501 research outputs found
Partnerships Between the Heartside Gleaning Initiative and Local Businesses in the Grand Rapids, MI Area
Many nonprofit organizations are in need of ways to create funding opportunities to maintain the integrity of their operating systems. One way to raise funds is to invite local businesses to participate and provide ways to become involved in the inner workings of the nonprofit organization. By partnering a nonprofit organization and local businesses, ideas and funds can be spread to both partners in order to increase the viability of the overall community.
For one local nonprofit agency, The Heartside Gleaning Initiative, the possibility of partnering with local businesses in the Grand Rapids area is promising. Research regarding various fundraising opportunities was conducted in order to create four fundraising categories: (1) providing customers with donation information through the form of pamphlets, (2) use of donation boxes in the place of business, (3) donation of a certain percentage of sales for a set duration of time, and (4) participation in a fundraising event with other community partners. These options, compiled in an informational pamphlet, along with a generated contact list of local potential business partners are the result of this semester long collaboration and provided to the Heartside Gleaning Initiative to begin the process of recruiting partners.
The many challenges associated with this project included conflicting schedules among project members as well as with local community partners. By utilizing the information we have gathered, one could survey the potential partners for feedback or plan a future fundraising event involving various community partners
On the mass of the neutron star in V395 Car/2S 0921-630
We report high-resolution optical spectroscopy of the low-mass X-ray binary
V395 Car/2S 0921-630 obtained with the MIKE echelle spectrograph on the
Magellan-Clay telescope. Our spectra are obtained near superior conjunction of
the mass donor star and we exploit the absorption lines originating from the
back-side of the K-type object to accurately derive its rotational velocity.
Using K0-K1 III templates, we find vsini=32.9 +/- 0.8 km/s. We show that the
choice of template star and the assumed limb darkening coefficient has little
impact on the derived rotational velocity. This value is a significant revision
downwards compared to previously published values. We derive new system
parameter constraints in the light of our much lower rotational velocity. We
find M_1=1.44 +/- 0.10 Msun, M_2=0.35 +/- 0.03 Msun, and q=0.24 +/- 0.02 where
the errors have been estimated through a Monte-Carlo simulation. A possible
remaining systematic effect is the fact that we may be over-estimating the
orbital velocity of the mass donor due to irradiation effects. However, any
correction for this effect will only reduce the compact object mass further,
down to a minimum mass of M_1=1.05 +/- 0.08 Msun. There is thus strong evidence
that the compact object in this binary is a neutron star of rather typical mass
and that the previously reported mass values of 2-4Msun were too high due to an
over-estimate of the rotational broadening.Comment: 4 pages, 3 figures, accepted for publication in ApJ Letter
Optical and Infrared Light Curves of the Eclipsing X-ray Binary V395 Car = 2S 0921-630
We present results of optical and infrared photometric monitoring of the
eclipsing low-mass X-ray binary V395 Car (2S 0921-630). Our observations reveal
a clear, repeating orbital modulation with an amplitude of about one magnitude
in B, and V and a little less in J. Combining our data with archival
observations spanning about 20 years, we derive an updated ephemeris with
orbital period 9.0026+/-0.0001d. We attribute the modulation to a combination
of the changing aspect of the irradiated face of the companion star and
eclipses of the accretion disk around the neutron star. Both appear to be
necessary as a secondary eclipse of the companion star is clearly seen. We
model the B, V, and J lightcurves using a simple model of an accretion disk and
companion star and find a good fit is possible for binary inclinations of
82.2+/-1.0 degrees. We estimate the irradiating luminosity to be about 8x10^35
erg/s, in good agreement with X-ray constraints.Comment: 6 pages, accepted for publication in MNRA
New ephemeris of the ADC source 2A 1822-371: a stable orbital-period derivative over 30 years
We report on a timing of the eclipse arrival times of the low mass X-ray
binary and X-ray pulsar 2A 1822-371 performed using all available observations
of the Proportional Counter Array on board the Rossi X-ray Timing Explorer,
XMM-Newton pn, and Chandra. These observations span the years from 1996 to
2008. Combining these eclipse arrival time measurements with those already
available covering the period from 1977 to 1996, we obtain an orbital solution
valid for more than thirty years. The time delays calculated with respect to a
constant orbital period model show a clear parabolic trend, implying that the
orbital period in this source constantly increases with time at a rate s/s. This is 3 orders of magnitude larger than
what is expected from conservative mass transfer driven by magnetic braking and
gravitational radiation. From the conservation of the angular momentum of the
system we find that to explain the high and positive value of the orbital
period derivative the mass transfer rate must not be less than 3 times the
Eddington limit for a neutron star, suggesting that the mass transfer has to be
partially non-conservative. With the hypothesis that the neutron star accretes
at the Eddington limit we find a consistent solution in which at least 70% of
the transferred mass has to be expelled from the system.Comment: Published by A&
Phase-resolved optical and X-ray spectroscopy of low-mass X-ray binary X1822-371
(Abridged) X1822-371 is the prototypical accretion disc corona X-ray source,
a low-mass X-ray binary viewed at very high inclination, thereby allowing the
disc structure and extended disc coronal regions to be visible. We study the
structure of the accretion disc in X1822-371 by modelling the phase-resolved
spectra both in optical and X-ray regime. We analyse high time resolution
optical ESO/VLT spectra of X1822-371 to study the variability in the emission
line profiles. In addition, we use data from XMM-Newton space observatory to
study phase-resolved as well as high resolution X-ray spectra. We apply the
Doppler tomography technique to reconstruct a map of the optical emission
distribution in the system. We fit multi-component models to the X-ray spectra.
