Constant Luminosity Research Articles

Signatures of an eruptive phase before the explosion of the peculiar core-collapse SN 2013gc

We present photometric and spectroscopic analysis of the peculiar core-collapse SN 2013gc, spanning seven years of observations. The light curve shows an early maximum followed by a fast decline and a phase of almost constant luminosity. At +200 days from maximum, a brightening of 1 mag is observed in all bands, followed by a steep linear luminosity decline after +300 d. In archival images taken between 1.5 and 2.5 years before the explosion, a weak source is visible at the supernova location, with mag$\approx$20. The early supernova spectra show Balmer lines, with a narrow ($\sim$560 km s$^{-1}$) P-Cygni absorption superimposed on a broad ($\sim$3400 km s$^{-1}$) component, typical of type IIn events. Through a comparison of colour curves, absolute light curves and spectra of SN 2013gc with a sample of supernovae IIn, we conclude that SN 2013gc is a member of the so-called type IId subgroup. The complex profile of the H$\alpha$ line suggests a composite circumstellar medium geometry, with a combination of lower velocity, spherically symmetric gas and a more rapidly expanding bilobed feature. This circumstellar medium distribution has been likely formed through major mass-loss events, that we directly observed from 3 years before the explosion. The modest luminosity ($M_I\sim-16.5$ near maximum) of SN 2013gc at all phases, the very small amount of ejected $^{56}$Ni (of the order of $10^{-3}$ M$_\odot$), the major pre-supernova stellar activity and the lack of prominent [O I] lines in late-time spectra support a fall-back core-collapse scenario for the massive progenitor of SN~2013gc.

Recurrent Outbursts Revealed in 3XMM J031820.8-663034

Abstract 3XMM J031820.8-663034, first detected by ROSAT in NGC 1313, is one of a few known transient ultraluminous X-ray sources (ULXs). In this paper, we present decades of X-ray data of this source from ROSAT, XMM-Newton, Chandra, and the Neil Gehrels Swift Observatory. We find that its X-ray emission experienced four outbursts since 1992, with a typical recurrent time ∼1800 days, an outburst duration ∼240–300 days, and a nearly constant peak X-ray luminosity ∼1.5 × 1039 erg s−1. The upper limit of X-ray luminosity at the quiescent state is ∼5.6 × 1036 erg s−1, and the total energy radiated during one outburst is ∼1046 erg. The spectra at the high luminosity states can be described with an absorbed disk blackbody, and the disk temperature increases with the X-ray luminosity. We compare its outburst properties with other known transient ULXs including ESO 243-49 HLX-1. As its peak luminosity only marginally puts it in the category of ULXs, we also compare it with normal transient black hole binaries. Our results suggest that the source is powered by an accreting massive stellar-mass black hole, and the outbursts are triggered by the thermal-viscous instability.

Visual-inertial SLAM method based on optical flow in a GPS-denied environment

PurposeThis study aims to present a visual-inertial simultaneous localization and mapping (SLAM) method for accurate positioning and navigation of mobile robots in the event of global positioning system (GPS) signal failure in buildings, trees and other obstacles.Design/methodology/approachIn this framework, a feature extraction method distributes features on the image under texture-less scenes. The assumption of constant luminosity is improved, and the features are tracked by the optical flow to enhance the stability of the system. The camera data and inertial measurement unit data are tightly coupled to estimate the pose by nonlinear optimization.FindingsThe method is successfully performed on the mobile robot and steadily extracts the features on low texture environments and tracks features. The end-to-end error is 1.375 m with respect to the total length of 762 m. The authors achieve better relative pose error, scale and CPU load than ORB-SLAM2 on EuRoC data sets.Originality/valueThe main contribution of this study is the theoretical derivation and experimental application of a new visual-inertial SLAM method that has excellent accuracy and stability on weak texture scenes.

Aspherical Supernovae: Effects on Early Light Curves

Abstract Early light from core-collapse supernovae, now detectable in high-cadence surveys, holds clues to a star and its environment just before it explodes. However, effects that alter the early light have not been fully explored. We highlight the possibility of nonradial flows at the time of shock breakout. These develop in sufficiently nonspherical explosions if the progenitor is not too diffuse. When they do develop, nonradial flows limit ejecta speeds and cause ejecta–ejecta collisions. We explore these phenomena and their observational implications using global, axisymmetric, nonrelativistic FLASH simulations of simplified polytropic progenitors, which we scale to representative stars. We develop a method to track photon production within the ejecta, enabling us to estimate band-dependent light curves from adiabatic simulations. Immediate breakout emission becomes hidden as an oblique flow develops. Nonspherical effects lead the shock-heated ejecta to release a more constant luminosity at a higher, evolving color temperature at early times, effectively mixing breakout light with the early light curve. Collisions between nonradial ejecta thermalize a small fraction of the explosion energy; we will address emission from these collisions in a subsequent paper.

