- ID:
- ivo://CDS.VizieR/II/366
- Title:
- ASAS-SN catalog of variable stars
- Short Name:
- II/366
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The All-Sky Automated Survey for Supernovae (ASAS-SN) is the first optical survey to routinely monitor the whole sky with a cadence of ~2-3d down to V<~17mag. ASAS-SN has monitored the whole sky since 2014, collecting ~100-500 epochs of observations per field. The V-band light curves for candidate variables identified during the search for supernovae are classified using a random forest classifier and visually verified. In Paper I (Jayasinghe+ 2018MNRAS.477.3145J), we present a catalogue of 66179 bright, new variable stars discovered during our search for supernovae, including 27479 periodic variables and 38700 irregular variables. In paper II (Jayasinghe+ 2019MNRAS.486.1907J), We extracted the ASAS-SN light curves of ~412000 variable stars previously discovered by other surveys and in the VSX catalogue. In paper III (Jayasinghe+ 2019MNRAS.485..961J), we extracted the ASAS-SN light curves of ~1.3 million sources within 18deg of the Southern Ecliptic Pole. These sources are within the southern TESS CVZ and will have well-sampled TESS light curves.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/463/3813
- Title:
- ASASSN-15oi UBVI M2W1W2 light curves
- Short Name:
- J/MNRAS/463/3813
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ground-based and Swift photometric and spectroscopic observations of the tidal disruption event (TDE) ASASSN-15oi, discovered at the centre of 2MASX J20390918-3045201 (d~=216Mpc) by the All-Sky Automated Survey for SuperNovae. The source peaked at a bolometric luminosity of L~=1.3x10^44^erg/s and radiated a total energy of E~=6.6x10^50^ erg over the first ~3.5 months of observations. The early optical/UV emission of the source can be fit by a blackbody with temperature increasing from T~=2x10^4^K to T~=4x10^4^K while the luminosity declines from L~=1.3x10^44^erg/s to L~=2.3x10^43^erg/s, requiring the photosphere to be shrinking rapidly. The optical/UV luminosity decline during this period is most consistent with an exponential decline, L{prop.to}e^-(t-t_0)/tau_^, with {tau}~=46.5d for t_0_~=57241.6 (MJD), while a power-law decline of L{prop.to}(t-t_0_)^-{alpha}^ with t_0_~=57212.3 and {alpha}=1.62 provides a moderately worse fit. ASASSN-15oi also exhibits roughly constant soft X-ray emission that is significantly weaker than the optical/UV emission. Spectra of the source show broad helium emission lines and strong blue continuum emission in early epochs, although these features fade rapidly and are not present ~3 months after discovery. The early spectroscopic features and colour evolution of ASASSN-15oi are consistent with a TDE, but the rapid spectral evolution is unique among optically selected TDEs.
- ID:
- ivo://CDS.VizieR/J/AcA/59/33
- Title:
- ASAS. Variable stars catalog in Kepler field.
- Short Name:
- J/AcA/59/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog is a result of the analysis of VI photometry obtained during the first 17-month observations in the ASAS3-North station. The variable stars we present are divided into eleven groups according to the presented variability; the groups are briefly discussed. The catalog is intended to be a source of information for target selection process and follow-up programs.
- ID:
- ivo://CDS.VizieR/J/other/NewA/51.1
- Title:
- AS CrB BVRI light curves
- Short Name:
- J/other/NewA/51.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The first high-precision BVRI light curves of the eclipsing binary AS CrB were presented and were analyzed by the 2015 version of the W-D code. It is found that AS CrB is an extreme mass-ratio, deep contact binary with a fill-out factor of f=59.6+/-2.5% and a mass ratio of q=0.172+/-0.008q=0.172+/-0.008. Based on the photometric solution and the Dartmouth isochrones model, the masses, radii, and luminosities of the components are estimated as follows: M_1_=1.25+/-0.15M_{sun}_, M_1_=1.25+/-0.15M_{sun}_, M_2_=0.21+/-0.06M_{sun}_, M_2_=0.21+/-0.06M_{sun}_, R_1_=1.40+/-0.07R_{sun}_, R_1_=1.40+/-0.07R_{sun}_, R_2_=0.67+/-0.04R_{sun}_, R_2_=0.67+/-0.04R_{sun}_, L_1_=3.2+/-0.2L_{sun}_, L_1_=3.2+/-0.2L_{sun}_, and L_2_=0.72+/-0.04L_{sun}_, L_2_=0.72+/-0.04L_{sun}_, with an estimated distance 459+/-42pc. These uncertainties mainly come from the errors of the color used to estimate the temperature of the primary star. By investigating all of the available times of light minima, it is found that the Observed-Calculated [(O-C)(O-C)] curve shows a long-term period increase, with a rate of dP/dt=+(3.46+/-0.01)x10^-7^dP/dt=+(3.46+/-0.01)x10^-7^day/year. As an extreme mass-ratio contact binary, AS CrB may merge into a single star, such as an FK Com-type star or a blue straggler, because of the orbital instability.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A156
- Title:
- A search for accreting young companions
- Short Name:
- J/A+A/622/A156
