arXiv subjects

Joshua B. Haislip

Publications and source records attributed to Joshua B. Haislip.

18 recordsLinked to original sources

arXiv2026

An Extreme Scattering Event Toward PSR J2313+4253

We present evidence of an extreme scattering event (ESE) toward PSR J2313+4253 using high-cadence observations taken with the Green Bank Observatory 20m telescope. The high density of observations in time allow for detailed tracking of the event. We observe a pair of spikes along with the characteristic drop in scintillation bandwidth that is expected during an ESE. This pattern implies that the structures predominantly responsible for scattering occur at different distances than those from previous and subsequent epochs. A secondary spectrum processed during the event shows a detached feature similar to those found in double lensing events from previously observed ESEs. We measure this event as originating from a scattering region with a distance of 1.04(1) kpc, a transverse size of 15 AU, and a duration of approximately 220 days. These rare events provide opportunities to study the properties of small-scale structures in the ISM.

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arXiv2024

The Pulsar Science Collaboratory: Multi-Epoch Scintillation Studies of Pulsars

We report on findings from scintillation analyses using high-cadence observations of eight canonical pulsars with observing baselines ranging from one to three years. We obtain scintillation bandwidth and timescale measurements for all pulsars in our survey, scintillation arc curvature measurements for four, and detect multiple arcs for two. We find evidence of a previously undocumented scattering screen along the line of sight (LOS) to PSR J1645$-$0317, as well as evidence that a scattering screen along the LOS to PSR J2313$+$4253 may reside somewhere within the Milky Way's Orion-Cygnus arm. We report evidence of a significant change in the scintillation pattern in PSR J2022$+$5154 from the previous two decades of literature, wherein both the scintillation bandwidth and timescale decreased by an order of magnitude relative to earlier observations at the same frequencies, potentially as a result of a different screen dominating the observed scattering. By augmenting the results of previous studies, we find general agreement with estimations of scattering delays from pulsar observations and predictions by the NE2001 electron density model but not for the newest data we have collected, providing some evidence of changes in the ISM along various LOSs over the timespans considered. In a similar manner, we find additional evidence of a correlation between a pulsar's dispersion measure and the overall variability of its scattering delays over time. The plethora of interesting science obtained through these observations demonstrates the capabilities of the Green Bank Observatory's 20m telescope to contribute to pulsar-based studies of the interstellar medium.

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arXiv2024

A Statistical Analysis of Crab Pulsar Giant Pulse Rates

A small number of pulsars are known to emit giant pulses, single pulses much brighter than average. Among these is PSR J0534+2200, also known as the Crab pulsar, a young pulsar with high giant pulse rates. Long-term monitoring of the Crab pulsar presents an excellent opportunity to perform statistical studies of its giant pulses and the processes affecting them, potentially providing insight into the behavior of other neutron stars that emit bright single pulses. Here, we present an analysis of a set of 24,985 Crab giant pulses obtained from 88 hours of daily observations at a center frequency of 1.55 GHz by the 20-meter telescope at the Green Bank Observatory, spread over 461 days. We study the effects of refractive scintillation at higher frequencies than previous studies and compare methods of correcting for this effect. We also search for deterministic patterns seen in other single-pulse sources, possible periodicities seen in several rotating radio transients and fast radio bursts, and clustering of giant pulses like that seen in the repeating fast radio burst FRB121102.

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arXiv2022

Skynet's New Observing Mode: The Campaign Manager

Built in 2004, the Skynet robotic telescope network originally consisted of six 0.4 m telescopes located at the Cerro-Tololo Inter-American Observatory in the Chilean Andes. The network was designed to carry out simultaneous multi-wavelength observations of gamma-ray bursts (GRBs) when they are only tens of seconds old. To date, the network has been expanded to ~20 telescopes, including a 20 m radio telescope, that span four continents and five countries. The Campaign Manager (CM) is a new observing mode that has been developed for Skynet. Available to all Skynet observers, the CM semi-autonomously and indefinitely scales and schedules exposures on the observer's behalf while allowing for modification to scaling parameters in real time. The CM is useful for follow up to various transient phenomena including gravitational-wave events, GRB localizations, young supernovae, and eventually, sufficiently bright Argus Optical Array and Large Synoptic Survey Telescope events.

