1,204 research outputs found
The Amazing Old Nova Q Cygni: A Far Ultraviolet Synthetic Spectral Analysis
Q Cygni (Nova Cygni 1876) is the third oldest old novae (after WY Sge and
V841 Oph) with a long orbital period of 10.08 hours and spectroscopic
peculiarities in the optical including the presence of variable wind outflow
revealed by optical P Cygni profiles in the HeI lines and H alpha beta (Kafka
et al. 2003). We have carried out a synthetic spectral analysis of a far
ultraviolet IUE archival spectrum of Q Cygni using our optically thick, steady
state, accretion disk models and model white dwarf photospheres. We find that
the accretion light of a luminous accretion disk dominates the FUV flux of the
hot component with a rate of accretion 2-3 1.E-9 Msun/yr. We find that Q Cygni
lies at a distance of 741 \pm 110 pc . The implications of our results for
theoretical predictions for old novae are presented.Comment: PASP, August 201
Time-resolved measurement of single pulse femtosecond laser-induced periodic surface structure formation
Time-resolved diffraction microscopy technique has been used to observe the
formation of laser-induced periodic surface structures (LIPSS) from the
interaction of a single femtosecond laser pulse (pump) with a nano-scale groove
mechanically formed on a single-crystal Cu substrate. The interaction dynamics
(0-1200 ps) was captured by diffracting a time-delayed, frequency-doubled pulse
from nascent LIPSS formation induced by the pump with an infinity-conjugate
microscopy setup. The LIPSS ripples are observed to form sequentially outward
from the groove edge, with the first one forming after 50 ps. A 1-D analytical
model of electron heating and surface plasmon polariton (SPP) excitation
induced by the interaction of incoming laser pulse with the groove edge
qualitatively explains the time-evloution of LIPSS formation.Comment: 4 pages, 5 figure
p_T-fluctuations in high-energy p-p and A-A collisions
The event-by-event p_T-fluctuations in proton-proton and central Pb-Pb
collisions, which have been experimentally studied by means of the so-called
Phi-measure, are analyzed. The contribution due to the correlation which
couples the average p_T to the event multiplicity is computed. The correlation
appears to be far too weak to explain the preliminary experimental value of Phi
(p_T) in p-p interactions. The significance of the result is discussed.Comment: 5 pages, 2 figures, minor improvement
Recent atmospheric neutrino results from Soudan 2
An updated measurement of the atmospheric nu_mu/nu_e ratio-of-ratios,
0.68+-0.11+-0.06, has been obtained using a 4.6-kty exposure of the Soudan-2
iron tracking calorimeter. The L/E distributions have been analyzed for effects
of nu_mu -> nu_x oscillations, and an allowed region in the Delta m^2 vs. sin^2
2 theta plane has been determined.Comment: 3 pages, 4 figures; presented at TAUP99, the 6th Int. Workshop on
Topics in Astroparticle and Underground Physics, Sept. 6-10, 1999, College de
France, Paris, Franc
Implications of a Minimal SO(10) Higgs Structure
A minimal SO(10) Higgs structure involving a single adjoint field along with
spinors, vectors and singlets has been shown to break the SO(10) gauge symmetry
to the standard model while stabilizing the F-flat directions and solving the
doublet-triplet splitting problem naturally. With this minimal set of Higgs
fields, we show how to construct quark and lepton mass matrices which explain
well the many features of the observed spectrum, including the Georgi-Jarlskog
mass relations. A large mixing of the muon- and tau-neutrinos results naturally
as observed in the atmospheric neutrino data. A particular model relying on a
family symmetry has been constructed which realizes the desired mass matrices.Comment: 10 pages, REVTEX, contribution submitted to NEUTRINO 98 Conferenc
The Factory and The Beehive II. Activity and Rotation in Praesepe and the Hyades
Open clusters are collections of stars with a single, well-determined age,
and can be used to investigate the connections between angular-momentum
evolution and magnetic activity over a star's lifetime. We present the results
of a comparative study of the relationship between stellar rotation and
activity in two benchmark open clusters: Praesepe and the Hyades. As they have
the same age and roughly solar metallicity, these clusters serve as an ideal
laboratory for testing the agreement between theoretical and empirical
rotation-activity relations at 600 Myr. We have compiled a sample of
720 spectra --- more than half of which are new observations --- for 516
high-confidence members of Praesepe; we have also obtained 139 new spectra for
130 high-confidence Hyads. We have collected rotation periods () for
135 Praesepe members and 87 Hyads. To compare emission, an indicator
of chromospheric activity, as a function of color, mass, and Rossby number
, we first calculate an expanded set of values, with which we can
obtain the to bolometric luminosity ratio, ,
even when spectra are not flux-calibrated and/or stars lack reliable distances.
