We present inferences on the geometry and kinematics of the broad-Hβ line-emitting region in four active galactic nuclei monitored as part of the fall 2010 reverberation mapping campaign at MDM ...Observatory led by the Ohio State University. From modeling the continuum variability and response in emission-line profile changes as a function of time, we infer the geometry of the Hβ-emitting broad-line regions (BLRs) to be thick disks that are close to face-on to the observer with kinematics that are well-described by either elliptical orbits or inflowing gas. We measure the black hole mass to be for Mrk 335, for Mrk 1501, for 3C 120, and for PG 2130+099. These black hole mass measurements are not based on a particular assumed value of the virial scale factor f, allowing us to compute individual f factors for each target. Our results nearly double the number of targets that have been modeled in this manner, and we investigate the properties of a more diverse sample by including previously modeled objects. We measure an average scale factor in the entire sample of when the line dispersion is used to characterize the line width, which is consistent with the values derived using the normalization of the - relation. We find that the scale factor f for individual targets is likely correlated with the black hole mass, inclination angle, and opening angle of the BLR, but we do not find any correlation with the luminosity.
We present a new procedure for the internal (night-to-night) calibration of timeseries spectra, with specific applications to optical AGN reverberation mapping data. The traditional calibration ...technique assumes that the narrow O iii λ5007 emission-line profile is constant in time; given a reference O iii λ5007 line profile, nightly spectra are aligned by fitting for a wavelength shift, a flux rescaling factor, and a change in the spectroscopic resolution. We propose the following modifications to this procedure: (1) we stipulate a constant spectral resolution for the final calibrated spectra, (2) we employ a more flexible model for changes in the spectral resolution, and (3) we use a Bayesian modeling framework to assess uncertainties in the calibration. In a test case using data for MCG+08-11-011, these modifications result in a calibration precision of ∼1 millimagnitude, which is approximately a factor of five improvement over the traditional technique. At this level, other systematic issues (e.g., the nightly sensitivity functions and Feii contamination) limit the final precision of the observed light curves. We implement this procedure as a python package (mapspec), which we make available to the community.
ABSTRACT We present ground-based optical photometric monitoring data for NGC 5548, part of an extended multiwavelength reverberation mapping campaign. The light curves have nearly daily cadence from ...2014 January to July in nine filters (BVRI and ugriz). Combined with ultraviolet data from the Hubble Space Telescope and Swift, we confirm significant time delays between the continuum bands as a function of wavelength, extending the wavelength coverage from 1158 Å to the z band (~9160 Å). We find that the lags at wavelengths longer than the V band are equal to or greater than the lags of high-ionization-state emission lines (such as He ii λ 1640 and λ 4686 ), suggesting that the continuum-emitting source is of a physical size comparable to the inner broad-line region (BLR). The trend of lag with wavelength is broadly consistent with the prediction for continuum reprocessing by an accretion disk with τ ∝ λ 4 / 3 . However, the lags also imply a disk radius that is 3 times larger than the prediction from standard thin-disk theory, assuming that the bolometric luminosity is 10% of the Eddington luminosity ( L = 0.1 L Edd ). Using optical spectra from the Large Binocular Telescope, we estimate the bias of the interband continuum lags due to BLR emission observed in the filters. We find that the bias for filters with high levels of BLR contamination (~20%) can be important for the shortest continuum lags and likely has a significant impact on the u and U bands owing to Balmer continuum emission.
Swift intensive accretion disk reverberation mapping of four AGN yielded light curves sampled ∼200-350 times in 0.3-10 keV X-ray and six UV/optical bands. Uniform reduction and cross-correlation ...analysis of these data sets yields three main results: (1) The X-ray/UV correlations are much weaker than those within the UV/optical, posing severe problems for the lamp-post reprocessing model in which variations in a central X-ray corona drive and power those in the surrounding accretion disk. (2) The UV/optical interband lags are generally consistent with as predicted by the centrally illuminated thin accretion disk model. While the average interband lags are somewhat larger than predicted, these results alone are not inconsistent with the thin disk model given the large systematic uncertainties involved. (3) The one exception is the U band lags, which are on average a factor of ∼2.2 larger than predicted from the surrounding band data and fits. This excess appears to be due to diffuse continuum emission from the broad-line region (BLR). The precise mixing of disk and BLR components cannot be determined from these data alone. The lags in different AGN appear to scale with mass or luminosity. We also find that there are systematic differences between the uncertainties derived by JAVELIN versus more standard lag measurement techniques, with JAVELIN reporting smaller uncertainties by a factor of 2.5 on average. In order to be conservative only standard techniques were used in the analyses reported herein.
We present the first results from an optical reverberation mapping campaign executed in 2014 targeting the active galactic nuclei (AGNs) MCG+08-11-011, NGC 2617, NGC 4051, 3C 382, and Mrk 374. Our ...targets have diverse and interesting observational properties, including a "changing look" AGN and a broad-line radio galaxy. Based on continuum-Hβ lags, we measure black hole masses for all five targets. We also obtain Hγ and He ii λ4686 lags for all objects except 3C 382. The He ii λ4686 lags indicate radial stratification of the BLR, and the masses derived from different emission lines are in general agreement. The relative responsivities of these lines are also in qualitative agreement with photoionization models. These spectra have extremely high signal-to-noise ratios (100-300 per pixel) and there are excellent prospects for obtaining velocity-resolved reverberation signatures.
