Science Publications
See New LBT Science Journal Articles Here
12/13/2007
Go Long, Go Deep: Finding Optical Jet Breaks for Swift-Era GRBs with the LBT
Using the 8.4m Large Binocular Telescope, we observed six GRB afterglows from 2.8 hours to 30.8 days after the burst
triggers to systematically probe the late time behaviors of afterglows including jet breaks, flares, and supernova
bumps. We detected five afterglows with Sloan r' magnitudes ranging from 23.0--26.3 mag. The depth of our observations
allows us to extend the temporal baseline for measuring jet breaks by another decade in time scale. We detected two jet
breaks and a third candidate, all of which are not detectable without deep, late time optical observations. In the
other three cases, we do not detect the jet breaks either because of contamination from the host galaxy light, the
presence of a supernova bump, or the intrinsic faintness of the optical afterglow. This suggests that the basic picture
that GRBs are collimated is still valid and that the apparent lack of Swift jet breaks is due to poorly sampled afterglow
light curves, particularly at late times.
● Read the Full Publication
11/6/2007
A deep Large Binocular Telescope view of the Canes Venatici I dwarf galaxy
We present the first deep color-magnitude diagram of the Canes Venatici I (CVnI) dwarf galaxy from
observations with the wide field Large Binocular Camera on the Large Binocular Telescope. Reaching down
to the main-sequence turnoff of the oldest stars, it reveals a dichotomy in the stellar populations of
CVnI: it harbors an old (> 10 Gyr), metal-poor ([Fe/H] ~ -2.0) and spatially extended population along
with a much younger (~ 1.4-2.0 Gyr), 0.5 dex more metal-rich, and spatially more concentrated population.
These young stars are also offset by 64_{-20}^{+40} pc to the East of the galaxy center. The data suggest
that this young population, which represent ~ 3-5 % of the stellar mass of the galaxy within its half-light
radius, should be identified with the kinematically cold stellar component found by Ibata et al. (2006).
CVnI therefore follows the behavior of the other remote MW dwarf spheroidals which all contain intermediate
age and/or young populations: a complex star formation history is possible in extremely low-mass galaxies.
● Read the Full Publication
11/2/2007
Optical Photometry and Spectroscopy of the Accretion-Powered Millisecond Pulsar HETE
We present phase resolved optical photometry and spectroscopy of the accreting millisecond pulsar HETE J1900.1-2455.
Our R-band light curves exhibit a sinusoidal modulation, at close to the orbital period, which we initially
attributed to X-ray heating of the irradiated face of the secondary star. However, further analysis reveals that the
source of the modulation is more likely due to superhumps caused by a precessing accretion disc. Doppler tomography
of a broad Halpha emission line reveals an emission ring, consistent with that expected from an accretion disc. Using
the velocity of the emission ring as an estimate for the projected outer disc velocity, we constrain the maximum
projected velocity of the secondary to be 200 km/s, placing a lower limit of 0.05 Msun on the secondary mass. For a
1.4 Msun primary, this implies that the orbital inclination is low, < 20 degrees. Utilising the observed relationship
between the secondary mass and orbital period in short period cataclysmic variables, we estimate the secondary mass to
be ~0.085 Msun, which implies an upper limit of ~2.4 Msun for the primary mass.
● Read the Full Publication
10/09/2007
A near-ultraviolet view of the Inner Region of M31 with the Large Binocular Telescope
We present a 900 sec, wide-field U image of the inner region of the Andromeda galaxy obtained during the
commissioning of the blue channel of the Large Binocular Camera mounted on the prime focus of the Large
Binocular Telescope. Relative photometry and absolute astrometry of individual sources in the image was
obtained along with morphological parameters aimed at discriminating between stars and extended sources,
e.g. globular clusters. The image unveils the near-ultraviolet view of the inner ring of star formation
recently discovered in the infrared by the Spitzer Space Telescope and shows in great detail the fine
structure of the dust lanes associated with the galaxy inner spiral arms. The capabilities of the blue
channel of the Large Binocular Camera at the Large Binocular Telescope (LBC-Blue) are probed by direct
comparison with ultraviolet GALEX observations of the same region in M31. We discovered 6 new candidate
stellar clusters in this high-background region of M31. We also recovered 62 bona-fide globulars and 62
previously known candidates from the Revised Bologna Catalogue of the M31 globular clusters, and firmly
established the extended nature of 19 of them.
