- ID:
- ivo://CDS.VizieR/J/ApJ/720/862
- Title:
- Afterglow light curve of GRB 090926A
- Short Name:
- J/ApJ/720/862
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present VLT/FORS2 spectroscopy and Gamma-ray Optical/Near-Infrared Detector optical/near-IR photometry of the afterglow of the bright Fermi/LAT GRB 090926A. The spectrum shows prominent Lyman-{alpha} absorption with N_HI_=10^21.73+/-0.07^cm^-2^ and a multitude of metal lines at a common redshift of z=2.1062+/-0.0004, which we associate with the redshift of the gamma-ray burst (GRB). The metallicity derived from SII is log(Z/Z_{sun}_)~-1.9, one of the lowest values ever found in a GRB Damped Lyman-{alpha} (DLA) system. This confirms that the spread of metallicity in GRB-DLAs at z~2 is at least two orders of magnitude. We argue that this spread in metallicity does not require a similar range in abundances of the GRB progenitors, since the neutral interstellar medium probed by the DLA is expected to be at a significant distance from the explosion site. The hydrogen column density derived from the Swift/XRT afterglow spectrum (assuming log(Z/Z_{sun}_)~-1.9) is ~100 times higher than the N_HI_ obtained from the Lyman-{alpha} absorptions. This suggests either a large column density of ionized gas or a higher metallicity of the circum-burst medium compared to the gas traced by the DLA. We also discuss the afterglow light curve evolution and energetics. The absence of a clear jet-break like steeping until at least 21 days post-burst suggests a beaming-corrected energy release of E_{gamma}_>3.5x10^52^erg, indicating that GRB 090926A may have been one of the most energetic bursts ever detected.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/701/824
- Title:
- Afterglows of short and long-duration GRBs
- Short Name:
- J/ApJ/701/824
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comparative study of the observed properties of the optical and X-ray afterglows of short- and long-duration {gamma}-ray bursts (GRBs). Using a large sample of 37 short and 421 long GRBs, we find a strong correlation between the afterglow brightness measured after 11hr and the observed fluence of the prompt emission. Both the optical (R band) and X-ray flux densities (F_R_ and F_X_) scale with the {gamma}-ray fluence, F_{gamma}_. For bursts with a known redshift, a tight correlation exists between the afterglow flux densities at 11hr (rest frame) and the total isotropic {gamma}-ray energy, E_{gamma},ISO_: F_R,X_{prop.to}E_{gamma},ISO_^{alpha}^, with {alpha}~1.
- ID:
- ivo://CDS.VizieR/J/AJ/149/68
- Title:
- A-F type variable stars from Kepler
- Short Name:
- J/AJ/149/68
- Date:
- 03 Dec 2021 00:36:02
- Publisher:
- CDS
- Description:
- The light curves of 2768 stars with effective temperatures and surface gravities placing them near the gamma Doradus ({gamma} Dor)/delta Scuti ({delta} Sct) instability region were observed as part of the Kepler Guest Observer program from Cycles 1 through 5. The light curves were analyzed in a uniform manner to search for {gamma} Dor, {delta} Sct, and hybrid star pulsations. The {gamma} Dor, {delta} Sct, and hybrid star pulsations extend asteroseismology to stars slightly more massive (1.4-2.5M_{sun}_) than our Sun. We find 207 {gamma} Dor, 84 {delta} Sct, and 32 hybrid candidate stars. Many of these stars are cooler than the red edge of the {gamma} Dor instability strip as determined from ground-based observations made before Kepler. A few of our {gamma} Dor candidate stars lie on the hot side of the ground-based {gamma} Dor instability strip. The hybrid candidate stars cover the entire region between 6200K and the blue edge of the ground-based {delta} Sct instability strip. None of our candidate stars are hotter than the hot edge of the ground-based {delta} Sct instability strip. Our discoveries, coupled with the work of others, show that Kepler has discovered over 2000 {gamma} Dor, {delta} Sct, and hybrid star candidates in the 116 square degree Kepler field of view. We found relatively few variable stars fainter than magnitude 15, which may be because they are far enough away to lie between spiral arms in our Galaxy, where there would be fewer stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/693/1840
- Title:
- A3266 galaxies at 24um
- Short Name:
- J/ApJ/693/1840
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Multiband Imaging Photometer observations of the cluster A3266. About 100 spectroscopic cluster members have been detected at 24um. The infrared (IR) luminosity function (LF) in A3266 is very similar to that in the Coma cluster down to the detection limit LIR~10^43^erg/s, suggesting a universal form of the bright-end IR LF for local rich clusters with M~10^15^M_{sun}_. The shape of the bright end of the A3266-Coma composite IR LF is not significantly different from that of nearby field galaxies, but the fraction of IR-bright galaxies (star formation rate (SFR)>0.2M_{sun}_/yr) in both clusters increases with cluster-centric radius. The decrease of the blue galaxy fraction toward the high-density cores only accounts for part of the trend; the fraction of red galaxies with moderate SFRs (0.2M_{sun}_/yr<SFR<1M_{sun}/yr) also decreases with increasing galaxy density. These results suggest that for the IR-bright galaxies nearby rich clusters are distinguished from the field by a lower star forming galaxy fraction, but not by a change in L*_IR_.