Discovery of pulsations from NGC 300 ULX1 and its fast period evolution

Abstract The supernova impostor SN 2010da located in the nearby galaxy NGC 300, later identified as a likely supergiant B[e] high-mass X-ray binary, was simultaneously observed by NuSTAR and XMM–Newton between 2016 December 16 and 20, over a total time span of ∼310 ks. We report the discovery of a strong periodic modulation in the X-ray flux with a pulse period of 31.6 s and a very rapid spin-up, and confirm therefore that the compact object is a neutron star. We find that the spin period is changing from 31.71 s to 31.54 s over that period, with a spin-up rate of −5.56 × 10−7 s s−1, likely the largest ever observed from an accreting neutron star. The spectrum is described by a power-law and a disc blackbody model, leading to a 0.3–30 keV unabsorbed luminosity of 4.7 × 1039 erg s−1. Applying our best-fitting model successfully to the spectra of an XMM–Newton observation from 2010, suggests that the lower fluxes of NGC 300 ULX1 reported from observations around that time are caused by a large amount of absorption, while the intrinsic luminosity was similar as seen in 2016. A more constant luminosity level is also consistent with the long-term pulse period evolution approaching an equilibrium value asymptotically. We conclude that the source is another candidate for the new class of ultraluminous X-ray pulsars.

Optical spectroscopy of the recurrent nova RS Ophiuchi – from the outburst of 2006 to quiescence

Optical spectra of the 2006 outburst of RS Ophiuchi beginning one day after discovery to over a year after the outburst are presented here. The spectral evolution is found to be similar to that in previous outbursts. The early phase spectra are dominated by hydrogen and helium (I & II) lines. Coronal and nebular lines appear in the later phases. Emission line widths are found to narrow with time, which is interpreted as a shock expanding into the red giant wind. Using the photoionisation code CLOUDY, spectra at nine epochs spanning 14 months after the outburst peak, thus covering a broad range of ionisation and excitation levels in the ejecta, are modelled. The best-fit model parameters indicate the presence of a hot white dwarf source with a roughly constant luminosity of 1.26 x 10^{37} erg/s. During first three months, the abundances (by number) of He, N, O, Ne, Ar, Fe, Ca, S and Ni are found above solar abundances; abundances of these elements decreased in the later phase. Also presented are spectra obtained during quiescence. Photoionisation model of the quiescence spectrum indicates the presence of a low luminosity accretion disk. The helium abundance is found to be subsolar at quiescence.

First Detection of Mid-infrared Variability from an Ultraluminous X-Ray Source Holmberg II X-1

Abstract We present mid-infrared (IR) light curves of the Ultraluminous X-ray Source (ULX) Holmberg II X-1 from observations taken between 2014 January 13 and 2017 January 5 with the Spitzer Space Telescope at 3.6 and 4.5 μm in the Spitzer Infrared Intensive Transients Survey. The mid-IR light curves, which reveal the first detection of mid-IR variability from a ULX, is determined to arise primarily from dust emission rather than from a jet or an accretion disk outflow. We derived the evolution of the dust temperature ( ), IR luminosity ( ), mass ( ), and equilibrium temperature radius ( ). A comparison of X-1 with a sample of spectroscopically identified massive stars in the Large Magellanic Cloud on a mid-IR color–magnitude diagram suggests that the mass donor in X-1 is a supergiant (sg) B[e]-star. The sgB[e]-interpretation is consistent with the derived dust properties and the presence of the [Fe ii] ( ) emission line revealed from previous near-IR studies of X-1. We attribute the mid-IR variability of X-1 to the increased heating of dust located in a circumbinary torus. It is unclear what physical processes are responsible for the increased dust heating; however, it does not appear to be associated with the X-ray flux from the ULX, given the constant X-ray luminosities provided by serendipitous, near-contemporaneous X-ray observations around the first mid-IR variability event in 2014. Our results highlight the importance of mid-IR observations of luminous X-ray sources traditionally studied at X-ray and radio wavelengths.

