Садржај
Слике
Уплоадјуј своје слике
DSS Images Other Images
Везани чланци
Late-Time Radio Observations of 68 Type Ibc Supernovae: Strong Constraints on Off-Axis Gamma-Ray Bursts
We present late-time radio observations of 68 local Type Ibc supernovae,including six events with broad optical absorption lines(``hypernovae''). None of these objects exhibit radio emissionattributable to off-axis gamma-ray burst jets spreading into our line ofsight. Comparison with our afterglow models reveals the followingconclusions. (1) Less than ~10% of Type Ibc supernovae are associatedwith typical gamma-ray bursts initially directed away from our line ofsight; this places an empirical constraint on the GRB beaming factor of<~104, corresponding toan average jet opening angle, θj>~0.8d. (2) Thisholds in particular for the broad-lined supernovae (SNe 1997dq, 1997ef,1998ey, 2002ap, 2002bl, and 2003jd), which have been argued to host GRBjets. Our observations reveal no evidence for typical (or evensubenergetic) GRBs and rule out the scenario in which every broad-linedSN harbors a GRB at the 84% confidence level. Their large photosphericvelocities and asymmetric ejecta (inferred from spectropolarimetry andnebular spectroscopy) appear to be characteristic of the nonrelativisticSN explosion and do not necessarily imply the existence of associatedGRB jets.
| The SAI Catalog of Supernovae and Radial Distributions of Supernovae of Various Types in Galaxies
We describe the Sternberg Astronomical Institute (SAI) catalog ofsupernovae. We show that the radial distributions of type-Ia, type-Ibc,and type-II supernovae differ in the central parts of spiral galaxiesand are similar in their outer regions, while the radial distribution oftype-Ia supernovae in elliptical galaxies differs from that in spiraland lenticular galaxies. We give a list of the supernovae that arefarthest from the galactic centers, estimate their relative explosionrate, and discuss their possible origins.
| The UZC-SSRS2 Group Catalog
We apply a friends-of-friends algorithm to the combined Updated ZwickyCatalog and Southern Sky Redshift Survey to construct a catalog of 1168groups of galaxies; 411 of these groups have five or more members withinthe redshift survey. The group catalog covers 4.69 sr, and all groupsexceed the number density contrast threshold, δρ/ρ=80. Wedemonstrate that the groups catalog is homogeneous across the twounderlying redshift surveys; the catalog of groups and their membersthus provides a basis for other statistical studies of the large-scaledistribution of groups and their physical properties. The medianphysical properties of the groups are similar to those for groupsderived from independent surveys, including the ESO Key Programme andthe Las Campanas Redshift Survey. We include tables of groups and theirmembers.
| Optical Spectroscopy of Type IB/C Supernovae
We present 84 spectra of Type Ib/c and Type IIb supernovae (SNe),describing the individual SNe in detail. The relative depths of thehelium absorption lines in the spectra of the SNe Ib appear to provide ameasurement of the temporal evolution of the SN, with He I λ5876and He I λ7065 growing in strength relative to He I λ6678over time. Light curves for three of the SNe Ib provide a sequence forcorrelating the helium line strengths. We find that some SNe Ic showevidence for weak helium absorption, but most do not. Aside from thepresence or absence of the helium lines, there are other spectroscopicdifferences between SNe Ib and SNe Ic. On average, the O I λ7774line is stronger in SNe Ic than in SNe Ib. In addition, the SNe Ic havedistinctly broader emission lines at late times, indicating aconsistently larger explosion energy and/or lower envelope mass for SNeIc than for SNe Ib. While SNe Ib appear to be basically homogeneous, theSNe Ic are quite heterogeneous in their spectroscopic characteristics.Three SNe Ic that may have been associated with gamma-ray bursts arealso discussed; two of these have clearly peculiar spectra, while thethird seems fairly typical.
| Arcsecond Positions of UGC Galaxies
We present accurate B1950 and J2000 positions for all confirmed galaxiesin the Uppsala General Catalog (UGC). The positions were measuredvisually from Digitized Sky Survey images with rms uncertaintiesσ<=[(1.2")2+(θ/100)2]1/2,where θ is the major-axis diameter. We compared each galaxymeasured with the original UGC description to ensure high reliability.The full position list is available in the electronic version only.
| Supernovae discovered in the period of July 1996-June 1997 at the BAO.
Not Available
| Supernova 1997C in NGC 3160
IAUC 6536 available at Central Bureau for Astronomical Telegrams.
| Supernova 1997C in NGC 3160.
Not Available
| An image database. II. Catalogue between δ=-30deg and δ=70deg.
A preliminary list of 68.040 galaxies was built from extraction of35.841 digitized images of the Palomar Sky Survey (Paper I). For eachgalaxy, the basic parameters are obtained: coordinates, diameter, axisratio, total magnitude, position angle. On this preliminary list, weapply severe selection rules to get a catalog of 28.000 galaxies, wellidentified and well documented. For each parameter, a comparison is madewith standard measurements. The accuracy of the raw photometricparameters is quite good despite of the simplicity of the method.Without any local correction, the standard error on the total magnitudeis about 0.5 magnitude up to a total magnitude of B_T_=17. Significantsecondary effects are detected concerning the magnitudes: distance toplate center effect and air-mass effect.
|
Додај нови чланак
Линкови у сродству са темом
Додај нови линк
Чланови следећих група \:
|
Посматрања и Астрометриски подаци
Каталог и designations:
|
