- ID:
- ivo://CDS.VizieR/J/ApJ/845/171
- Title:
- Rapidly pulsating sdB stars search with GALEX
- Short Name:
- J/ApJ/845/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NASA's Galaxy Evolution Explorer (GALEX) provided near- and far-UV observations for approximately 77% of the sky over a 10-year period; however, the data reduction pipeline initially only released single NUV and FUV images to the community. The recently released Python module gPhoton changes this, allowing calibrated time-series aperture photometry to be extracted easily from the raw GALEX data set. Here we use gPhoton to generate light curves for all hot subdwarf B (sdB) stars that were observed by GALEX, with the intention of identifying short-period, p-mode pulsations. We find that the spacecraft's short visit durations, uneven gaps between visits, and dither pattern make the detection of hot subdwarf pulsations difficult. Nonetheless, we detect UV variations in four previously known pulsating targets and report their UV pulsation amplitudes and frequencies. Additionally, we find that several other sdB targets not previously known to vary show promising signals in their periodograms. Using optical follow-up photometry with the Skynet Robotic Telescope Network, we confirm p-mode pulsations in one of these targets, LAMOST J082517.99+113106.3, and report it as the most recent addition to the sdBVr class of variable stars.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/629/A131
- Title:
- Reduced X-shooter spectra of GRB 190114A
- Short Name:
- J/A+A/629/A131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detections of molecular hydrogen (H_2_), vibrationally-excited H_2_ (H_2_*), and neutral atomic carbon (CI), an efficient tracer of molecular gas, in two new afterglow spectra of GRBs 181020A (z=2.938) and 190114A (z=3.376), observed with X-shooter at the Very Large Telescope (VLT). Both host-galaxy absorption systems are characterized by strong damped Lyman-alpha absorbers (DLAs) and substantial amounts of molecular hydrogen with logN(HI,H_2_)=22.20+/-0.05, 20.40+/-0.04 (GRB 181020A) and logN(HI, H_2_)=22.15+/-0.05, 19.44+/-0.04 (GRB 190114A). The DLA metallicites, depletion levels, and dust extinctions are within the typical regimes probed by GRBs with [Zn/H]=-1.57+/-0.06, [Zn/Fe]=0.67+/-0.03, and AV=0.27+/-0.02mag (GRB 181020A) and [Zn/H]=-1.23+/-0.07, [Zn/Fe]=1.06+/-0.08, and AV=0.36+/-0.02mag (GRB 190114A). In addition, we examine the molecular gas content of all known H2-bearing GRB-DLAs and explore the physical conditions and characteristics required to simultaneously probe CI and H_2_*. We confirm that H2 is detected in all CI- and H2*-bearing GRB absorption systems, but that these rarer features are not necessarily detected in all GRB H2 absorbers. We find that a large molecular fraction of f_H2_>~10^-3^ is required for CI to be detected. The defining characteristic for H_2_* to be present is less clear, though a large H_2_ column density is an essential factor. We also find that the observed line profiles of the molecular-gas tracers are kinematically "cold", with small velocity offsets of {delta}v<20km/s from the bulk of the neutral absorbing gas. We then derive the H_2_ excitation temperatures of the molecular gas and find that they are relatively low with Tex~=100-300K, however, there could be evidence of warmer components populating the high-J H_2_ levels in GRBs 181020A and 190114A. Finally, we demonstrate that even though the X-shooter GRB afterglow campaign has been successful in recovering several H2-bearing GRB-host absorbers, this sample is still hampered by a significant dust bias excluding the most dust-obscured H_2_ absorbers from identification. CI and H_2_* could open a potential route to identify molecular gas even in low-metallicity or highly dust-obscured bursts, though they are only efficient tracers for the most H2-rich GRB-host absorption systems.
