Search

Start Over Subject optical astronomy
301. Bright white dwarfs for high-speed photometry
ID:
ivo://CDS.VizieR/J/MNRAS/472/4173
Title:
Bright white dwarfs for high-speed photometry
Short Name:
J/MNRAS/472/4173
Date:
21 Oct 2021
Publisher:
CDS
Description:
The upcoming NASA Transiting Exoplanet Survey Satellite (TESS) will obtain space-based uninterrupted light curves for a large sample of bright white dwarfs distributed across the entire sky, providing a very rich resource for asteroseismological studies and the search for transits from planetary debris. We have compiled an all-sky catalogue of ultraviolet, optical and infrared photometry as well as proper motions, which we propose as an essential tool for the preliminary identification and characterization of potential targets. We present data for 1864 known white dwarfs and 305 high-probability white dwarf candidates brighter than 17mag. We describe the spectroscopic follow-up of 135 stars, of which 82 are white dwarfs and 25 are hot subdwarfs. The new confirmed stars include six pulsating white dwarf candidates (ZZ Cetis), and nine white dwarf binaries with a cool main- sequence companion. We identify one star with a spectroscopic distance of only 25pc from the Sun. Around the time TESS is launched, we foresee that all white dwarfs in this sample will have trigonometric parallaxes measured by the ESA Gaia mission next year.
302. BRI light curves of 2MASS J02272637+1156494
ID:
ivo://CDS.VizieR/J/AJ/149/111
Title:
BRI light curves of 2MASS J02272637+1156494
Short Name:
J/AJ/149/111
Date:
21 Oct 2021
Publisher:
CDS
Description:
The star 1SWASP J022727.03+115641.7 was reported as a contact binary with a period shorter than the empirical limit of such systems. Our study shows the star not to be variable. Instead, it is the nearby star, 2MASS 02272637+1156494, that exhibits variability. The BRI CCD light curves of 2MASS 02272637+1156494 show the system to be a moderate mass ratio (2.154_-0.074_^+0.008^), and shallow contact (10.4_-1.9_^+1.4^%) W-type contact binary. The masses, radii, and luminosities of the binary components are, respectively, M_1_=0.25_-0.01_^+0.05^M_{sun}_, M_2_=0.54_-0.04_^+0.11^M_{sun}_, R_1_=0.45_-0.01_^+0.02^R_{sun}_, R_2_=0.63_-0.02_^+0.04^R_{sun}_, L_1_=0.038_-0.005_^+0.018^L_{sun}_, and L_2_=0.071_-0.010_^+0.037^L_{sun}_, with an estimated distance 326_-46_^+127^ pc. These uncertainties mainly come from the errors of the colors used to estimate the temperature of the primary star. A dark spot was introduced on the massive component in the final solution.
303. BRI observations of the QSO Zw III 2
ID:
ivo://CDS.VizieR/J/ApJS/226/17
Title:
BRI observations of the QSO Zw III 2
Short Name:
J/ApJS/226/17
Date:
21 Oct 2021
Publisher:
CDS
Description:
III Zw 2 is the prototype of radio-intermediate quasars. Although there is the evidence of possessing strong jet, significant {gamma}-ray emission has not been reported before. In this work, we carry out a detailed analysis of the latest Fermi-LAT Pass 8 data. No significant {gamma}-ray signal has been detected in the time-averaged 7-year Fermi-LAT data of III Zw 2; however, we have identified two distinct {gamma}-ray flares with isotropic luminosities of ~10^45^erg/s. Multiwavelength data analysis (also including the optical photometric observations from Yunnan Observatories) are presented and the main finding is simultaneous optical and {gamma}-ray flares of III Zw 2 appearing in 2009 November. Violent {gamma}-ray variability with a doubling timescale of 2.5hr was detected in another {gamma}-ray flare in May 2010, for which the 3-hr {gamma}-ray peak flux is ~250 times of the average flux in 7 years. Rather similar behaviors are observed in blazars and the blazar model can reasonably reproduce the spectral energy distribution of III Zw 2 in a wide energy range, strongly suggesting that its central engine resembles that of blazars. In view of its core, which shares radio similarities with young radio sources, together with weak extended radio lobe emission, we suggest that III Zw 2 harbors a recurrent activity core and thus serves as a valuable target for investigating the fueling and triggering of the activity in radio-loud active galactic nuclei.