NuSTARobservations of the supergiant X-ray pulsar IGR J18027−2016: accretion from the stellar wind and possible cyclotron absorption line

We report on the first focused hard X-ray view of the absorbed supergiant system IGRJ18027-2016 performed with the NuSTAR observatory. The pulsations are clearly detected with a period of $P_{spin}=139.866(1)$ s and a pulse fraction of about 50-60% at energies from 3 to 80 keV. The source demonstrates an approximately constant X-ray luminosity on a time scale of more than dozen years with an average spin-down rate of $dP/dt\simeq6\times10^{-10}$ s/s. This behaviour of the pulsar can be explained in terms of the wind accretion model in the settling regime. The detailed spectral analysis at energies above 10 keV was performed for the first time and revealed a possible cyclotron absorption feature at energy ~23 keV. This energy corresponds to the magnetic field $B\simeq3\times10^{12}$ G at the surface of the neutron star, which is typical for X-ray pulsars.

NuSTARandXMM–Newtonobservations of the ultraluminous X-ray source NGC 5643 X-1

We present a high-quality hard X-ray spectrum of the ultraluminous X-ray source (ULX) NGC 5643 X-1 measured with NuSTAR in May-June 2014. We have obtained this spectrum by carefully separating the signals from the ULX and from the active nucleus of its host galaxy NGC 5643 located 0.8 arcmin away. Together with long XMM-Newton observations performed in July 2009 and August 2014, the NuSTAR data confidently reveal a high-energy cutoff in the spectrum of NGC 5643 X-1 above ~10 keV, which is a characteristic signature of ULXs. The NuSTAR and XMM-Newton data are consistent with the source having a constant luminosity ~1.5E40 erg/s (0.2-12 keV) in all but the latest observation (August 2014) when it brightened to ~3E40 erg/s. This increase is associated with the dominant, hard spectral component (presumably collimated emission from the inner regions of a supercritical accretion disc), while an additional, soft component (with a temperature ~0.3 keV if described by multicolor disk emission), possibly associated with a massive wind outflowing from the disk, is also evident in the spectrum but does not exhibit significant variability.

All known hot RCB stars are fading fast over the last century

The R Coronae Borealis (RCB) stars are cool supergiants that display irregular and deep dips in their light curves, caused by dust formation. There are four known hot RCB stars (DY Cen, MV Sgr, V348 Sgr, and HV 2671), with surface temperatures of 15,000--25,000 K, and prior work has suggested that three of these have secular fading in brightness. I have tested this result by measuring century-long light curves in the Johnson B-band with modern comparison star magnitudes, and I have extended this by measuring many magnitudes over a wide time range as well as for the fourth hot RCB star. In all four cases, the B-band magnitude of the maximum light is now fast fading. The fading rates (in units of magnitudes per century) are 2.5 for DY Cen after 1960, 1.3 for MV Sgr, 1.3 for V348 Sgr, and 0.7 for HV 2671. This secular fading is caused by the expected evolution of the star across the top of the HR diagram at constant luminosity, as the temperature rises and the bolometric correction changes. For DY Cen, the brightness at maximum light is rising from 1906 to 1932, and this is caused by the temperature increase from near 5,800 to 7,500 K. Before 1934 DY Cen had frequent dust dips, while after 1934 there are zero dust dips, so there is some apparent connection between the rising temperature and the formation of the dust. Thus, we have watched DY Cen evolve from an ordinary RCB star up to a hot RCB star and now appearing as an extreme helium star, all in under one century.

DISCOVERY OF MOLECULAR HYDROGEN IN SN 1987A

ABSTRACT Both CO and SiO have been observed at early and late phases in SN 1987A. H2 was predicted to form at roughly the same time as these molecules, but was not detected at early epochs. Here, we report the detection of NIR lines from H2 at 2.12 and 2.40 μ m in VLT/SINFONI spectra obtained between days 6489 and 10,120. The emission is concentrated to the core of the SN in contrast to Hα and approximately coincides with the [Si i]/[Fe ii] emission detected previously in the ejecta. Different excitation mechanisms and power sources of the emission are discussed. From the nearly constant H2 luminosities, we favor excitation resulting from the 44 Ti decay.

