arXiv subjects

T. J. Maccarone

Publications and source records attributed to T. J. Maccarone.

At least 37 records · Page 2Linked to original sources

arXiv2025

Detection of Millimeter-Wavelength Flares from Two Accreting White Dwarf Systems in the SPT-3G Galactic Plane Survey

Blind discoveries of millimeter-wave (mm-wave) transient events in non-targeted surveys, as opposed to follow-up or pointed observations, have only become possible in the past decade using cosmic microwave background surveys. Here we present the first results from the SPT-3G Galactic Plane Survey -- the first dedicated high-sensitivity, wide-field, time-domain, mm-wave survey of the Galactic Plane, conducted with the South Pole Telescope (SPT) using the SPT-3G camera. The survey field covers approximately 100 $\text{deg}^2$ near the Galactic center. In 2023 and 2024, this survey consists of roughly 1,500 individual 20-minute observations in three bands centered at 95, 150, and 220 GHz, with plans for more observations in the coming years. We report the detection of two transient events exceeding a 5$σ$ threshold in both the 95 and 150 GHz bands in the first two years of SPT-3G Galactic Plane Survey data. Both events are unpolarized and exhibit durations of approximately one day, with peak flux densities at 150 GHz of at least 50 mJy. The peak isotropic luminosities at 150 GHz are on the order of $10^{31}~\text{erg}~\text{s}^{-1}$. Both events are associated with previously identified accreting white dwarfs. Magnetic reconnection in the accretion disk is a likely explanation for the observed millimeter flares. In the future, we plan to expand the transient search in the Galactic Plane by lowering the detection threshold, enabling single-band detections, analyzing lightcurves on a range of timescales, and including additional data from future observations.

astro-ph.SR↗

arXiv2025

The Mid-infrared Emitting Jet in the Black Hole V404 Cygni in Quiescence

Observations of some quiescent black hole X-ray binaries have revealed an excess of mid-infrared (MIR) emission above that expected from their donor stars. In one system, V404 Cygni, this excess has been variously suggested to arise from the accretion disk, circumbinary material, or a compact relativistic jet. Here we present simultaneous James Webb Space Telescope (JWST), Atacama Large Millimeter/submillimeter Array (ALMA), and complementary multi-wavelength observations undertaken to resolve this uncertainty. We observed large-amplitude 21 $μ$m variability on short timescales with JWST, particularly a dramatic flare which swiftly rose to $\approx2.4$ mJy, over 10 times the lowest observed MIR flux density. Similar variability was simultaneously observed from radio to X-ray wavelengths with other facilities throughout the campaign. This variability and the flat radio/mm/MIR spectral index ($α= 0.04 \pm 0.01$) suggest that the MIR excess at and longward of 21 $μ$m in V404 Cyg does not arise from the accretion disk or circumbinary material. Instead, the emission at 21 $μ$m is dominated by synchrotron radiation from a jet which persists into quiescence. This result reinforces the ubiquity of the disk-jet connection in accreting black holes across a range of masses and accretion rates.

astro-ph.HE↗

arXiv2024

Calibrating the clock of JWST

JWST, despite not being designed to observe astrophysical phenomena that vary on rapid time scales, can be an unparalleled tool for such studies. If timing systematics can be controlled, JWST will be able to open up the sub-second infrared timescale regime. Rapid time-domain studies, such as lag measurements in accreting compact objects and Solar System stellar occultations, require both precise inter-frame timing and knowing when a time series begins to an absolute accuracy significantly below 1s. In this work we present two long-duration observations of the deeply eclipsing double white dwarf system ZTF J153932.16+502738.8, which we use as a natural timing calibrator to measure the absolute timing accuracy of JWST's clock. From our two epochs, we measure an average clock accuracy of $0.12\pm0.06$s, implying that JWST can be used for sub-second time-resolution studies down to the $\sim100$ms level, a factor $\sim5$ improvement upon the pre-launch clock accuracy requirement. We also find an asymmetric eclipse profile in the F322W2 band, which we suggest has a physical origin.

