- 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.
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- ID:
- ivo://CDS.VizieR/J/PAZh/35/403
- Title:
- Optical Variabilities in 3C 120
- Short Name:
- J/PAZh/35/403
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on our UBVRI observations and X-ray data from the RXTE satellite we have investigated the variabilities of the Seyfert Galaxy 3C 120 over the period 1996-2008.
- ID:
- ivo://CDS.VizieR/J/PAZh/21/652
- Title:
- Optical variability in NGC 7469
- Short Name:
- J/PAZh/21/652
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of three-color UBV observations of rapid variability in the nucleus of the Seyfert galaxy NGC 7469 carried out in 1990-1994 are presented. The observations have been carried out during 15 different nights using the 60- and 125-cm telescopes with time resolution of 6-8min (50 hours monitoring) with the aperture of 27.5". The mean errors of one measurement are 1.8, 1.2 and 1.4% for U, B and V. The data set length during one night is from 2 up to 5h. The different nights show the variations at different level: from weak, when the standard deviation during the night exceeds the error of one measurement only by 10-20%, up to strong ones, when the standard deviation exceeds the error of the measurement by factor two.
- ID:
- ivo://CDS.VizieR/J/ApJ/894/24
- Title:
- Optical variability of AGN from the HSC SSP survey
- Short Name:
- J/ApJ/894/24
- Date:
- 03 Dec 2021 00:44:13
- Publisher:
- CDS
- Description:
- We study variability of active galactic nuclei (AGNs) by using the deep optical multiband photometry data obtained from the Hyper Suprime-Cam Subaru Strategic Program (HSC SSP) survey in the COSMOS field. The images analyzed here were taken with 8, 10, 13, and 15 epochs over three years in the g, r, i, and z bands, respectively. We identified 491 robust variable AGN candidates, down to i=25mag and with redshift up to 4.26. Ninety percent of the variability-selected AGNs are individually identified with the X-ray sources detected in the Chandra COSMOS Legacy survey. We investigate their properties in variability by using structure function analysis and find that the structure function for low-luminosity AGNs (L_bol_<~10^45^erg/s) shows a positive correlation with luminosity, which is the opposite trend for the luminous quasars. This trend is likely to be caused by a larger contribution of the host galaxy light for lower-luminosity AGNs. Using the model templates of galaxy spectra, we evaluate the amount of host galaxy contribution to the structure function analysis and find that dominance of the young stellar population is needed to explain the observed luminosity dependence. This suggests that low-luminosity AGNs at 0.8<~z<~1.8 are predominantly hosted in star-forming galaxies. The X-ray stacking analysis reveals the significant emission from the individually X-ray undetected AGNs in our variability-selected sample. The stacked samples show very large hardness ratios in their stacked X-ray spectrum, which suggests that these optically variable sources have large soft X-ray absorption by dust-free gas.
- ID:
- ivo://CDS.VizieR/J/PAZh/25/403
- Title:
- Optical variability of NGC 4151
- Short Name:
- J/PAZh/25/403
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The UBV observations of performed between 1972 and 1998 are presented. The aperture is 27.5".
- ID:
- ivo://CDS.VizieR/J/AJ/157/95
- Title:
- Optical variability of OJ 287 in 2016-2017
- Short Name:
- J/AJ/157/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a recent multiband optical photometric and polarimetric observational campaign of the blazar OJ 287 that was carried out during 2016 September-2017 December. We employed nine telescopes in Bulgaria, China, Georgia, Japan, Serbia, Spain, and the United States. We collected over 1800 photometric image frames in BVRI bands and over 100 polarimetric measurements over ~175 nights. In 11 nights with many quasi-simultaneous multiband (V, R, I) observations, we did not detect any genuine intraday variability in flux or color. On longer timescales, multiple flaring events were seen. Large changes in color with respect to time and in a color-magnitude diagram were seen, and while only a weak systematic variability trend was noticed in color with respect to time, the color-magnitude diagram shows a bluer-when-brighter trend. Large changes in the degree of polarization and substantial swings in the polarization angle were detected. The fractional Stokes parameters of the polarization showed a systematic trend with time in the beginning of these observations, followed by chaotic changes and then an apparently systematic variation at the end. These polarization changes coincide with the detection and duration of the source at very high energies as seen by VERITAS. The spectral index shows a systematic variation with time and V-band magnitude. We briefly discuss possible physical mechanisms that could explain the observed flux, color, polarization, and spectral variability.
- ID:
- ivo://CDS.VizieR/J/PAZh/23/277
- Title:
- Optical variability of WW Vul
- Short Name:
- J/PAZh/23/277
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The UBV observations of WW Vul performed between 1983 and 1993 are presented. All UBV observations of WW Vul are reduced to GAISh photometric system.
