We present photometry and spectroscopy of four hydrogen-poor luminous supernovae discovered during the 2-month long science commissioning and early operations of the Zwicky Transient Facility (ZTF) ...survey. Three of these objects, SN 2018bym (ZTF18aapgrxo), SN 2018avk (ZTF18aaisyyp), and SN 2018bgv (ZTF18aavrmcg), resemble typical SLSN-I spectroscopically, while SN 2018don (ZTF18aajqcue) may be an object similar to SN 2007bi experiencing considerable host galaxy reddening, or an intrinsically long-lived, luminous, and red SN Ic. We analyze the light curves, spectra, and host galaxy properties of these four objects and put them in context of the population of SLSN-I. SN 2018bgv stands out as the fastest-rising SLSN-I observed to date, with a rest-frame g-band rise time of just 10 days from explosion to peak-if it is powered by magnetar spin-down, the implied ejecta mass is only 1 M . SN 2018don also displays unusual properties-in addition to its red colors and comparatively massive host galaxy, the light curve undergoes some of the strongest light-curve undulations postpeak seen in an SLSN-I, which we speculate may be due to interaction with circumstellar material. We discuss the promises and challenges of finding SLSNe in large-scale surveys like ZTF given the observed diversity in the population.
Context.
We present a novel probabilistic flux variation gradient (PFVG) approach to separate the contributions of active galactic nuclei (AGN) and host galaxies in the context of photometric ...reverberation mapping (PRM) of AGN.
Aims.
We explored the ability of recovering the fractional contribution in a model-independent way using the entire set of light curves obtained through different filters and photometric apertures simultaneously.
Methods.
The method is based on the observed “bluer when brighter” phenomenon that is attributed to the superimposition of a two-component structure; the red host galaxy, which is constant in time, and the varying blue AGN. We describe the PFVG mathematical formalism and demonstrate its performance using simulated light curves and available PRM observations.
Results.
The new probabilistic approach is able to recover host-galaxy fluxes to within 1% precision as long as the light curves do not show a significant contribution from time delays. This represents a significant improvement with respect to previous applications of the traditional FVG method to PRM data.
Conclusions.
The proposed PFVG provides an efficient and accurate way to separate the AGN and host-galaxy luminosities in PRM monitoring data. The method will be especially helpful in the case of large upcoming photometric survey telescopes such as the public optical/near-infrared Legacy Survey of Space and Time (LSST) at the
Vera C. Rubin
Observatory. Finally, we have made the algorithms freely available as part of our Julia PFVG package.
Aims. A strong X-ray outburst was detected in HE 1136-2304 in 2014. Accompanying optical spectra revealed that the spectral type has changed from a nearly Seyfert 2 type (1.95), classified by spectra ...taken 10 and 20 years ago, to a Seyfert 1.5 in our most recent observations. We seek to investigate a detailed spectroscopic campaign on the spectroscopic properties and spectral variability behavior of this changing look AGN and compare this to other variable Seyfert galaxies. Methods. We carried out a detailed spectroscopic variability campaign of HE 1136-2304 with the 10 m Southern African Large Telescope (SALT) between 2014 December and 2015 July. Results. The broad-line region (BLR) of HE 1136-2304 is stratified with respect to the distance of the line-emitting regions. The integrated emission line intensities of Hα, Hβ, He I λ5876, and He II λ4686 originate at distances of 15.0−3.8+4.2 15 . 0 − 3.8 + 4.2 $ 15.0^{+4.2}_{-3.8} $ , 7.5−5.7+4.6 7 . 5 − 5.7 + 4.6 $ 7.5^{+4.6}_{-5.7} $ , 7.3−4.4+2.8 7 . 3 − 4.4 + 2.8 $ 7.3^{+2.8}_{-4.4} $ , and 3.0−3.7+5.3 3 . 0 − 3.7 + 5.3 $ 3.0^{+5.3}_{-3.7} $ light days with respect to the optical continuum at 4570 Å. The variability amplitudes of the integrated emission lines are a function of distance to the ionizing continuum source as well. We derived a central black hole mass of 3.8 ± 3.1 × 107 M⊙ based on the linewidths and distances of the BLR. The outer line wings of all BLR lines respond much faster to continuum variations indicating a Keplerian disk component for the BLR. The response in the outer wings is about two light days shorter than the response of the adjacent continuum flux with respect to the ionizing continuum flux. The vertical BLR structure in HE 1136-2304 confirms a general trend that the emission lines of narrow line active galactic nuclei (AGNs) originate at larger distances from the midplane in comparison to AGNs showing broader emission lines. Otherwise, the variability behavior of this changing look AGN is similar to that of other AGN.
