42 research outputs found
EIFIS: a modular extreme integral field spectrograph for the 10.4m GTC
EIFIS (Extreme Integral FIeld Spectrograph) is a modular integral field
spectrograph, based on image slicers, and makes use of new, large format
detectors. The concept is thought to cover the largest possible field of view
while producing spectroscopy over the complete optical range (3 000 - 10 000
\r{A}) at a medium resolving power of about 2400. In the optimal concept, each
module covers a field of view of 38" x 38" with 0.3" spaxels, which is fed into
a double spectrograph with common collimator optics. The blue arm covers the
spectral range between 3000 and 5600 \r{A} and the red arm between 5400 and
10100 \r{A}, allowing for an overlap range. The spectra are imaged onto 9.2k x
9.2k detectors using a double pseudoslit. The proposed design for the 10.4m
Gran Telescopio Canarias uses a total of 6 such modules to cover a total of
2.43 square arcminutes. Here we will present the conceptual design of the
instrument and a feasibility study of the optical and mechanical design of the
spectrographs. We discuss the limitations and alternative designs and its
potential to produce leading edge science in the era of extremely large
telescopes and the James Webb Space Telescope.Comment: Submitted to the Proceedings of the SPIE, Astronomical Telescopes and
Instrumentatio
NGC 2770 - a supernova Ib factory?
NGC 2770 has been the host of three supernovae of Type Ib during the last 10
years, SN 1999eh, SN 2007uy and SN 2008D. SN 2008D attracted special attention
due to the serendipitous discovery of an associated X-ray transient. In this
paper, we study the properties of NGC 2770 and specifically the three SN sites
to investigate whether this galaxy is in any way peculiar to cause a high
frequency of SNe Ib. We model the global SED of the galaxy from broadband data
and derive a star-formation and SN rate comparable to the values of the Milky
Way. We further study the galaxy using longslit spectroscopy covering the major
axis and the three SN sites. From the spectroscopic study we find subsolar
metallicities for the SN sites, a high extinction and a moderate star-formation
rate. In a high resolution spectrum, we also detect diffuse interstellar bands
in the line-of-sight towards SN 2008. A comparison of NGC 2770 to the global
properties of a galaxy sample with high SN occurance (at least 3 SN in the last
100 years) suggests that NGC 2770 is not particularly destined to produce such
an enhancement of observed SNe observed. Its properties are also very different
from gamma-ray burst host galaxies. Statistical considerations on SN Ib
detection rates give a probability of ~1.5% to find a galaxy with three Ib SNe
detected in 10 years. The high number of rare Ib SNe in this galaxy is
therefore likely to be a coincidence rather than special properties of the
galaxy itself. NGC 2770 has a small irregular companion, NGC 2770B, which is
highly starforming, has a very low mass and one of the lowest metallicities
detected in the nearby universe as derived from longslit spectroscopy. In the
most metal poor part, we even detect Wolf-Rayet features, against the current
models of WR stars which require high metallicities.Comment: 15 pages, 10 figures, submitted to Ap
A revised host galaxy association for GRBÂ 020819B: a high-redshift dusty starburst, not a low-redshift gas-poor spiral
The purported spiral host galaxy of GRB 020819B at z = 0.41 has been seminal in establishing our view of the diversity of long-duration gamma-ray burst environments: Optical spectroscopy of this host provided evidence that gamma-ray bursts (GRBs) can form even at high metallicities, whereas millimetric observations suggested that GRBs may preferentially form in regions with minimal molecular gas. We report new observations from the Very Large Telescope (Multi Unit Spectroscopic Explorer and X-shooter), which demonstrate that the purported host is an unrelated foreground galaxy. The probable radio afterglow is coincident with a compact, highly star forming, dusty galaxy at z = 1.9621. The revised redshift naturally explains the apparent non-detection of CO (3–2) line emission at the afterglow site from the Atacama Large Millimetre Observatory. There is no evidence that molecular gas properties in GRB host galaxies are unusual, and limited evidence that GRBs can form readily at a super-Solar metallicity
The Exotic Type Ic Broad-Lined Supernova SN 2018gep: Blurring the Line Between Supernovae and Fast Optical Transients
In the last decade a number of rapidly evolving transients have been
discovered that are not easily explained by traditional supernovae models. We
present optical and UV data on onee such object, SN 2018gep, that displayed a
fast rise with a mostly featureless blue continuum around maximum light, and
