61 research outputs found
A Possible Cepheid-Like Luminosity Estimator for the Long Gamma-Ray Bursts
We present a possible Cepheid-like luminosity estimator for the long
gamma-ray bursts based on the variability of their light curves. To construct
the luminosity estimator, we use CGRO/BATSE data for 13 bursts, Wind/KONUS data
for 5 bursts, Ulysses/GRB data for 1 burst, and NEAR/XGRS data for 1 burst.
Spectroscopic redshifts, peak fluxes, and high resolution light curves are
available for 11 of these bursts; partial information is available for the
remaining 9 bursts. We find that the isotropic-equivalent luminosities L of
these bursts positively correlate with a rigorously-constructed measure V of
the variability of their light curves. We fit a model to these data that
accommodates both intrinsic scatter (statistical variance) and extrinsic
scatter (sample variance). If one excludes GRB 980425 from the fit on the
grounds that its association with SN 1998bw at a redshift of z = 0.0085 is not
secure, the luminosity estimator spans approx. 2.5 orders of magnitude in L,
and the slope of the correlation between L and V is positive with a probability
of 1 - 1.4 x 10^-4 (3.8 sigma). Although GRB 980425 is excluded from this fit,
its L and V values are consistent with the fitted model, which suggests that
GRB 980425 may well be associated with SN 1998bw, and that GRB 980425 and the
cosmological bursts may share a common physical origin. If one includes GRB
980425 in the fit, the luminosity estimator spans approx. 6.3 orders of
magnitude in L, and the slope of the correlation is positive with a probability
of 1 - 9.3 x 10^-7 (4.9 sigma). Independently of whether or not GRB 980425
should be included in the fit, its light curve is unique in that it is much
less variable than the other approx. 17 light curves in our sample for which
the signal-to-noise is reasonably good.Comment: Accepted to The Astrophysical Journal, 31 pages, 13 figures, LaTe
Planetary Collisions outside the Solar System: Time Domain Characterization of Extreme Debris Disks
Luminous debris disks of warm dust in the terrestrial planet zones around
solar-like stars are recently found to vary, indicative of ongoing large-scale
collisions of rocky objects. We use Spitzer 3.6 and 4.5 {\mu}m time-series
observations in 2012 and 2013 (extended to 2014 in one case) to monitor 5 more
debris disks with unusually high fractional luminosities ("extreme debris
disk"), including P1121 in the open cluster M47 (80 Myr), HD 15407A in the AB
Dor moving group (80 Myr), HD 23514 in the Pleiades (120 Myr), HD 145263 in the
Upper Sco Association (10 Myr), and the field star BD+20 307 (>1 Gyr). Together
with the published results for ID8 in NGC 2547 (35 Myr), this makes the first
systematic time-domain investigation of planetary impacts outside the solar
system. Significant variations with timescales shorter than a year are detected
in five out of the six extreme debris disks we have monitored. However,
different systems show diverse sets of characteristics in the time domain,
including long-term decay or growth, disk temperature variations, and possible
periodicity.Comment: 50 pages, 14 figures, 9 tables; Accepted for publication in the
Astrophysical Journa
Photometric Observations of Three High Mass X-Ray Binaries and a Search for Variations Induced by Orbital Motion
We searched for long period variation in V-band, Ic-band and RXTE X-ray light
curves of the High Mass X-ray Binaries (HMXBs) LS 1698 / RX J1037.5-5647, HD
110432 / 1H 1249-637 and HD 161103 / RX J1744.7-2713 in an attempt to discover
orbitally induced variation. Data were obtained primarily from the ASAS
database and were supplemented by shorter term observations made with the 24-
and 40-inch ANU telescopes and one of the robotic PROMPT telescopes. Fourier
periodograms suggested the existence of long period variation in the V-band
light curves of all three HMXBs, however folding the data at those periods did
not reveal convincing periodic variation. At this point we cannot rule out the
existence of long term V-band variation for these three sources and hints of
longer term variation may be seen in the higher precision PROMPT data. Long
term V-band observations, on the order of several years, taken at a frequency
of at least once per week and with a precision of 0.01 mag, therefore still
have a chance of revealing long term variation in these three HMXBs.Comment: Accepted, RAA, May, 201
Sloan Digital Sky Survey Multicolor Observations of GRB010222
The discovery of an optical counterpart to GRB010222 (detected by BeppoSAX;
Piro 2001) was announced 4.4 hrs after the burst by Henden (2001a). The Sloan
Digital Sky Survey's 0.5m photometric telescope (PT) and 2.5m survey telescope
were used to observe the afterglow of GRB010222 starting 4.8 hours after the
GRB. The 0.5m PT observed the afterglow in five, 300 sec g' band exposures over
the course of half an hour, measuring a temporal decay rate in this short
period of F_nu \propto t^{-1.0+/-0.5}. The 2.5m camera imaged the counterpart
nearly simultaneously in five filters (u' g' r' i' z'), with r' = 18.74+/-0.02
at 12:10 UT. These multicolor observations, corrected for reddening and the
afterglow's temporal decay, are well fit by the power-law F_nu \propto
nu^{-0.90+/-0.03} with the exception of the u' band UV flux which is 20% below
this slope. We examine possible interpretations of this spectral shape,
including source extinction in a star forming region.Comment: 8 pages, 4 figures, accepted for publication in ApJ. Two figures
added, minor changes to text in this draft. Related material can be found at:
http://sdss.fnal.gov:8000/grb
Large Impacts around a Solar Analog Star in the Era of Terrestrial Planet Formation
The final assembly of terrestrial planets occurs via massive collisions,
which can launch copious clouds of dust that are warmed by the star and glow in
the infrared. We report the real-time detection of a debris-producing impact in
the terrestrial planet zone around a 35-million year-old solar analog star. We
observed a substantial brightening of the debris disk at 3-5 {\mu}m, followed
by a decay over a year, with quasi-periodic modulations of the disk flux. The
behavior is consistent with the occurrence of a violent impact that produced
vapor out of which a thick cloud of silicate spherules condensed that were
ground into dust by collisions. These results demonstrate how the time domain
can become a new dimension for the study of terrestrial planet formation.Comment: 25 pages, 7 figures (fixed a typo in name
SARS-CoV-2 entry factors are highly expressed in nasal epithelial cells together with innate immune genes.
