Slavko Bogdanov - Columbia

Slavko Bogdanov
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Name
Slavko Bogdanov
Affiliation
Columbia
Country
Colombia

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High Energy Astrophysical Phenomena (26)
 
Astrophysics (9)
 
Solar and Stellar Astrophysics (3)
 
Instrumentation and Methods for Astrophysics (2)
 
Cosmology and Nongalactic Astrophysics (2)
 
Nuclear Theory (2)
 
Astrophysics of Galaxies (2)
 
Earth and Planetary Astrophysics (1)
 
General Relativity and Quantum Cosmology (1)
 
Nuclear Experiment (1)

Publications Authored By Slavko Bogdanov

47 Tuc X9 is a low mass X-ray binary (LMXB) in the globular cluster 47 Tucanae, and was previously thought to be a cataclysmic variable. However, Miller-Jones et al. (2015) recently identified a radio counterpart to X9 (inferring a radio/X-ray luminosity ratio consistent with black hole LMXBs), and suggested that the donor star might be a white dwarf. Read More

We observed the field of the Fermi source 3FGL J0838.8-2829 in optical and X-rays, initially motivated by the cataclysmic variable (CV) 1RXS J083842.1-282723 that lies within its error circle. Read More

2017Jan
Affiliations: 1McGill U., 2ASTRON, 3Cornell U., 4ASIAA, 5UC Berkeley, 6Cornell U., 7ASTRON, 8Columbia U., 9NRAO, WVU, 10NRAO, 11NRAO, 12ASTRON, API, 13McGill U., 14JPL, 15ASTRON, 16JIVE, 17WVU, 18JIVE, 19NRAO, 20DRAO, 21Arecibo, 22MPIfR, 23JIVE, Leiden, 24Cornell U.

The precise localization of the repeating fast radio burst (FRB 121102) has provided the first unambiguous association (chance coincidence probability $p\lesssim3\times10^{-4}$) of an FRB with an optical and persistent radio counterpart. We report on optical imaging and spectroscopy of the counterpart and find that it is an extended ($0.6^{\prime\prime}-0. Read More

Transitional millisecond pulsars (tMSPs) switch, on roughly multi-year timescales, between rotation-powered radio millisecond pulsar (RMSP) and accretion-powered low-mass X-ray binary (LMXB) states. The tMSPs have raised several questions related to the nature of accretion flow in their LMXB state and the mechanism that causes the state switch. The discovery of coherent X-ray pulsations from PSR J1023+0038 (while in the LMXB state) provides us with the first opportunity to perform timing observations and to compare the neutron star's spin variation during this state to the measured spin-down in the RMSP state. Read More

We present Chandra ACIS-S sub-array observations of the quiescent neutron star low-mass X-ray binaries X7 and X5 in the globular cluster 47 Tuc. The large reduction in photon pile-up compared to previous deep exposures enables a substantial improvement in the spectroscopic determination of the neutron star radius and mass of these neutron stars. Modeling the thermal emission from the neutron star surface with a non-magnetized hydrogen atmosphere and accounting for numerous sources of uncertainties, we obtain for the neutron star in X7 a radius of $R=11. Read More

Rotation-powered "recycled" millisecond pulsars are a variety of rapidly-spinning neutron stars that typically show thermal X-ray radiation due to the heated surface of their magnetic polar caps. Detailed numerical modeling of the rotation-induced thermal X-ray pulsations observed from recycled millisecond pulsars, including all relevant relativistic and stellar atmospheric effects, has been identified as a promising approach towards an astrophysical determination of the true neutron star mass-radius relation, and by extension the state of cold matter at densities exceeding those of atomic nuclei. Herein, I review the basic model and methodology commonly used to extract information regarding neutron star structure from the pulsed X-ray radiation observed from millisecond pulsars. Read More

I present a 40 kilosecond Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the recently identified low-luminosity X-ray binary and transitional millisecond pulsar (tMSP) candidate 1RXS J154439.4-112820, which is associated with the high-energy gamma-ray source 3FGL J1544.6--1125. Read More

We present X-ray, ultraviolet, and optical observations of 1RXS J154439.4-112820, the most probable counterpart of the unassociated Fermi LAT source 3FGL J1544.6-1125. Read More

The Square Kilometre Array (SKA) is an integral part of the next-generation observatories that will survey the Universe across the electromagnetic spectrum, and beyond, revolutionizing our view of fundamental physics, astrophysics and cosmology. Owing to their extreme nature and clock-like properties, pulsars discovered and monitored by SKA will enable a broad range of scientific endeavour and play a key role in this quest. This chapter summarizes the pulsar-related science goals that will be reached with coordinated efforts among SKA and other next-generation astronomical facilities. Read More