We find that our results from both the optical and X-ray analysis can be
explained with a model where the accretion disc has a thick rim in the region
where the accretion stream impacts the disc. The behaviour of the H_beta line
complex implies that some of the accreting matter creates an outburst around
the accretion stream impact location and that the resulting outflow of matter
moves both away from the accretion disc and towards the centre of the disc.
Such behaviour can be explained by an almost isotropic outflow of matter from
the accretion stream impact region. The optical emission lines of HeII 4686 and
5411 show double peaked profiles, typical for an accretion disc at high
inclination. However, their velocities are slower than expected for an
accretion disc in a system like X1822-371. This, combined with the fact that
the HeII emission lines do not get eclipsed during the partial eclipse in the
continuum, suggests that the line emission does not originate in the orbital
plane and is more likely to come from above the accretion disc, for example the
accretion disc wind.Comment: 10 pages, 13 figures, accepted for publication in A&
XMM-Newton observations of UW CrB -- detection of X-ray bursts and evidence for accretion disc evolution
UW CrB (MS1603+2600) is a peculiar short period X-ray binary that exhibits
extraordinary optical behaviour. The optical light curve shape of the system
changes drastically from night to night, without any changes in overall
brightness. Here we report X-ray observations of UW CrB obtained with {\it
XMM-Newton}. We find evidence for several X-ray bursts confirming a neutron
star primary. This considerably strengthens the case that UW CrB is an
Accretion Disc Corona (ADC) system located at a distance of at least 5--7 kpc,
(3--5 kpc above the galactic plane). The X-ray and optical monitor
(UV+optical) light curves show remarkable shape variation from one observing
run to another, which we suggest are due to large scale variations in the
accretion disc shape resulting from a warp which periodically obscures the
optical and soft X-ray emission. This is also supported by the changes in
phase-resolved X-ray spectra.Comment: Accepted for publication in MNRA
The rotational broadening of V395 Car - implications on compact object's mass
CONTEXT: The masses previously obtained for the X-ray binary 2S0921-630
inferred a compact object that was either a high-mass neutron star or low-mass
black-hole, but used a previously published value for the rotational broadening
(vsini) with large uncertainties. AIMS: We aim to determine an accurate mass
for the compact object through an improved measurement of the secondary star's
projected equatorial rotational velocity. METHODS: We have used UVES echelle
spectroscopy to determine the vsini of the secondary star (V395 Car) in the
low-mass X-ray binary 2S0921-630 by comparison to an artificially broadened
spectral-type template star. In addition, we have also measured vsini from a
single high signal-to-noise ratio absorption line profile calculated using the
method of Least-Squares Deconvolution (LSD). RESULTS: We determine vsini to lie
between 31.3+/-0.5km/s to 34.7+/-0.5km/s (assuming zero and continuum limb
darkening, respectively) in disagreement with revious results based on
intermediate resolution spectroscopy obtained with the 3.6m NTT. Using our
revised vsini value in combination with the secondary star's radial velocity
gives a binary mass ratio of 0.281+/-0.034. Furthermore, assuming a binary
inclination angle of 75 degrees gives a compact object mass of 1.37+/-0.13Mo.