astro-ph.IM↗

arXiv2024

A NuSTAR Census of the X-ray Binary Population of the M31 Disk

Using hard (E>10 keV) X-ray observations with NuSTAR, we are able to differentiate between accretion states, and thus compact object types, of neutron stars and black holes in X-ray binaries (XRBs) in M31, our nearest Milky Way-type neighbor. Using ten moderate-depth (20-50 ks) observations of the disk of M31 covering a total of ~0.45 deg$^{2}$, we detect 20 sources at 2$σ$ in the 4-25 keV band pass, 14 of which we consider to be XRB candidates. This complements an existing deeper (100-400 ks) survey covering ~0.2 deg$^{2}$ of the bulge and the northeastern disk. We make tentative classifications of 9 of these sources with the use of diagnostic color-intensity and color-color diagrams, which separate sources into various neutron star and black hole regimes, identifying 3 black holes and 6 neutron stars. In addition, we create X-ray luminosity functions for both the full (4-25 keV) and hard (12-25 keV) band, as well as sub-populations of the full band based on compact object type and association with globular clusters. Our best fit globular cluster XLF is shallower than the field XLF, and preliminary BH and NS XLFs suggest a difference in shape based on compact object type. We find that the cumulative disk XLFs in the full and hard band are best fit by power laws with indices of 1.32 and 1.28 respectively. This is consistent with models of the Milky Way XLF from Grimm et al. (2002), Voss & Ajello (2010), and Doroshenko et al. (2014).

astro-ph.HE↗

arXiv2024

Spectro-photometric follow up of the outbursting AM CVn system ASASSN-21br

We report on spectroscopic and photometric observations of the AM CVn system ASASSN-21br, which was discovered in outburst by the All-Sky Automated Survey for Supernovae in February 2021. The outburst lasted for around three weeks, and exhibited a pronounced brightness dip for $\approx$ 4 days, during which the spectra showed a sudden transition from emission- to absorption-line dominated. Only $\approx$ 60 AM CVn systems with derived orbital periods are found in the Galaxy, therefore increasing the sample of AM CVn systems with known orbital periods is of tremendous importance to (1) constrain the physical mechanisms of their outbursts and (2) establish a better understanding of the low-frequency background noise of future gravitational wave surveys. Time-resolved photometry taken during the outburst of ASASSN-21br showed modulation with a period of around 36.65 minutes, which is likely the superhump or orbital period of the system. Time-resolved spectroscopy taken with the Southern African Large Telescope did not show any sign of periodicity in the He I absorption lines. This is possibly due to the origin of these lines in the outbursting accretion disc, which makes it challenging to retrieve periodicity from the spectral lines. Future follow up spectral observations during quiescence might allow us better constrain the orbital period of ASASSN-21br.

astro-ph.HE↗

arXiv2024

Rapid Mid-Infrared Spectral-Timing with JWST. I. The prototypical black hole X-ray Binary GRS 1915+105 during a MIR-bright and X-ray-obscured state

We present mid-infrared (MIR) spectral-timing measurements of the prototypical Galactic microquasar GRS 1915+105. The source was observed with the Mid-Infrared Instrument (MIRI) onboard JWST in June 2023 at a MIR luminosity L(MIR)~10^{36} erg/s exceeding past IR levels by about a factor of 10. By contrast, the X-ray flux is much fainter than the historical average, in the source's now-persistent 'obscured' state. The MIRI low-resolution spectrum shows a plethora of emission lines, the strongest of which are consistent with recombination in the hydrogen Pfund (Pf) series and higher. Low amplitude (~1%) but highly significant peak-to-peak photometric variability is found on timescales of ~1,000 s. The brightest Pf(6-5) emission line lags the continuum. Though difficult to constrain accurately, this lag is commensurate with light-travel timescales across the outer accretion disc or with expected recombination timescales inferred from emission line diagnostics. Using the emission line as a bolometric indicator suggests a moderate (~5-30% Eddington) intrinsic accretion rate. Multiwavelength monitoring shows that JWST caught the source close in-time to unprecedentedly bright MIR and radio long-term flaring. Assuming a thermal bremsstrahlung origin for the MIRI continuum suggests an unsustainably high mass-loss rate during this time unless the wind remains bound, though other possible origins cannot be ruled out. PAH features previously detected with Spitzer are now less clear in the MIRI data, arguing for possible destruction of dust in the interim. These results provide a preview of new parameter space for exploring MIR spectral-timing in XRBs and other variable cosmic sources on rapid timescales.