LATE TIME MULTI-WAVELENGTH OBSERVATIONS OF SWIFT J1644+5734: A LUMINOUS OPTICAL/IR BUMP AND QUIESCENT X-RAY EMISSION

ABSTRACT We present late time multi-wavelength observations of Swift J1644+57, suggested to be a relativistic tidal disruption flare (TDF). Our observations extend to >4 years from discovery and show that 1.4 years after outburst the relativistic jet switched off on a timescale less than tens of days, corresponding to a power-law decay faster than t −70. Beyond this point weak X-rays continue to be detected at an approximately constant luminosity of L X ∼ 5 × 1042 erg s−1 and are marginally inconsistent with a continuing decay of t −5/3, similar to that seen prior to the switch-off. Host photometry enables us to infer a black hole mass of M BH = 3 × 106 M ⊙, consistent with the late time X-ray luminosity arising from sub-Eddington accretion onto the black hole in the form of either an unusually optically faint active galactic nucleus or a slowly varying phase of the transient. Optical/IR observations show a clear bump in the light curve at timescales of 30–50 days, with a peak magnitude (corrected for host galaxy extinction) of M R ∼ −22 to −23. The luminosity of the bump is significantly higher than seen in other, non-relativistic TDFs and does not match any re-brightening seen at X-ray or radio wavelengths. Its luminosity, light curve shape, and spectrum are broadly similar to those seen in superluminous supervnovae, although subject to large uncertainties in the correction of the significant host extinction. We discuss these observations in the context of both TDF and massive star origins for Swift J1644+5734 and other candidate relativistic tidal flares.

The most luminous H α emitters atz∼ 0.8–2.23 from HiZELS: evolution of AGN and star-forming galaxies

We use new near-infrared spectroscopic observations to investigate the nature and evolution of the most luminous H\alpha (Ha) emitters at z~0.8-2.23, which evolve strongly in number density over this period, and compare them to more typical Ha emitters. We study 59 luminous Ha emitters with $L_{H\alpha}>L_{H\alpha}^*$, roughly equally split per redshift slice at z~0.8, 1.47 and 2.23 from the HiZELS and CF-HiZELS surveys. We find that, overall, 30$\pm$8% are AGN (80$\pm$30% of these AGN are broad-line AGN, BL-AGN), and we find little to no evolution in the AGN fraction with redshift, within the errors. However, the AGN fraction increases strongly with Ha luminosity and correlates best with $L_{H\alpha}/L_{H\alpha}^*(z)$. While $L_{H\alpha}<L_{\rm H\alpha}^*(z)$ Ha emitters are largely dominated by star-forming galaxies (>80%), the most luminous Ha emitters ($L_{H\alpha}>10L_{H\alpha}^*(z)$) at any cosmic time are essentially all BL-AGN. Using our AGN-decontaminated sample of luminous star-forming galaxies, and integrating down to a fixed Ha luminosity, we find a factor of ~1300x evolution in the star formation rate density from z=0 to z=2.23. This is much stronger than the evolution from typical Ha star-forming galaxies and in line with the evolution seen for constant luminosity cuts used to select "Ultra-Luminous" Infrared Galaxies and/or sub-millimetre galaxies. By taking into account the evolution in the typical Ha luminosity, we show that the most strongly star-forming Ha-selected galaxies at any epoch ($L_{H\alpha}>L^*_{H\alpha}(z)$) contribute the same fractional amount of ~15% to the total star-formation rate density, at least up to z=2.23.

Shaping the X-ray spectrum of galaxy clusters with AGN feedback and turbulence

Abstract The hot plasma filling galaxy clusters emits copious X-ray radiation. The classic unheated and unperturbed cooling flow model predicts dramatic cooling rates and an isobaric X-ray spectrum with constant differential luminosity distribution. The observed cores of clusters (and groups) show instead a strong deficit of soft X-ray emission: dLx/dT ∝ (T/Thot)α = 2 ± 1. Using 3D hydrodynamic simulations, we show that such deficit arises from the tight self-regulation between thermal instability condensation and AGN outflow injection: condensing clouds boost the AGN outflows, which quench cooling as they thermalize through the core. The resultant average distribution slope is α ≃ 2, oscillating within the observed 1 &amp;lt; α &amp;lt; 3. In the absence of thermal instability, the X-ray spectrum remains isothermal (α ≳ 8), while unopposed cooling drives a too shallow slope, α &amp;lt; 1. AGN outflows deposit their energy inside-out, releasing more heat in the inner cooler phase; radially distributed heating alone induces a declining spectrum, 1 &amp;lt; α &amp;lt; 2. Turbulence further steepens the spectrum and increases the scatter: the turbulent Mach number in the hot phase is subsonic, while it becomes transonic in the cooler phase, making perturbations to depart from the isobaric mode. Such increase in dln P/dln T leads to α ≈ 3. Self-regulated AGN outflow feedback can address the soft X-ray problem through the interplay of heating and turbulence.