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arXiv2022

Optical Time-Series Photometry of the Symbiotic Nova V1835 Aquilae

We present time-series CCD photometry in the $BVRI$ passbands of the recently identified symbiotic nova V1835 Aquilae (NSV 11749) over an interval of 5.1 years with 7-14 day cadence, observed during its quiescence. We find slow light variations with a range of $\sim$0.9 mag in $V$ and $\sim$0.3 mag in $I$. Analysis of these data show strong periodicity at $419 \pm 10$ days, which we interpret to be the system's orbital period. A dip in the otherwise-sinusoidal phased light curve suggests a weak ellipsoidal effect due to tidal distortion of the giant star, which in turn opens the possibility that V1835 Aql transfers some of its mass to the hot component via Roche lobe overflow rather than via a stellar wind. We also find evidence that V1835 Aql is an S-type symbiotic star, relatively free of circumstellar dust, and include it among the nuclear burning group of symbiotics. Finally, we provide photometry, periods, and light curve classifications for 22 variable stars in the field around V1835 Aql, about half of which are newly identified.

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arXiv2021

Changing look AGN Mrk 590: Broad line region and black hole mass from photometric reverberation mapping

We present the results of photometric reverberation mapping observations on the changing look active galactic nucleus Mrk 590 at z = 0.026. The observations were carried out from July to December, 2018 using broad band B, R and narrow band Hα and S II filters. B-band traces the continuum emission from the accretion disk, R-band encompasses both the continuum emission from the accretion disk and the redshifted Hα line from the broad line region (BLR), S II band contains the redshifted Hα emission and the Hα band traces the continuum emission underneath the S II band. All the light curves showed strong variation with a fractional root-mean-square variation of 0.132 (+/-) 0.001 in B-band and 0.321 (+/-) 0.001 in Hα line. From cross-correlation function analysis, we obtained a delayed response of Hα line emission to the optical B-band continuum emission of 21.44(+1.49/-2.11) days in the rest-frame of the source, corresponding to a linear size of the BLR of 0.018 pc. This is consistent with previous estimates using Hβ. By combining the BLR size with the Hα line full width at half maximum of 6478 (+/-) 240 km/s measured from a single-epoch spectrum obtained with the Subaru telescope, we derived a black hole mass of 1.96 (+0.15 / -0.21) X 10^8 Msun.

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arXiv2019

A Multi-Year Search For Transits Of Proxima Centauri. II: No Evidence For Transit Events With Periods Between 1-30 Days

Using a global network of small telescopes, we have obtained light curves of Proxima Centauri at 329 observation epochs from 2006 - 2017. The planet Proxima b discovered by Anglada-Escude et al. (2016) with an orbital period of 11.186 d has an a priori transit probability of ~1.5%; if it transits, the predicted transit depth is about 5 millimagnitudes. In Blank et al. (2018), we analyzed 96 of our light curves that overlapped with predicted transit ephemerides from previously published tentative transit detections, and found no evidence in our data that would corroborate claims of transits with a period of 11.186 d. Here we broaden our analysis, using 262 high-quality light curves from our data set to search for any periodic transit-like events over a range of periods from 1 - 30 d. We also inject a series of simulated planet transits and find that our data are sufficiently sensitive to have detected transits of 5 millimagnitude depth, with recoverability ranging from ~100% for an orbital period of 1 d to ~20% for an orbital period of 20 d for the parameter spaces tested. Specifically at the 11.186 d period and 5 millimagnitude transit depth, we rule out transits in our data with high confidence. We are able to rule out virtually all transits of other planets at periods shorter than 5 d and depths greater than 3 millimagnitudes; however, we cannot confidently rule out transits at the period of Proxima b due to incomplete orbital phase coverage and a lack of sensitivity to transits shallower than 4 millimagnitudes.