astro-ph.HE↗

arXiv2024

The VISTA Variables in the Vía Láctea eXtended (VVVX) ESO public survey: Completion of the observations and legacy

The ESO public survey VISTA Variables in the Vía Láctea (VVV) surveyed the inner Galactic bulge and the adjacent southern Galactic disk from $2009-2015$. Upon its conclusion, the complementary VVV eXtended (VVVX) survey has expanded both the temporal as well as spatial coverage of the original VVV area, widening it from $562$ to $1700$ sq. deg., as well as providing additional epochs in $JHK_{\rm s}$ filters from $2016-2023$. With the completion of VVVX observations during the first semester of 2023, we present here the observing strategy, a description of data quality and access, and the legacy of VVVX. VVVX took $\sim 2000$ hours, covering about 4% of the sky in the bulge and southern disk. VVVX covered most of the gaps left between the VVV and the VISTA Hemisphere Survey (VHS) areas and extended the VVV time baseline in the obscured regions affected by high extinction and hence hidden from optical observations. VVVX provides a deep $JHK_{\rm s}$ catalogue of $\gtrsim 1.5\times10^9$ point sources, as well as a $K_{\rm s}$ band catalogue of $\sim 10^7$ variable sources. Within the existing VVV area, we produced a $5D$ map of the surveyed region by combining positions, distances, and proper motions of well-understood distance indicators such as red clump stars, RR Lyrae, and Cepheid variables. In March 2023 we successfully finished the VVVX survey observations that started in 2016, an accomplishment for ESO Paranal Observatory upon 4200 hours of observations for VVV+VVVX. The VVV+VVVX catalogues complement those from the Gaia mission at low Galactic latitudes and provide spectroscopic targets for the forthcoming ESO high-multiplex spectrographs MOONS and 4MOST.

astro-ph.GA↗

arXiv2024

Variable radio emission of neutron star X-ray binary Ser X-1 during its persistent soft state

Ser X-1 is a low mass neutron star X-ray binary and has been persistently accreting since its discovery in the 1960s. It has always been observed to be in a soft spectral state and has never showed substantial long-term X-ray variability. Ser X-1 has one previous radio observation in the literature in which radio emission was detected during this soft state, which is contrary to the behavior of black hole X-ray binaries. We have recently obtained 10 randomly sampled radio epochs of Ser X-1 in order to further investigate its anomalous soft state radio emission. Out of 10 epochs, we find 8 non-detections and 2 detections at 10 GHz flux densities of 19.9 +/- 4.2 uJy and 32.2 +/- 3.6 uJy. We do not detect polarization in either epoch, ruling out very high polarization levels (< 63% and 34%). We compare these Ser X-1 results to other X-ray binaries and consider explanations for its long term variable radio behavior.

astro-ph.HE↗

arXiv2024

An arcsecond view at 1-2 GHz into the Galactic Bulge

We present the results of a high angular resolution (1.1") and sensitivity (maximum of ~0.1 mJy) radio survey at 1-2 GHz in the Galactic Bulge. This complements the X-ray Chandra Galactic Bulge Survey, and investigates the full radio source population in this dense Galactic region. Radio counterparts to sources at other wavelengths can aid in classification, as there are relatively few types of objects that are reasonably detectable in radio at kiloparsec distances, and even fewer that are detected in both X-rays and radio. This survey covers about 3 square degrees of the Galactic Bulge Survey area (spanning the Galactic coordinate range of -3deg < l < +3deg and +1.6deg < b < +2.1deg as a first look into this region of the Galaxy with this combination of frequency, resolution, and sensitivity. Spectral indices within the observed band of 1-2 GHz were calculated for each source to assist in determining its emission mechanism. We find 1617 unique sources in the survey, 25 of which are radio counterparts to X-ray sources, and about 100 of which are steep-spectrum (alpha <~ -1.4) point sources that are viable pulsar candidates. Four radio sources are of particular interest: a compact binary; an infrared transient with an inverted radio spectrum; a potential transitional millisecond pulsar candidate; and a very steep spectrum radio source with an X-ray and bright infrared counterpart. We discuss other notable sources, including possible radio transients, potential new planetary nebulae, and active galactic nuclei.

