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Miller-Jones J.C.A.,Curtin University Australia | Sivakoff G.R.,University of Virginia | Altamirano D.,University of Amsterdam | Kording E.G.,University Paris Diderot | And 12 more authors.
Proceedings of the International Astronomical Union | Year: 2010

Relationships between the X-ray and radio behavior of black hole X-ray binaries during outbursts have established a fundamental coupling between the accretion disks and radio jets in these systems. I begin by reviewing the prevailing paradigm for this disk-jet coupling, also highlighting what we know about similarities and differences with neutron star and white dwarf binaries. Until recently, this paradigm had not been directly tested with dedicated high-angular resolution radio imaging over entire outbursts. Moreover, such high-resolution monitoring campaigns had not previously targetted outbursts in which the compact object was either a neutron star or a white dwarf. To address this issue, we have embarked on the Jet Acceleration and Collimation Probe Of Transient X-Ray Binaries (JACPOT XRB) project, which aims to use high angular resolution observations to compare disk-jet coupling across the stellar mass scale, with the goal of probing the importance of the depth of the gravitational potential well, the stellar surface and the stellar magnetic field, on jet formation. Our team has recently concluded its first monitoring series, including (E)VLA, VLBA, X-ray, optical, and near-infrared observations of entire outbursts of the black hole candidate H 1743-322, the neutron star system Aquila X-1, and the white dwarf system SS Cyg. Here I present preliminary results from this work, largely confirming the current paradigm, but highlighting some intriguing new behavior, and suggesting a possible difference in the jet formation process between neutron star and black hole systems. © International Astronomical Union 2011. Source

Scudder J.M.,University of Victoria | Scudder J.M.,University of Sussex | Ellison S.L.,University of Victoria | Momjian E.,Domenici Science Operations Center | And 7 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2015

New spectral line observations, obtained with the Jansky Very Large Array (VLA), of a sample of 34 galaxies in 17 close pairs are presented in this paper. The sample of galaxy pairs is selected to contain galaxies in close, major interactions (i.e. projected separations <30 h-1 70 kpc, and mass ratios less extreme than 4:1), while still having a sufficiently large angular separation that the VLA can spatially resolve both galaxies in the pair. Of the 34 galaxies, 17 are detected at >3σ. We compare the HI gas fraction of the galaxies with the triggered star formation present in that galaxy. When compared to the star formation rates (SFRs) of non-pair galaxies matched in mass, redshift, and local environment, we find that the star formation enhancement is weakly positively correlated (~2.5σ) with HI gas fraction. In order to help understand the physical mechanisms driving this weak correlation, we also present results from a small suite of binary galaxy merger simulations with varying gas fractions. The simulated galaxies indicate that larger initial gas fractions are associated with lower levels of interaction-triggered star formation (relative to an identical galaxy in isolation), but also show that high gas fraction galaxies have higher absolute SFRs prior to an interaction.We show that when interaction-driven SFR enhancements are calculated relative to a galaxy with an average gas fraction for its stellarmass, the relationship between SFR and initial gas fraction dominates over the SFR enhancements driven by the interaction. Simulated galaxy interactions that are matched in stellar mass but not in gas fraction, like our VLA sample, yield the same general positive correlation between SFR enhancement and gas fraction that we observe. © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Source

McIntyre T.P.,University of New Mexico | Henning P.A.,University of New Mexico | Minchin R.F.,Arecibo Observatory | Momjian E.,Domenici Science Operations Center | Butcher Z.,University of Massachusetts Amherst
Astronomical Journal | Year: 2015

The Arecibo L-band Feed Array Zone of Avoidance (ALFA ZOA) Deep Survey is the deepest and most sensitive blind H i survey undertaken in the ZOA. ALFA ZOA Deep will cover about 300 square degrees of sky behind the Galactic Plane in both the inner (30 ° ≤ l ≤ 75°; b ≤ |2°|) and outer (175° ≤ l ≤ 207°;-2° ≤ b ≤ + 1°) Galaxy, using the Arecibo Radio Telescope. First results from the survey have found 61 galaxies within a 15 square degree area centered on and b = -2°. The survey reached its expected sensitivity of rms = 1 mJy at 9 km s-1 channel resolution, and is shown to be complete above integrated flux, FHi = 0.5 Jy km s-1. The positional accuracy of the survey is 28″ and detections are found out to a recessional velocity of nearly 19,000 km s-1. The survey confirms the extent of the Orion and Abell 539 clusters behind the plane of the Milky Way and discovers expansive voids, at 10,000 and 18,000 km s-1. Twenty-six detections (43%) have a counterpart in the literature, but only two of these have known redshifts. Counterparts are 20% less common beyond vhel = 10,000 km s-1 and 33% less common at extinctions higher than AB = 3.5 mag. The ALFA ZOA Deep survey is able to probe large scale structure beyond redshifts that even the most modern wide-angle surveys have been able to detect in the ZOA at any wavelength. © 2015. The American Astronomical Society. All rights reserved. Source

Miller-Jones J.C.A.,NRAO Headquarters | Sivakoff G.R.,University of Virginia | Altamirano D.,University of Amsterdam | Tudose V.,Netherlands Institute for Radio Astronomy | And 24 more authors.
Astrophysical Journal Letters | Year: 2010

The 2009 November outburst of the neutron star X-ray binary Aquila X-1 (Aql X-1) was observed with unprecedented radio coverage and simultaneous pointed X-ray observations, tracing the radio emission around the full X-ray hysteresis loop of the outburst for the first time. We use these data to discuss the disk-jet coupling, finding the radio emission to be consistent with being triggered at state transitions, both from the hard to the soft spectral state and vice versa. Our data appear to confirm previous suggestions of radio quenching in the soft state above a threshold X-ray luminosity of ∼10% of the Eddington luminosity. We also present the first detections of Aql X-1 with very long baseline interferometry, showing that any extended emission is relatively diffuse and consistent with steady jets rather than arising from discrete, compact knots. In all cases where multi-frequency data were available, the source radio spectrum is consistent with being flat or slightly inverted, suggesting that the internal shock mechanism that is believed to produce optically thin transient radio ejecta in black hole X-ray binaries is not active in Aql X-1. © 2010. The American Astronomical Society. All rights reserved.. Source

McIntyre T.P.,University of New Mexico | Minchin R.F.,Arecibo Observatory | Momjian E.,Domenici Science Operations Center | Henning P.A.,University of New Mexico | And 2 more authors.
Astrophysical Journal Letters | Year: 2011

The Arecibo L-Band Feed Array Zone of Avoidance (ALFA ZOA) Survey has discovered a nearby galaxy, ALFA ZOA J1952+1428, at a heliocentric velocity of +279km s-1. The galaxy was discovered at low Galactic latitude by 21cm emission from neutral hydrogen (H I). We have obtained follow-up observations with the Expanded Very Large Array and the 0.9m Southeastern Association for Research in Astronomy optical telescope. The H I distribution overlaps an uncataloged, potential optical counterpart. The H I linear size is 1.4kpc at our adopted distance of D = 7Mpc, but the distance estimate is uncertain as Hubble's law is unreliable at low recessional velocities. The optical counterpart has mB = 16.9mag and B - R = 0.1mag. These characteristics, including = 107.0 M⊙ and L B = 107.5 L⊙, if at 7Mpc, indicate that this galaxy is a blue compact dwarf, but this remains uncertain until further follow-up observations are complete. Optical follow-up observations are ongoing and near-infrared follow-up observations have been scheduled. © 2011. The American Astronomical Society. All rights reserved.. Source

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