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arXiv2018

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}$) component, typical of type IIn events. Through a comparison of colour curves, absolute light curves and spectra of SN 2013gc with a sample of supernovae IIn, we conclude that SN 2013gc is a member of the so-called type IId subgroup. The complex profile of the H$α$ 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.

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arXiv2018

A Multi-Year Search For Transits Of Proxima Centauri. I: Light Curves Corresponding To Published Ephemerides

Proxima Centauri has become the subject of intense study since the radial-velocity discovery by Anglada-Escudé et al. 2016 of a planet orbiting this nearby M-dwarf every ~ 11.2 days. If Proxima Centauri b transits its host star, independent confirmation of its existence is possible, and its mass and radius can be measured in units of the stellar host mass and radius. To date, there have been three independent claims of possible transit-like event detections in light curve observations obtained by the MOST satellite (in 2014-15), the BSST telescope in Antarctica (in 2016), and the Las Campanas Observatory (in 2016). The claimed possible detections are tentative, due in part to the variability intrinsic to the host star, and in the case of the ground-based observations, also due to the limited duration of the light curve observations. Here, we present preliminary results from an extensive photometric monitoring campaign of Proxima Centauri, using telescopes around the globe and spanning from 2006 to 2017, comprising a total of 329 observations. Considering our data that coincide directly and/or phased with the previously published tentative transit detections, we are unable to independently verify those claims. We do, however, verify the previously reported ubiquitous and complex variability of the host star. We discuss possible interpretations of the data in light of the previous claims, and we discuss future analyses of these data that could more definitively verify or refute the presence of transits associated with the radial-velocity discovered planet.

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arXiv2016

KELT-10b: The First Transiting Exoplanet from the KELT-South Survey -- A Hot Sub-Jupiter Transiting a V = 10.7 Early G-Star

We report the discovery of KELT-10b, the first transiting exoplanet discovered using the KELT-South telescope. KELT-10b is a highly inflated sub-Jupiter mass planet transiting a relatively bright $V = 10.7$ star (TYC 8378-64-1), with T$_{eff}$ = $5948\pm74$ K, $\log{g}$ = $4.319_{-0.030}^{+0.020}$ and [Fe/H] = $0.09_{-0.10}^{+0.11}$, an inferred mass M$_{*}$ = $1.112_{-0.061}^{+0.055}$ M$_{\odot}$ and radius R$_{*}$ = $1.209_{-0.035}^{+0.047}$ R$_{\odot}$. The planet has a radius R$_{P}$ = $1.399_{-0.049}^{+0.069}$ R$_{J}$ and mass M$_{P}$ = $0.679_{-0.038}^{+0.039}$ M$_{J}$. The planet has an eccentricity consistent with zero and a semi-major axis $a$ = $0.05250_{-0.00097}^{+0.00086}$ AU. The best fitting linear ephemeris is $T_{0}$ = 2457066.72045$\pm$0.00027 BJD$_{TDB}$ and P = 4.1662739$\pm$0.0000063 days. This planet joins a group of highly inflated transiting exoplanets with a radius much larger and a mass much less than those of Jupiter. The planet, which boasts deep transits of 1.4%, has a relatively high equilibrium temperature of T$_{eq}$ = $1377_{-23}^{+28}$ K, assuming zero albedo and perfect heat redistribution. KELT-10b receives an estimated insolation of $0.817_{-0.054}^{+0.068}$ $\times$ 10$^9$ erg s$^{-1}$ cm$^{-2}$, which places it far above the insolation threshold above which hot Jupiters exhibit increasing amounts of radius inflation. Evolutionary analysis of the host star suggests that KELT-10b is unlikely to survive beyond the current subgiant phase, due to a concomitant in-spiral of the planet over the next $\sim$1 Gyr. The planet transits a relatively bright star and exhibits the third largest transit depth of all transiting exoplanets with V $<$ 11 in the southern hemisphere, making it a promising candidate for future atmospheric characterization studies.

