Doppler tomography and photometry of the cataclysmic variable 1RXS J064434.5+334451

We have obtained simultaneous photometric and spectroscopic observations of the cataclysmic variable 1RXS J064434.5+334451. We have calibrated the spectra for slit losses using simultaneous photometry, allowing us to construct reliable Doppler images from H? and He?ii 4686-Å emission lines. We have improved the ephemeris of the object based on new photometric eclipse timings, obtaining HJD = 245?3403.759?533 + 0.269?374?46E. Some eclipses present a clear internal structure, which we attribute to a central He?ii emission region surrounding the white dwarf, a finding supported by Doppler tomography. This indicates that the system has a large inclination angle i = 78 ± 2°. We have also analysed the radial velocity curve from the emission lines to measure its semi-amplitude, K1, from H? and He?ii 4686 and derive the masses of the components M1 = 0.82 ± 0.06 M?, M2 = 0.78 ± 0.04 M? and their separation a = 2.01 ± 0.06 R?. The Doppler tomography and other observed features in this nova-like system strongly suggest that this is a SW Sex type system

Testing super-eddington accretion on to a supermassive black hole : reverberation mapping of PG 1119+120

KH and JVHS acknowledge support from STFC grant ST/R000824/1. CH acknowledges support from the National Science Foundation of China (12122305). PD acknowledges support from NSFC grant 12022301, 11991051, and 11991054, and from National Key R&D Program of China (grant 2021YFA1600404). LCH was supported by the National Science Foundation of China (grants 11721303, 11991052,12011540375, and 12233001) and the China Manned Space Project (CMS-CSST-2021-A04, CMS-CSST-2021-A06).We measure the black hole mass and investigate the accretion flow around the local (z = 0.0502) quasar PG 1119+120. Spectroscopic monitoring with Calar Alto provides H β lags and linewidths from which we estimate a black hole mass of log (M•/M⊙) = 7.0, uncertain by ∼0.4 dex. High cadence photometric monitoring over 2 yr with the Las Cumbres Observatory provides light curves in seven optical bands suitable for intensive continuum reverberation mapping. We identify variability on two time-scales. Slower variations on a 100-d time-scale exhibit excess flux and increased lag in the u′ band and are thus attributable to diffuse bound-free continuum emission from the broad-line region. Faster variations that we attribute to accretion disc reprocessing lack a u′-band excess and have flux and delay spectra consistent with either τ ∝ λ4/3, as expected for a temperature structure of T(R) ∝ R−3/4 for a thin accretion disc, or τ ∝ λ2 expected for a slim disc. Decomposing the flux into variable (disc) and constant (host galaxy) components, we find the disc SED to be flatter than expected with ƒv ∼ const. Modelling the SED predicts an Eddington ratio of λEdd > 1, where the flat spectrum can be reproduced by a slim disc with little dust extinction or a thin disc that requires more dust extinction. While this accretion is super-Eddington, the geometry is still unclear; however, a slim disc is expected due to the high radiation pressure at these accretion rates, and is entirely consistent with our observations.Publisher PDFPeer reviewe

The Sloan Digital Sky Survey Reverberation Mapping Project : how broad emission line widths change when luminosity changes

Funding: National Science Foundation of China (11721303, 11890693, 11991052) and the National Key R&D Program of China (2016YFA0400702, 2016YFA0400703). YS acknowledges support from an Alfred P. Sloan Research Fellowship and NSF grant AST-1715579. CJG, WNB, JRT, and DPS acknowledge support from NSF grants AST-1517113 and AST-1516784. KH acknowledges support from STFC grant ST/R000824/1. PBH acknowledges support from NSERC grant 2017-05983. YH acknowledges support from NASA grant HST-GO-15650.Quasar broad emission lines are largely powered by photoionization from the accretion continuum. Increased central luminosity will enhance line emissivity in more distant clouds, leading to increased average distance of the broad-line-emitting clouds and decreased averaged line width, known as the broad-line region (BLR) "breathing". However, different lines breathe differently, and some high-ionization lines, such as C IV, can even show "anti-breathing" where the line broadens when luminosity increases. Using multi-year photometric and spectroscopic monitoring data from the Sloan Digital Sky Survey Reverberation Mapping project, we quantify the breathing effect (Δlog W=αΔlog L) of broad Hα, Hβ, Mg II, C IV,and C III] for statistical quasar samples over z≈0.1−2.5. We found that Hβ displays the most consistent normal breathing expected from the virial relation (α∼−0.25), Mg II and Hα on average show no breathing (α∼0), and C IV (and similarly C III] and Si IV mostly shows anti-breathing (α>0). The anti-breathing of C IV can be well understood by the presence of a non-varying core component in addition to a reverberating broad-base component, consistent with earlier findings. The deviation from canonical breathing introduces extra scatter (aluminosity-dependent bias) in single-epoch virial BH mass estimates due to intrinsic quasar variability, which underlies the long argued caveats of C IV single-epoch masses. Using the line dispersion instead of FWHM leads to less, albeit still substantial, deviations from canonical breathing in most cases. Our results strengthen the need for reverberation mapping to provide reliable quasar BH masses, and quantify the level of variability-induced bias in single-epoch BH masses based on various lines.PostprintPeer reviewe