A scheme for radiation pressure and photon diffusion with the M1 closure in ramses-rt

We describe and test an updated version of radiation-hydrodynamics (RHD) in the RAMSES code, that includes three new features: i) radiation pressure on gas, ii) accurate treatment of radiation diffusion in an unresolved optically thick medium, and iii) relativistic corrections that account for Doppler effects and work done by the radiation to first order in v/c. We validate the implementation in a series of tests, which include a morphological assessment of the M1 closure for the Eddington tensor in an astronomically relevant setting, dust absorption in a optically semi-thick medium, direct pressure on gas from ionising radiation, convergence of our radiation diffusion scheme towards resolved optical depths, correct diffusion of a radiation flash and a constant luminosity radiation, and finally, an experiment from Davis et al. of the competition between gravity and radiation pressure in a dusty atmosphere, and the formation of radiative Rayleigh-Taylor instabilities. With the new features, RAMSES-RT can be used for state-of-the-art simulations of radiation feedback from first principles, on galactic and cosmological scales, including not only direct radiation pressure from ionising photons, but also indirect pressure via dust from multi-scattered IR photons reprocessed from higher-energy radiation, both in the optically thin and thick limits.

New luminous blue variables in the Andromeda galaxy

We performed spectroscopy of five Luminous Blue Variable (LBV) candidates and two known LBV stars (AE And and Var A-1) in M31. We obtained the same-epoch near-infrared (NIR) and optical spectra of these stars. The NIR spectra were taken with Triplespec spectrograph at the 3.5-m telescope at Apache Point Observatory, and the optical spectroscopy was done with SCORPIO focal reducer at the 6-m BTA telescope (SAO RAS). The candidates demonstrate typical LBV features in their spectra: broad and strong hydrogen lines, HeI, FeII, and [FeII] lines. All our candidates show photometric variability. We develop a new approach to the LBV parameters estimation based on the inherent property of LBVs to change their spectral type at constant bolometric luminosity. We compare the spectral energy distributions of the variable stars obtained in two or more different states and estimate temperatures, reddening, radii and luminosities of the stars using this method. Two considered candidates (J004526.62+415006.3 and J004051.59+403303.0) have to be classified as new LBV stars. Two more candidates are, apparently, B[e]-supergiants. The nature of one more star (J004350.50+414611.4) is not clear. It does not show obvious LBV-like variability and remains an LBV-candidate.

Magnetic flux of progenitor stars sets gamma-ray burst luminosity and variability

Long-duration gamma-ray bursts (GRBs) are thought to come from the core-collapse of Wolf-Rayet stars. Whereas their stellar masses $M_*$ have a rather narrow distribution, the population of GRBs is very diverse, with gamma-ray luminosities $L_\gamma$ spanning several orders of magnitude. This suggests the existence of a "hidden" stellar variable whose burst-to-burst variation leads to a spread in $L_\gamma$. Whatever this hidden variable is, its variation should not noticeably affect the shape of GRB lightcurves, which display a constant luminosity (in a time-average sense) followed by a sharp drop at the end of the burst seen with Swift/XRT. We argue that such a hidden variable is progenitor star's large-scale magnetic flux. Shortly after the core collapse, most of stellar magnetic flux accumulates near the black hole (BH) and remains there. The flux extracts BH rotational energy and powers jets of roughly a constant luminosity, $L_j$. However, once BH mass accretion rate $\dot M$ falls below $\sim L_j/c^2$, the flux becomes dynamically important and diffuses outwards, with the jet luminosity set by the rapidly declining mass accretion rate, $L_j\sim \dot M c^2$. This provides a potential explanation for the sharp end of GRBs and the universal shape of their lightcurves. During the GRB, gas infall translates spatial variation of stellar magnetic flux into temporal variation of $L_j$. We make use of the deviations from constancy in $L_j$ to perform stellar magnetic flux "tomography". Using this method, we infer the presence of magnetised tori in the outer layers of progenitor stars for GRB 920513 and GRB 940210.