astro-ph.HE↗

arXiv2023

The nature of very-faint X-ray binaries: Near-infrared spectroscopy of 1RXH J173523.7$-$354013 reveals a giant companion

Very-faint X-ray binaries (VFXBs) are a sub-class of black holes and neutron stars in binaries that appear to be accreting at a very low rate. In addition to providing interesting constraints on poorly understood forms of accretion, elucidating the nature of VFXBs is particularly interesting for binary evolution and population modeling. Through near-infrared (nIR) spectroscopy, we here investigate the nature of the bursting neutron star and VFXB 1RXH J173523.7$-$354013 (J1735), which persistently accretes at an X-ray luminosity of $L_X \sim 10^{34} - 10^{35}~L_{\odot}$. Our analysis shows that the nIR emission is dominated by that of the companion star, which we find to be a late G or early K-type giant, making this the second neutron star identified as a VFXB found to have a giant companion. We discuss how several of the system properties are difficult to reconcile with a wind-fed symbiotic X-ray binary. We therefore also propose an alternative scenario wherein J1735 is a wide binary system (supported by the discovery of a 7.5 d modulation in the nIR light curves) with a quiescent luminosity of $L_X \sim 10^{34} - 10^{35}~L_{\odot}$, in which the donor star is overflowing its Roche lobe. This raises the possibility that J1735 may, every century or more, exhibit very long and very bright outbursts during which it reaches accretion rates around the Eddington limit like the neutron star Z sources.

astro-ph.HE↗

arXiv2023

An infrared FWHM-$K_2$ correlation to uncover highly reddened quiescent black holes

Among the sample of Galactic transient X-ray binaries (SXTs) discovered to date, about 70 have been proposed as likely candidates to host a black hole. Yet, only 19 have been dynamically confirmed. Such a reliable confirmation requires phase-resolved spectroscopy of their companion stars, which is generally feasible when the system is in a quiescent state. However, since most of the SXT population lies in the galactic plane, which is strongly affected by interstellar extinction, their optical brightness during quiescence usually falls beyond the capabilities of the current instrumentation ($R\gtrsim22$). To overcome these limitations and thereby increase the number of confirmed Galactic black holes, a correlation between the full-width at half maximum (FWHM) of the H$α$ line and the semi-amplitude of the donor's radial velocity curve ($K_2$) was presented in the past. Here, we extend the FWHM-$K_2$ correlation to the near-infrared (NIR), exploiting disc lines such as He I $λ$10830, Pa$γ$, and Br$γ$, in a sample of dynamically confirmed black-hole SXTs. We obtain $K_2 = 0.22(3) ~\textrm{FWHM}$, in good agreement with the optical correlation derived using H$α$. The similarity of the two correlations seems to imply that the widths of H$α$ and the NIR lines are consistent in quiescence. When combined with information on orbital periods, the NIR correlation allows us to constrain the mass of the compact object of systems in quiescence by using single-epoch spectroscopy. We anticipate that this new correlation will give access to highly reddened black-hole SXTs, which cannot be otherwise studied at optical wavelengths.

astro-ph.HE↗

arXiv2023

New Compact Object Binary Populations with Precision Astrometry (Roman White Paper)

