- ID:
- ivo://CDS.VizieR/J/ApJ/886/33
- Title:
- MIR reverberation mapping analysis of 87 z<0.5 PG AGNs
- Short Name:
- J/ApJ/886/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The continued operation of the Wide-field Infrared Survey Explorer (WISE), combined with several ground-based optical transient surveys (e.g., CRTS, ASAS-SN, and PTF), offers an unprecedented opportunity to explore the dust structures in luminous active galactic nuclei (AGNs). We use these data for a mid-IR dust reverberation mapping (RM) study of 87 archetypal Palomar-Green quasars at z<~0.5. To cope with various contaminations of the photometry data and the sparse time sampling of the light curves, procedures to combine these data sets and retrieve the dust RM signals have been developed. We find that ~70% of the sample (with a completeness correction up to 95%) has convincing mid-IR time lags in the WISE W1 (~3.4{mu}m) and W2 (~4.5{mu}m) bands, and they are proportional to the square root of the AGN luminosity. Combined with previous K-band (~2.2{mu}m) RM results in the literature, the inferred dust emission size ratios are R_K_:R_W1_:R_W2_=0.6:1:1.2. Under simple assumptions, we put preliminary constraints on the projected dust surface density at these bands and reveal the possibly different torus structures among hot-dust-deficient, warm-dust-deficient, and normal quasars from the reverberation signals. With multi-epoch Spitzer data and later WISE photometry, we also explore AGN IR variability at 10-24{mu}m over a 5yr timescale. Except for blazars and flat-spectrum radio sources, the majority of AGNs have typical variation amplitudes at 24{mu}m of no more than 10% of that in the W1 band, indicating that the dust reverberation signals damp out quickly at longer wavelengths. In particular, steep-spectrum radio quasars also lack strong 24{mu}m variability, consistent with the unification picture of radio-loud AGNs.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/463/1831
- Title:
- M67 Kepler/K2 variable stars
- Short Name:
- J/MNRAS/463/1831
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the third paper of this series we continue the exploitation of Kepler/K2 data in dense stellar fields using our PSF-based method. This work is focused on a ~720-arcmin^2^ region centred on the Solar-metallicity and Solar-age open cluster M 67. We extracted light curves for all detectable sources in the Kepler channels 13 and 14, adopting our technique based on the usage of a high-angular-resolution input catalogue and target-neighbour subtraction. We detrended light curves for systematic errors, and searched for variables and exoplanets using several tools. We found 451 variables, of which 299 are new detection. Three planetary candidates were detected by our pipeline in this field. Raw and detrended light curves, catalogues, and K2 stacked images used in this work will be released to the community.
- ID:
- ivo://CDS.VizieR/J/ApJS/154/623
- Title:
- M31 Long Period Variables : Photometry
- Short Name:
- J/ApJS/154/623
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A significant fraction of the disk of M31 has been surveyed for long-period variable stars. We report the results, including near-infrared photometry of almost 2000 variables, and light curves in the i band. The period-luminosity relation suggests that most of the variables are asymptotic giant branch stars, and their luminosity function can be understood in terms of mass-loss rates, which increase with increasing luminosity on the giant branch, and star formation rates, which were a few times higher a billion years ago in M31 than they are today. We see some supergiant long-period variables, but somewhat fewer than expected based on their frequency in M33, and confined to the ring of star formation in M31 seen in the IRAS and 2MASS surveys.
- ID:
- ivo://CDS.VizieR/J/AJ/157/231
- Title:
- MLSDSS-GaiaDR2 sample of M and L dwarfs
- Short Name:
- J/AJ/157/231
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 74216 M and L dwarfs constructed from two existing catalogs of cool dwarfs spectroscopically identified in the Sloan Digital Sky Survey (SDSS). We cross-matched the SDSS catalog with Gaia DR2 (Cat. I/345) to obtain parallaxes and proper motions and modified the quality cuts suggested by the Gaia Collaboration to make them suitable for late-M and L dwarfs. We also provide relations between Gaia colors and absolute magnitudes with spectral type and conclude that (G-G_RP_) has the tightest relation to spectral type for M and L dwarfs. In addition, we study magnetic activity as a function of position on the color-magnitude diagram, finding that H{alpha} magnetically active stars have, on average, redder colors and/or brighter magnitudes than inactive stars. This effect cannot be explained by youth alone and might indicate that active stars are magnetically inflated, binaries, and/or high metallicity. Moreover, we find that vertical velocity and vertical action dispersion are correlated with H{alpha} emission, confirming that these two parameters are age indicators. We also find that stars below the main sequence have high tangential velocity, which is consistent with a low metallicity and old population of stars that belong to the halo or thick disk.