evolved to develop broad features more typical of a SN Ic-bl while retaining
significant amounts of blue flux throughout its observations. The blue excess
is most evident in its near-UV flux that is over 4 magnitudes brighter than
other stripped envelope supernovae, but also visible in optical gr colors at
early times. Its fast rise time of days
puts it squarely in the emerging class of Fast Evolving Luminous Transients, or
Fast Blue Optical Transients. With a peak absolute magnitude of M mag it is on the extreme end of both the rise time and peak magnitude
distribution for SNe Ic-bl. Only one other SN Ic-bl has similar properties,
iPTF16asu, for which less of the important early time and UV data have been
obtained. We show that the objects SNe 2018gep and iPTF16asu have similar
photometric and spectroscopic properties and that they overall share many
similarities with both SNe Ic-bl and Fast Evolving Transients. We obtain IFU
observations of the SN 2018gep host galaxy and derive a number of properties
for it. We show that the derived host galaxy properties for both SN 2018gep and
iPTF16asu are overall consistent with the SNe Ic-bl and GRB/SNe sample while
being on the extreme edge of the observed Fast Evolving Transient sample. These
photometric observations are consistent with a simple SN Ic-bl model that has
an additional form of energy injection at early times that drives the observed
rapid, blue rise, and we speculate that this additional power source may
extrapolate to the broader Fast Evolving Transient sample
Prevention and Intervention Studies with Telmisartan, Ramipril and Their Combination in Different Rat Stroke Models
The effects of AT1 receptor blocker, telmisartan, and the ACE inhibitor, ramipril, were tested head-to head and in combination on stroke prevention in hypertensive rats and on potential neuroprotection in acute cerebral ischemia in normotensive rats. Normotensive Wistar rats were treated s.c. 5 days prior to middle cerebral artery occlusion (MCAO) for 90 min with reperfusion. Groups (n = 10 each): (1) sham, (2) vehicle (V; 0,9% NaCl), (3) T (0,5 mg/kg once daily), (4) R (0,01 mg/kg twice daily), (5) R (0,1 mg/kg twice daily) or (6) T (0,5 mg/kg once daily) plus R (0,01 mg/kg twice daily). Twenty-four and 48 h after MCAO, neurological outcome (NO) was determined. Forty-eight h after MCAO, infarct volume by MRI, neuronal survival, inflammation factors and neurotrophin receptor (TrkB) were analysed.Stroke incidence was reduced, survival was prolonged and neurological outcome was improved in all treated SHR-SP with no differences between treated groups. In the acute intervention study, T and T+R, but not R alone, improved NO, reduced infarct volume, inflammation (TNFα), and induced TrkB receptor and neuronal survival in comparison to V.T, R or T+R had similar beneficial effects on stroke incidence and NO in hypertensive rats, confirming BP reduction as determinant factor in stroke prevention. In contrast, T and T+R provided superior neuroprotection in comparison to R alone in normotensive rats with induced cerebral ischemia
Prompt emission and early optical afterglow of very-high-energy detected GRB 201015A and GRB 201216C : onset of the external forward shock
We present a detailed prompt emission and early optical afterglow analysis of the two very-high-energy (VHE) detected bursts GRB 201015A and GRB 201216C, and their comparison with a subset of similar bursts. Time-resolved spectral analysis of multistructured GRB 201216C using the Bayesian binning algorithm revealed that during the entire duration of the burst, the low-energy spectral index (αpt) remained below the limit of the synchrotron line of death. However, statistically some of the bins supported the additional thermal component. Additionally, the evolution of spectral parameters showed that both the peak energy (Ep) and αpt tracked the flux. These results were further strengthened using the values of the physical parameters obtained by synchrotron modeling of the data. Our earliest optical observations of both bursts using the F/Photometric Robotic Atmospheric Monitor Observatorio del Roque de los Muchachos and Burst Observer and Optical Transient Exploring System robotic telescopes displayed a smooth bump in their early optical light curves, consistent with the onset of the afterglow due to synchrotron emission from an external forward shock. Using the observed optical peak, we constrained the initial bulk Lorentz factors of GRB 201015A and GRB 201216C to Γ0 = 204 and Γ0 = 310, respectively. The present early optical observations are the earliest known observations constraining outflow parameters and our analysis indicate that VHE detected bursts could have a diverse range of observed luminosity within the detectable redshift range of present VHE facilities