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arXiv2016

Supernova 2010ev: A reddened high velocity gradient type Ia supernova

Aims. We present and study the spectroscopic and photometric evolution of the type Ia supernova (SN Ia) 2010ev. Methods. We obtain and analyze multi-band optical light curves and optical-near-infrared spectroscopy at low and medium resolution spanning from -7 days to +300 days from the B-band maximum. Results. A photometric analysis shows that SN 2010ev is a SN Ia of normal brightness with a light curve shape of $Δm_{15}(B)=1.12 \pm 0.02$ and a stretch s = $0.94 \pm 0.01$ suffering significant reddening. From photometric and spectroscopic analysis, we deduce a color excess of $E(B - V) = 0.25 \pm 0.05$ and a reddening law of $R_v = 1.54 \pm 0.65$. Spectroscopically, SN 2010ev belongs to the broad-line SN Ia group, showing stronger than average Si II λ6355 absorption features. We also find that SN 2010ev is a high-velocity gradient SN, with a value of $164 \pm 7$ km s$^{-1}$ d$^{-1}$. The photometric and spectral comparison with other supernovae shows that SN 2010ev has similar colors and velocities to SN 2002bo and SN 2002dj. The analysis of the nebular spectra indicates that the [Fe II] λ7155 and [Ni II] λ7378 lines are redshifted, as expected for a high velocity gradient supernova. All these common intrinsic and extrinsic properties of the high velocity gradient (HVG) group are different from the low velocity gradient (LVG) normal SN Ia population and suggest significant variety in SN Ia explosions.

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arXiv2014

Supernova 2010as: the Lowest-Velocity Member of a Family of Flat-Velocity Type IIb Supernovae

We present extensive optical and near-infrared photometric and spectroscopic observations of the stripped-envelope (SE) supernova SN 2010as. Spectroscopic peculiarities, such as initially weak helium features and low expansion velocities with a nearly flat evolution, place this object in the small family of events previously identified as transitional Type Ib/c supernovae (SNe). There is ubiquitous evidence of hydrogen, albeit weak, in this family of SNe, indicating that they are in fact a peculiar kind of Type IIb SNe that we name "flat-velocity Type IIb". The flat velocity evolution---which occurs at different levels between 6000 and 8000 km/s for different SNe---suggests the presence of a dense shell in the ejecta. Despite the spectroscopic similarities, these objects show surprisingly diverse luminosities. We discuss the possible physical or geometrical unification picture for such diversity. Using archival HST images we associate SN 2010as with a massive cluster and derive a progenitor age of ~6 Myr, assuming a single star-formation burst, which is compatible with a Wolf-Rayet progenitor. Our hydrodynamical modelling, on the contrary, indicates the pre-explosion mass was relatively low, of ~4 M_sol. The seeming contradiction between an young age and low pre-SN mass may be solved by a massive interacting binary progenitor.

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arXiv2013

GRB 081007 and GRB 090424: the surrounding medium, outflows and supernovae

We discuss the results of the analysis of multi-wavelength data for the afterglows of GRB 081007 and GRB 090424, two bursts detected by Swift. One of them, GRB 081007, also shows a spectroscopically confirmed supernova, SN 2008hw, which resembles SN 1998bw in its absorption features, while the maximum luminosity is only about half as large as that of SN 1998bw. Bright optical flashes have been detected in both events, which allows us to derive solid constraints on the circumburst-matter density profile. This is particularly interesting in the case of GRB 081007, whose afterglow is found to be propagating into a constant-density medium, yielding yet another example of a GRB clearly associated with a massive star progenitor which did not sculpt the surroundings with its stellar wind. There is no supernova component detected in the afterglow of GRB 090424, likely due to the brightness of the host galaxy, comparable to the Milky Way. We show that the afterglow data are consistent with the presence of both forward- and reverse-shock emission powered by relativistic outflows expanding into the interstellar medium. The absence of optical peaks due to the forward shock strongly suggests that the reverse shock regions should be mildly magnetized. The initial Lorentz factor of outflow of GRB 081007 is estimated to be Γ~ 200, while for GRB 090424 a lower limit of Γ> 170 is derived. We also discuss the prompt emission of GRB 081007, which consists of just a single pulse. We argue that neither the external forward-shock model nor the shock-breakout model can account for the prompt emission data and suggest that the single-pulse-like prompt emission may be due to magnetic energy dissipation of a Poynting-flux dominated outflow or to a dissipative photosphere.