We present optical continuum lags for two Seyfert 1 galaxies, MCG+08-11-011 and NGC 2617, using monitoring data from a reverberation mapping campaign carried out in 2014. Our light curves span the ...ugriz filters over four months, with median cadences of 1.0 and 0.6 days for MCG+08-11-011 and NGC 2617, respectively, combined with roughly daily X-ray and near-UV data from Swift for NGC 2617. We find lags consistent with geometrically thin accretion-disk models that predict a lag-wavelength relation of τ ∝ λ4/3. However, the observed lags are larger than predictions based on standard thin-disk theory by factors of 3.3 for MCG+08-11-011 and 2.3 for NGC 2617. These differences can be explained if the mass accretion rates are larger than inferred from the optical luminosity by a factor of 4.3 in MCG+08-11-011 and a factor of 1.3 in NGC 2617, although uncertainty in the SMBH masses determines the significance of this result. While the X-ray variability in NGC 2617 precedes the UV/optical variability, the long (2.6 day) lag is problematic for coronal reprocessing models.
ABSTRACT
We present photometric and spectroscopic observations of the unusual Type Ia supernova ASASSN-18tb, including a series of Southern African Large Telescope spectra obtained over the course of ...nearly six months and the first observations of a supernova by the Transiting Exoplanet Survey Satellite. We confirm a previous observation by Kollmeier et al. showing that ASASSN-18tb is the first relatively normal Type Ia supernova to exhibit clear broad (∼1000 km s−1) H α emission in its nebular-phase spectra. We find that this event is best explained as a sub-Chandrasekhar mass explosion producing $M_{\mathrm{ Ni}} \approx 0.3\,\, \rm {M}_\odot$. Despite the strong H α signature at late times, we find that the early rise of the supernova shows no evidence for deviations from a single-component power-law and is best fit with a moderately shallow power law of index 1.69 ± 0.04. We find that the H α luminosity remains approximately constant after its initial detection at phase +37 d, and that the H α velocity evolution does not trace that of the Fe iii λ4660 emission. These suggest that the H α emission arises from a circumstellar medium (CSM) rather than swept-up material from a non-degenerate companion. However, ASASSN-18tb is strikingly different from other known CSM-interacting Type Ia supernovae in a number of significant ways. Those objects typically show an H α luminosity two orders of magnitude higher than what is seen in ASASSN-18tb, pushing them away from the empirical light-curve relations that define ‘normal’ Type Ia supernovae. Conversely, ASASSN-18tb exhibits a fairly typical light curve and luminosity for an underluminous or transitional SN Ia, with MR ≈ −18.1 mag. Moreover, ASASSN-18tb is the only SN Ia showing H α from CSM interaction to be discovered in an early-type galaxy.
The Transiting Exoplanet Survey Satellite (TESS) recently observed 18 transits of the hot Jupiter WASP-4b. The sequence of transits occurred 81.6 11.7 s earlier than had been predicted, based on data ...stretching back to 2007. This is unlikely to be the result of a clock error, because TESS observations of other hot Jupiters (WASP-6b, 18b, and 46b) are compatible with a constant period, ruling out an 81.6 s offset at the 6.4 level. The 1.3 day orbital period of WASP-4b appears to be decreasing at a rate of ms per year. The apparent period change might be caused by tidal orbital decay or apsidal precession, although both interpretations have shortcomings. The gravitational influence of a third body is another possibility, though at present there is minimal evidence for such a body. Further observations are needed to confirm and understand the timing variation.
ABSTRACT
We present observations from the Transiting Exoplanet Survey Satellite (TESS) of twenty bright core-collapse supernovae with peak TESS-band magnitudes ≲18 mag. We reduce this data with an ...implementation of the image subtraction pipeline used by the All-Sky Automated Survey for Supernovae (ASAS-SN) optimized for use with the TESS images. In empirical fits to the rising light curves, we do not find strong correlations between the fit parameters and the peak luminosity. Existing semi-analytic models fit the light curves of the Type II supernovae well, but do not yield reasonable estimates of the progenitor radius or explosion energy, likely because they are derived for use with ultraviolet observations while TESS observes in the near-infrared. If we instead fit the data with numerically simulated light curves, the rising light curves of the Type II supernovae are consistent with the explosions of red supergiants. While we do not identify shock breakout emission for any individual event, when we combine the fit residuals of the Type II supernovae in our sample, we do find a >5σ flux excess in the ∼1 d before the start of the light-curve rise. It is likely that this excess is due to shock breakout emission, and that during its extended mission TESS will observe a Type II supernova bright enough for this signal to be detected directly.
ABSTRACT Reverberation-mapping-based scaling relations are often used to estimate the masses of black holes from single-epoch spectra of active galactic nuclei (AGNs). While the radius-luminosity ...relation that is the basis of these scaling relations is determined using reverberation mapping of the Hβ line in nearby AGNs, the scaling relations are often extended to use other broad emission lines, such as Mg ii, in order to get black hole masses at higher redshifts when Hβ is redshifted out of the optical waveband. However, there is no radius-luminosity relation determined directly from Mg ii. Here, we present an attempt to perform reverberation mapping using Mg ii in the well-studied nearby Seyfert 1 NGC 5548. We used Swift to obtain UV grism spectra of NGC 5548 once every two days from 2013 April to September. Concurrent photometric UV monitoring with Swift provides a well determined continuum light curve that shows strong variability. The Mg ii emission line, however, is not strongly correlated with the continuum variability, and there is no significant lag between the two. We discuss these results in the context of using Mg ii scaling relations to estimate high-redshift black hole masses.
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