)
X-ray spectral state transitions are a key signature of black hole X-ray binaries and follow a well-defined pattern. We examined 12 XMM-Newton observations of the nearby spiral galaxy NGC 1313, which...
The temporal and spectral properties of ultraluminous X-ray sources (ULXs, L>2x10^39 ergs/s) and bright X-ray sources (L>3x10^38 ergs/s) are examined and compared in two extremely different host...
Double-Layer Silicon PIN Photodiode X-Ray Detector for a Future X-ray Timing Mission (2006)
Feng, Hua, Kaaret, Philip, Andersson, Hans
A double-layer silicon detector consisting of two 500micron-thick silicon PIN photodiodes with independent readouts was mounted in a vacuum chamber and tested with X-ray sources. The detector is...
A 62 Day X-Ray Periodicity and an X-Ray Flare from the Ultraluminous X-Ray Source in M82 (2006)
Kaaret, Philip, Simet, Melanie G., Lang, Cornelia C.
In 240 days of X-ray monitoring of M82, we have discovered an X-ray periodicity at $62.0 \pm 2.5$ days with a peak to peak amplitude corresponding to an isotropic luminosity of $2.4 \times 10^{40}...
Identifications of Four INTEGRAL Sources in the Galactic Plane via Chandra Localizations (2006)
Tomsick, John A., Chaty, Sylvain, Rodriguez, Jerome, Foschini, Luigi, Walter, Roland, Kaaret, Philip
Hard X-ray imaging of the Galactic plane by the INTEGRAL satellite is uncovering large numbers of 20-100 keV "IGR" sources. We present results from Chandra, INTEGRAL, optical, and IR observations of...
The Orbital Period of the Ultraluminous X-ray Source in M82 (2006)
Kaaret, Philip, Simet, Melanie G., Lang, Cornelia C.
The ultraluminous x-ray source (ULX) in the galaxy M82 has been identified as a possible intermediate-mass black hole. We have found that the x-ray flux from M82 is modulated with a peak-to-peak...
The Low Quiescent X-Ray Luminosity of the Transient X-Ray Burster EXO 1747-214 (2005)
Tomsick, John A., Gelino, Dawn M., Kaaret, Philip
We report on X-ray and optical observations of the X-ray burster EXO 1747-214. This source is an X-ray transient, and its only known outburst was observed in 1984-1985 by the EXOSAT satellite. We...
XMM-Newton Observations of Ultraluminous X-Ray Sources in Nearby Galaxies (2005)
We examined X-ray spectral and timing properties of ultraluminous X-ray sources (ULXs) in nearby galaxies in XMM-Newton archival data. There appear to be three distinct classes of spectra. One class...
Optical Sources Near the Bright X-Ray Source in NGC 1073 (2005)
New HST observations show that the bright X-ray source in the face-on spiral galaxy NGC 1073 is located near a ring of recent star formation with an age of 8-16 Myr. This strengthens the association...
Multiwavelength Observations of Ultraluminous X-Ray Sources (2004)
Multiwavelength observations may help us understand the physical nature of the ultraluminous X-ray sources (ULXs) found in external galaxies. Enabled by the arcsecond X-ray source positions now...
Tomsick, John A., Lingenfelter, Richard, Corbel, Stephane, Goldwurm, Andrea, Kaaret, Philip
We report on results from a 2003 February INTEGRAL observation of the black hole candidate (BHC) 4U 1630-47 and the high energy sources in the Norma Region of the Galaxy and on RXTE and radio...
The Low Quiescent X-Ray Luminosity of the Neutron Star Transient XTE J2123-058 (2004)
Tomsick, John A., Gelino, Dawn M., Halpern, Jules P., Kaaret, Philip
We report on the first X-ray observations of the neutron star soft X-ray transient (SXT) XTE J2123-058 in quiescence, made by Chandra and BeppoSAX, as well as contemporaneous optical observations. In...
Chandra ACIS and Newton EPIC Observations of the X-ray Luminous SN1978K in NGC 1313 (2003)
Schlegel, Eric M., Kong, Albert, Kaaret, Philip, DiStefano, Rosanne, Murray, Steve
We describe an observation of the X-ray luminous SN1978K in NGC 1313 using the ACIS detector on Chandra and an archival Newton EPIC observation. The models that provided good fits to the ASCA SIS and...
Chandra Detections of Two Quiescent Black Hole X-Ray Transients (2003)
Tomsick, John A., Corbel, Stephane, Fender, Rob, Miller, Jon M., Orosz, Jerome A., Rupen, Michael P., ...