Origin of X-ray Spectral Variation and the Seemingly Broad Iron-Line Spectral Feature in Seyfert Galaxies

We present systematic X-ray data analysis of the Seyfert galaxies observed by Suzaku to study origin of their hard X-ray (2 - 40 keV) variations. In particular, we examine if the "Variable Partial Covering (VPC) model" proposed by Miyakawa, Ebisawa and Inoue (2012), which was successful to explain spectral variations of MCG{6-30-15, is also valid for other Seyfert galaxies or not. In this model, intrinsic X-ray luminosity of the AGN is not signicantly variable, and most observed flux and spectral variations are caused by change of the geometrical covering fraction of the extended X-ray source by ionized absorbing clouds in the line of sight. We found that the observed flux and spectral variations of 20 targets in addition to MCG{6-30-15 are successfully explained by the VPC model. The transmitted spectral component through the absorbing clouds has a characteristics spectral feature of the ionized iron K-edge, which is considered to be the origin of the seemingly broad iron-line feature commonly observed in Seyfert galaxies. Variation of the partial covering fraction of the constant X-ray luminosity source causes such an anti-correlation between the direct (non-obscured) component and the transmitted (obscured) component, that cancels their variations each other. The cancellation works most effectively at the energy band where intensities of the two components are the closest to each other, namely, just below the iron K-edge. This explains the signicantly small fractional variations in the iron K-energy band, another well-known observational characteristic of Seyfert galaxies.

ON THE BINARY HELIUM STAR DY CENTAURI: CHEMICAL COMPOSITION AND EVOLUTIONARY STATE

DY Cen has shown a steady fading of its visual light by about 1 magnitude in the last 40 years suggesting a secular increase in its effective temperature. We have conducted non-LTE and LTE abundance analyses to determine the star's effective temperature, surface gravity, and chemical composition using high-resolution spectra obtained over two decades. The derived stellar parameters for three epochs suggest that DY Cen has evolved at a constant luminosity and has become hotter by about 5000 K in 23 years. We show that the derived abundances remain unchanged for the three epochs. The derived abundances of the key elements, including F and Ne, are as observed for the extreme helium stars resulting from a merger of an He white dwarf with a C-O white dwarf. Thus, DY Cen by chemical composition appears to be also a product of a merger of two white dwarfs. This appearance seems to be at odds with the recent suggestion that DY Cen is a single-lined spectroscopic binary.

WASP 1628+10 – an EL CVn-type binary with a very low mass stripped red giant star and multiperiodic pulsations

The star 1SWASP J162842.31+101416.7 (WASP 1628+10) is one of several EL CVn-type stars recently identified using the WASP database, i.e., an eclipsing binary star in which an A-type dwarf star (WASP 1628+10A) eclipses the remnant of a disrupted red giant star (WASP1628+10B). We have measured the masses, radii and luminosities of the stars in WASP 1628+10 using photometry obtained in three bands (u', g', r') with the Ultracam instrument and medium-resolution spectroscopy. The properties of the remnant are well-matched by models for stars in a rarely-observed state evolving to higher effective temperatures at nearly constant luminosity prior to becoming a very low-mass white dwarf composed almost entirely of helium, i.e., we confirm that WASP 1628+10B is a pre-He-WD. WASP 1628+10A appears to be a normal A2V star with a mass of $1.36 \pm 0.05 M_{\odot}$. By fitting models to the spectrum of this star around the H$\gamma$ line we find that it has an effective temperature T$_{\rm eff,A} = 7500 \pm 200$K and a metallicity [Fe/H]$ = -0.3 \pm 0.3$. The mass of WASP 1628+10B is only $0.135 \pm 0.02M_{\odot}$. The effective temperature of this pre-He-WD is approximately 9200K. The Ultracam photometry of WASP 1628+10 shows variability at several frequencies around 40 cycles per day, which is typical for $\delta$ Sct-type pulsations often observed in early A-type stars like WASP 1628+10A. We also observe frequencies near 114 cycles/day and 129 cycles/day, much higher than the frequencies normally seen in $\delta$ Sct stars. Additional photometry through the primary eclipse will be required to confirm that these higher frequencies are due to pulsations in WASP 1628+10B. If confirmed, this would be only the second known example of a pre-He-WD showing high-frequency pulsations.