The PSR J1023+0038 binary system hosts a neutron star and a low-mass, main-sequence-like star. It switches on year timescales between states as an eclipsing radio millisecond pulsar and a low-mass X-ray binary. We present a multi-wavelength observational campaign of PSR J1023+0038 in its most recent low-mass X-ray binary state. Read More

Accreting millisecond X-ray pulsars are an important subset of low-mass X-ray binaries in which coherent X-ray pulsations can be observed during occasional, bright outbursts (X-ray luminosity $L_X\sim 10^{36}$ erg s$^{-1}$). These pulsations show that matter is being channeled onto the neutron star's magnetic poles. However, such sources spend most of their time in a low-luminosity, quiescent state ($L_X\lesssim 10^{34}$ erg s$^{-1}$), where the nature of the accretion flow onto the neutron star (if any) is not well understood. Read More

Central compact objects (CCOs) constitute a population of radio-quiet, slowly-spinning ($\ge$100 ms) young neutron stars with anomalously high thermal X-ray luminosities. Their spin-down properties imply weak dipole magnetic fields ($\sim$$10^{10-11}$ G) and characteristic ages much greater than the ages of their host supernova remnants (SNRs). However, CCOs may possess strong "hidden" internal magnetic fields that may re-emerge on timescales $\gtrsim$10 kyr, with the neutron star possibly activating as a radio pulsar in the process. Read More

2014Jun
Affiliations: 1Caltech, 2McGill U. and NSSC Beijing, 3McGill U., 4McGill U., 5ASTRON, 6ASTRON, 7Caltech, 8Columbia, 9Caltech, 10ASTRON and U. Amsterdam, 11ASTRON, 12Jodrell Bank, 13Leiden and ASTRON, 14Jodrell Bank, 15JPL, 16UC Berkeley, 17UC Berkeley, 18MIT, 19DTU, 20UC Berkeley and LLNL, 21Columbia, 22GSFC

We report NuSTAR observations of the millisecond pulsar - low mass X-ray binary (LMXB) transition system PSR J1023+0038 from June and October 2013, before and after the formation of an accretion disk around the neutron star. Between June 10-12, a few days to two weeks before the radio disappearance of the pulsar, the 3-79 keV X-ray spectrum was well fit by a simple power law with a photon index of Gamma=1.17 +/-0. Read More

I present modeling of the X-ray pulsations from the central compact object (CCO) PSR J1852+0040 in the Galactic supernova remnant Kesteven 79. In the context of thermal surface radiation from a rotating neutron star, a conventional polar cap model can reproduce the broad, large-amplitude X-ray pulse only with a "pencil plus fan" beam emission pattern, which is characteristic of strongly magnetized ($\gtrsim$10^12 Gauss) neutron star atmospheres, substantially stronger than the ~10^10 Gauss external dipole field inferred from the pulsar spin-down rate. This discrepancy can be explained by an axially displaced dipole. Read More

A number of radio pulsars exhibit intriguing mode-switching behavior. Recent observations of PSR B0943+10 revealed correlated radio and X-ray mode switches, providing a new avenue for understanding this class of objects. The large X-ray pulse fraction observed during the radio quiet phase (Q mode) was previously interpreted as a result of changing obscuration of X-rays by dense magnetosphere plasma. Read More

We present XMM-Newton and Chandra observations of the low-mass X-ray binary XSS J12270--4859, which experienced a dramatic decline in optical/X-ray brightness at the end of 2012, indicative of the disappearance of its accretion disk. In this new state, the system exhibits previously absent orbital-phase-dependent, large-amplitude X-ray modulations with a decline in flux at superior conjunction. The X-ray emission remains predominantly non-thermal but with an order of magnitude lower mean luminosity and significantly harder spectrum relative to the previous high flux state. Read More

We present X-ray observations of the "redback" eclipsing radio millisecond pulsar and candidate radio pulsar/X-ray binary transition object PSR J1723-2837. The X-ray emission from the system is predominantly non-thermal and exhibits pronounced variability as a function of orbital phase, with a factor of ~2 reduction in brightness around superior conjunction. Such temporal behavior appears to be a defining characteristic of this variety of peculiar millisecond pulsar binaries and is likely caused by a partial geometric occultation by the main-sequence-like companion of a shock within the binary. Read More