Photometric reverberation mapping employs a wide band pass to measure the AGN continuum variations and a suitable narrow band to trace the echo of an emission line in the broad line region (BLR). The ...narrow band catches both the emission line and the underlying continuum, and one needs to extract the pure emission line light curve. We performed a test on two local AGNs, PG0003+199 and Ark120, by observing well-sampled broad- (B, V) and narrow-band light curves with the robotic 15 cm telescope VYSOS-6 on Cerro Armazones, Chile. We find that, as long as the emission line contributes 50% to the band pass, the pure emission line light curve can be reconstructed from photometric monitoring data so that the time lag τ can be measured. For both objects the lags are consistent with spectroscopic reverberation results. We calculated virial black hole masses in agreement with literature values, by combining the BLR size RBLR (τ) from photometric monitoring with the velocity dispersion of a single contemporaneous spectrum. Applying the flux variation gradient method, we estimate the host galaxy contribution in the apertures used and the host-subtracted restframe 5100 Å luminosity LAGN. Our LAGN differs significantly from previous estimates, placing both sources ~50% closer to the RBLR − LAGN relation. This suggests that the scatter in the current RBLR − LAGN relation is largely caused by uncertainties in RBLR due to undersampled light curves and by uncertainties in the host-subtracted AGN luminosities inferred so far. If the scatter can be reduced, then two quasar samples matching in RBLR should also match in intrinsic LAGN, independent of redshift, thus offering the prospect of probing cosmological models. Photometric reverberation mapping opens the door to efficiently measuring hundreds of BLR sizes and host-subtracted AGN luminosities even with small telescopes, but also routinely with upcoming large survey telescopes like the LSST.
ABSTRACT
We present the results of a continuum reverberation mapping study of the radio-quiet type 1 Seyfert galaxy IRAS 09149−6206. The analysis was performed using X-ray, ultraviolet (UV), and ...optical observations made with the Swift telescope between 2017 January and December. The time delays between different light curves were measured using three different algorithms: PyI2CCF, PyROA, and JAVELIN. Our results show that the time delays increase with wavelength after τ ∝ λ4/3, as predicted for a geometrically thin and optically thick accretion disc, but only after accounting for significant diffuse continuum emission from the broad-line region. However, the measured size of the accretion disc can be up to five times larger than that predicted by standard theory. To our surprise, the strong increase in soft X-ray fluxes is delayed by about 15 d compared to the optical UV fluctuations, which challenges the prediction of the lamp-post model. Our analysis of the X-ray variability reveals the presence of a non-variable spectral component at 0.3–6.0 keV along with variable excess emission at 2.0–3.0 keV, which could be partly related to relativistic reflection in the inner region of the accretion disc. IRAS 09149−6206 joins the list of objects for which the traditional lamp-post model cannot explain the observed time delays. A scenario that incorporates other geometric considerations into the lamp-post model, e.g. an extended corona along a scattering source, might be better suited to explain the observed long time delays.
ABSTRACT
Photometric reverberation mapping can detect the radial extent of the accretion disc (AD) in Active Galactic Nuclei by measuring the time delays between light curves observed in different ...continuum bands. Quantifying the constraints on the efficiency and accuracy of the delay measurements is important for recovering the AD size-luminosity relation, and potentially using quasars as standard candles. We have explored the possibility of determining the AD size of quasars using next-generation Big Data surveys. We focus on the Legacy Survey of Space and Time (LSST) at the Vera C. Rubin Observatory, which will observe several thousand quasars with the Deep Drilling Fields and up to 10 million quasars for the main survey in six broadband filter during its 10-yr operational lifetime. We have developed extensive simulations that take into account the characteristics of the LSST survey and the intrinsic properties of the quasars. The simulations are used to characterize the light curves from which AD sizes are determined using various algorithms. We find that the time delays can be recovered with an accuracy of 5 and 15 per cent for light curves with a time sampling of 2 and 5 d, respectively. The results depend strongly on the redshift of the source and the relative contribution of the emission lines to the bandpasses. Assuming an optically thick and geometrically thin AD, the recovered time-delay spectrum is consistent with black hole masses derived with 30 per cent uncertainty.
Abstract
We present the results of a two year optical continuum photometric reverberation mapping campaign carried out on the nucleus of the Seyfert-1 galaxy Mrk509. Specially designed narrow-band ...filters were used in order to mitigate the line and pseudo-continuum contamination of the signal from the broad line region, while allowing for high-accuracy flux-calibration over a large field of view. We obtained light curves with a sub-day time sampling and typical flux uncertainties of 1%. The high photometric precision allowed us to measure inter-band continuum time delays of up to ∼2 days across the optical range. The time delays are consistent with the relation τ∝λ4/3 predicted for an optically thick and geometrically thin accretion disk model. The size of the disk is, however, a factor of 1.8 larger than predictions based on the standard thin-disk theory. We argue that, for the particular case of Mrk509, a larger black hole mass due to the unknown geometry scaling factor can reconcile the difference between the observations and theory.