- ID:
- ivo://CDS.VizieR/J/ApJ/887/196
- Title:
- REQUIEM survey. I. Ly{alpha} halos around QSOs
- Short Name:
- J/ApJ/887/196
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The discovery of quasars a few hundred megayears after the Big Bang represents a major challenge to our understanding of black holes as well as galaxy formation and evolution. Quasars' luminosity is produced by extreme gas accretion onto black holes, which have already reached masses of M_BH_>10^9^M_{sun}_ by z~6. Simultaneously, their host galaxies form hundreds of stars per year, using up gas in the process. To understand which environments are able to sustain the rapid formation of these extreme sources, we started a Very Large Telescope/Multi-Unit Spectroscopic Explorer (MUSE) effort aimed at characterizing the surroundings of a sample of 5.7<z<6.6 quasars, which we have dubbed the Reionization Epoch QUasar InvEstigation with MUSE (REQUIEM) survey. We here present results of our searches for extended Ly{alpha} halos around the first 31 targets observed as part of this program. Reaching 5{sigma} surface brightness limits of 0.1-1.1x10^-17^erg/s/cm^2^/arcsec^2^ over a 1arcsec^2^ aperture, we were able to unveil the presence of 12 Ly{alpha} nebulae, eight of which are newly discovered. The detected nebulae show a variety of emission properties and morphologies with luminosities ranging from 8x10^42^ to 2x10^44^erg/s, FWHMs between 300 and 1700km/s, sizes <30pkpc, and redshifts consistent with those of the quasar host galaxies. As the first statistical and homogeneous investigation of the circumgalactic medium of massive galaxies at the end of the reionization epoch, the REQUIEM survey enables the study of the evolution of the cool gas surrounding quasars in the first 3Gyr of the universe. A comparison with the extended Ly{alpha} emission observed around bright (M_1450_<~-25mag) quasars at intermediate redshift indicates little variations on the properties of the cool gas from z~6 to z~3, followed by a decline in the average surface brightness down to z~2.
- ID:
- ivo://CDS.VizieR/II/335
- Title:
- Revised catalog of GALEX UV sources (GUVcat_AIS GR6+7)
- Short Name:
- II/335
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Galaxy Evolution Explorer (GALEX) imaged the sky in two ultraviolet (UV) bands, far-UV (FUV, {lambda}_eff_~1528{AA}), and near-UV (NUV, {lambda}_eff_~2310{AA}), delivering the first comprehensive sky surveys at these wavelengths. The GALEX database contains FUV and NUV images, ~500 million source measurements and over 100000 low-resolution UV spectra. The UV surveys are a unique resource for statistical studies of hot stellar objects, z<~2 QSOs, star-forming galaxies, nebulae and the interstellar medium, and provide a roadmap for planning future UV instrumentation and follow-up observing programs. We present science-enhanced, "clean" catalogs of GALEX UV sources, with useful tags to facilitate scientific investigations. The catalogs are an improved and expanded version of our previous catalogs of UV sources (BCScat; Bianchi+, 2011, J/MNRAS/411/2770 ; II/312 and 2014AdSpR..53..900B). With respect to BCScat, we have patched 640 fields for which the pipeline had improperly coadded non-overlapping observations, and we provide a version with a larger sky coverage (about 10%) by relaxing the restriction to the central area of the GALEX field to 1.1{deg} diameter (GUVcat_AIS_fov055: GUVcat_AIS FOV_radius <0.55{deg}), as well as the cleaner, more restrictive version using only the 1{deg} central portion of each field as in BCScat (GUVcat_AIS_fov050: GUVcat_AIS FOV_radius <0.50{deg}). We added new tags to facilitate selection and cleaning of statistical samples for science applications: we flag sources within the footprint of extended objects (nearby galaxies, stellar clusters) so that these regions can be excluded for estimating source density. As in our previous catalogs, in GUVcat duplicate measurements of the same source are removed, so that each astrophysical object has only one entry. Such a unique-source catalog is needed to study the density and distributions of sources, and to match UV sources with catalogs at other wavelengths. The catalog includes all observations from the All-Sky Imaging Survey (AIS), the survey with the largest area coverage, with both FUV and NUV detectors exposed: over 28700 fields, made up of a total of 57000 observations ("visits"). The total area covered, when overlaps are removed and gaps are accounted for, is 24790 square degrees for GUVcat_AIS_fov055 (GUVcat_AIS_fov055) and 22125 square degrees for (GUVcat_AIS_fov050). The total numbers of "unique" AIS sources (eliminating duplicate measurements) are 82,992,086 (GUVcat_AIS_fov055) and 69,772,677 (GUVcat_AIS_fov050). The typical depth of the GUVcat_AIS catalog is FUV=19.9, NUV=20.8 AB mag.
