- ID:
- ivo://CDS.VizieR/J/MNRAS/402/2087
- Title:
- Optical polarization of OJ 287 in 2005-2009
- Short Name:
- J/MNRAS/402/2087
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- OJ287 is a BL Lac object at redshift z=0.306 that has shown double-peaked bursts at regular intervals of ~12yr during the last ~40yr. We analyse optical photopolarimetric monitoring data from 2005-2009, during which the latest double-peaked outburst occurred. The aim of this study is twofold: firstly, we aim to analyse variability patterns and statistical properties of the optical polarization light-curve. We find a strong preferred position angle in optical polarization. The preferred position angle can be explained by separating the jet emission into two components: an optical polarization core and chaotic jet emission. The optical polarization core is stable on time scales of years and can be explained as emission from an underlying quiescent jet component. The chaotic jet emission sometimes exhibits a circular movement in the Stokes plane. We find six such events, all on the timescales of 10-20days. We interpret these events as a shock front moving forwards and backwards in the jet, swiping through a helical magnetic field. Secondly, we use our data to assess different binary black hole models proposed to explain the regularly appearing double-peaked bursts in OJ287. We compose a list of requirements a model has to fulfil to explain the mysterious behaviour observed in OJ287. The list includes not only characteristics of the light-curve but also other properties of OJ287, such as the black hole mass and restrictions on accretion flow properties. We rate all existing models using this list and conclude that none of the models is able to explain all observations. We discuss possible new explanations and propose a new approach to understanding OJ287. We suggest that both the double-peaked bursts and the evolution of the optical polarization position angle could be explained as a sign of resonant accretion of magnetic field lines, a 'magnetic breathing' of the disc.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/686/1209
- Title:
- Optical properties of GRB afterglows
- Short Name:
- J/ApJ/686/1209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multiwavelength analysis of 63 gamma-ray bursts observed with the world's three largest robotic optical telescopes, the Liverpool and Faulkes Telescopes (North and South). Optical emission was detected for 24 GRBs with brightnesses ranging from R=10 to 22mag in the first 10 minutes after the burst. By comparing optical and X-ray light curves from t=100 to ~106 seconds, we introduce four main classes, defined by the presence or absence of temporal breaks at optical and/or X-ray wavelengths. While 14/24 GRBs can be modeled with the forward-shock model, explaining the remaining 10 is very challenging in the standard framework even with the introduction of energy injection or an ambient density gradient. Early X-ray afterglows, even segments of light curves described by a power law, may be due to additional emission from the central engine. Thirty-nine GRBs in our sample were not detected and have deep upper limits (R<22mag) at early time. Of these, only 10 were identified by other facilities, primarily at near infrared wavelengths, resulting in a dark burst fraction of ~50%. Additional emission in the early-time X-ray afterglow due to late-time central engine activity may also explain some dark bursts by making the bursts brighter than expected in the X-ray band compared to the optical band.
- ID:
- ivo://CDS.VizieR/J/ApJS/170/33
- Title:
- Optical properties of Markarian galaxies
- Short Name:
- J/ApJS/170/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A database for the entire Markarian catalog is presented that combines extensive new measurements of their optical parameters with a literature and database search. The measurements were made using images extracted from the STScI Digitized Sky Survey (DSS) of F_pg_(red) and J_pg_(blue) band photographic sky survey plates obtained by the Palomar and UK Schmidt telescopes. We provide accurate coordinates, morphological type, spectral and activity classes, red and blue apparent magnitudes, apparent diameters, axial ratios, and position angles, as well as number counts of neighboring objects in a circle of radius 50kpc. Special attention was paid to the individual descriptions of the galaxies in the original Markarian lists, which clarified many cases of misidentifications of the objects, particularly among interacting systems, larger galaxies with knots of star formation, possible stars, and cases of stars projected on galaxies. The total number of individual Markarian objects in the database is now 1544.