Using the Chandra X-ray Observatory, we have detected the black hole transients V4641 Sgr and XTE J1859+226 in their low luminosity, quiescent states. The 0.3-8 keV luminosities are...
Tomsick, John A., Kalemci, Emrah, Kaaret, Philip
Using the Chandra X-ray Observatory and the Rossi X-ray Timing Explorer, we have studied the black hole candidate (BHC) X-ray transient XTE J1650-500 near the end of its 2001-2002 outburst after its...
Tomsick, John A., Kalemci, Emrah, Corbel, Stephane, Kaaret, Philip
We report on X-ray observations made with the Rossi X-ray Timing Explorer of the black hole candidate (BHC) transient XTE J1650-500 at the end of its first, and currently only, outburst. By...
Radio Emission from an Ultraluminous X-Ray Source (2003)
Kaaret, Philip, Corbel, Stephane, Prestwich, Andrea H., Zezas, Andreas
The physical nature of ultraluminous x-ray sources is uncertain. Stellar mass black holes with beamed radiation and intermediate mass black holes with isotropic radiation are two plausible...
X-Ray Jet Emission from the Black Hole X-Ray Binary XTE J1550-564 with Chandra in 2000 (2002)
Tomsick, John A., Corbel, Stephane, Fender, Rob, Miller, Jon M., Orosz, Jerome A., Tzioumis, Tasso, ...
We have discovered an X-ray jet due to material ejected from the black hole X-ray transient XTE J1550-564. The discovery was first reported by Corbel et al. (Science, 298, 196 and astro-ph/0210224),...
Rotational Broadening Measurement for the Neutron Star X-Ray Transient XTE J2123-058 (2002)
Tomsick, John A., Heindl, William A., Chakrabarty, Deepto, Kaaret, Philip
We used optical spectroscopy of the neutron star X-ray transient XTE J2123-058 to measure the rotational broadening of the binary companion's stellar absorption lines and determined that the...
A Chandra High-Resolution Camera Observation of X-Ray Point Sources in M31 (2002)
We present results from a 47 ks observation of the Andromeda galaxy, M31, using the High-Resolution Camera of the Chandra X-Ray Observatory. We detect 142 point sources spanning three orders of...
Chandra X-Ray Point Sources, including Supernova 1979C, in the Spiral Galaxy M100 (2001)
Six x-ray point sources, with luminosities of $4 \times 10^{38} - 2 \times 10^{39} \rm ergs s^{-1}$ in the 0.4--7 keV band, were detected in Chandra observations of the spiral galaxy M100. One source...
Keck Measurement of the XTE J2123-058 Radial Velocity Curve (2001)
Tomsick, John A., Heindl, William A., Chakrabarty, Deepto, Halpern, Jules P., Kaaret, Philip
We measured the radial velocity curve of the companion of the neutron star X-ray transient XTE J2123-058. Its semi-amplitude (K_2) of 298.5 +/- 6.9 km/s is the highest value that has been measured...
Tomsick, John A., Corbel, Stephane, Kaaret, Philip
We report on the evolution of the X-ray energy spectrum for the black hole candidate (BHC) X-ray transient XTE J1550-564 during the decay of the 2000 outburst. The Rossi X-ray Timing Explorer (RXTE)...
X-Ray Observations of XTE J1550-564 During the Decay of the 2000 Outburst - II. Timing (2001)
Kalemci, Emrah, Tomsick, John A., Rothschild, R. E., Pottschmidt, Katja, Kaaret, Philip
We investigate the timing behavior of XTE J1550-564 with the Rossi X-ray Timing Explorer (RXTE) as the source made a transition to the hard state during the decay of the 2000 outburst. We detect a...
Tomsick, John A., Kaaret, Philip
We present a study of the properties of strong 0.8-3.0 Hz quasi-periodic oscillations (QPOs) that occurred during 1997 RXTE observations of the microquasar GRS 1915+105 in the low-hard state. The...
Spectral Signatures of KiloHertz Quasi-Periodic Oscillations from Accreting Neutron Stars (2000)
Correlations discovered between millisecond timing properties and spectral properties in neutron star x-ray binaries are described and then interpreted in relation to accretion flows in the systems....
Tomsick, John A., Kaaret, Philip
We report on the X-ray spectral and timing behavior of the recurrent X-ray transient 4U 1630-47 for 51 RXTE observations made during the decay of its 1998 outburst. The observations began when the...
Relations Between Timing Features and Colors in the X-Ray Binary 4U 0614+09 (2000)
Van Straaten, Steve, Ford, Eric C., Van Der Klis, Michiel, Mendez, Mariano, Kaaret, Philip
We study the correlations between timing and X-ray spectral properties in the low mass X-ray binary 4U 0614+09 using a large (265-ks) data set obtained with the Rossi X-ray Timing Explorer. We find...