- ID:
- ivo://CDS.VizieR/J/AJ/159/259
- Title:
- Opt-NIR light curve of the quasar 3C 273
- Short Name:
- J/AJ/159/259
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We monitored the z=0.158 quasar 3C273 between 2015 and 2019 in the optical (BVrz) and near-infrared (JHK) with the aim to perform dust reverberation mapping. Accounting for host galaxy and accretion disk contributions, we obtained pure dust light curves in JHK. Cross correlations between the V-band and the dust light curves yield an average rest-frame delay for the hot dust of {tau}cent~410days. This is a factor of two shorter than that expected from the the dust ring radius R_x_~900lt-day reported from interferometric studies. The dust covering factor (CF) is about 8%, much smaller than that predicted from the half covering angle of 45{deg} found for active galactic nuclei (AGNs). We analyze the asymmetric shape of the correlation functions and explore whether an inclined biconical bowl-shaped dust torus geometry could bring these findings ({tau}cent, Rx and CF) into a consistent picture. The hot varying dust emission originates from the edge of the bowl rim with a small covering angle 40{deg}<{theta}<45{deg}, and we see only the near side of the biconus. Such a dust gloriole with R_x_= 900{+/-}200lt-day and an inclination 12{deg} matches the data remarkably well. Comparing the results of 3C273 with literature for less luminous AGN, we find a lag-luminosity relation {tau}{prop}L{alpha} with {alpha}=0.33-0.40, flatter than the widely adopted relation with {alpha}~0.5. We address several explanations for the new lag-luminosity relation.
- ID:
- ivo://CDS.VizieR/J/ApJ/866/83
- Title:
- Opt/NIR obs. of 1FGLJ1417.7-4407 neutron star bin.
- Short Name:
- J/ApJ/866/83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Fermi {gamma}-ray source 1FGL J1417.7-4407 (J1417) is a compact X-ray binary with a neutron star primary and a red giant companion in a ~5.4 days orbit. This initial conclusion, based on optical and X-ray data, was confirmed when a 2.66ms radio pulsar was found at the same location (and with the same orbital properties) as the optical/X-ray source. However, these initial studies found conflicting evidence about the accretion state and other properties of the binary. We present new optical, radio, and X-ray observations of J1417 that allow us to better understand this unusual system. We show that one of the main pieces of evidence previously put forward for an accretion disk-the complex morphology of the persistent H{alpha} emission line-can be better explained by the presence of a strong, magnetically driven stellar wind from the secondary and its interaction with the pulsar wind. The radio spectral index derived from VLA/ATCA observations is broadly consistent with that expected from a millisecond pulsar, further disfavoring an accretion disk scenario. X-ray observations show evidence for a double-peaked orbital light curve, similar to that observed in some redback millisecond pulsar binaries and likely due to an intrabinary shock. Refined optical light-curve fitting gives a distance of 3.1+/-0.6kpc, confirmed by a Gaia DR2 parallax measurement. At this distance the X-ray luminosity of J1417 is (1.0_-0.3_^+0.4^)x10^33^erg/s, which is more luminous than all known redback systems in the rotational-powered pulsar state, perhaps due to the wind from the giant companion. The unusual phenomenology of this system and its differing evolutionary path from redback millisecond pulsar binaries points to a new eclipsing pulsar "spider" subclass that is a possible progenitor of normal field millisecond pulsar binaries.
- ID:
- ivo://CDS.VizieR/J/ApJ/833/149
- Title:
- Opt/NIR obs. of M31N 2008-12a 2015 eruption
- Short Name:
- J/ApJ/833/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Andromeda Galaxy recurrent nova M31N 2008-12a had been observed in eruption 10 times, including yearly eruptions from 2008 to 2014. With a measured recurrence period of P_rec_=351+/-13days (we believe the true value to be half of this) and a white dwarf very close to the Chandrasekhar limit, M31N 2008-12a has become the leading pre-explosion supernova type Ia progenitor candidate. Following multi-wavelength follow-up observations of the 2013 and 2014 eruptions, we initiated a campaign to ensure early detection of the predicted 2015 eruption, which triggered ambitious ground- and space-based follow-up programs. In this paper we present the 2015 detection, visible to near-infrared photometry and visible spectroscopy, and ultraviolet and X-ray observations from the Swift observatory. The LCOGT 2m (Hawaii) discovered the 2015 eruption, estimated to have commenced at August 28.28+/-0.12UT. The 2013-2015 eruptions are remarkably similar at all wavelengths. New early spectroscopic observations reveal short-lived emission from material with velocities ~13000km/s, possibly collimated outflows. Photometric and spectroscopic observations of the eruption provide strong evidence supporting a red giant donor. An apparently stochastic variability during the early supersoft X-ray phase was comparable in amplitude and duration to past eruptions, but the 2013 and 2015 eruptions show evidence of a brief flux dip during this phase. The multi-eruption Swift/XRT spectra show tentative evidence of high-ionization emission lines above a high-temperature continuum. Following Henze+ (2015A&A...582L...8H), the updated recurrence period based on all known eruptions is P_rec_=174+/-10days, and we expect the next eruption of M31N 2008-12a to occur around 2016 mid-September.
