268 research outputs found
Connecting GRBs and galaxies: the probability of chance coincidence
Studies of GRB host galaxies are crucial to understanding GRBs. However,
since they are identified by the superposition in the plane of the sky of a GRB
afterglow and a galaxy there is always a possibility that an association
represents a chance alignment, rather than a physical connection. We examine a
uniform sample of 72 GRB fields to explore the probability of chance
superpositions. There is typically a ~1% chance that an optical afterglow will
coincide with a galaxy by chance. While spurious host galaxy detections will,
therefore, be rare, the possibility must be considered when examining
individual GRB/host galaxy examples. It is also tempting to use the large and
uniform collection of X-ray afterglow positions to search for GRB-associated
galaxies. However, we find that approximately half of the 14 superpositions in
our sample are likely to occur by chance, so in the case of GRBs localized only
by an X-ray afterglow, even statistical studies are suspect.Comment: edited, accepted by Ap
Talks From The Bible: Why The Church Means So Much?
https://digitalcommons.acu.edu/crs_books/1472/thumbnail.jp
Talks From The Bible: The Elements Of Christian Worship
https://digitalcommons.acu.edu/crs_books/1473/thumbnail.jp
Talks From The Bible: Seven-Ones
https://digitalcommons.acu.edu/crs_books/1474/thumbnail.jp
Talks From The Bible: Questions ??? About The Church
https://digitalcommons.acu.edu/crs_books/1471/thumbnail.jp
Talks From The Bible: The Undenominational Church
https://digitalcommons.acu.edu/crs_books/1470/thumbnail.jp
IR Monitoring of the Microquasar GRS 1915+105: Detection of Orbital and Superhump Signatures
We present the results of seven years of K-band monitoring of the low-mass
X-ray binary GRS 1915+105. Positive correlations between the infrared flux and
the X-ray flux and X-ray hardness are demonstrated. Analysis of the frequency
spectrum shows that the orbital period of the system is
days. The phase and amplitude of the orbital modulation suggests that the
modulation is due to the heating of the face of the secondary star. We also
report another periodic signature between 31.2 and 31.6 days, most likely due
to a superhump resonance. From the superhump period we then obtain a range on
the mass ratio of the system, .Comment: 16 pages, 6 figures; v2: minor change
Initial Clinical Experience with Swiss LithoClast Trilogy During Percutaneous Nephrolithotomy
Introduction and Objective: Current available lithotrites have clinical stone clearance rates averaging 24 to 32 mm2/minute. The objective of this study was to critically evaluate the initial experience with the Swiss LithoClast® Trilogy lithotrite during percutaneous nephrolithotomy (PCNL).
Methods: We prospectively enrolled patients with a minimum of 15 mm of stone in axial diameter at three locations (Indiana University, University of California Davis, and University of California San Diego) scheduled to undergo PCNL for nephrolithiasis over a 60-day trial period. We assessed objective measures of stone clearance time, stone clearance rate, device malfunction, stone-free rate, and complications. Each surgeon also evaluated subjective parameters from each case related to the use of Trilogy on a 1 to 10 scale (10 = extremely effective), and compared it with their usual lithotrite on a 1 to 5 scale (5 = much better).
Results: We included 43 patients and had 7 bilateral (16.3%) cases, for a total of 50 renal units. One case was a mini-PCNL. Two cases experienced device malfunctions requiring troubleshooting but no transition to another lithotrite. The mean stone clearance rate was 68.9 mm2/minute. The stone-free rate on postoperative imaging was 67.6% (25 of 37 patients with available imaging). The lowest subjective rating was the ergonomic score of 6.7, and the highest subjective rating was the ease of managing settings score of 9.2. The surgeon impressions of ultrasound (7.3), ballistics (8.1), combination of ultrasound and ballistics (8.7), and suction (8.4) were high. One patient experienced an intraoperative renal pelvis perforation, one patient required a blood transfusion, one patient had a pneumothorax requiring chest tube placement, and one patient had a renal artery pseudoaneurysm requiring endovascular embolization.
Conclusions: This multi-institutional study evaluated a new and efficient combination lithotrite that was perceived by surgeons to be highly satisfactory, with an excellent safety and durability profile
Short GRB Host Galaxies. II. A Legacy Sample of Redshifts, Stellar Population Properties, and Implications for their Neutron Star Merger Origins
We present the stellar population properties of 69 short gamma-ray burst
(GRB) host galaxies, representing the largest uniformly-modeled sample to-date.
Using the Prospector stellar population inference code, we jointly fit
photometry and/or spectroscopy of each host galaxy. We find a population median
redshift of ( confidence), including 10 new or
revised photometric redshifts at . We further find a median
mass-weighted age of Gyr, stellar mass of
, star formation rate of
SFR=yr, stellar metallicity of
, and dust attenuation of
~mag (68\% confidence). Overall, the majority of
short GRB hosts are star-forming (), with small fractions that are
either transitioning () or quiescent (); however, we
observe a much larger fraction () of quiescent and transitioning
hosts at , commensurate with galaxy evolution. We find that
short GRB hosts populate the star-forming main sequence of normal field
galaxies, but do not include as many high-mass galaxies, implying that their
binary neutron star (BNS) merger progenitors are dependent on a combination of
host star formation and stellar mass. The distribution of ages and redshifts
implies a broad delay-time distribution, with a fast-merging channel at
and a decreased BNS formation efficiency at lower redshifts. If short GRB hosts
are representative of BNS merger hosts within the horizon of current
gravitational wave detectors, these results can inform future searches for
electromagnetic counterparts. All of the data and modeling products are
available on the BRIGHT website.Comment: 32 pages, 15 figures, 3 tables, accepted to Ap
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