UV/Optical disk reverberation lags despite a faint X-ray corona in the AGN Mrk 335

We present the first results from a 100-day Swift, NICER and ground-based X-ray/UV/optical reverberation mapping campaign of the Narrow-Line Seyfert 1 Mrk 335, when it was in an unprecedented low X-ray flux state. Despite dramatic suppression of the X-ray variability, we still observe UV/optical lags as expected from disk reverberation. Moreover, the UV/optical lags are consistent with archival observations when the X-ray luminosity was >10 times higher. Interestingly, both low- and high-flux states reveal UV/optical lags that are 6-11 times longer than expected from a thin disk. These long lags are often interpreted as due to contamination from the broad line region, however the u band excess lag (containing the Balmer jump from the diffuse continuum) is less prevalent than in other AGN. The Swift campaign showed a low X-ray-to-optical correlation (similar to previous campaigns), but NICER and ground-based monitoring continued for another two weeks, during which the optical rose to the highest level of the campaign, followed ~10 days later by a sharp rise in X-rays. While the low X-ray countrate and relatively large systematic uncertainties in the NICER background make this measurement challenging, if the optical does lead X-rays in this flare, this indicates a departure from the zeroth-order reprocessing picture. If the optical flare is due to an increase in mass accretion rate, this occurs on much shorter than the viscous timescale. Alternatively, the optical could be responding to an intrinsic rise in X-rays that is initially hidden from our line-of-sight.Comment: Accepted for publication in the Astrophysical Journal. 15 pages, 8 figures, 3 table

Multi-wavelength observations of accreting compact objects

The study of compact binaries invokes core astrophysical concepts ranging from stellar and sub-stellar atmospheres and interiors, stellar and binary evolution to physics of accretion. All of these systems are hosts to a compact object a white dwarf,neutron star or black hole - which produces a wide variety of exotic and energetic phenomena across the full electromagnetic spectrum. In this thesis, I will make use of multi-wavelength observations ranging from far-ultraviolet to near-infrared in order to investigate two main topics: a) the late evolution of cataclysmic variables, and b) the accreting state of transitional millisecond pulsars.Firstly, I analyse the Very Large Telescope X-Shooter time-resolved spectroscopy of the short orbital period cataclysmic variable, SDSS J1433+1011,in Chapter 2. The wide wavelength coverage allowed me to perform a detailed characterisation of the system, as well as a direct mass measurement of the brown dwarf companion. I show that the donor in SDSS J1433+1011 successfully transitioned from the stellar to sub-stellar regime, as predicted by evolutionary models. Further light-curve modelling allowed me to show that allow albedo as well as a low heat circulation efficiency is present in the atmosphere of the sub-stellar donor. In Chapter 3, I analyse data from large synoptic surveys, such as SDSS and PTF, to search for the predicted population of dead cataclysmic variables. Following the non-detection of dead CVs, I was able to estimate the space density (p0 &lt; 2 x 10-5 pc-3) of this hidden population via a Monte Carlo simulation of the Galactic CV population. In Chapter 4, I present Hubble Space Telescope ultraviolet observations of the transitional millisecond pulsar PSR J1023+0038, during its latest accretion state. In combination with optical and near-infrared data, I show that a standard accretion disc does not reach the magnetosphere of the neutron star. Instead,the overall spectrum is consistent with a truncated disc at ∼ 2:3 x 109 cm away from the compact object. Furthermore, the ultraviolet data shares remarkable similarities with the only accreting white dwarf in a propeller regime, AE Aqr. Finally, I summarise my results in Chapter 5 and provide future lines of research in accreting compact binaries based on this work.</p

Mrk 110 dataset

Mrk 110 intensive monitoring campaign. All files are time series with errors and are have MJD on the x axis. SDSS bands are intercalibrated normalized fluxed using Zowada, Liverpool Telescope and Las Cumbres Observatory. UVOT data are expressed in erg cm^-2 s^-1 X-ray data is in counts per second</span

Mrk 110 dataset

Mrk 110 intensive monitoring campaign. All files are time series with errors and are have MJD on the x axis. SDSS bands are intercalibrated normalized fluxed using Zowada, Liverpool Telescope and Las Cumbres Observatory. UVOT data are expressed in erg cm^-2 s^-1 X-ray data is in counts per secon