- ID:
- ivo://CDS.VizieR/J/MNRAS/284/265
- Title:
- Rotational Velocities of 373 OB stars
- Short Name:
- J/MNRAS/284/265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of homogeneous measures of the linewidth parameter, v_e_.sin(i), for 373 O-type stars and early supergiants (including the separate components of 25 binary and triple systems), produced by cross-correlating high-resolution, short-wavelength IUE spectra against a `template' spectrum of {tau} Sco. We also tabulate terminal velocities. There are no O supergiants in our sample with v_e_.sin(i)<65km/s, and only one supergiant earlier than B5 has v_e_.sin(i)<50km/s, confirming that an important line broadening mechanism in addition to rotation must be present in these objects. A calibration of the area under the cross-correlation peak against spectral type is used to obtain estimates of continuum intensity ratios of the components in 28 spectroscopically binary or multiple systems. At least seven SB2 systems show evidence for the `Struve-Sahade effect', a systematic variation in relative line strength as a function of orbital phase. The stellar wind of the most rapid rotator in our sample, the O9III:n* star HD 191423 (v_e_.sin(i)<=436km/s), show it to have a `wind-compressed disc' similar to that of HD 93521; this star and other rapid rotators are good candidates for studies of non-radial pulsation.
- ID:
- ivo://CDS.VizieR/J/ApJ/700/844
- Title:
- Rotation rates of very massive stars
- Short Name:
- J/ApJ/700/844
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present projected rotational velocity values for 96 Galactic, 55 SMC, and 106 LMC O-B type stars from archival FUSE observations. The evolved and unevolved samples from each environment are compared through the Kolmogorov-Smirnov test to determine if the distribution of equatorial rotational velocities is metallicity dependent for these massive objects. Stellar interior models predict that massive stars with SMC metallicity will have significantly reduced angular momentum loss on the main sequence compared to their Galactic counterparts. Our results find some support for this prediction but also show that even at Galactic metallicity, evolved and unevolved massive stars have fairly similar fractions of stars with large Vsin i values. Macroturbulent broadening that is present in the spectral features of Galactic evolved massive stars is lower in the LMC and SMC samples. This suggests the processes that lead to macroturbulence are dependent upon metallicity.
337. RR Tel UV emission
- ID:
- ivo://CDS.VizieR/J/A+AS/124/425
- Title:
- RR Tel UV emission
- Short Name:
- J/A+AS/124/425
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/MNRAS/476/4725
- Title:
- SC4K catalogue of candidate LAEs
- Short Name:
- J/MNRAS/476/4725
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present and explore deep narrow- and medium-band data obtained with the Subaru and the Isaac Newton Telescopes in the ~2deg^2^ COSMOS field. We use these data as an extremely wide, low-resolution (R~20-80) Integral Field Unit survey to slice through the COSMOS field and obtain a large sample of ~4000 Ly{alpha} emitters (LAEs) from z~2 to 6 in 16 redshift slices (SC4K). We present new Ly {alpha} luminosity functions (LFs) covering a comoving volume of ~10^8^Mpc^3^. SC4K extensively complements ultradeep surveys, jointly covering over 4dex in Ly{alpha} luminosity and revealing a global (2.5<z<6) synergy LF with {alpha}=-1.93^+0.12^_-0.12_, log_10_{Phi}^*^_Ly{alpha}_=-3.45^+0.22^_-0.29_Mpc^-3^, and log_10_L^*^_Ly{alpha}_=42.93^+0.15^_-0.11_erg/s. The Schechter component of the Ly{alpha} LF reveals a factor ~5 rise in L^*^_Ly{alpha}_ and a ~7 x decline in {Phi}^*^_Ly{alpha}_ from z~2 to 6. The data reveal an extra power-law (or Schechter) component above L_Ly{alpha}_~=10^43.3^erg/s at z~2.2-3.5 and we show that it is partially driven by X-ray and radio active galactic nucleus (AGN), as their Ly{alpha} LF resembles the excess. The power-law component vanishes and/or is below our detection limits above z>3.5, likely linked with the evolution of the AGN population. The Ly {alpha} luminosity density rises by a factor ~2 from z~2 to 3 but is then found to be roughly constant (1.1^+0.2^_-0.2_x10^40^erg/s/Mpc^3^) to z~6, despite the ~0.7 dex drop in ultraviolet (UV) luminosity density. The Ly{alpha}/UV luminosity density ratio rises from 4+/-1 per cent to 30+/-6 per cent from z~2.2 to 6. Our results imply a rise of a factor of ~=2 in the global ionization efficiency ({xi}_ion_) and a factor ~=4+/-1 in the Ly{alpha} escape fraction from z~2 to 6, hinting for evolution in both the typical burstiness/stellar populations and even more so in the typical interstellar medium conditions allowing Ly{alpha} photons to escape.