We investigated SARS-CoV-2 potential tropism by surveying expression of viral entry-associated genes in single-cell RNA-sequencing data from multiple tissues from healthy human donors. We co-detected these transcripts in specific respiratory, corneal and intestinal epithelial cells, potentially explaining the high efficiency of SARS-CoV-2 transmission. These genes are co-expressed in nasal epithelial cells with genes involved in innate immunity, highlighting the cells' potential role in initial viral infection, spread and clearance. The study offers a useful resource for further lines of inquiry with valuable clinical samples from COVID-19 patients and we provide our data in a comprehensive, open and user-friendly fashion at www.covid19cellatlas.org.This work was supported by the Wellcome Sanger Institute core funding (WT206194) and the Wellcome Strategic Scientific Support award âPilot projects for the Human Cell Atlasâ (WT211276/Z/18/Z), a Seed Network grant from the Chan Zuckerberg Initiative to P.B., T.D., T.E.D., O.E., P.H., N.H., N.K., M.K., K.B.M., A.M., M.C.N., M.N., D.P., J.R., P.R.T., S.Q., A.R., O.R., M.S., J.S., J.G.S., C.E.S., H.B.S., D.S., A.T., J.W. and K.Z. and by the European Unionâs H2020 research and innovation program under grant agreement No 874656 (discovAIR) to P.B., A.B., M.K., S.L., J.L., K.B.M., M.C.N., K.S.P., C.S., H.B.S., J.S., F.J.T. and M.vd.B. W.S. acknowledges funding from the Newton Fund, Medical Research Council (MRC), The Thailand Research Fund (TRF), and Thailandâs National Science and Technology Development Agency (NSTDA). M.C.N acknowledges funding from GSK Ltd, Netherlands Lung Foundation project no. 5.1.14.020 and 4.1.18.226. T.D. acknowledges funding from HubMap consortium and Stanford Child Health Research Institute- Woods Family Faculty Scholarship. T.E.D. acknowledges funding from HubMap. P.H. acknowledges funding from LENDULET-BIOMAG Grant (2018-342) and the European Regional Development Funds (GINOP-2.3.2-15-2016-00006, GINOP-2.3.2-15-2016-00026, GINOP-2.3.2-15-2016-00037). J.L.B. acknowledges funding from Medical Research Council (MRC), and the UK Regenerative Medicine Platform (MR/ 5005579/1). P.B. acknowledges funding from Fondation pour la Recherche MĂ©dicale (DEQ20180339158), Agence Nationale de la Recherche (UCAJEDI, ANR-15-IDEX-01; SAHARRA, ANR-19-CE14-0027; France GĂ©nomique, ANR-10-INBS-09-03), and Conseil DĂ©partemental des Alpes Maritimes (2016-294DGADSH-CV; 2019-390DGADSH-CV). N.E.B. and J.K. acknowledge funding from NIH grant R01HL145372 and DOD grant W81XWH1910416. I.G. acknowledges funding from NIH (5R24HD000836) and the Eunice Kennedy Shriver National Institute of Child Health and Human. N.H., J.G.S. and C.E.S. acknowledge funding by the Leducq foundation. N.H. is recipient of an ERC Advanced Grant. J.K. acknowledges funding from NIH grant K08HL130595 and the Doris Duke Charitable Foundation. N.K. acknowledges funding from NIH grants R01HL127349, U01HL145567 and an unrestricted grant from Three Lakes Foundation. M.K. acknowledges HHMI and Wall Center for Pulmonary Vascular Disease. H.L. acknowledges funding from National Research Foundation of Korea. K.M. acknowledges funding from Wellcome Trust. A.M. acknowledges funding from NIH grants HL135124, AG049665 and AI135964. M.Z.N. acknowledges funding from Rutherford Fund Fellowship allocated by the Medical Research Council and the UK Regenerative Medicine Platform (MR/ 5005579/1 to M.Z.N.). M.Z.N. and M.Y. have been funded by the Rosetrees Grant (Grant number M899). M.N. acknowledges funding from a BHF/DZHK grant and British Heart Foundation (PG/16/47/32156). J.O.-M. acknowledges funding from Richard and Susan Smith Family Foundation. D.P. acknowledges funding from Alan and Sandra Gerry Metastasis and Tumor Ecosystems Center. J.P. acknowledges funding from National Health and Medical Research Council. P.R.T. acknowledges funding from R01HL146557 from NHLBI/NIH. E.L.R. acknowledges funding from MRC MR/P009581/1 and MR/SO35907/1. A.R. and O. R. acknowledge HHMI, the Klarman Cell Observatory, and the Manton Foundation. K.S.