Kaaret, Philip, Piraino, Santina, Halpern, Jules, Eracleous, Michael
We have discovered an x-ray source, SAX J0635+0533, with a hard spectrum within the error box of the GeV gamma-ray source in Monoceros, 2EG J0635+0521. The unabsorbed x-ray flux is 1.2*10^-11 erg...
Pulsar Radiation and Quantum Gravity (1999)
Quantum gravity may lead to an energy dependence in the speed of light. The high energy radiation from gamma-ray pulsars can be used to place limits on such effects. We find that emission from the...
XTE J2123-058: A New Neutron Star X-Ray Transient (1999)
Tomsick, John A., Halpern, Jules P., Kemp, Jonathan, Kaaret, Philip
We report on optical and RXTE observations of a new high-latitude bursting X-ray transient, XTE J2123-058. We identified the optical counterpart, measured the 5.9573 hr orbital period and constrained...
Discovery of Microsecond Soft Lags in the X-Ray Emission of the Atoll Source 4U1636-536 (1999)
Kaaret, Philip, Piraino, Santina, Ford, Eric C., Santangelo, Andrea
Exploiting the presence of kilohertz quasi-periodic oscillations (QPOs) in the timing power spectrum, we find that the soft x-ray emission of the neutron-star X-ray binary and atoll source 4U1636-536...
Ford, Eric C., Van Der Klis, Michiel, Mendez, Mariano, Van Paradijs, Jan, Kaaret, Philip
Using the Rossi X-ray Timing Explorer we have measured lags of the 9 to 33 keV photons relative to the 2 to 9 keV photons in the timing noise between 0.01 and 100 Hz in the accreting neutron stars 4U...
Discovery of a Second Kilohertz QPO in the X-ray Binary 4U 1735-44 (1998)
Ford, Eric C., Van Der Klis, Michiel, Van Paradijs, Jan, Mendez, Mariano, Wijnands, Rudy, Kaaret, Philip
In recent observations with the Rossi X-Ray Timing Explorer we have detected two simultaneous quasi-periodic oscillation (QPO) peaks in the low mass X-ray binary and atoll source 4U 1735-44. The...
Broad-band X-Ray Spectra of the Black Hole Candidate GRO J1655-40 (1998)
Tomsick, John A., Kaaret, Philip, Kroeger, Richard A., Remillard, Ronald A.
We present broad-band (2 keV to 2 MeV) X-ray spectra of GRO J1655-40, a luminous X-ray transient and occasional source of relativistic radio jets, obtained with RXTE and OSSE. In one observation, the...
Discovery of Kilohertz QPOs in the Atoll X-Ray Binary 4U 1705-44 (1998)
Ford, Eric C., Van Der Klis, Michiel, Kaaret, Philip
In observations with the Rossi X-ray Timing Explorer we have discovered quasi-periodic oscillations (QPOs) near 1 kHz from 4U 1705-44, a low--mass X-ray binary with a neutron star classified as an...
Energy Spectra and High Frequency Oscillations in 4U 0614+091 (1997)
Ford, Eric C., Kaaret, Philip, Chen, Kaiyou, Tavani, Marco, Barret, Didier, Bloser, Peter, ...
We investigate the behavior of the high frequency quasi-periodic oscillations (QPOs) in 4U 0614+091, combining timing and spectral analysis of RXTE observations. The energy spectra of the source can...
Strong-field general relativity and quasi-periodic oscillations in x-ray binaries (1997)
Kaaret, Philip, Ford, Eric, Chen, Kaiyou
Quasi-periodic oscillations (QPOs) at frequencies near 1000 Hz were recently discovered in several x-ray binaries containing neutron stars. Two sources show no correlation between QPO frequency and...
The Unidentified Galactic EGRET Sources (1996)
The nature of the unidentified gamma-ray point sources in the galactic plane is a long standing puzzle of gamma-ray astronomy. Kaaret and Cottam (1996) showed that 16 of the 25 unidentified gamma-ray...
The Inverse-Compton And Extragalactic Components Of The Diffuse Gamma-Ray Emission (1995)
Chen, Andrew, Dwyer, Joseph, Kaaret, Philip
We present spectra of the inverse-Compton and extragalactic components of the high-energy gamma-radiation based on an analysis of the emission at high galactic latitudes ($\vert$b$\vert$ $\geq$...
Analysis of the Casimir effect for parallel plates / (1984)
Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1984.