The X-ray transient IGR J18245-2452 in the globular cluster M28 contains the first neutron star (NS) seen to switch between rotation-powered and accretion-powered pulsations. We analyse its 2013 March-April 25d-long outburst as observed by Swift, which had a peak bolometric luminosity of ~6% of the Eddington limit (L$_{E}$), and give detailed properties of the thermonuclear burst observed on 2013 April 7. We also present a detailed analysis of new and archival Chandra data, which we use to study quiescent emission from IGR J18245-2452 between 2002 and 2013. Read More

2013Jun
Authors: Kirpal Nandra1, Didier Barret2, Xavier Barcons3, Andy Fabian4, Jan-Willem den Herder5, Luigi Piro6, Mike Watson7, Christophe Adami8, James Aird9, Jose Manuel Afonso10, Dave Alexander11, Costanza Argiroffi12, Lorenzo Amati13, Monique Arnaud14, Jean-Luc Atteia15, Marc Audard16, Carles Badenes17, Jean Ballet18, Lucia Ballo19, Aya Bamba20, Anil Bhardwaj21, Elia Stefano Battistelli22, Werner Becker23, Michaël De Becker24, Ehud Behar25, Stefano Bianchi26, Veronica Biffi27, Laura Bîrzan28, Fabrizio Bocchino29, Slavko Bogdanov30, Laurence Boirin31, Thomas Boller32, Stefano Borgani33, Katharina Borm34, Nicolas Bouché35, Hervé Bourdin36, Richard Bower37, Valentina Braito38, Enzo Branchini39, Graziella Branduardi-Raymont40, Joel Bregman41, Laura Brenneman42, Murray Brightman43, Marcus Brüggen44, Johannes Buchner45, Esra Bulbul46, Marcella Brusa47, Michal Bursa48, Alessandro Caccianiga49, Ed Cackett50, Sergio Campana51, Nico Cappelluti52, Massimo Cappi53, Francisco Carrera54, Maite Ceballos55, Finn Christensen56, You-Hua Chu57, Eugene Churazov58, Nicolas Clerc59, Stephane Corbel60, Amalia Corral61, Andrea Comastri62, Elisa Costantini63, Judith Croston64, Mauro Dadina65, Antonino D'Ai66, Anne Decourchelle67, Roberto Della Ceca68, Konrad Dennerl69, Klaus Dolag70, Chris Done71, Michal Dovciak72, Jeremy Drake73, Dominique Eckert74, Alastair Edge75, Stefano Ettori76, Yuichiro Ezoe77, Eric Feigelson78, Rob Fender79, Chiara Feruglio80, Alexis Finoguenov81, Fabrizio Fiore82, Massimiliano Galeazzi83, Sarah Gallagher84, Poshak Gandhi85, Massimo Gaspari86, Fabio Gastaldello87, Antonis Georgakakis88, Ioannis Georgantopoulos89, Marat Gilfanov90, Myriam Gitti91, Randy Gladstone92, Rene Goosmann93, Eric Gosset94, Nicolas Grosso95, Manuel Guedel96, Martin Guerrero97, Frank Haberl98, Martin Hardcastle99, Sebastian Heinz100, Almudena Alonso Herrero101, Anthony Hervé102, Mats Holmstrom103, Kazushi Iwasawa104, Peter Jonker105, Jelle Kaastra106, Erin Kara107, Vladimir Karas108, Joel Kastner109, Andrew King110, Daria Kosenko111, Dimita Koutroumpa112, Ralph Kraft113, Ingo Kreykenbohm114, Rosine Lallement115, Giorgio Lanzuisi116, J. Lee117, Marianne Lemoine-Goumard118, Andrew Lobban119, Giuseppe Lodato120, Lorenzo Lovisari121, Simone Lotti122, Ian McCharthy123, Brian McNamara124, Antonio Maggio125, Roberto Maiolino126, Barbara De Marco127, Domitilla de Martino128, Silvia Mateos129, Giorgio Matt130, Ben Maughan131, Pasquale Mazzotta132, Mariano Mendez133, Andrea Merloni134, Giuseppina Micela135, Marco Miceli136, Robert Mignani137, Jon Miller138, Giovanni Miniutti139, Silvano Molendi140, Rodolfo Montez141, Alberto Moretti142, Christian Motch143, Yaël Nazé144, Jukka Nevalainen145, Fabrizio Nicastro146, Paul Nulsen147, Takaya