- ID:
- ivo://CDS.VizieR/J/ApJ/810/158
- Title:
- M,L,T dwarfs fundamental parameters and SEDs
- Short Name:
- J/ApJ/810/158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine optical, near-infrared, and mid-infrared spectra and photometry to construct expanded spectral energy distributions for 145 field age (>500 Myr) and 53 young (lower age estimate <500 Myr) ultracool dwarfs (M6-T9). This range of spectral types includes very low mass stars, brown dwarfs, and planetary mass objects, providing fundamental parameters across both the hydrogen and deuterium burning minimum masses for the largest sample assembled to date. A subsample of 29 objects have well constrained ages as probable members of a nearby young moving group. We use 182 parallaxes and 16 kinematic distances to determine precise bolometric luminosities (L_bol_) and radius estimates from evolutionary models give semi-empirical effective temperatures (T_eff_) for the full range of young and field age late-M, L, and T dwarfs. We construct age-sensitive relationships of luminosity, temperature, and absolute magnitude as functions of spectral type and absolute magnitude to disentangle the effects of degenerate physical parameters such as T_eff_, surface gravity, and clouds on spectral morphology. We report bolometric corrections in J for both field age and young objects and find differences of up to a magnitude for late-L dwarfs. Our correction in Ks shows a larger dispersion but not necessarily a different relationship for young and field age sequences. We also characterize the NIR-MIR reddening of low gravity L dwarfs and identify a systematically cooler T_eff_ of up to 300 K from field age objects of the same spectral type and 400 K cooler from field age objects of the same M_H_ magnitude.
- ID:
- ivo://CDS.VizieR/J/A+A/646/A119
- Title:
- M31 luminous red nova AT 2019zhd photometry
- Short Name:
- J/A+A/646/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the follow-up campaign of the luminous red nova (LRN) AT 2019zhd, the third event of this class observed in M 31. The object was followed by several sky surveys for about five months before the outburst, during which it showed a slow luminosity rise. In this phase, the absolute magnitude ranged from M_r_=-2.8+/-0.2mag to M_r_=-5.6+/-0.1mag. Then, over a four to five day period, AT 2019zhd experienced a major brightening, reaching a peak of M_r_=-9.61+/-0.08mag and an optical luminosity of 1.4x10^39^erg/s. After a fast decline, the light curve settled onto a short-duration plateau in the red bands. Although less pronounced, this feature is reminiscent of the second red maximum observed in other LRNe. This phase was followed by a rapid linear decline in all bands. At maximum, the spectra show a blue continuum with prominent Balmer emission lines. The post-maximum spectra show a much redder continuum, resembling that of an intermediate-type star. In this phase, Halpha becomes very weak, Hbeta is no longer detectable, and a forest of narrow absorption metal lines now dominate the spectrum. The latest spectra, obtained during the post-plateau decline, show a very red continuum (Teff~3000K) with broad molecular bands of TiO, similar to those of M-type stars. The long-lasting, slow photometric rise observed before the peak resembles that of LRN V1309 Sco, which was interpreted as the signature of the common-envelope ejection. The subsequent outburst is likely due to the gas outflow following a stellar merging event. The inspection of archival HST images taken 22 years before the LRN discovery reveals a faint red source (M_F555W_=0.21+/-0.14mag, with F555W-F814W=2.96+/-0.12mag) at the position of AT 2019zhd, which is the most likely quiescent precursor. The source is consistent with expectations for a binary system including a predominant M5-type star.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A133
- Title:
- M45, M44 and M67 flare stars
- Short Name:
- J/A+A/622/A133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The presence and strength of a stellar magnetic field and activity is rooted in a star's fundamental parameters such as mass and age. Can flares serve as an accurate stellar "clock"? To explore if we can quantify an activity-age relation in the form of a flaring-age relation, we measured trends in the flaring rates and energies for stars with different masses and ages. We investigated the time- domain photometry provided by Kepler's follow-up mission K2 and searched for flares in three solar metallicity open clusters with well-known ages, M45 (0.125Gyr), M44 (0.63Gyr), and M67 (4.3Gyr). We updated and employed the automated flare finding and analysis pipeline Appaloosa, originally designed for Kepler. We introduced a synthetic flare injection and recovery subroutine to ascribe detection and energy recovery rates for flares in a broad energy range for each light curve. We collected a sample of 1761 stars, mostly late-K to mid-M dwarfs and found 751 flare candidates with energies ranging from 4x10^32^erg to 6x10^34^erg, of which 596 belong to M45, 155 to M44, and none to M67. We find that flaring activity depends both on Teff, and age. But all flare frequency distributions have similar slopes with alpha from 2.0 to 2.4, supporting a universal flare generation process. We discuss implications for the physical conditions under which flares occur, and how the sample's metallicity and multiplicity affect our results.