- ID:
- ivo://CDS.VizieR/J/ApJ/616/71
- Title:
- Optical properties of SCUBA galaxies
- Short Name:
- J/ApJ/616/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical and near-infrared photometry for a sample of 96 dusty, far-infrared luminous galaxies. We have precise spectroscopic redshifts for all these galaxies, yielding a median redshift of <z>=2.2. The majority, 78, are submillimeter-detected galaxies lying at z=0.2-3.6, while the remaining 18 are optically faint {mu}Jy radio galaxies at z=0.9-3.4 that are proposed to be similarly luminous, dusty galaxies whose dust emission is too hot to be detected in the submillimeter waveband.
- ID:
- ivo://CDS.VizieR/J/ApJ/758/25
- Title:
- Optical properties of WISE galaxies
- Short Name:
- J/ApJ/758/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a dense, complete redshift survey, the Smithsonian Hectospec Lensing Survey (SHELS), covering a 4deg^2^ region of a deep imaging survey, the Deep Lens Survey (DLS), to study the optical spectral properties of Wide-field Infrared Survey Explorer (WISE) 22{mu}m selected galaxies. Among 507 WISE 22{mu}m selected sources with (S/N)_22{mu}m_>=3 ({approx}S_22{mu}m_>~2.5mJy), we identify the optical counterparts of 481 sources (~98%) at R<25.2 in the very deep, DLS R-band source catalog. Among them, 337 galaxies at R<21 have SHELS spectroscopic data. Most of these objects are at z<0.8. The infrared (IR) luminosities are in the range 4.5x10^8^(L_{sun}_)<~L_IR_<~5.4x10^12^(L_{sun}_). Most 22{mu}m selected galaxies are dusty star-forming galaxies with a small (<1.5) 4000{AA} break. The stacked spectra of the 22 {mu}m selected galaxies binned in IR luminosity show that the strength of the [O III] line relative to H{beta} grows with increasing IR luminosity. The optical spectra of the 22{mu}m selected galaxies also show that there are some (~2.8%) unusual galaxies with very strong [Ne III] {lambda}3869, 3968 emission lines that require hard ionizing radiation such as active galactic nuclei (AGNs) or extremely young massive stars. The specific star formation rates (sSFRs) derived from the 3.6 and 22{mu}m flux densities are enhanced if the 22{mu}m selected galaxies have close late-type neighbors. The sSFR distribution of the 22{mu}m selected galaxies containing AGNs is similar to the distribution for star-forming galaxies without AGNs. We identify 48 dust-obscured galaxy candidates with large (>~1000) mid-IR to optical flux density ratio. The combination of deep photometric and spectroscopic data with WISE data suggests that WISE can probe the universe to z~2.
- ID:
- ivo://CDS.VizieR/J/ApJS/191/124
- Title:
- Optical spectroscopy of ECDF-S X-ray sources
- Short Name:
- J/ApJS/191/124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a program to acquire high-quality optical spectra of X-ray sources detected in the Extended-Chandra Deep Field-South (E-CDF-S) and its central 2Ms area. New spectroscopic redshifts, up to z=4, are measured for 283 counterparts to Chandra sources with deep exposures (t~2-9hr per pointing) using multi-slit facilities on both VLT (VIMOS) and Keck (DEIMOS), thus bringing the total number of spectroscopically identified X-ray sources to over 500 in this survey field. Since our new spectroscopic identifications are mainly associated with X-ray sources in the shallower 250ks coverage, we provide a comprehensive catalog of X-ray sources detected in the E-CDF-S including the optical and near-infrared counterparts, determined by a likelihood routine, and redshifts (both spectroscopic and photometric), that incorporate published spectroscopic catalogs, thus resulting in a final sample with a high fraction (80%) of X-ray sources having secure identifications. Our redshift catalog includes 17 type-2 QSOs at 1<~z<~3.5. Based on our deepest (9 hr) VLT/VIMOS observation, we identify "elusive" optically faint galaxies (Rmag~25) at z~2-3 based upon the detection of interstellar absorption lines (e.g., OII+SiIV, CII], CIV).