CONCLUSIONS: We find that using relatively low-resolution spectroscopy can
result in systemic uncertainties in the measured vsini values obtained using
standard methods. We suggest the use of LSD as a secondary, reliable check of
the results as LSD allows one to directly discern the shape of the absorption
line profile. In the light of the new vsini measurement, we have revised down
the compact object's mass, such that it is now compatible with a canonical
neutron star mass.Comment: 5 pages, 7 figures, accpeted by A
Near-infrared/optical identification of five low-luminosity X-ray pulsators
We present the identification of the most likely near-infrared/optical
counterparts of five low-luminosity X-ray pulsators (AX J1700.1-4157, AX
1740.1-2847, AX J1749.2-2725, AX J1820.5-1434 and AX J1832.3-0840) which have
long pulse periods (> 150 s). The X-ray properties of these systems suggest
that they are likely members of persistent high mass X-ray binaries or
intermediate polars. Using our Chandra observations, we detected the most
likely counterparts of three sources (excluding AX J1820.5-1434 and AX
J1832.3-0840) in their ESO - NTT near-infrared observations, and a possible
counterpart for AX J1820.5-1434 and AX J1832.3-0840 in the 2MASS and DSS
observations respectively. We also performed the X-ray timing and spectral
analysis for all the sources using our XMM-Newton observations, which further
helped us to constrain the nature of these systems. Our multiwavelength
observations suggest that AX J1749.2-2725 and AX J1820.5-1434 most likely
harbor accreting neutron stars while AX J1700.1-4157, AX J1740.1-2847 and AX
J1832.3-0840 could be intermediate polars.Comment: 11 pages, 5 figures, Submitted to MNRA
The Structure of the Accretion Disk in the ADC X-Ray Binary 4U 1822-371 at Optical and Ultraviolet Wavelengths
The eclipsing low-mass X-ray binary 4U 1822-371 is the prototypical accretion
disk corona (ADC) system. We have obtained new time-resolved UV spectroscopy of
4U 1822-371 with the Advanced Camera for Surveys/Solar Blind Channel (ACS/SBC)
on the Hubble Space Telescope (HST) and new V- and J-band photometry with the
1.3-m SMARTS telescope at CTIO. We use the new data to construct its UV/optical
spectral energy distribution and its orbital light curve in the UV, V, and J
bands. We derive an improved ephemeris for the optical eclipses and confirm
that the orbital period is changing rapidly, indicating extremely high rates of
mass flow in the system; and we show that the accretion disk in the system has
a strong wind with projected velocities up to 4000 km/s.
We show that the disk has a vertically-extended, optically-thick component at
optical wavelengths.This component extends almost to the edge of the disk and
has a height equal to ~0.5 of the disk radius. As it has a low brightness
temperature, we identify it as the optically-thick base of a disk wind, not as
the optical counterpart of the ADC. Like previous models of 4U 1822-371, ours
needs a tall obscuring wall near the edge of the accretion disk, but we
interpret the wall as a layer of cooler material at the base of the disk wind,
not as a tall, luminous disk rim.Comment: 37 pages, 12 figures, submitted to Ap
The radial velocity of the companion star in the low-mass X-ray binary 2S 0921-630: limits on the mass of the compact object
In this Paper we report on optical spectroscopic observations of the low-mass
X-ray binary 2S 0921-630 obtained with the Very Large Telescope. We found
sinusoidal radial velocity variations of the companion star with a
semi-amplitude of 99.1+-3.1 km s^-1 modulated on a period of 9.006+-0.007 days,
consistent with the orbital period found before for this source, and a systemic
velocity of 44.4+-2.4 km s^-1. Due to X-ray irradiation the centre-of-light
measured by the absorption lines from the companion star is likely shifted with
respect to the centre-of-mass. We try to correct for this using the so-called
K-correction. Conservatively applying the maximum correction possible and using
the previously measured rotational velocity of the companion star, we find a
lower limit to the mass of the compact object in 2S 0921-630 of M_X sin^3 i >
1.90+-0.25 Msun (1 sigma errors). The inclination in this system is well
constrained since partial eclipses have been observed in X-rays and optical
bands. For inclinations between 60< i<90 degrees we find
1.90+-0.25<M_X<2.9+-0.4 Msun. However, using this maximum K-correction we find
that the ratio between the mass of the companion star and that of the compact
object, q, is 1.32+-0.37 implying super-Eddington mass transfer rates; however,
evidence for that has not been found in 2S 0921-630. We conclude that the
compact object in 2S 0921-630 is either a (massive) neutron star or a low-mass
black hole.Comment: 6 pages, 3 figures, accepted for publication in MNRA
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