D. ~A. Boboltz

Publications (11)6.02 Total impact

• Article: R Aquarii: First Detection of Circumstellar SiO Maser Proper Motions

  D. A. Boboltz, P. J. Diamond, and A. J. Kemball
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  ABSTRACT: We have made the first detection of circumstellar SiO maser proper motions in the envelope of a late-type star. Using the Very Long Baseline Array (VLBA), we have obtained observations at four epochs of the 43 GHz, v = 1, J = 1-0 SiO maser emission toward the Mira variable in the symbiotic binary R Aqr. The maser emission has a ringlike structure approximately 31 mas across with a slight elongation in the north-south direction. We find that the emission changes significantly over a timescale of about 1-2 months with almost no similarity in structure for timescales 6 months. Our observations show that over a 98 day period the masers have an average inward proper motion of about 1 mas. This contraction of the ring implies an infall velocity of about 4 km s-1 for the SiO masers in the circumstellar envelope.
  The Astrophysical Journal 01/2009; 487(2):L147. · 6.02 Impact Factor
• Source

  Available from: Kevin Marvel

  Article: OH 12.8-0.9: A New Water-Fountain Source

  D. A. Boboltz, K. B. Marvel
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  ABSTRACT: We present observational evidence that the OH/IR star OH 12.8-0.9 is the fourth in a class of objects previously dubbed "water-fountain" sources. Using the Very Long Baseline Array, we produced the first images of the water maser emission associated with OH 12.8-0.9. We find that the masers are located in two compact regions with an angular separation of ~109 mas on the sky. The axis of separation between the two maser regions is at a position angle of 1.5 deg. East of North with the blue-shifted (-80.5 to -85.5 km/s) masers located to the North and the red-shifted (-32.0 to -35.5 km/s) masers to the South. In addition, we find that the blue- and red-shifted masers are distributed along arc-like structures ~10-12 mas across oriented roughly perpendicular to the separation axis. The morphology exhibited by the water masers is suggestive of an axisymmetric wind with the masers tracing bow shocks formed as the wind impacts the ambient medium. This bipolar jet-like structure is typical of the three other confirmed water-fountain sources. When combined with the previously observed spectral characteristics of OH 12.8-0.9, the observed spatio-kinematic structure of the water masers provides strong evidence that OH 12.8-0.9 is indeed a member of the water-fountain class. Comment: 12 pages, 2 figures (1 color), accepted for publication in the Ap J Letters
  05/2005;
• Source

  Available from: arxiv.org

  Article: Axial Symmetry and Rotation in the SiO Maser Shell of IK Tauri

  D. A. Boboltz, P. J. Diamond
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  ABSTRACT: We observed v=1, J=1-0 43-GHz SiO maser emission toward the Mira variable IK Tauri (IK Tau) using the Very Long Baseline Array (VLBA). The images resulting from these observations show that SiO masers form a highly elliptical ring of emission approximately 58 x 32 mas with an axial ratio of 1.8:1. The major axis of this elliptical distribution is oriented at position angle of ~59 deg. The line-of-sight velocity structure of the SiO masers has an apparent axis of symmetry consistent with the elongation axis of the maser distribution. Relative to the assumed stellar velocity of 35 km/s, the blue- and red-shifted masers were found to lie to the northwest and southeast of this symmetry axis respectively. This velocity structure suggests a NW-SE rotation of the SiO maser shell with an equatorial velocity, which we determine to be ~3.6 km/s. Such a NW-SE rotation is in agreement with a circumstellar envelope geometry invoked to explain previous water and OH maser observations. In this geometry, water and OH masers are preferentially created in a region of enhanced density along the NE-SW equator orthogonal to the rotation/polar axis suggested by the SiO maser velocities. Comment: 17 Pages, 4 figures (2 color); accepted for publication in ApJ
  03/2005;
• Article: Rotation in the Envelope of an Evolved Star: Observations of the SIO Masers Toward NML Cygni

  D. ~A. Boboltz, K. ~B. Marvel
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  ABSTRACT: {We have discovered a new peak of emission in the v=
  apjl. 12/2000; 545:L149-L152.
• Source

  Available from: Kevin Marvel

  Article: Observations of Water Masers Associated with the Proto-Planetary Nebula Candidate IRAS 19296+2227

