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1161. Fermi blazars with Doppler factors
ID:
ivo://CDS.VizieR/J/ApJ/835/L38
Title:
Fermi blazars with Doppler factors
Short Name:
J/ApJ/835/L38
Date:
21 Oct 2021
Publisher:
CDS
Description:
Blazars are an extreme subclass of active galactic nuclei. Their rapid variability, luminous brightness, superluminal motion, and high and variable polarization are probably due to a beaming effect. However, this beaming factor (or Doppler factor) is very difficult to measure. Currently, a good way to estimate it is to use the timescale of their radio flares. In this Letter, we use multiwavelength data and Doppler factors reported in the literature for a sample of 86 flaring blazars detected by Fermi to compute their intrinsic multiwavelength data and intrinsic spectral energy distributions and investigate the correlations among observed and intrinsic data. Quite interestingly, intrinsic data show a positive correlation between luminosity and peak frequency, in contrast with the behavior of observed data, and a tighter correlation between {gamma}-ray luminosity and the lower-energy ones. For flaring blazars detected by Fermi, we conclude that (1) observed emissions are strongly beamed; (2) the anti-correlation between luminosity and peak frequency from the observed data is an apparent result, the correlation between intrinsic data being positive; and (3) intrinsic {gamma}-ray luminosity is strongly correlated with other intrinsic luminosities.
1162. 8 Fermi GRB afterglows follow-up
ID:
ivo://CDS.VizieR/J/ApJ/806/52
Title:
8 Fermi GRB afterglows follow-up
Short Name:
J/ApJ/806/52
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Fermi Gamma-ray Space Telescope has greatly expanded the number and energy window of observations of gamma-ray bursts (GRBs). However, the coarse localizations of tens to a hundred square degrees provided by the Fermi GRB Monitor instrument have posed a formidable obstacle to locating the bursts' host galaxies, measuring their redshifts, and tracking their panchromatic afterglows. We have built a target-of-opportunity (TOO) mode for the intermediate Palomar Transient Factory (iPTF) in order to perform targeted searches for Fermi afterglows. Here, we present the results of one year of this program: 8 afterglow discoveries out of 35 searches. Two of the bursts with detected afterglows (GRBs 130702A and 140606B) were at low redshift (z=0.145 and 0.384, respectively) and had spectroscopically confirmed broad-line Type Ic supernovae. We present our broadband follow-up including spectroscopy as well as X-ray, UV, optical, millimeter, and radio observations. We study possible selection effects in the context of the total Fermi and Swift GRB samples. We identify one new outlier on the Amati relation. We find that two bursts are consistent with a mildly relativistic shock breaking out from the progenitor star rather than the ultra-relativistic internal shock mechanism that powers standard cosmological bursts. Finally, in the context of the Zwicky Transient Facility, we discuss how we will continue to expand this effort to find optical counterparts of binary neutron star mergers that may soon be detected by Advanced LIGO and Virgo.
1163. FF Aql BV light curves
ID:
ivo://CDS.VizieR/J/AZh/91/299
Title:
FF Aql BV light curves
Short Name:
J/AZh/91/299
Date:
21 Oct 2021
Publisher:
CDS
Description:
Photographic plates of the Harvard Observatory stacks have been used to obtain 1261 brightness estimates for the low-amplitude Cepheid FF Aql (P=4.47 days). Combined with published visual, photoelectric, and CCD observations, these data enable the construction of an O-C diagram spanning 122 years. The resulting O-C diagram is parabola-shaped, enabling the determination of quadratic brightness elements for the first time. The evolutionary rate of increase of the period, dP/dt=0.072+/-0.011s/year, is in agreement with theoretical computations for the third crossing of the instability strip. The available data, reduced using the technique of by Eddington and Plakidis, reveal the presence of small, random period fluctuations, {epsilon}=0.0061d+/-0.0044d, that do not distort the evolutionary trend of the O-C residuals.
1164. F, G and K stars BVRI photometry
ID:
ivo://CDS.VizieR/J/A+AS/131/197
Title:
F, G and K stars BVRI photometry
Short Name:
J/A+AS/131/197
Date:
15 Dec 2021 08:12:40
Publisher:
CDS
Description:
We present accurate BV(RI)c photometry for a sample of F, G and K stars detected in selected areas of the ROSAT all-sky survey (RASS). We have used the photometry, in addition to low-resolution spectroscopy, to estimate spectral classifications, distances and X-ray luminosities. The log(L_X_/L_V_) in the sample lies below -2. Although the sample contains also nearby, inactive stars, it is dominated by active objects. The median X-ray luminosity in our sample is <L_X_>=29.88 and the mean value of the hardness ratios <HR1>=0.13+/-0.35. We compare the derived X-ray luminosity function with similar functions obtained from the serendipitous samples of the Einstein Observatory medium sensitivity survey (EMSS, Cat. <IX/15>) and EXOSAT (Cat. <J/A+AS/115/41>). Our sample is completely consistent with the EMSS sample of solar type stars, indicating that both our sources and the EMSS sources are representative of the high galactic latitude X-ray stellar population. We do not find extremely active stars (log(L_X_)>=32), as are found in the EMSS sample, and we argue that these objects are rare.