- ID:
- ivo://CDS.VizieR/J/A+A/458/173
- Title:
- Optical spectroscopy of 253 IRAS sources
- Short Name:
- J/A+A/458/173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the optical spectral properties of a sample of stars showing far infrared colours similar to those of well-known planetary nebulae. The large majority of them were unidentified sources or poorly known in the literature at the time when this spectroscopic survey started, some 15 years ago. We present low-resolution optical spectroscopy, finding charts and improved astrometric coordinates of a sample of 253 IRAS sources.
- ID:
- ivo://CDS.VizieR/J/ApJS/230/3
- Title:
- Optical & Spitzer photometry in IC 1805
- Short Name:
- J/ApJS/230/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep wide-field optical CCD photometry and mid-infrared Spitzer/IRAC and MIPS 24{mu}m data for about 100000 stars in the young open cluster IC 1805. The members of IC 1805 were selected from their location in the various color-color and color-magnitude diagrams, and the presence of H{alpha} emission, mid-infrared excess emission, and X-ray emission. The reddening law toward IC 1805 is nearly normal (R_V_=3.05+/-0.06). However, the distance modulus of the cluster is estimated to be 11.9+/-0.2mag (d=2.4+/-0.2kpc) from the reddening-free color-magnitude diagrams, which is larger than the distance to the nearby massive star-forming region W3(OH) measured from the radio VLBA astrometry. We also determined the age of IC 1805 ({tau}_MSTO_=3.5Myr). In addition, we critically compared the age and mass scale from two pre-main-sequence evolution models. The initial mass function with a Salpeter-type slope of {Gamma}=-1.3+/-0.2 was obtained and the total mass of IC 1805 was estimated to be about 2700+/-200M_{sun}_. Finally, we found our distance determination to be statistically consistent with the Tycho-Gaia Astrometric Solution Data Release 1, within the errors. The proper motion of the B-type stars shows an elongated distribution along the Galactic plane, which could be explained by some of the B-type stars being formed in small clouds dispersed by previous episodes of star formation or supernova explosions.
- ID:
- ivo://CDS.VizieR/J/ApJ/537/101
- Title:
- Optical Study for blazars. I.
- Short Name:
- J/ApJ/537/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric observations of AGNs are important to construct light curves and to study variability behavior over different timescales. In this paper, the historical optical data compiled from the published literature are presented in tabular form as an optical database for 28 radio-selected BL Lacertae objects. Maximum optical variations are found and compared with the infrared ones. The faintest, brightest, and averaged magnitudes are presented for individual object. The variation is found correlated with polarization. The light curves are shown in figures along with the relation between color index and magnitude. For the color-magnitude relation, two objects, 0735+178 and 0537-441, show evidence that the color index increases with magnitude, indicating that the spectrum flattens when the source brightens, while three objects (0219+428, 1514-241, 2200+420) show the opposite behavior; an object, 0235+164, shows a brightness-dependent color index- magnitude correlation, while the rest of the objects do not show any clear tendency.
- ID:
- ivo://CDS.VizieR/J/MNRAS/454/3094
- Title:
- Optical transit light curves of WASP-57
- Short Name:
- J/MNRAS/454/3094
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Transits in the WASP-57 planetary system have been found to occur half an hour earlier than expected. We present 10 transit light curves from amateur telescopes, on which this discovery was based, 13 transit light curves from professional facilities which confirm and refine this finding, and high-resolution imaging which show no evidence for nearby companions. We use these data to determine a new and precise orbital ephemeris, and measure the physical properties of the system. Our revised orbital period is 4.5 s shorter than found from the discovery data alone, which explains the early occurrence of the transits. We also find both the star and planet to be larger and less massive than previously thought. The measured mass and radius of the planet are now consistent with theoretical models of gas giants containing no heavy-element core, as expected for the subsolar metallicity of the host star. Two transits were observed simultaneously in four passbands. We use the resulting light curves to measure the planet's radius as a function of wavelength, finding that our data are sufficient in principle but not in practise to constrain its atmospheric properties. We conclude with a discussion of the current and future status of transmission photometry studies for probing the atmospheres of gas-giant transiting planets.