Ohashi148, Paul O'Brien149, Julian Osborne150, Lida Oskinova151, Florian Pacaud152, Frederik Paerels153, Mat Page154, Iossif Papadakis155, Giovanni Pareschi156, Robert Petre157, Pierre-Olivier Petrucci158, Enrico Piconcelli159, Ignazio Pillitteri160, C. Pinto161, Jelle de Plaa162, Etienne Pointecouteau163, Trevor Ponman164, Gabriele Ponti165, Delphine Porquet166, Ken Pounds167, Gabriel Pratt168, Peter Predehl169, Daniel Proga170, Dimitrios Psaltis171, David Rafferty172, Miriam Ramos-Ceja173, Piero Ranalli174, Elena Rasia175, Arne Rau176, Gregor Rauw177, Nanda Rea178, Andy Read179, James Reeves180, Thomas Reiprich181, Matthieu Renaud182, Chris Reynolds183, Guido Risaliti184, Jerome Rodriguez185, Paola Rodriguez Hidalgo186, Mauro Roncarelli187, David Rosario188, Mariachiara Rossetti189, Agata Rozanska190, Emmanouil Rovilos191, Ruben Salvaterra192, Mara Salvato193, Tiziana Di Salvo194, Jeremy Sanders195, Jorge Sanz-Forcada196, Kevin Schawinski197, Joop Schaye198, Axel Schwope199, Salvatore Sciortino200, Paola Severgnini201, Francesco Shankar202, Debora Sijacki203, Stuart Sim204, Christian Schmid205, Randall Smith206, Andrew Steiner207, Beate Stelzer208, Gordon Stewart209, Tod Strohmayer210, Lothar Strüder211, Ming Sun212, Yoh Takei213, V. Tatischeff214, Andreas Tiengo215, Francesco Tombesi216, Ginevra Trinchieri217, T. G. Tsuru218, Asif Ud-Doula219, Eugenio Ursino220, Lynne Valencic221, Eros Vanzella222, Simon Vaughan223, Cristian Vignali224, Jacco Vink225, Fabio Vito226, Marta Volonteri227, Daniel Wang228, Natalie Webb229, Richard Willingale230, Joern Wilms231, Michael Wise232, Diana Worrall233, Andrew Young234, Luca Zampieri235, Jean In't Zand236, Silvia Zane237, Andreas Zezas238, Yuying Zhang239, Irina Zhuravleva240
Affiliations: 1DE, 2FR, 3ES, 4UK, 5NL, 6IT, 7UK, 8FR, 9UK, 10PT, 11UK, 12IT, 13IT, 14FR, 15FR, 16CH, 17US, 18FR, 19IT, 20JP, 21IN, 22IT, 23DE, 24BE, 25IL, 26IT, 27IT, 28NL, 29IT, 30US, 31FR, 32DE, 33IT, 34DE, 35FR, 36IT, 37UK, 38IT, 39IT, 40UK, 41US, 42US, 43DE, 44DE, 45DE, 46US, 47IT, 48CZ, 49IT, 50US, 51IT, 52IT, 53IT, 54ES, 55ES, 56DK, 57US, 58DE, 59DE, 60FR, 61GR, 62IT, 63NL, 64UK, 65IT, 66IT, 67FR, 68IT, 69DE, 70DE, 71UK, 72CZ, 73US, 74CH, 75UK, 76IT, 77JP, 78US, 79UK, 80FR, 81FI, 82IT, 83IT, 84CA, 85UK, 86IT, 87IT, 88DE, 89GR, 90DE, 91IT, 92US, 93FR, 94BE, 95FR, 96AT, 97ES, 98DE, 99UK, 100US, 101ES, 102FR, 103SE, 104ES, 105NL, 106NL, 107UK, 108CZ, 109US, 110UK, 111FR, 112FR, 113US, 114D, 115FR, 116GR, 117US, 118FR, 119UK, 120IT, 121DE, 122IT, 123UK, 124CA, 125IT, 126UK, 127DE, 128IT, 129ES, 130IT, 131UK, 132IT, 133NL, 134DE, 135IT, 136IT, 137IT, 138US, 139ES, 140IT, 141ES, 142IT, 143FR, 144BE, 145FI, 146IT, 147US, 148JP, 149UK, 150UK, 151DE, 152DE, 153US, 154UK, 155GR, 156IT, 157US, 158FR, 159IT, 160IT, 161UK, 162NL, 163FR, 164UK, 165DE, 166FR, 167UK, 168FR, 169DE, 170US, 171US, 172NL, 173DE, 174IT, 175US, 176DE, 177BE, 178IT, 179UK, 180UK, 181DE, 182FR, 183US, 184IT, 185FR, 186CA, 187IT, 188DE, 189IT, 190PL, 191UK, 192IT, 193DE, 194IT, 195DE, 196ES, 197CH, 198NL, 199D, 200IT, 201IT, 202FR, 203UK, 204IE, 205DE, 206US, 207US, 208IT, 209UK, 210US, 211DE, 212US, 213JP, 214FR, 215IT, 216US, 217IT, 218JP, 219US, 220NL, 221US, 222IT, 223UK, 224IT, 225NL, 226IT, 227FR, 228US, 229FR, 230UK, 231DE, 232NL, 233UK, 234UK, 235IT, 236NL, 237UK, 238GR, 239DE, 240US