1165. 504 F-G dwarfs photometric metallicities
ID:
ivo://CDS.VizieR/J/other/ApSS/364.172
Title:
504 F-G dwarfs photometric metallicities
Short Name:
J/other/ApSS/364
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this study, photometric metallicity and absolute magnitude calibrations were derived using F-G spectral type main-sequence stars in the Solar neighbourhood with precise spectroscopic, photometric and Gaia astrometric data for UBV photometry. The sample consists of 504 main-sequence stars covering the temperature, surface gravity and colour index intervals 5300<Teff<7300K, logg>4 (cgs) and 0.3<(B-V)0<0.8mag, respectively. Stars with relative trigonometric parallax errors {sigma}_{pi}/{pi}<=0.01 were preferred from Gaia DR2 data for the estimation of their M_V absolute magnitudes. In order to obtain calibrations, (U-B)0 and (B-V)0 colour indices of stars were preferred and a multi-variable second order equation was used. Calibrations are valid for main-sequence stars in the metallicity and absolute magnitude ranges -2<[Fe/H]<0.5dex and 2.5<M_V_<6mag, respectively. The mean value and standard deviation of the differences between original and estimated values for the metal abundance and absolute magnitude are <{Delta}[Fe/H]>=0.00+/-0.11dex and <{Delta}M_V_>=0.00+/-0.22mag, respectively. In this work, it has been shown that more precise iron abundance and absolute magnitude values were obtained with the new calibrations, compared to previous calibrations in the literature.
1166. 342 FGK-dwarfs ages using GALEX FUV magnitudes
ID:
ivo://CDS.VizieR/J/AJ/160/217
Title:
342 FGK-dwarfs ages using GALEX FUV magnitudes
Short Name:
J/AJ/160/217
Date:
21 Oct 2021
Publisher:
CDS
Description:
Stellar age cannot be directly measured, yet age determinations are fundamental to understanding the evolution of stars, planets, and galaxies. The work presented here builds upon the idea of a stellar-activity age. We utilized far-ultraviolet (FUV) photometry acquired by the Galaxy Evolution Explorer (GALEX) space telescope as an indicator of chromospheric activity to infer ages of late-F, G, and K type dwarf stars. We derived a purely empirical correlation between FUV magnitudes and stellar age in conjunction with (B-V) color. Our attention is restricted to Sun-like stars with color range 0.55<=(B-V)<=0.71 and absolute magnitude range 4.3<=MV<=5.3. The correlation is defined in terms of a FUV-excess parameter Q(FUV-B,B-V). We related stellar age, {tau}, to Q through the relation log_e_({tau})=log_e_(a)+bQ, where a and b are fit parameters and functions of (B-V). This correlation is functional up to 6Gyr for FGK dwarfs. With such a correlation, one only needs Johnson (B-V) and FUV measurements to estimate the stellar age for Population i dwarf stars of solar-like temperature and metallicity. Such a calibration has utility in population studies of FGK dwarfs for further understanding of the chemical evolution of the Milky Way. As an illustration of one such application, we have constructed activity and FUV-age distributions for a sample of thin and thick disk stars, as distinguished by their chemical abundances. Considerable overlap is found between the activity distribution and age range of the two populations. We discuss the possibility that some high-[{alpha}/Fe] thick disk stars were formed as a result of the accretion of dwarf galaxies as recently as 4Gyr ago.
1167. FGK dwarf stars limb darkening coefficients
ID:
ivo://CDS.VizieR/J/A+A/556/A86
Title:
FGK dwarf stars limb darkening coefficients
Short Name:
J/A+A/556/A86
Date:
21 Oct 2021
Publisher:
CDS
Description:
Limb darkening is a fundamental ingredient for interpreting observations of planetary transits, eclipsing binaries, optical/infrared interferometry and microlensing events. However, this modeling traditionally represents limb darkening by a simple law having one or two coefficients that have been derived from plane-parallel model stellar atmospheres, which has been done by many researchers. More recently, researchers have gone beyond plane-parallel models and considered other geometries. We previously studied the limb-darkening coefficients from spherically symmetric and plane-parallel model stellar atmospheres for cool giant and supergiant stars, and in this investigation we apply the same techniques to FGK dwarf stars. We present limb-darkening coefficients, gravity-darkening coefficients and interferometric angular diameter corrections from Atlas and SAtlas model stellar atmospheres. We find that sphericity is important even for dwarf model atmospheres, leading to significant differences in the predicted coefficients.