Compact object binaries (a black hole or a neutron star orbiting a non-degenerate stellar companion) are key to our understanding of late massive star evolution, in addition to being some of the best probes of extreme gravity and accretion physics. Gaia has opened the door to astrometric studies of these systems, enabling geometric distance measurements, kinematic estimation, and the ability to find new previously unknown systems through measurement of binary orbital elements. Particularly puzzling are newly found massive black holes in wide orbits (~AU or more) whose evolutionary history is difficult to explain. Astrometric identification of such binaries is challenging for Gaia, with only two such examples currently known. Roman's enormous grasp, superb sensitivity, sharp PSF and controlled survey strategy can prove to be a game-changer in this field, extending astrometric studies of compact object binaries several mag deeper than Gaia. We propose to use the microlensing Galactic Bulge Time Domain Survey to identify new wide-orbit black hole compact object binaries, determine their prevalence and their spatial distribution, thus opening up new parameter space in binary population studies.

astro-ph.IM↗

arXiv2023

A transient ultraviolet outflow in the short-period X-ray binary UW CrB

Accreting low mass X-ray binaries (LMXBs) are capable of launching powerful outflows such as accretion disc winds. In disc winds, vast amounts of material can be carried away, potentially greatly impacting the binary and its environment. Previous studies have uncovered signatures of disc winds in the X-ray, optical, near-infrared, and recently even the UV band, predominantly in LMXBs with large discs ($P_{orb}{\geq}20$ hrs). Here, we present the discovery of transient UV outflow features in UW CrB, a high-inclination ($i{\geq}77$°) neutron star LMXB with an orbital period of only $P_{orb}{\approx}111$ min. We present P-Cygni profiles detected for Si iv 1400Å and tentatively for N v 1240Å in one 15 min exposure, which is the only exposure covering orbital phase $ϕ{\approx}0.7{-}0.8$, with a velocity of ${\approx}1500$ km/s. We show that due to the presence of black body emission from the neutron star surface and/or boundary layer, a thermal disc wind can be driven despite the short $P_{orb}$, but explore alternative scenarios as well. The discovery that thermal disc winds may occur in NS-LMXBs with $P_{orb}$ as small as ${\approx}111$ min, and can potentially be transient on time scales as short as ${\approx}15$ min, warrants further observational and theoretical work.

astro-ph.HE↗

arXiv2023

Tracking the Enigmatic Globular Cluster Ultracompact X-ray Binary X1850--087: Extreme Radio Variability in the Hard State

The conditions under which accreting neutron stars launch radio-emitting jets and/or outflows are still poorly understood. The ultracompact X-ray binary X1850--087, located in the globular cluster NGC 6712, is a persistent atoll-type X-ray source that has previously shown unusual radio continuum variability. Here we present the results of a pilot radio monitoring program of X1850--087 undertaken with the Karl G. Jansky Very Large Array, with simultaneous or quasi-simultaneous Swift/XRT data obtained at each epoch. The binary is clearly detected in the radio in two of the six new epochs. When combined with previous data, these results suggest that X1850--087 shows radio emission at a slightly elevated hard state X-ray luminosity of L_X > 2x10^36 erg/s, but no radio emission in its baseline hard state L_X ~10^36 erg/s. No clear X-ray spectral changes are associated with this factor of > 10 radio variability. At all detected epochs X1850--087 has a flat-to-inverted radio spectral index, more consistent with the partially absorbed optically thick synchrotron of a compact jet rather than the evolving optically thick to thin emission associated with transient expanding synchrotron-emitting ejecta. If the radio emission in X1850--087 is indeed due to a compact jet, then it is plausibly being launched and quenched in the hard state on timescales as short as a few days. Future radio monitoring of X1850--087 could help elucidate the conditions under which compact jets are produced around hard state accreting neutron stars.

astro-ph.HE↗

arXiv2022

Globular Cluster Ultraluminous X-ray Sources in the Furthest Early-Type Galaxies

Ultraluminous X-ray Sources (ULXs) in globular clusters are low mass X-ray binaries that achieve high X-ray luminosities through a currently uncertain accretion mechanism. Using archival Chandra and Hubble Space Telescope observations, we perform a volume-limited search ($\lesssim$ 70 Mpc) of 21 of the most massive ($>10^{11.5} M_\odot$) early-type galaxies to identify ULXs hosted by globular cluster (GC) candidates. We find a total of 34 ULX candidates above the expected background within 5 times the effective radius of each galaxy, with 10 of these ($\sim29.4\%$) potentially hosted by a GC. A comparison of the spatial and luminosity distributions of these new candidate GC ULXs with previously identified GC ULXs shows that they are similar: both samples peak at $L_X \sim$ a few $\times 10^{39}$ erg/s and are typically located within a few effective radii of their host galaxies.