● Read the Full Publication
9/21/2007
A deep Large Binocular Telescope view of the Canes Venatici I dwarf galaxy
We present the first deep color-magnitude diagram of the Canes Venatici I (CVnI) dwarf galaxy from
observations with the wide field Large Binocular Camera of the Large Binocular Telescope. Reaching
down to the main-sequence turnoff of the oldest stars, it reveals a dichotomy in the stellar
populations of CVnI: it harbors an old (>~ 10 Gyr), metal-poor ([Fe/H] ~ -2.0) and spatially
extended population along with a much younger (~1.4-2.0 Gyr), 0.5 dex more metal-rich, and
spatially more concentrated population. These young stars are also offset by ~100 pc to the East of
the center of the galaxy. The data suggest that this young population should be identified with the
kinematically cold stellar component found by Ibata et al. (2006). CVnI therefore follows the behavior
of the other remote MW dwarf spheroidals which all contain intermediate age and/or young populations:
a complex star formation history is possible in extremely low-mass galaxies.
● Read the Full Publication
9/15/2007
LBT Discovery of a Yellow Supergiant Eclipsing Binary in the Dwarf Galaxy Holmberg XI
In a variability survey of M81 using the Large Binocular Telescope we have
discovered a peculiar eclipsing binary (MV ~ -7.1) in the field of the dwarf
galaxy Holmberg IX. It has a period of 272 days and the light curve is well-fit by
an overcontact model in which both stars are overflowing their Roche lobes. It
is composed by two yellow supergiants (V − I 
1 mag, Teff 4800 K), rather
than the far more common red or blue supergiants. Such systems must be rare.
● Read the Full Publication (PDF)
8/20/2007
First Results From the Large Binocular Telescope:
Deep Photometry of New dSphs
This contribution describes photometry for two Galactic dSphs obtained with the Large Binocular
Telescope to a magnitude of ~25.5. Using the Large Binocular Camera, a purpose-built wide-field
imager for the LBT, we have examined the structure and star formation histories of two
newly-discovered Local Group members, the Hercules dSph and the Leo T dSph/dIrr system. We have
constructed a structural map for the Hercules system using three-filter photometry to V ~ 25.5.
This is the first deep photometry for this system, and it indicates that Hercules is unusually
elongated, possibly indicating distortion due to the Galactic tidal field. We have also derived
the first star formation history for the Leo T system, and find that its oldest population of
stars (age ~ 13 Gyr) were relatively metal-rich, with [Fe/H] ~ -1.5.
● First Results From the Large Binocular Telescope:
Deep Photometry of New dSphs
6/11/2007
The Elongated Structure of the Hercules DSPH from Deep LBT Imaging
● astro-ph preprint to appear in Astrophysical Journal Letters (October 2007) - (pdf file)
Other Publications
● GCN Circular 6486 - GRB 070419A, deep LBT photometry and possible supernova detection
● GCN Circular 6462 - GRB
070518, deep LBT photometry -
Image of GRB 070518
● GCN Circular 6406 - GRB
070419A, Deep LBT photometry -
Image of GRB 070419a
● GCN Circular 6374 - GRB
070412, deep LBT imaging -
Image of GRB 070412
● GCN Circular 6351 - GRB
070411, further deep LBT photometry -
Image of GRB 070411
● GCN Circular 6346 - GRB
070411, deep LBT photometry
● GCN Circular 6245 - GRB
070311, deep optical photometry
● GCN Circular 6219 - GRB
070311, deep optical photometry -
Image of GRB 070311
● GCN Circular 6165 - GRB
070125, deep late-time optical observation -
Image of GRB 070125
The origin of long gamma-ray bursts (GRB) was a mystery for a very long time. They were detected in the
1960's by military satellites looking for Soviet nuclear tests. When the existence of GRB became
declassified, models placed their origin from within the Solar System, to the Galactic bulge to
cosmological distances. Only when the Beppo-Sax satellite localized GRB by observing the X-ray afterglow
was it possible to show that the orgin was at cosmological distances. The large distances to the GRB
implies a huge amount of energy is required to account for the observed gamma-ray intensity and this is
hard to explain with any theory. But optical observations of the GRB afterglows demonstrated that the
burst are beamed with small opening angles, greatly reducing the required energy output. The total
gamma-ray energy turns out to be similar to the energy produced in core-collapse supernovae. Indeed,
the smoothly declining afterglows of a few well-studied GRB showed "bumps" about a month after the burst
that roughly matched powerful supernova light curves. Confirmation that energetic supernovae (SN) produce
long GRB came in 2003 with spectra of the nearby event 030329 (Stanek et al. 2003).
(Courtesy of Peter Garnavich)
Engineering Publications
● LBT Technical Journal Articles
● LBT Technical Conference Proceedings
● Generalized SCIDAR Measurements at Mount Graham
● SPIE 2006 in Orlando (PDF format)
● SPIE 2004 in Glasgow
● SPIE 2002 in Waikoloa
● SPIE 2000 in Munich
● Technical Memoranda (telescope design phase) (In Construction)
● LBT Booklet
● BCV Documents
● Other Conferences & Symposia
● ADS & EIE Engineering Reports
● Science with the LBT
● Other Reports & Publications
● SPIE Conferences