1168. FGK stars magnetic activity in LAMOST-Kepler field
ID:
ivo://CDS.VizieR/J/ApJS/247/9
Title:
FGK stars magnetic activity in LAMOST-Kepler field
Short Name:
J/ApJS/247/9
Date:
21 Oct 2021
Publisher:
CDS
Description:
Monitoring chromospheric and photospheric indexes of magnetic activity can provide valuable information, especially the interaction between different parts of the atmosphere and their response to magnetic fields. We extract chromospheric indexes, S and R_HK_^+^, for 59816 stars from LAMOST spectra in the LAMOST-Kepler program, and photospheric index, Reff, for 5575 stars from Kepler light curves. The log Reff shows positive correlation with logR_HK_^+^. We estimate the power-law indexes between Reff and R_HK_^+^ for F-, G-, and K-type stars, respectively. We also confirm the dependence of both chromospheric and photospheric activity on stellar rotation. Ca ii H and K emissions and photospheric variations generally decrease with increasing rotation periods for stars with rotation periods exceeding a few days. The power-law indexes in exponential decay regimes show different characteristics in the two activity-rotation relations. The updated largest sample including the activity proxies and reported rotation periods provides more information to understand the magnetic activity for cool stars.
1169. 2FGL J0846.0+2820 opt. counterpart follow-up
ID:
ivo://CDS.VizieR/J/ApJ/851/31
Title:
2FGL J0846.0+2820 opt. counterpart follow-up
Short Name:
J/ApJ/851/31
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present optical photometric and spectroscopic observations of the likely stellar counterpart to the unassociated Fermi Large Area Telescope (LAT) {gamma}-ray source 2FGL J0846.0+2820, selected for study based on positional coincidences of optical variables with unassociated LAT sources. Using optical spectroscopy from the SOAR telescope, we have identified a late-G giant in an eccentric (e=0.06) 8.133-day orbit with an invisible primary. Modeling the spectroscopy and photometry together led us to infer a heavy neutron star primary of ~2M_{sun}_ and a partially stripped giant secondary of ~0.8M_{sun}_. H{alpha} emission is observed in some of the spectra, perhaps consistent with the presence of a faint accretion disk. We find that the {gamma}-ray flux of 2FGL J0846.0+2820 dropped substantially in mid-2009, accompanied by an increased variation in the optical brightness, and since then, it has not been detected by Fermi. The long period and giant secondary are reminiscent of the {gamma}-ray bright binary 1FGL J1417.7-4407, which hosts a millisecond pulsar (MSP) apparently in the final stages of the pulsar recycling process. The discovery of 2FGL J0846.0+2820 suggests the identification of a new subclass of MSP binaries that are the likely progenitors of typical field MSPs.
1170. Field early-type galaxies at 0.2<z<0.8
ID:
ivo://CDS.VizieR/J/MNRAS/393/1467
Title:
Field early-type galaxies at 0.2<z<0.8
Short Name:
J/MNRAS/393/1467
Date:
21 Oct 2021
Publisher:
CDS
Description:
We explore the properties of 24 field early-type galaxies in the redshift range 0.20<z<0.75 down to M_B<=-19.30 in a sample extracted from the FORS Deep Field and the William Herschel Deep Field. Target galaxies were selected on the basis of a combination of luminosity, spectrophotometric type, morphology and photometric redshift or broad-band colours. High signal-to-noise intermediate-resolution spectroscopy has been acquired at the Very Large Telescope, complemented by deep high-resolution imaging with the Advanced Camera for Surveys onboard the HST and additional ground-based multi-band photometry. All galaxy spectra were observed under sub-arcsecond conditions and allow to derive accurate kinematics and stellar population properties of the galaxies. To clarify the low level of star formation detected in some galaxies, we identify the amount of active galactic nuclei (AGN) activity in our sample using archive data of Chandra and XMM-Newton X-ray surveys. None of the galaxies in our sample were identified as secure AGN sources based on their X-ray emission. The rest-frame B and K-band scaling relations of the Faber-Jackson relation and the Fundamental Plane display a moderate evolution for the field early-type galaxies. Lenticular (S0) galaxies feature on average a stronger luminosity evolution and bluer rest-frame colours which can be explained that they comprise more diverse stellar populations compared to elliptical galaxies. The evolution of the FP can be interpreted as an average change in the dynamical (effective) mass-to-light ratio of our galaxies as <{Delta}log(M/L_B_)/z>=-0.74+/-0.08. The M/L evolution of these field galaxies suggests a continuous mass assembly of field early-type galaxies during the last 5Gyr, that gets support by recent studies of field galaxies up to z~1. Independent evidence for recent star formation activity is provided by spectroscopic (OII emission, Hdelta) and photometric (rest-frame broad-band colors) diagnostics. Based on the Hdelta absorption feature we detect a weak residual star formation for galaxies that accounts for 5%-10% in the total stellar mass of these galaxies. The co-evolution in the luminosity and mass of our galaxies favours a downsizing formation process. We find some evidence that our galaxies experienced a period of star formation quenching, possible triggered by AGN activity that is in good agreement with recent results on both observational and theoretical side.