Apollo 7 retrofire and reentry of service propulsion module. Further study of Intelsat 2 F-2 apogee burn

Photography of Apollo 7 retrofire and service propulsion module reentry and apogee burn of Intelsat 2 F-2 satellit

The Host Galaxy of GRB980703 at Radio Wavelengths - a Nuclear Starburst in a ULIRG

We present radio observations of GRB980703 at 1.43, 4.86, and 8.46 GHz for the period of 350 to 1000 days after the burst. These radio data clearly indicate that there is a persistent source at the position of GRB980703 with a flux density of approximately 70 $\mu$Jy at 1.43 GHz, and a spectral index, $\beta\approx 0.32$, where $F_\nu\propto \nu^{-\beta}$. We show that emission from the afterglow of GRB980703 is expected to be one to two orders of magnitude fainter, and therefore cannot account for these observations. We interpret this persistent emission as coming from the host galaxy --- the first example of a gamma-ray burst (GRB) host detection at radio wavelengths. We show that emission from an AGN is unlikely, and find that it can be explained as a result of a star-formation rate (SFR) of massive stars (M>5M$_\odot$) of 90 M$_\odot$/yr, which gives a total SFR of $\approx 500$ M$_\odot$/yr. Using the correlation between the radio and far-IR (FIR) luminosities of star-forming galaxies, we find that the host of GRB980703 is at the faint end of the class of Ultra Luminous Infrared Galaxies (ULIRGs), with L_{FIR}\sim few\times 10^{12} L$_\odot$. From the radio measurements of the offset between the burst and the host, and the size of the host, we conclude that GRB980703 occurred near the center of the galaxy in a region of maximum star formation. A comparison of the properties of this galaxy with radio and optical surveys at a similar redshift ($z\approx 1$) reveals that the host of GRB980703 is an average star-forming galaxy. This result has significant implications for the potential use of a GRB-selected galaxy sample for the study of galaxies and the IGM at high redshifts.Comment: Submitted to Ap

The pre-WDVV ring of physics and its topology

We show how a simplicial complex arising from the WDVV (Witten-Dijkgraaf-Verlinde-Verlinde) equations of string theory is the Whitehouse complex. Using discrete Morse theory, we give an elementary proof that the Whitehouse complex $\Delta_n$ is homotopy equivalent to a wedge of $(n-2)!$ spheres of dimension $n-4$. We also verify the Cohen-Macaulay property. Additionally, recurrences are given for the face enumeration of the complex and the Hilbert series of the associated pre-WDVV ring.Comment: 13 pages, 4 figures, 2 table

Cellular structure of qq-Brauer algebras

In this paper we consider the $q$-Brauer algebra over $R$ a commutative noetherian domain. We first construct a new basis for $q$-Brauer algebras, and we then prove that it is a cell basis, and thus these algebras are cellular in the sense of Graham and Lehrer. In particular, they are shown to be an iterated inflation of Hecke algebras of type $A_{n-1}.$ Moreover, when $R$ is a field of arbitrary characteristic, we determine for which parameters the $q$-Brauer algebras are quasi-heredity. So the general theory of cellular algebras and quasi-hereditary algebras applies to $q$-Brauer algebras. As a consequence, we can determine all irreducible representations of $q$-Brauer algebras by linear algebra methods

The Locations of Gamma-Ray Bursts Measured by COMPTEL

The COMPTEL instrument on the Compton Gamma Ray Observatory is used to measure the locations of gamma-ray bursts through direct imaging of MeV photons. In a comprehensive search, we have detected and localized 29 bursts observed between 1991 April 19 and 1995 May 31. The average location accuracy of these events is 1.25\arcdeg (1$\sigma$), including a systematic error of \sim0.5\arcdeg, which is verified through comparison with Interplanetary Network (IPN) timing annuli. The combination of COMPTEL and IPN measurements results in locations for 26 of the bursts with an average ``error box'' area of only $\sim$0.3 deg$^2$ (1$\sigma$). We find that the angular distribution of COMPTEL burst locations is consistent with large-scale isotropy and that there is no statistically significant evidence of small-angle auto-correlations. We conclude that there is no compelling evidence for burst repetition since no more than two of the events (or $\sim$7% of the 29 bursts) could possibly have come from the same source. We also find that there is no significant correlation between the burst locations and either Abell clusters of galaxies or radio-quiet quasars. Agreement between individual COMPTEL locations and IPN annuli places a lower limit of $\sim$100~AU (95% confidence) on the distance to the stronger bursts.Comment: Accepted for publication in the Astrophysical Journal, 1998 Jan. 1, Vol. 492. 33 pages, 9 figures, 5 table

INTEGRAL upper limits on gamma-ray emission associated with the gravitational wave event GW150914

Using observations of the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL), we put upper limits on the gamma-ray and hard X-ray prompt emission associated with the gravitational wave event GW150914, discovered by the LIGO/Virgo collaboration. The omni-directional view of the INTEGRAL/SPI-ACS has allowed us to constrain the fraction of energy emitted in the hard X-ray electromagnetic component for the full high-probability sky region of LIGO trigger. Our upper limits on the hard X-ray fluence at the time of the event range from $F_{\gamma}=2 \times 10^{-8}$ erg cm$^{-2}$ to $F_{\gamma}=10^{-6}$ erg cm$^{-2}$ in the 75 keV - 2 MeV energy range for typical spectral models. Our results constrain the ratio of the energy promptly released in gamma-rays in the direction of the observer to the gravitational wave energy E$_\gamma/$E$_\mathrm{GW}<10^{-6}$. We discuss the implication of gamma-ray limits on the characteristics of the gravitational wave source, based on the available predictions for prompt electromagnetic emission.Comment: accepted for publication in ApJ