- ID:
- ivo://CDS.VizieR/J/ApJ/819/154
- Title:
- SDSS-DR7 QSOs with X-ray and UV luminosities
- Short Name:
- J/ApJ/819/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The observed relation between the soft X-ray and the optical-ultraviolet emission in active galactic nuclei (AGNs) is nonlinear and it is usually parametrized as a dependence between the logarithm of the monochromatic luminosity at 2500{AA} and at 2keV. Previous investigations have found that the dispersion of this relation is rather high (~0.35-0.4 in log units), which may be caused by measurement uncertainties, variability, and intrinsic dispersion due to differences in the AGN physical properties (e.g., different accretion modes). We show that, once optically selected quasars with homogeneous SED and X-ray detection are selected, and dust reddened and/or gas obscured objects are not included, the measured dispersion drops to significantly lower values (i.e., ~0.21-0.24dex). We show that the residual dispersion is due to some extent to variability, and to remaining measurement uncertainties. Therefore, the real physical intrinsic dispersion should be <0.21dex. Such a tight relation, valid over four decades in luminosity, must be the manifestation of an intrinsic (and universal) physical relation between the disk, emitting the primary radiation, and the hot electron corona emitting X-rays.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A184
- Title:
- SDSS J151349.52+035211.28 Xshooter spectra
- Short Name:
- J/A+A/618/A184
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the detection and detailed analysis of a diffuse molecular cloud at z_abs_=2.4636 towards the quasar SDSS J151349.52+035211.28 (hereafter J1513+0352) (zem~=2.68) observed with the X-shooter spectrograph at the Very Large Telescope. We measure very high column densities of atomic and molecular hydrogen, with logN(HI,H_2_)~=21.8,21.3. This is the highest H_2_ column density ever measured in an intervening damped Lyman-{alpha}system but we do not detect CO, implying log N(CO)/N(H_2_)<-7.8, which could be due to a low metallicity of the cloud. From the metal absorption lines, we derive the metallicity to be Z~=0.15Z_{sun}_ and determine the amount of dust by measuring the induced extinction of the background quasar light, AV~=0.4. We simultaneously detect Ly{alpha} emission at the same redshift, with a centroid located at a most probable impact parameter of only {rho}~=1.4kpc. We argue that the line of sight is therefore likely passing through the interstellar medium of a galaxy, as opposed to the circumgalactic medium. The relation between the surface density of gas and that of star formation seems to follow the global empirical relation derived in the nearby Universe although our constraints on the star formation rate and on the galaxy extent remain too loose to be conclusive. We study the transition from atomic to molecular hydrogen using a theoretical description based on the microphysics of molecular hydrogen.We use the derived chemical properties of the cloud and physical conditions (Tk~=90K and n~=250cm^-3^) derived through the excitation of H_2_ rotational levels and neutral carbon fine structure transitions to constrain the fundamental parameters that govern this transition. By comparing the theoretical and observed HI column densities, we are able to bring an independent constraint on the incident UV flux, which we find to be in agreement with that estimated from the observed star formation rate.