304. BRJK photometry of Seyfert galaxy WPVS48
ID:
ivo://CDS.VizieR/J/A+A/561/L8
Title:
BRJK photometry of Seyfert galaxy WPVS48
Short Name:
J/A+A/561/L8
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using robotic telescopes of the Universitatssternwarte Bochum near Cerro Armazones in Chile, we monitored the z=0.0377 Seyfert 1 galaxy WPVS48 in the optical (B and R) and near-infrared (NIR, J and K) with a cadence of two days.
305. BR light curves of GJ1214b
ID:
ivo://CDS.VizieR/J/A+A/579/A113
Title:
BR light curves of GJ1214b
Short Name:
J/A+A/579/A113
Date:
21 Oct 2021
Publisher:
CDS
Description:
The atmospheric composition and vertical structure of the super-Earth GJ 1214b has been a subject of debate since its discovery in 2009. Recent studies have indicated that high-altitude clouds might mask the lower layers. However, some data points that were gathered at different times and facilities do not fit this picture, probably because of a combination of stellar activity and systematic errors. We observed two transits of GJ 1214b with the Large Binocular Camera, the dual-channel camera at the Large Binocular Telescope. For the first time, we simultaneously measured the relative planetary radius k=R_p_/R_*_ at blue and red optical wavelengths (B+R), thus constraining the Rayleigh scattering on GJ 1214b after correcting for stellar activity effects. To the same purpose, a long-term photometric follow-up of the host star was carried out with WiFSIP at STELLA, revealing a rotational period that is significantly longer than previously reported. Our new unbiased estimates of k yield a flat transmission spectrum extending to shorter wavelengths, thus confirming the cloudy atmosphere scenario for GJ 1214b.
306. Broad Absorption Line Quasars from SDSS
ID:
ivo://CDS.VizieR/J/AJ/125/1711
Title:
Broad Absorption Line Quasars from SDSS
Short Name:
J/AJ/125/1711
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of 224 broad absorption line quasars (BALQSOs) from the Sloan Digital Sky Survey's Early Data Release Quasar Catalog, (Schneider et al., 2002, Cat. <J/AJ/123/567>) including a relatively complete and homogeneous subsample of 131 BALQSOs. Since the identification of BALQSOs is subject to considerable systematic uncertainties, we attempt to create a complete sample of SDSS BALQSOs by combining the results of two automated selection algorithms and a by-eye classification scheme. One of these automated algorithms finds broad absorption line troughs by comparing with a composite quasar spectrum. We present the details of this algorithm and compare this method with one that uses a power-law fit to the continuum. The BALQSOs in our sample are further classified as high-ionization BALQSOs (HiBALs), low-ionization BALQSOs (LoBALs), and BALQSOs with excited iron absorption features (FeLoBALs); composite spectra of each type are presented. We further present a study of the properties of the BALQSOs in terms of the balnicity distribution, which rises with decreasing balnicity. This distribution of balnicities suggests that the fraction of quasars with intrinsic outflows may be significantly underestimated. The balnicity index defined by Weymann et al. (1991ApJ...373...23W) amounts to a sort of equivalent width: a quasar is declared to be a BAL when its balnicity index is >=0.
307. Broad-line AGN with host galaxy colors
ID:
ivo://CDS.VizieR/J/ApJ/763/133
Title:
Broad-line AGN with host galaxy colors
Short Name:
J/ApJ/763/133
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first quantified, statistical map of broad-line active galactic nucleus (AGN) frequency with host galaxy color and stellar mass in nearby (0.01<z<0.11) galaxies. Aperture photometry and z-band concentration measurements from the Sloan Digital Sky Survey are used to disentangle AGN and galaxy emission, resulting in estimates of uncontaminated galaxy rest-frame color, luminosity, and stellar mass. Broad-line AGNs are distributed throughout the blue cloud and green valley at a given stellar mass, and are much rarer in quiescent (red sequence) galaxies. This is in contrast to the published host galaxy properties of weaker narrow-line AGNs, indicating that broad-line AGNs occur during a different phase in galaxy evolution. More luminous broad-line AGNs have bluer host galaxies, even at fixed mass, suggesting that the same processes that fuel nuclear activity also efficiently form stars. The data favor processes that simultaneously fuel both star formation activity and rapid supermassive black hole accretion. If AGNs cause feedback on their host galaxies in the nearby universe, the evidence of galaxy-wide quenching must be delayed until after the broad-line AGN phase.