- ID:
- ivo://CDS.VizieR/J/MNRAS/368/651
- Title:
- A3653 galaxies redshift catalogue
- Short Name:
- J/MNRAS/368/651
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of galaxies in Abell 3653 from observations made with the 2-degree field (2dF) spectrograph at the Anglo-Australian Telescope. Of the 391 objects observed, we find 111 are bona fide members of Abell 3653.
- ID:
- ivo://CDS.VizieR/J/AJ/125/2393
- Title:
- A2256 galaxies redshifts and 1.4GHz fluxes
- Short Name:
- J/AJ/125/2393
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Abell 2256 is a nearby (z~0.06), rich cluster of galaxies with fascinating observed properties across a range of wavelengths. Long believed to represent a cluster merger, recent X-ray and optical results have suggested that in addition to the primary cluster and subcluster there is evidence for a third, poorer system. We present wide-field high-sensitivity 1.4GHz VLA radio observations of Abell 2256 in conjunction with optical imaging and additional spectroscopy. Over 40 cluster radio galaxies are identified, with optical spectroscopy indicating the emission source (star formation or active galactic nucleus) for most of them. While the overall fraction of galaxies exhibiting radio emission is consistent with a large sample of other nearby clusters, we find an increase in the activity level of galaxies belonging to the third system (hereafter "the Group"). Specifically, the Group has relatively more star formation than both the primary cluster and main subcluster. The position of the Group is also coincident with the observed cluster radio relic. We suggest that the Group recently (0.3Gyr) merged with the primary cluster and that this merger, not the ongoing merger of the primary and the main subcluster, might be responsible for many of the unusual radio properties of Abell 2256. Furthermore, the greater star formation activity of the Group suggests that the infall of groups is an important driver of galaxy evolution in clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/495/15
- Title:
- A959 galaxies r' magnitude and radial velocities
- Short Name:
- J/A+A/495/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The connection of cluster mergers with the presence of extended, diffuse radio sources in galaxy clusters is still being debated. We aim to obtain new insights into the internal dynamics of Abell 959, showing evidence of a diffuse radio source, analyzing velocities and positions of member galaxies. Our analysis is based on redshift data for 107 galaxies in the cluster field acquired at the Telescopio Nazionale Galileo. We also use photometric data from the Sloan Digital Sky Survey (Data Release 6). We combine galaxy velocities and positions to select 81 galaxies recognized as cluster members and determine global dynamical properties. We analyze the cluster searching for substructures by using the weighted gap analysis, the KMM method and the Dressler-Shectman statistics. We also study the 2D galaxy distribution in the field of the cluster. We compare our results with those from X-ray and gravitational lensing analyses.
- ID:
- ivo://CDS.VizieR/J/ApJS/192/6
- Title:
- A GALEX UV imaging survey of nearby galaxies
- Short Name:
- J/ApJS/192/6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a GALEX ultraviolet (UV) survey of a complete sample of 390 galaxies within ~11Mpc of the Milky Way. The UV data are a key component of the composite Local Volume Legacy, an ultraviolet-to-infrared imaging program designed to provide an inventory of dust and star formation in nearby spiral and irregular galaxies. The ensemble data set is an especially valuable resource for studying star formation in dwarf galaxies, which comprise over 80% of the sample. We describe the GALEX survey programs that obtained the data and provide a catalog of far-UV (~1500{AA}) and near-UV (~2200{AA}) integrated photometry. General UV properties of the sample are briefly discussed. We compute two measures of the global star formation efficiency, the star formation rate (SFR) per unit HI gas mass, and the SFR per unit stellar mass, to illustrate the significant differences that can arise in our understanding of dwarf galaxies when the FUV is used to measure the SFR instead of H{alpha}.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A56
- Title:
- A gamma-ray emission zone in 3C 279
- Short Name:
- J/A+A/630/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the relationship between the variable gamma-ray emission and jet properties in the blazar 3C 279, by combining the Fermi/LAT data spanning a period of eight years with concurrent radio measurements made at multiple epochs with VLBA at 15 and 43 GHz within the MOJAVE and VLBA-BU monitoring programs. The aim of this paper is to compare the flux variability of the different components found in the VLBA observations, to the variability in the gamma-rays. This analysis helps to investigate whether any of the jet components can be associated with the gamma-ray variability. Through Spearman rank correlation we found that the gamma-ray variability is correlated with a particular region (feature B, in the MOJAVE images) downstream from the observed base (core) of the jet. This jet component is therefore a likely location at which an important fraction of the variable gamma-ray emission is produced. We also calculated the average proper motion of the component with respect to the VLBA core and found that it moves at an apparent superluminal velocity of (3.70+/-0.35)c, implying that one of the gamma-ray emission zones is not stationary. This jet component is also found between 6.86mas and 8.68mas, which translates to a distance from the radio core of at least 42pc.
- ID:
- ivo://CDS.VizieR/J/A+A/421/509
- Title:
- AGAPE catalogue of M31 variables
- Short Name:
- J/A+A/421/509
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the AGAPE astrometric and photometric catalogue of 1579 variable stars in a 14' x 10' field centred on M31. Each variable star in the catalogue is identified as AGPVm, m running from 1 to 1579. Then are given: Fn(x,y) (F being the letter of identification of AGAPE field and n the variable star number in this field; x and y being the pixel coordinates in the reference frame), right ascension and declination for 2000.0, R_max_ magnitude at observed maximum, and L the likelihood function. When the variable star is a nova discovered by eye, no L value is given.