Our values cover a broader range of stellar masses and colors (roughly
equivalent to spectral types from K0 to M9), and exhibit better agreement
between independent calculations, than existing values. We find no difference
between the two clusters in their equivalent width or
distributions, and therefore take the merged
and data to be representative of 600-Myr-old stars. Our analysis
shows that activity in these stars is saturated for
. Above that value activity declines as a
power-law with slope , before dropping off rapidly
at ...Comment: 17 pages, 15 figures, Accepted by Ap
Photometric study of selected cataclysmic variables
We present time-resolved photometry of five relatively poorly-studied
cataclysmic variables: V1193 Ori, LQ Peg, LD 317, V795 Her, and MCT 2347-3144.
The observations were made using four 1m-class telescopes for a total of more
than 250 h of observation and almost 16,000 data points. For LQ Peg WHT
spectroscopic data have been analysed as well.
The light curves show a wide range of variability on different time scales
from minutes to months. We detect for the first time a brightness variation of
0.05 mag in amplitude in V1193 Ori on the same timescale as the orbital period,
which we interpret as the result of the irradiation of the secondary. A 20-min
quasi-periodic oscillation is also detected. The mean brightness of the system
has changed by 0.5 mag on a three-month interval, while the flickering was
halved. In LQ Peg a 0.05 mag modulation was revealed with a period of about 3
h. The flickering was much smaller, of the order of 0.025 mag. A possible
quasi-periodic oscillation could exist near 30 min. For this object, the WHT
spectra are single-peaked and do not show any radial-velocity variations. The
data of LD 317 show a decrease in the mean magnitude of the system. No periodic
signal was detected but this is certainly attributable to the very large
flickering observed: between 0.07 and 0.1 mag. For V795 Her, the 2.8-hour
modulation, thought to be a superhump arising from the precession of the disc,
is present. We show that this modulation is not stable in terms of periodicity,
amplitude, and phase. Finally, for MCT 2347-3144, a clear modulation is seen in
a first dataset obtained in October 2002. This modulation is absent in August
2003, when the system was brighter and showed much more flickering.Comment: 19 pages, 15 figures, 7 tables. Accepted for pubication by A&
Gravitational-wave research as an emerging field in the Max Planck Society. The long roots of GEO600 and of the Albert Einstein Institute
On the occasion of the 50th anniversary since the beginning of the search for
gravitational waves at the Max Planck Society, and in coincidence with the 25th
anniversary of the foundation of the Albert Einstein Institute, we explore the
interplay between the renaissance of general relativity and the advent of
relativistic astrophysics following the German early involvement in
gravitational-wave research, to the point when gravitational-wave detection
became established by the appearance of full-scale detectors and international
collaborations. On the background of the spectacular astrophysical discoveries
of the 1960s and the growing role of relativistic astrophysics, Ludwig Biermann
and his collaborators at the Max Planck Institute for Astrophysics in Munich
became deeply involved in research related to such new horizons. At the end of
the 1960s, Joseph Weber's announcements claiming detection of gravitational
waves sparked the decisive entry of this group into the field, in parallel with
the appointment of the renowned relativist Juergen Ehlers. The Munich area
group of Max Planck institutes provided the fertile ground for acquiring a
leading position in the 1970s, facilitating the experimental transition from
resonant bars towards laser interferometry and its innovation at increasingly
large scales, eventually moving to a dedicated site in Hannover in the early
1990s. The Hannover group emphasized perfecting experimental systems at pilot
scales, and never developed a full-sized detector, rather joining the LIGO
Scientific Collaboration at the end of the century. In parallel, the Max Planck
Institute for Gravitational Physics (Albert Einstein Institute) had been
founded in Potsdam, and both sites, in Hannover and Potsdam, became a unified
entity in the early 2000s and were central contributors to the first detection
of gravitational waves in 2015.Comment: 94 pages. Enlarged version including new results from further
archival research. A previous version appears as a chapter in the volume The
Renaissance of General Relativity in Context, edited by A. Blum, R. Lalli and
J. Renn (Boston: Birkhauser, 2020
CP and T violation test in neutrino oscillation
We examine how large violation of CP and T is allowed in long base line
neutrino experiments. When we attribute only the atmospheric neutrino anomaly
to neutrino oscillation we may have large CP violation effect. When we
attribute both the atmospheric neutrino anomaly and the solar neutrino deficit
to neutrino oscillation we may have a sizable T violation effect proportional
to the ratio of two mass differences; it is difficult to see CP violation since
we can't ignore the matter effect. We give a simple expression for T violation
in the presence of matter.Comment: 12 pages + 2 eps figures, Latex, In order to avoid misunderstanding
we have refined our English and rewritten the parts which might be
misleading. Several typographical errors are correcte
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