- ID:
- ivo://CDS.VizieR/J/A+A/553/A54
- Title:
- M100 (NGC4321) HII region IRAC photometry
- Short Name:
- J/A+A/553/A54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We systematically study the relations between the H{alpha} luminosity and the near-IR luminosity and temperature of a set of selected HII regions in the disc of M100. By using the technique of cross-reference between the optical H{alpha} image (the catalogue of HII regions in M100 and the Spitzer IRAC images, we locate the selected HII regions in the IRAC image frames. By using the chi-squared non-linear fitting technique, we estimate the IRAC-3-band colour temperature T_col(IRAC)_ of selected HII regions, and calculate their near-IR luminosities.
- ID:
- ivo://CDS.VizieR/J/A+A/558/A12
- Title:
- M5 (NGC5904) UBVRI photometry
- Short Name:
- J/A+A/558/A12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar evolution is modified if energy is lost in a "dark channel" similar to neutrino emission. Comparing modified stellar evolution sequences with observations provides some of the most restrictive limits on axions and other hypothetical low-mass particles and on non-standard neutrino properties. In particular, a putative neutrino magnetic dipole moment {mu}_{nu}_ enhances the plasmon decay process, postpones helium ignition in low-mass stars, and therefore extends the red-giant branch (RGB) in globular clusters (GCs). The brightness of the tip of the RGB (TRGB) remains the most sensitive probe for {mu}_{nu}_ and we revisit this argument from a modern perspective. Based on a large set of archival observations, we provide high-precision photometry for the Galactic GC M5 (NGC 5904) and carefully determine its TRGB position.
- ID:
- ivo://CDS.VizieR/J/ApJ/839/113
- Title:
- Molecular clouds with GLIMPSE/MIPSGAL data
- Short Name:
- J/ApJ/839/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the star-formation (SF) law in 12 Galactic molecular clouds with ongoing high-mass star-formation (HMSF) activity, as traced by the presence of a bright IRAS source and other HMSF tracers. We define the molecular cloud (MC) associated with each IRAS source using ^13^CO line emission, and count the young stellar objects (YSOs) within these clouds using GLIMPSE and MIPSGAL 24{mu}m Spitzer databases. The masses for high-luminosity YSOs (L_bol_>10L_{sun}_) are determined individually using pre-main-sequence evolutionary tracks and the evolutionary stages of the sources, whereas a mean mass of 0.5M_{sun}_ was adopted to determine the masses in the low-luminosity YSO population. The star-formation rate surface density ({Sigma}SFR) corresponding to a gas surface density ({Sigma}gas) in each MC is obtained by counting the number of the YSOs within successive contours of ^13^CO line emission. We find a break in the relation between {Sigma}SFR and {Sigma}gas, with the relation being a power law ({Sigma}SFR{propto}{Sigma}gas^N^) with the index N varying between 1.4 and 3.6 above the break. The {Sigma}gas at the break is between 150-360M_{sun}_/pc^2^ for the sample clouds, which compares well with the threshold gas density found in recent studies of Galactic star-forming regions. Our clouds treated as a whole lie between the Kennicutt relation and the linear relation for Galactic and extra-galactic dense star-forming regions. We find a tendency for the high- mass YSOs to be found preferentially in dense regions at densities higher than 1200M_{sun}_/pc^2^ (~0.25g/cm^2^).