ABSTRACT
We report on the results of a multiwavelength monitoring campaign of the bright, nearby Seyfert galaxy Ark 120, using a ∼50-d observing programme with Swift and a ∼4-month co-ordinated ...ground-based observing campaign, pre-dominantly using the Skynet Robotic Telescope Network. We find Ark 120 to be variable at all optical, UV, and X-ray wavelengths, with the variability observed to be well correlated between wavelength bands on short time-scales. We perform cross-correlation analysis across all available wavelength bands, detecting time delays between emission in the X-ray band and the Swift V, B, and UVW1 bands. In each case, we find that the longer wavelength emission is delayed with respect to the shorter wavelength emission. Within our measurement uncertainties, the time delays are consistent with the τ ∼ λ4/3 relation, as predicted by a disc reprocessing scenario. The measured lag centroids are τcent = 11.90 ± 7.33, 10.80 ± 4.08, and 10.60 ± 2.87 d between the X-ray and V, B, and UVW1 bands, respectively. These time delays are longer than those expected from standard accretion theory and, as such, Ark 120 may be another example of an active galaxy whose accretion disc appears to exist on a larger scale than predicted by the standard thin-disc model. Additionally, we detect further inter-band time delays: most notably between the ground-based I and B bands (τcent = 3.46 ± 0.86 d), and between both the Swift XRT and UVW1 bands and the I band (τcent = 12.34 ± 4.83 and 2.69 ± 2.05 d, respectively), highlighting the importance of co-ordinated ground-based optical observations.
A survey for high-mass eclipsing binaries Pozo Nuñez, F; Chini, R; Barr Domínguez, A ...
Monthly notices of the Royal Astronomical Society,
12/2019, Letnik:
490, Številka:
4
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
We report results from a search for Galactic high-mass eclipsing binaries. The photometric monitoring campaign was performed in Sloan r and i with the robotic twin refractor RoBoTT at the ...Universitätssternwarte Bochum in Chile and complemented by Johnson UBV data. Comparison with the SIMBAD data base reveals 260 variable high-mass stars. Based on well-sampled light curves, we discovered 35 new eclipsing high-mass systems and confirm the properties of six previously known systems. For all objects, we provide the first light curves and determine orbital periods through the Lafler–Kinman algorithm. Apart from GSC 08173-0018 and Pismis 24-13 ($P = 19.47\, d$ and $20.14\, d$) and the exceptional short-period system TYC 6561-1765-1 ($P = 0.71\, d$), all systems have orbital periods between 1 and 9 d. We model the light curves of 26 systems within the framework of the Roche geometry and calculate fundamental parameters for each system component. The Roche lobe analysis indicates that 14 systems have a detached geometry, while 12 systems have a semidetached geometry; seven of them are near-contact systems. The deduced mass ratios q = M2/M1 reach from 0.4 to 1.0 with an average value of 0.8. The similarity of masses suggests that these high-mass binaries were created during the star formation process rather than by tidal capture.
We present the results of a five month monitoring campaign of the local active galactic nuclei (AGN) 3C 120. Observations with a median sampling of two days were conducted with the robotic 15 cm ...telescope VYSOS-6 located near Cerro Armazones in Chile. Broad band (B, V) and narrow band (NB) filters were used in order to measure fluxes of the AGN and the Hβ broad line region (BLR) emission line. The NB flux is constituted by about 50% continuum and 50% Hβ emission line. To disentangle line and continuum flux, a synthetic Hβ light curve was created by subtracting a scaled V-band light curve from the NB light curve. Here we show that the Hβ emission line responds to continuum variations with a rest frame lag of 23.6 ± 1.69 days. We estimate a virial mass of the central black hole MBH = 57 ± 27 × 106 M⊙, by combining the obtained lag with the velocity dispersion of a single contemporaneous spectrum. Using the flux variation gradient method, we determined the host galaxy subtracted rest frame 5100 Å luminosity at the time of our monitoring campaign with an uncertainty of 10% (LAGN = (6.94 ± 0.71) × 1043 erg s-1). Compared with recent spectroscopic reverberation results, 3C 120 shifts in the RBLR − LAGN diagram remarkably close to the theoretically expected relation of R ∝ L0.5. Our results demonstrate the performance of photometric AGN reverberation mapping, in particular for efficiently determining the BLR size and the AGN luminosity.
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