60 research outputs found
Spill-over effects in multi-partner loyalty programs
A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and EconomicsThis study analyses spill-over effects in multi-partner loyalty programs. In
particular the effect of high prestige companies entering a multi-partner loyalty
program on the initial individual partners is under examination. The effect of size
(number of partners) is also examined. Results generally report a significant influence
of the entrant on the other individual partners that ally; negative spill-over effects are
observed. The study further shows that the strength of spill-over effects isn’t influenced
by the size of the partner loyalty program. Results have been confirmed through a
replication study
Numerical Assessment of Packing Structures for Gas-Particle Trickle Flow Heat Exchanger for Application in CSP Plants
REBOOKING MEETING ROOM WHEN MEETING ROOM BECOMES UNAVAILABLE
In organizations with multiple meeting rooms or conference rooms, meeting rooms can become unavailable after a meeting has already been scheduled in that room. The described system can respond to an indication that the meeting room is unavailable by finding another meeting room for the meeting that meets the requirements for the meeting. The system can notify the participants or attendees of the meeting of the new meeting room
Refining the prediction for OJ 287 next impact flare arrival epoch
The bright blazar OJ~287 routinely parades high brightness bremsstrahlung
flares which are explained as being a result of a secondary supermassive black
hole (SMBH) impacting the accretion disk of a primary SMBH in a binary system.
We begin by showing that these flares occur at times predicted by a simple
analytical formula, based on the Kepler equation, which explains flares since
1888. The next impact flare, namely the flare number 26, is rather peculiar as
it breaks the typical pattern of two impact flares per 12 year cycle. This will
be the third bremsstrahlung flare of the current cycle that follows the already
observed 2015 and 2019 impact flares from OJ~287. Unfortunately, astrophysical
considerations make it difficult to predict the exact arrival epoch of the
flare number 26. In the second part of the paper, we describe our recent OJ~287
observations. They show that the pre-flare light curve of flare number 22,
observed in 2005, exhibits similar activity as the pre-flare light curve in
2022, preceding the expected flare number 26 in our model. We argue that the
pre-flare activity most likely arises in the primary jet whose activity is
modulated by the transit of the secondary SMBH through the accretion disk of
the primary. Observing the next impact flare of OJ~287 in October 2022 will
substantiate the theory of disk impacts in binary black hole systems.Comment: 16 pages, 2 figure
Spitzer Observations of the Predicted Eddington Flare from Blazar OJ 287
Binary black hole (BH) central engine description for the unique blazar OJ
287 predicted that the next secondary BH impact-induced bremsstrahlung flare
should peak on 2019 July 31. This prediction was based on detailed general
relativistic modeling of the secondary BH trajectory around the primary BH and
its accretion disk. The expected flare was termed the Eddington flare to
commemorate the centennial celebrations of now-famous solar eclipse
observations to test general relativity by Sir Arthur Eddington. We analyze the
multi-epoch Spitzer observations of the expected flare between 2019 July 31 and
2019 September 6, as well as baseline observations during 2019 February-March.
Observed Spitzer flux density variations during the predicted outburst time
display a strong similarity with the observed optical pericenter flare from OJ
287 during 2007 September. The predicted flare appears comparable to the 2007
flare after subtracting the expected higher base-level Spitzer flux densities
at 3.55 and 4.49 m compared to the optical R-band. Comparing the 2019 and
2007 outburst lightcurves and the previously calculated predictions, we find
that the Eddington flare arrived within 4 hours of the predicted time. Our
Spitzer observations are well consistent with the presence of a nano-Hertz
gravitational wave emitting spinning massive binary BH that inspirals along a
general relativistic eccentric orbit in OJ 287. These multi-epoch Spitzer
observations provide a parametric constraint on the celebrated BH no-hair
theorem.Comment: 8 pages, 4 figures, 1 table, to appear in ApJ
Refining the 2022 OJ 287 impact flare arrival epoch
The bright blazar OJ~287 routinely parades high brightness bremsstrahlung
flares, which are explained as being a result of a secondary supermassive black
hole (SMBH) impacting the accretion disc of a more massive primary SMBH in a
binary system. The accretion disc is not rigid but rather bends in a calculable
way due to the tidal influence of the secondary. Below we refer to this
phenomenon as a variable disc level. We begin by showing that these flares
occur at times predicted by a simple analytical formula, based on general
relativity inspired modified Kepler equation, which explains impact flares
since 1888.
The 2022 impact flare, namely flare number 26, is rather peculiar as it
breaks the typical pattern of two impact flares per 12-year cycle. This is the
third bremsstrahlung flare of the current cycle that follows the already
observed 2015 and 2019 impact flares from OJ~287.