308. Brown dwarfs with spectral type later than T6
ID:
ivo://CDS.VizieR/J/ApJ/842/118
Title:
Brown dwarfs with spectral type later than T6
Short Name:
J/ApJ/842/118
Date:
21 Oct 2021
Publisher:
CDS
Description:
The survey of the mid-infrared sky by the Wide-field Infrared Survey Explorer (WISE) led to the discovery of extremely cold, low-mass brown dwarfs, classified as Y dwarfs, which extend the T class to lower temperatures. Twenty-four Y dwarfs are known at the time of writing. Here we present improved parallaxes for four of these, determined using Spitzer images. We give new photometry for four late-type T and three Y dwarfs and new spectra of three Y dwarfs, obtained at Gemini Observatory. We also present previously unpublished photometry taken from HST, ESO, Spitzer, and WISE archives of 11 late-type T and 9 Y dwarfs. The near-infrared data are put onto the same photometric system, forming a homogeneous data set for the coolest brown dwarfs. We compare recent models to our photometric and spectroscopic data set. We confirm that nonequilibrium atmospheric chemistry is important for these objects. Nonequilibrium cloud-free models reproduce well the near-infrared spectra and mid-infrared photometry for the warmer Y dwarfs with 425<=T_eff_(K)<=450. A small amount of cloud cover may improve the model fits in the near-infrared for the Y dwarfs with 325<=T_eff_(K)<=375. Neither cloudy nor cloud-free models reproduce the near-infrared photometry for the T_eff_=250K Y dwarf WISEJ085510.83-071442.5 (W0855). We use the mid-infrared region, where most of the flux originates, to constrain our models of W0855. We find that W0855 likely has a mass of 1.5-8 Jupiter masses and an age of 0.3-6Gyr. The Y dwarfs with measured parallaxes are within 20pc of the Sun and have tangential velocities typical of the thin disk. The metallicities and ages we derive for the sample are generally solar-like. We estimate that the known Y dwarfs are 3 to 20 Jupiter-mass objects with ages of 0.6-8.5Gyr.
309. BR photometry of 2012 precursor flare in OJ287
ID:
ivo://CDS.VizieR/J/ApJ/764/5
Title:
BR photometry of 2012 precursor flare in OJ287
Short Name:
J/ApJ/764/5
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have studied three most recent precursor flares in the light curve of the blazar OJ 287 while invoking the presence of a precessing binary black hole in the system to explain the nature of these flares. Precursor flare timings from the historical light curves are compared with theoretical predictions from our model that incorporate effects of an accretion disk and post-Newtonian description for the binary black hole orbit. We find that the precursor flares coincide with the secondary black hole descending toward the accretion disk of the primary black hole from the observed side, with a mean z-component of approximately z_c_=4000AU. We use this model of precursor flares to predict that precursor flare of similar nature should happen around 2020.96 before the next major outburst in 2022.
310. BS Cas BVR light curves
ID:
ivo://CDS.VizieR/J/AJ/136/594
Title:
BS Cas BVR light curves
Short Name:
J/AJ/136/594
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present multicolor charge-coupled device (CCD) photometry for the eclipsing binary BS Cassiopeiae, observed on four nights between 2007 December and 2008 January. Using the Wilson-Devinney program, the photometric solution was derived from our BVR observations. Photometric results indicated that BS Cas is a W-subtype binary, whose mass ratio and overcontact degree are q=0.2834(+/-0.0010) and f=31.6%(+/-1.1%), respectively. Light curves of BS Cas present a typical O'Connell effect, which may be attributed to dark spot activity of the primary component.