-P. acknowledges NIHR Cambridge Biomedical Research Centre. C.S. acknowledges Swedish research Council, Swedish Cancer Society, and CPI. H.B.S. acknowledges German Center for Lung Research and Helmholtz Association. J.S. acknowledges Boehringer Ingelheim, by the German Research Foundation (DFG; EXC2151/1, ImmunoSensation2 - the immune sensory system, project number 390873048), project numbers 329123747, 347286815) and by the HGF grant sparse2big. A.K.S. acknowledges the Beckman Young Investigator Program, a Sloan Fellowship in Chemistry, the NIH (5U24AI118672), and the Bill and Melinda Gates Foundation. F.J.T. acknowledges the German Center for Lung Research. M.vd.B. acknowledges from Ministry of Economic Affairs and Climate Policy by means of the PPP. K.B.W. is funded by the University College London-Birkbeck MRC Doctoral Training Programme. J.W. and Y.Y. acknowledge NIH, U01 HL148856 LungMap Phase II. R.X. acknowledges the NIH (DK043351). H.Z. is supported by the National Key R&D Program (no. 2019YFA0801703) and National Natural Science Foundation of China (no. 31871370
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
The Highly Energetic Expansion of SN2010bh Associated with GRB 100316D
We present the spectroscopic and photometric evolution of the nearby (z =
0.059) spectroscopically confirmed type Ic supernova, SN 2010bh, associated
with the soft, long-duration gamma-ray burst (X-ray flash) GRB 100316D.
Intensive follow-up observations of SN 2010bh were performed at the ESO Very
Large Telescope (VLT) using the X-shooter and FORS2 instruments. Owing to the
detailed temporal coverage and the extended wavelength range (3000--24800 A),
we obtained an unprecedentedly rich spectral sequence among the hypernovae,
making SN 2010bh one of the best studied representatives of this SN class. We
find that SN 2010bh has a more rapid rise to maximum brightness (8.0 +/- 1.0
rest-frame days) and a fainter absolute peak luminosity (L_bol~3e42 erg/s) than
previously observed SN events associated with GRBs. Our estimate of the ejected
(56)Ni mass is 0.12 +/- 0.02 Msun. From the broad spectral features we measure
expansion velocities up to 47,000 km/s, higher than those of SNe 1998bw (GRB
980425) and 2006aj (GRB 060218). Helium absorption lines He I lambda5876 and He
I 1.083 microm, blueshifted by ~20,000--30,000 km/s and ~28,000--38,000 km/s,
respectively, may be present in the optical spectra. However, the lack of
coverage of the He I 2.058 microm line prevents us from confirming such
identifications. The nebular spectrum, taken at ~186 days after the explosion,
shows a broad but faint [O I] emission at 6340 A. The light-curve shape and
photospheric expansion velocities of SN 2010bh suggest that we witnessed a
highly energetic explosion with a small ejected mass (E_k ~ 1e52 erg and M_ej ~
3 Msun). The observed properties of SN 2010bh further extend the heterogeneity
of the class of GRB supernovae.Comment: 37 pages and 12 figures (one-column pre-print format), accepted for
publication in Ap
Spectroscopic Target Selection for the Sloan Digital Sky Survey: The Luminous Red Galaxy Sample
We describe the target selection and resulting properties of a spectroscopic
sample of luminous, red galaxies (LRG) from the imaging data of the Sloan
Digital Sky Survey (SDSS). These galaxies are selected on the basis of color
and magnitude to yield a sample of luminous, intrinsically red galaxies that
extends fainter and further than the main flux-limited portion of the SDSS
galaxy spectroscopic sample. The sample is designed to impose a
passively-evolving luminosity and rest-frame color cut to a redshift of 0.38.
Additional, yet more luminous, red galaxies are included to a redshift of 0.5.
Approximately 12 of these galaxies per square degree are targeted for
spectroscopy, so the sample will number over 100,000 with the full survey. SDSS
commissioning data indicate that the algorithm efficiently selects luminous
(M_g=-21.4), red galaxies, that the spectroscopic success rate is very high,
and that the resulting set of galaxies is approximately volume-limited out to
z=0.38. When the SDSS is complete, the LRG spectroscopic sample will fill over
1h^-3 Gpc^3 with an approximately homogeneous population of galaxies and will
therefore be well suited to studies of large-scale structure and clusters out
to z=0.5.Comment: 30 pages, LaTeX. Accepted to the Astronomical Journa
- âŠ