This White Paper, submitted to the recent ESA call for science themes to define its future large missions, advocates the need for a transformational leap in our understanding of two key questions in astrophysics: 1) How does ordinary matter assemble into the large scale structures that we see today? 2) How do black holes grow and shape the Universe? Hot gas in clusters, groups and the intergalactic medium dominates the baryonic content of the local Universe. To understand the astrophysical processes responsible for the formation and assembly of these large structures, it is necessary to measure their physical properties and evolution. This requires spatially resolved X-ray spectroscopy with a factor 10 increase in both telescope throughput and spatial resolving power compared to currently planned facilities. Read More

White dwarfs, neutron stars and stellar mass black holes are key laboratories to study matter in most extreme conditions of gravity and magnetic field. The unprecedented effective area of Athena+ will allow us to advance our understanding of emission mechanisms and accretion physics over a wide range of mass accretion rates, starting from lower and sub-luminous quiescent X-ray binaries up to super-Eddington ultra-luminous sources. Athena+ will measure stellar black hole spins in a much higher number of binaries than achievable now, opening the possibility to study how spin varies with black hole history. Read More

I present an analysis of the deepest X-ray exposure of a radio millisecond pulsar (MSP) to date, an X-ray Multi Mirror-Newton European Photon Imaging Camera spectroscopic and timing observation of the nearest known MSP, PSR J0437--4715. The timing data clearly reveal a secondary broad X-ray pulse offset from the main pulse by $\sim$0.55 in rotational phase. Read More

We present a Chandra X-ray Observatory ACIS-S variability, spectroscopy, and imaging study of the peculiar binary containing the millisecond pulsar J1023+0038. The X-ray emission from the system exhibits highly significant (12.5 sigma) large-amplitude (factor of 2-3) orbital variability over the five consecutive orbits covered by the observation, with a pronounced decline in the flux at all energies at superior conjunction. Read More

We have searched for optical identifications for 79 Chandra X-ray sources that lie within the half-mass radius of the nearby, core-collapsed globular cluster NGC 6397, using deep Hubble Space Telescope Advanced Camera for Surveys Wide Field Channel imaging in H-alpha, R, and B. Photometry of these images allows us to classify candidate counterparts based on color-magnitude diagram location. In addition to recovering nine previously detected cataclysmic variables (CVs), we have identified six additional faint CV candidates, a total of 42 active binaries (ABs), two millisecond pulsars (MSPs), one candidate active galactic nucleus, and one candidate interacting galaxy pair. Read More

We present a Chandra X-ray Observatory investigation of the millisecond pulsars (MSPs) in the globular cluster M28 (NGC 6626). In what is one of the deepest X-ray observations of a globular cluster, we firmly detect seven and possibly detect two of the twelve known M28 pulsars. With the exception of PSRs B1821-24 and J1824-2452H, the detected pulsars have relatively soft spectra, with X-ray luminosities 10^30-31 ergs s^-1 (0. Read More

We present a deep Chandra X-ray Observatory study of the peculiar binary radio millisecond pulsar PSR J1740--5340 and candidate millisecond pulsars (MSPs) in the globular cluster NGC 6397. The X-rays from PSR J1740--5340 appear to be non-thermal and exhibit variability at the binary period. These properties suggest the presence of a relativistic intrabinary shock formed due to interaction of a relativistic rotation-powered pulsar wind and outflow from the unusual "red-straggler/sub-subgiant" companion. Read More