  K. ~B. Marvel, D. ~A. Boboltz
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  ABSTRACT: We present the first very long baseline interferometric observations of the 6_16-5_23, 22 GHz H_2O maser emission associated with a proto-planetary nebula candidate. We obtained three epochs of observation of the water masers associated with IRAS 19296+2227, using the Very Long Baseline Array, operated by the National Radio Astronomy Observatory. These observations show that the water masers are distributed over a 50 mas arclike structure covering a limited velocity range of ~9 km s^-1. The masers most likely reside in an asymptotic giant branch-like circumstellar shell, although we cannot rule out the possibility that they lie in a shocked region. Over the 40 days spanning the epochs of observation, we have measured an error-weighted average proper motion of 6.16+/-1.32 km s^-1, indicating that the masers are not in a high-velocity outflow.
  aj. 10/1999; 118:1791-1797.
• Conference Proceeding: SiO Maser Emission Toward the Red Supergiant NML Cygni

  D. ~A. Boboltz, K. ~B. Marvel
  [show abstract] [hide abstract]
  ABSTRACT: {We have conducted full-polarization, spectral-line observations of the v=
  Bulletin of the American Astronomical Society; 05/1999
• Conference Proceeding: Observations of Water Masers Associated with the Proto-Planetary Nebula Candidate IRAS 19296+2227

  K. ~B. Marvel, D. ~A. Boboltz
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  ABSTRACT: We present the first VLBI observations of the 6_16-5_23, 22-GHz H_2O maser emission associated with a proto-planetary nebula candidate. Three epochs of observation of the water masers towards IRAS 19296+2227 were obtained with the Very Long Baseline Array operated by the National Radio Astronomy Observatory. These observations show that the water masers are distributed over a 40 milliarcsecond, arc-like structure covering a limited velocity range of ~ 4 km s(-1) . It is unclear whether the masers reside in a residual circumstellar shell or in a region shocked by a PN fast wind. Over the 40 days spanning Epochs 1 and 3, we have measured an average proper motion of 12.6 +/- 5.7 km s(-1) indicating that the masers are probably not in a high velocity outflow.
  Bulletin of the American Astronomical Society; 05/1999
• Source

  Available from: articles.adsabs.harvard.edu

  Conference Proceeding: Water Masers Near the Proto-Planetary Nebula Candidate IRAS 19296+2227

  K. ~B. Marvel, D. ~A. Boboltz
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  ABSTRACT: We present results from multi-epoch 22 GHz observations of the water masers associated with the proto-planetary nebula candidate IRAS 19296+2227 obtained with the Very Large Baseline Array (VLBA). The masers are distributed over a 50 mas arc-like structure and a limited velocity range. From VLA observations, we measure a position for the source of RA 19:29:37.336, Dec. +22:27:16.54 (1950.0). Using the VLBA observations we measure proper motions of the water masers similar to proper motions of water masers found in the atmospheres of evolved stars. We suggest that these masers exist in the extended, slow moving circumstellar wind created during the AGB mass-loss phase and that the star has only recently transitioned to the proto-planetary nebula evolutionary phase.
  Bulletin of the American Astronomical Society; 12/1998
• Source

  Available from: psu.edu

  Article: VLBA Polarization monitoring of SiO masers towards late-type stars

  P. J. Diamond, A. J. Kemball, D. A. Boboltz
  [show abstract] [hide abstract]
  ABSTRACT: Introduction We have been conducting an extensive VLBA monitoring program of the 43 GHz SiO maser emission from the Mira variables TX Cam (d ß 320pc), U Her (d ß 350pc) and R Aqr (d ß 220pc). The data were taken using 4 MHz channels on all 10 VLBA antennas with circular feeds. All four polarization products were generated in 128 spectral channels across the 4 MHz band. Continuum calibrators were observed both for delay, bandpass and polarization calibration. VLA observations of the polarization calibrators were made within a week or two of each VLBA session in order to determine the linear polarization position angle. The data reduction was performed following the recipes laid down by [2] and [5]. Our results on the changing structure in R Aqr are reported elsewhere [1]. Here we report on the the basic observational results obtained on U Her and TX Cam. Preprint submitted to Elsevier Preprint 7 March Mi
  04/1997;
• Source

  Available from: adsabs.harvard.edu

  Article: VLBA spectral line polarization survey of circumstellar OH masers.

  D. A. Boboltz, P. J. Diamond, A. J. Kemball, M. J. Claussen, L. Kogan
  11/1995; 27:1346-1347.
• Source

  Available from: articles.adsabs.harvard.edu

  Article: Multi-Epoch VLBA Observations of the SiO Maser Emission towards R Aquarii (R Aqr)

  D. A. Boboltz, P. J. Diamond, A. J. Kemball
  [show abstract] [hide abstract]
  ABSTRACT: We have observed v=1, J=1-0, 43-GHz SiO maser emission towards the symbiotic Mira variable R Aqr at four different epochs in the stellar pulsation cycle using the VLBA.
  144:243.