astro-ph.HE↗

arXiv2022

Astrometry of variable compact radio sources: A search for Galactic black hole X-ray binaries

We use the Very Long Baseline Array to conduct high precision astrometry of a sample of 33 compact, flat spectrum, variable radio sources in the direction of the Galactic plane (Becker et al. 2010). Although Becker et al. (2010) ruled out a few potential scenarios for the origin of the radio emission, the study could not rule out that these sources were black hole X-ray binaries (BHXBs). Most known BHXBs are first detected by X-ray or optical emission when they go into an outburst, leaving the larger quiescent BHXB population undiscovered. In this paper, we attempt to identify any Galactic sources amongst the Becker et al. (2010) sample by measuring their proper motions as a first step to finding quiescent BHXB candidates. Amongst the 33 targets, we could measure the proper motion of six sources. We find that G32.7193$-$0.6477 is a Galactic source and are able to constrain the parallax of this source with a 3$σ$ significance. We found three strong Galactic candidates, G32.5898$-$0.4468, G29.1075$-$0.1546, and G31.1494$-$0.1727, based purely on their proper motions, and suggest that G29.1075$-$0.1546, is also likely Galactic. We detected two resolved targets for multiple epochs (G30.1038+0.3984 and G29.7161$-$0.3178). We find six targets are only detected in one epoch and have an extended structure. We cross-match our VLBA detections with the currently available optical, infrared and X-ray surveys, and did not find any potential matches. We did not detect 19 targets in any VLBA epochs and suggest that this could be due to limited $uv$-coverage, drastic radio variability or faint, extended nature of the sources.

astro-ph.HE↗

arXiv2022

UGPS J194310+183851: an Unusual Optical and X-ray Faint Cataclysmic Variable?

The growing number of multi-epoch optical and infrared sky surveys are uncovering unprecedented numbers of new variable stars, of an increasing number of types. The short interval between observations in adjacent near infrared filters in the UKIDSS Galactic Plane Survey (UGPS) allows for the discovery of variability on the timescale of minutes. We report on the nature of one such object, through the use of optical spectroscopy, time-series photometry and targeted X-ray observations. We propose that UGPS J194310.32+183851.8 is a magnetic cataclysmic variable star of novel character, probably featuring a longer than average spin period and an orbital period likely to be shorter than the period gap (i.e. P$_{\text{orb}}$<2 hours). We reason that the star is likely a member of the short period Intermediate-Polar subclass that exist below this period boundary, but with the additional feature that system's SED is fainter and redder than other members of the group.

astro-ph.SR↗

arXiv2022

Using the bispectrum to probe radio X-ray correlations in GRS 1915+105

We present the results of bicoherence analysis on observations of GRS 1915+105 that exhibit quasi-periodic oscillations (QPOs). The bicoherence is a higher order statistic that can be used to probe the relation between the phases of a triplet of Fourier frequencies. Despite showing very similar power spectra, the observations exhibit different patterns in their bicoherence, indicating that the QPOs are phase coupled to the noise in different ways. We show that the bicoherence pattern exhibited correlates with the frequency of the QPO, the hardness ratio, as well as the radio properties of the source. In particular, we find that the nature of phase coupling between the QPO and the high and low frequency broadband components is different between radio quiet, radio plateau and radio steep conditions. We also investigate the phase lag behaviour of observations with QPO frequency above 2Hz that show different bicoherence patterns, and find statistically significant differences between them, indicating a change in the underlying physical mechanism. Finally, we present a scenario whereby the cooling of the jet electrons by soft photons from the accretion disc could explain the observed correlations between the bicoherence and radio properties.

astro-ph.HE↗