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arXiv2013

SN 2009ip á la PESSTO: No evidence for core-collapse yet

We present observations of the interacting transient SN 2009ip, from the start of the outburst in October 2012 until the end of the 2012 observing season. The transient reached a peak of $M_V$=-17.7 mag before fading rapidly, with a total integrated luminosity of 1.9$\times10^{49}$ erg over the period of August-December 2012. The optical and near infrared spectra are dominated by narrow emission lines, signaling a dense circumstellar environment, together with multiple components of broad emission and absorption in H and He at velocities between 0.5-1.2$\times10^4$ km s$^{-1}$\. We see no evidence for nucleosynthesized material in SN 2009ip, even in late-time pseudo-nebular spectra. We set a limit of $<$0.02 M$_{\odot}$\ on the mass of any synthesized $^{56}$Ni from the late time lightcurve. A simple model for the narrow Balmer lines is presented, and used to derive number densities for the circumstellar medium of between $\sim 10^{9}-10^{10}$ cm$^{-3}$. Our near-infrared data does not show any excess at longer wavelengths. Our last data, taken in December 2012, shows that SN 2009ip has spectroscopically evolved to something quite similar to its appearance in late 2009, albeit with higher velocities. It is possible that neither of the eruptive and high luminosity events of SN 2009ip were induced by a core-collapse. We show that the peak and total integrated luminosity can be due to the efficient conversion of kinetic energy from colliding ejecta, and that around 0.05-0.1 M$_{\odot}$\ of material moving at 0.5-1$\times10^4$ km s$^{-1}$\ could comfortably produce the observed luminosity. The ejection of multiple shells, lack of evidence for nucleosynthesied elements and broad nebular lines, are all consistent with the pulsational-pair instability scenario. In this case the progenitor star may still exist, and will be observed after the current outburst fades.

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arXiv2011

Eclipses During the 2010 Eruption of the Recurrent Nova U Scorpii

The eruption of the recurrent nova U Scorpii on 28 January 2010 is now the all-time best observed nova event. We report 36,776 magnitudes throughout its 67 day eruption, for an average of one measure every 2.6 minutes. This unique and unprecedented coverage is the first time that a nova has any substantial amount of fast photometry. With this, two new phenomena have been discovered: the fast flares in the early light curve seen from days 9-15 (which have no proposed explanation) and the optical dips seen out of eclipse from days 41-61 (likely caused by raised rims of the accretion disk occulting the bright inner regions of the disk as seen over specific orbital phases). The expanding shell and wind cleared enough from days 12-15 so that the inner binary system became visible, resulting in the sudden onset of eclipses and the turn-on of the supersoft X-ray source. On day 15, a strong asymmetry in the out-of-eclipse light points to the existence of the accretion stream. The normal optical flickering restarts on day 24.5. For days 15-26, eclipse mapping shows that the optical source is spherically symmetric with a radius of 4.1 R_sun. For days 26-41, the optical light is coming from a rim-bright disk of radius 3.4 R_sun. For days 41-67, the optical source is a center-bright disk of radius 2.2 R_sun. Throughout the eruption, the colors remain essentially constant. We present 12 eclipse times during eruption plus five just after the eruption.