We present deep XMM-Newton EPIC spectroscopic and timing X-ray observations of the nearby solitary radio millisecond pulsar, PSR J0030+0451. Its emission spectrum in the 0.1-10 keV range is found to be remarkably similar to that of the nearest and best studied millisecond pulsar, PSR J0437-4715, being well described by a predominantly thermal two-temperature model plus a faint hard tail evident above ~2 keV. Read More

Abridged) We model the X-ray properties of millisecond pulsars (MSPs) by considering hot spot emission from a weakly magnetized rotating neutron star (NS) covered by an optically-thick hydrogen atmosphere. We investigate the limitations of using the thermal X-ray pulse profiles of MSPs to constrain the mass-to-radius ($M/R$) ratio of the underlying NS. The accuracy is strongly dependent on the viewing angle and magnetic inclination. Read More

2007Nov

In recent years, X-ray observations with Chandra and XMM-Newton have significantly increased our understanding of rotation-powered (radio) millisecond pulsars (MSPs). Deep Chandra studies of several globular clusters have detected X-ray counterparts to a host of MSPs, including 19 in 47 Tuc alone. These surveys have revealed that most MSPs exhibit thermal emission from their heated magnetic polar caps. Read More

We present a model of thermal X-ray emission from hot spots on the surface of a rotating compact star with an unmagnetized light-element atmosphere. An application to ROSAT, Chandra, and XMM-Newton X-ray observations of the nearest known rotation-powered millisecond pulsar (MSP) PSR J0437--4715 reveals that the thermal emission from this pulsar is fully consistent with such a model, enabling constraints on important properties of the underlying neutron star. We confirm that the observed thermal X-ray pulsations from J0437--4715 are incompatible with blackbody emission and require the presence of an optically thick, light element (most likely hydrogen) atmosphere on the neutron star surface. Read More

The majority of X-ray-detected rotation-powered millisecond pulsars (MSPs) appear to exhibit predominantly thermal emission, believed to originate from the heated magnetic polar caps of the pulsar. In the nearest MSP, J0437--4715 a faint PL is also observed at >3 keV, usually associated with magnetospheric emission processes. However, the hard emission in this and other similar MSPs may instead be due to weak Comptonization of the thermal polar cap emission by energetic electrons/positrons of small optical depth most likely in the pulsar magnetosphere. Read More

X-ray emission from many rotation-powered millisecond pulsars (MSPs) is observed to be of predominantly thermal nature. In PSR J0437--4715, the nearest MSP known, an additional faint power-law tail is observed above 2.5 keV, commonly attributed to non-thermal magnetospheric radiation. Read More

We present spectral and long-timescale variability analyses of \textit{Chandra} ACIS-S observations of the 19 millisecond pulsars (MSPs) with precisely known positions in the globular cluster 47 Tucanae. The X-ray emission of the majority of these MSPs is well described by a thermal (blackbody or neutron star hydrogen atmosphere) spectrum with a temperature $T_{\rm eff}\sim(1-3)\times10^6$ K, emission radius $R_{\rm eff}\sim0.1-3$ km, and luminosity $L_{X}\sim10^{30-31}$ ergs s$^{-1}$. Read More

We present high-precision photometry of the hypervelocity star SDSS J090745.0+024507 (HVS), which has a Galactic rest-frame radial velocity of v=709 km/s, and so has likely been ejected from the supermassive black hole in the Galactic center. Our data were obtained on two nights using the MMT 6. Read More

We report the discovery of peculiar X-ray spectral variability in the binary radio millisecond pulsar PSR J0024--7204W in the globular cluster 47 Tucanae. The observed emission consists of a dominant non-thermal component, which is eclipsed for a portion of the orbit, and a thermal component, which appears to be persistent. We propose that the non-thermal X-rays originate in a relativistic intrabinary shock, formed due to interaction between the relativistic particle wind from the pulsar and matter from the main-sequence companion star, while the thermal photons are from the heated magnetic polar caps of the millisecond pulsar. Read More

2002Apr
Affiliations: 1Penn State University, 2Nicolaus Copernicus University, Torun, Poland, 3Nicolaus Copernicus University, Torun, Poland, 4Penn State University
Category: Astrophysics

We present interstellar scintillation velocity measurements for four millisecond pulsars obtained from long-term monitoring observations with the Arecibo radio telescope at 430 MHz. We also derive explicit expressions that relate the measured scintillation velocity to the effective transverse velocity responsible for the motion of the diffraction pattern for both binary and solitary pulsars. For B1257+12, B1534+12, J1640+2224, and J1713+0747 we derive velocity estimates of 197, 192, 38, and 82 km/s, respectively. Read More