It turns out that the arrival epoch of flare number 26 is sensitive to the
level of primary SMBH's accretion disc relative to its mean level in our model.
We incorporate these tidally induced changes in the level of the accretion disc
to infer that the thermal flare should have occurred during July-August 2022,
when it was not possible to observe it from the Earth. Thereafter, we explore
possible observational evidence for certain pre-flare activity by employing
spectral and polarimetric data from our campaigns in 2004/05 and 2021/22. We
point out theoretical and observational implications of two observed
mini-flares during January-February 2022.Comment: 29 pages, 6 figures, 1 table. arXiv admin note: text overlap with
arXiv:2209.0836
THE FIRST MAXIMUM-LIGHT ULTRAVIOLET THROUGH NEAR-INFRARED SPECTRUM OF A TYPE Ia SUPERNOVA
We present the first maximum-light ultraviolet (UV) through near-infrared (NIR) Type Ia supernova (SN Ia) spectrum. This spectrum of SN 2011iv was obtained nearly simultaneously by the Hubble Space Telescope at UV/optical wavelengths and the Magellan Baade telescope at NIR wavelengths. These data provide the opportunity to examine the entire maximum-light SN Ia spectral energy distribution. Since the UV region of an SN Ia spectrum is extremely sensitive to the composition of the outer layers of the explosion, which are transparent at longer wavelengths, this unprecedented spectrum can provide strong constraints on the composition of the SN ejecta, and similarly the SN explosion and progenitor system. SN 2011iv is spectroscopically normal, but has a relatively fast decline (Δm [subscript 15](B) = 1.69 ± 0.05 mag). We compare SN 2011iv to other SNe Ia with UV spectra near maximum light and examine trends between UV spectral properties, light-curve shape, and ejecta velocity. We tentatively find that SNe with similar light-curve shapes but different ejecta velocities have similar UV spectra, while those with similar ejecta velocities but different light-curve shapes have very different UV spectra. Through a comparison with explosion models, we find that both a solar-metallicity W7 and a zero-metallicity delayed-detonation model provide a reasonable fit to the spectrum of SN 2011iv from the UV to the NIR
On the need of an ultramassive black hole in OJ 287
The highly variable blazar OJ~287 is commonly discussed as an example of a
binary black hole system. The 130 year long optical light curve is well
explained by a model where the central body is a massive black hole of
18.3510 solar mass that supports a thin accretion disc. The
secondary black hole of 0.1510 solar mass impacts the disc twice
during its 12 year orbit, and causes observable flares. Recently, it has been
argued that an accretion disc with a typical AGN accretion rate and above
mentioned central body mass should be at least six magnitudes brighter than
OJ~287's host galaxy and would therefore be observationally excluded. Based on
the observations of OJ~287's radio jet, detailed in Marscher and Jorstad
(2011), and up-to-date accretion disc models of Azadi et al. (2022), we show
that the V-band magnitude of the accretion disc is unlikely to exceed the host
galaxy brightness by more than one magnitude, and could well be fainter than
the host. This is because accretion power is necessary to launch the jet as
well as to create electromagnetic radiation, distributed across many
wavelengths, and not concentrated especially on the optical V-band. Further, we
note that the claimed V-band concentration of accretion power leads to serious
problems while interpreting observations of other Active Galactic Nuclei.
Therefore, we infer that the mass of the primary black hole and its accretion
rate do not need to be smaller than what is determined in the standard model
for OJ~287
Glacial-interglacial modulation of the marine nitrogen cycle by high-latitude O2 supply to the global thermocline
Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 19 (2004): PA4007, doi:10.1029/2003PA001000.An analysis of sedimentary nitrogen isotope records compiled from widely distributed marine environments emphasizes the global synchrony of denitrification changes and provides evidence for a strong temporal coupling of these variations to changes in nitrogen fixation as previously inferred. We explain the global coherence of these records by a simple physical control on the flux of dissolved oxygen to suboxic zones and the coupling to fixation via the supply of phosphorus to diazotrophs in suitable environments. According to our hypothesis, lower glacial-stage sea surface temperature increased oxygen solubility, while stronger winds in high-latitude regions enhanced the rate of thermocline ventilation. The resultant colder, rapidly flushed thermocline lessened the spatial extent of denitrification and, consequently, N fixation. During warm periods, sluggish circulation of warmer, less oxygen rich thermocline waters caused expansion of denitrification zones and a concomitant increase in N fixation. Local fluctuations in export productivity would have modulated this global signal.Financial
support for this work was provided by the Natural Sciences and
Engineering Research Council of Canada and by a WHOI postdoctoral
fellowship to MK
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