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arXiv2011

Photometric Observations of Three High Mass X-Ray Binaries and a Search for Variations Induced by Orbital Motion

We searched for long period variation in V-band, Ic-band and RXTE X-ray light curves of the High Mass X-ray Binaries (HMXBs) LS 1698 / RX J1037.5-5647, HD 110432 / 1H 1249-637 and HD 161103 / RX J1744.7-2713 in an attempt to discover orbitally induced variation. Data were obtained primarily from the ASAS database and were supplemented by shorter term observations made with the 24- and 40-inch ANU telescopes and one of the robotic PROMPT telescopes. Fourier periodograms suggested the existence of long period variation in the V-band light curves of all three HMXBs, however folding the data at those periods did not reveal convincing periodic variation. At this point we cannot rule out the existence of long term V-band variation for these three sources and hints of longer term variation may be seen in the higher precision PROMPT data. Long term V-band observations, on the order of several years, taken at a frequency of at least once per week and with a precision of 0.01 mag, therefore still have a chance of revealing long term variation in these three HMXBs.

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arXiv2010

SN 2009bb: a Peculiar Broad-Lined Type Ic Supernova

Ultraviolet, optical, and near-infrared photometry and optical spectroscopy of the broad-lined Type Ic supernova (SN) 2009bb are presented, following the flux evolution from -10 to +285 days past B-band maximum. Thanks to the very early discovery, it is possible to place tight constraints on the SN explosion epoch. The expansion velocities measured from near maximum spectra are found to be only slightly smaller than those measured from spectra of the prototype broad-lined SN 1998bw associated with GRB 980425. Fitting an analytical model to the pseudo-bolometric light curve of SN 2009bb suggests that 4.1+-1.9 Msun of material was ejected with 0.22 +-0.06 Msun of it being 56Ni. The resulting kinetic energy is 1.8+-0.7x10^52 erg. This, together with an absolute peak magnitude of MB=-18.36+-0.44, places SN 2009bb on the energetic and luminous end of the broad-lined Type Ic (SN Ic) sequence. Detection of helium in the early time optical spectra accompanied with strong radio emission, and high metallicity of its environment makes SN 2009bb a peculiar object. Similar to the case for GRBs, we find that the bulk explosion parameters of SN 2009bb cannot account for the copious energy coupled to relativistic ejecta, and conclude that another energy reservoir (a central engine) is required to power the radio emission. Nevertheless, the analysis of the SN 2009bb nebular spectrum suggests that the failed GRB detection is not imputable to a large angle between the line-of-sight and the GRB beamed radiation. Therefore, if a GRB was produced during the SN 2009bb explosion, it was below the threshold of the current generation of gamma-ray instruments.

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arXiv2008

The Rapidly Flaring Afterglow of the Very Bright and Energetic GRB 070125

We report on multi-wavelength observations, ranging from the X-ray to radio wave bands, of the IPN-localized gamma-ray burst GRB 070125. Spectroscopic observations reveal the presence of absorption lines due to O I, Si II, and C IV, implying a likely redshift of z = 1.547. The well-sampled light curves, in particular from 0.5 to 4 days after the burst, suggest a jet break at 3.7 days, corresponding to a jet opening angle of ~7.0 degrees, and implying an intrinsic GRB energy in the 1 - 10,000 keV band of around E = (6.3 - 6.9)x 10^(51) erg (based on the fluences measured by the gamma-ray detectors of the IPN network). GRB 070125 is among the brightest afterglows observed to date. The spectral energy distribution implies a host extinction of Av < 0.9 mag. Two rebrightening episodes are observed, one with excellent time coverage, showing an increase in flux of 56% in ~8000 seconds. The evolution of the afterglow light curve is achromatic at all times. Late-time observations of the afterglow do not show evidence for emission from an underlying host galaxy or supernova. Any host galaxy would be subluminous, consistent with current GRB host-galaxy samples. Evidence for strong Mg II absorption features is not found, which is perhaps surprising in view of the relatively high redshift of this burst and the high likelihood for such features along GRB-selected lines of sight.

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