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In recent years, our understanding of giant planet formation progressed substantially. There have even been detections of a few young protoplanet candidates still embedded in the circumstellar disks of their host stars. The exact physics that describes the accretion of material from the circumstellar disk onto the suspected circumplanetary disk and eventually onto the young, forming planet is still an open question. We seek to detect and quantify observables related to accretion processes occurring locally in circumstellar disks, which could be attributed to young forming planets. We focus on objects known to host protoplanet candidates and/or disk structures thought to be the result of interactions with planets. We analyzed observations of six young stars and their surrounding environments with the SPHERE/ZIMPOL instrument on the Very Large Telescope (VLT) in the H{alpha} filter (656nm) and a nearby continuum filter (644.9nm). We redetect the known accreting M-star companion HD142527 B with the highest published signal to noise to date in both H{alpha} and the continuum. No other companions are detected. We analyzed observations of six young stars (age 3.5-10Myr) and their surrounding environments with the SPHERE/ZIMPOL instrument on the Very Large Telescope (VLT) in the H{alpha}filter (656nm) and a nearby continuum filter (644.9nm). We applied several point spread function (PSF) subtraction techniques to reach the highest possible contrast near the primary star, specifically investigating regions where forming companions were claimed or have been suggested based on observed disk morphology.
- ID:
- ivo://CDS.VizieR/J/ApJ/777/64
- Title:
- A search for double-peaked AGNs in AGES
- Short Name:
- J/ApJ/777/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dual supermassive black holes (SMBHs) with kiloparsec-scale separations in merger-remnant galaxies are informative tracers of galaxy evolution, but the avenue for identifying them in large numbers for such studies is not yet clear. One promising approach is to target spectroscopic signatures of systems where both SMBHs are fueled as dual active galactic nuclei (AGNs), or where one SMBH is fueled as an offset AGN. Dual AGNs may produce double-peaked narrow AGN emission lines, while offset AGNs may produce single-peaked narrow AGN emission lines with line-of-sight velocity offsets relative to the host galaxy. We search for such dual and offset systems among 173 Type 2 AGNs at z<0.37 in the AGN and Galaxy Evolution Survey (AGES), and we find two double-peaked AGNs and five offset AGN candidates. When we compare these results to a similar search of the DEEP2 Galaxy Redshift Survey and match the two samples in color, absolute magnitude, and minimum velocity offset, we find that the fraction of AGNs that are dual SMBH candidates increases from z=0.25 to z=0.7 by a factor of ~6 (from 2/70 to 16/91, or 2.9_-1.9_^+3.6^% to 18_-5_^+5^%). This may be associated with the rise in the galaxy merger fraction over the same cosmic time. As further evidence for a link with galaxy mergers, the AGES offset and dual AGN candidates are tentatively ~3 times more likely than the overall AGN population to reside in a host galaxy that has a companion galaxy (from 16/173 to 2/7, or 9_-2_^+3^% to 29_-19_^+26^%). Follow-up observations of the seven offset and dual AGN candidates in AGES will definitively distinguish velocity offsets produced by dual SMBHs from those produced by narrow-line region kinematics, and will help sharpen our observational approach to detecting dual SMBHs.
- ID:
- ivo://CDS.VizieR/J/ApJ/806/95
- Title:
- A search for ultra-compact HVC counterparts
- Short Name:
- J/ApJ/806/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report five Local Volume dwarf galaxies (two of which are presented here for the first time) uncovered during a comprehensive archival search for optical counterparts to ultra-compact high-velocity clouds (UCHVCs). The UCHVC population of HI clouds are thought to be candidate gas-rich, low-mass halos at the edge of the Local Group and beyond, but no comprehensive search for stellar counterparts to these systems has been presented. Careful visual inspection of all publicly available optical and ultraviolet imaging at the position of the UCHVCs revealed six blue, diffuse counterparts with a morphology consistent with a faint dwarf galaxy beyond the Local Group. Optical spectroscopy of all six candidate dwarf counterparts show that five have an H{alpha}-derived velocity consistent with the coincident HI cloud, confirming their association; the sixth diffuse counterpart is likely a background object. The size and luminosity of the UCHVC dwarfs is consistent with other known Local Volume dwarf irregular galaxies. The gas fraction (M_HI_/M_star_) of the five dwarfs are generally consistent with that of dwarf irregular galaxies in the Local Volume, although ALFALFA-Dw1 (associated with ALFALFA UCHVC HVC274.68+74.70-123) has a very high M_HI_/M_star_~40. Despite the heterogeneous nature of our search, we demonstrate that the current dwarf companions to UCHVCs are at the edge of detectability due to their low surface brightness, and that deeper searches are likely to find more stellar systems. If more sensitive searches do not reveal further stellar counterparts to UCHVCs, then the dearth of such systems around the Local Group may be in conflict with {Lambda}CDM simulations.
- ID:
- ivo://CDS.VizieR/J/ApJS/244/12
- Title:
- A search for variable stars in M4 with K2 LCs
- Short Name:
- J/ApJS/244/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We extract light curves for 4554 objects with 9<G<19 in the K2 superstamp observations of the globular cluster M4, including 3784 cluster members, and search for variability. Among cluster-member objects, we detect 66 variables, of which 52 are new discoveries. Among objects not belonging to the cluster, we detect 24 variables, of which 20 are new discoveries. We additionally discover 57 cluster-member suspected variables, 10 cluster-non-member suspected variables, and four variables with ambiguous cluster membership. Our light curves reach sub-millimagnitude precision for the cluster horizontal branch, permitting us to detect asteroseismic activity in six horizontal branch stars outside the instability strip and one inside the strip but with only ~1mmag amplitude variability. Nineteen additional stars along the red giant branch also have detected asteroseismic variability. Several eclipsing binaries are found in the cluster, including a 4.6 day detached eclipsing binary and an EW-class eclipsing binary, as well as an EW with uncertain cluster membership and three other candidate EWs. A 22 day detached eclipsing binary is also found outside the cluster. We identify a candidate X-ray binary that is a cluster member with quiescent and periodic ~20mmag optical variability. We also obtain high-precision light curves for 10 of the previously known RR Lyrae variables in the cluster and identify one as a candidate Blazhko variable with a Blazhko period in excess of 78d.
- ID:
- ivo://CDS.VizieR/J/ApJ/872/192
- Title:
- A spectroscopic census of A2029 members
- Short Name:
- J/ApJ/872/192
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A rich spectroscopic census of members of the local massive cluster A2029 includes 1215 members of A2029 and its two infalling groups, A2033 and the Southern Infalling Group. The two infalling groups are identified in spectroscopic, X-ray, and weak-lensing maps. We identify active galactic nuclei (AGNs), star-forming galaxies, E+A galaxies, and quiescent galaxies based on the spectroscopy. The fractions of AGN and post-starburst E+A galaxies in A2029 are similar to those of other clusters. We derive the stellar mass (M_*_)-metallicity relation of A2029 based on 227 star-forming members; A2029 members within 10^9^M_{sun}_<M_*_<10^9.5^M_{sun}_ are more metal-rich than Sloan Digital Sky Survey galaxies within the same mass range. We utilize the spectroscopic index D_n_4000, a strong age indicator, to trace past and future evolution of the A2029 system. The median D_n_4000 of the members decreases as the projected clustercentric distance increases for all three subsystems. The D_n_4000-M_*_ relations of the members in A2029 and its two infalling groups differ significantly, indicating the importance of stochastic effects for understanding the evolution of cluster galaxy populations.
- ID:
- ivo://CDS.VizieR/J/AJ/155/240
- Title:
- A spectroscopic survey of field RHB stars
- Short Name:
- J/AJ/155/240
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A metallicity, chemical composition, and kinematic survey has been conducted for a sample of 340 candidate field red horizontal-branch (RHB) stars. Spectra with high resolution and high signal-to-noise ratio were gathered with the McDonald Observatory 2.7 m Tull and the Hobby-Eberly Telescope echelle spectrographs, and were used to determine effective temperatures, surface gravities, microturbulent velocities, [Fe/H] metallicities, and abundance ratios [X/Fe] for seven {alpha} and Fe-group species. The derived temperatures and gravities confirm that at least half of the candidates are true RHB stars, with (average) parameters T_eff_~5000 K and log g~2.5. From the {alpha} abundances alone, the thin and thick Galactic populations are apparent in our sample. Space motions for 90% of the program stars were computed from Hipparcos and Gaia parallaxes and proper motions. Correlations between chemical compositions and Galactic kinematics clearly indicate the existence of both thin-disk and thick-disk RHB stars.