arXiv subjects

M. A. P. Torres

Publications and source records attributed to M. A. P. Torres.

At least 19 recordsLinked to original sources

arXiv2026

Multi-wavelength Constraints on the Transient EP250905a

Fast X-ray transients (FXTs) are a diverse class of high-energy suggested origins, ranging from stellar explosions to compact object mergers. The Einstein Probe (EP) satellite discovers approximately 100 FXTs per year. We aim to constrain the physical origin of EP250905a. We analyze X-ray, optical, near-infrared (NIR), and radio temporal and spectral properties of EP250905a. In addition, we assess the possible role of weak gravitational lensing in shaping its observed characteristics. EP250905a fades rapidly in X-rays, and we detect no NIR or radio emission, but we detect early optical emission that rapidly fades beyond the detection limits. Two nearby galaxies are identified for which we derive spectroscopic redshifts of $z=0.374$ (G1) and $z=2.714$ (G2). Our analysis favors G2 as the host of the FXT EP250905a. The angular separation of 2.56\arcsec\, between the FXT's optical counterpart and the center of the G1 galaxy suggests the emission of the FXT might be moderately magnified by lensing effects ($μ\approx3.9$) given the inferred Einstein radius of G1 ($θ_E\approx1.9$ arcsec). The data are best explained as an afterglow from a mildly off-axis structured jet at $z=2.714$, providing a consistent broadband interpretation that also allows for weakly lensed emission of EP250905a.

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arXiv2026

X-ray luminous late-type giants: an overlooked population contributing to the Galactic ridge iron line emission

The origin of the highly ionized iron emission (Fe XXV at $6.7\,\mathrm{keV}$) characterizing the Galactic ridge X-ray emission (GRXE) remains a fundamental puzzle in high-energy astrophysics. Although the GRXE continuum is largely resolved into discrete populations of cataclysmic variables and coronally active stars, these sources exhibit Fe XXV equivalent widths significantly lower than that of the total GRXE, leaving the intense iron line emission unexplained. In this work, we cross-correlated the XMM-Newton survey of the inner Galactic disk with Gaia DR3 astrometry to identify and characterize hard X-ray sources ($>2\,\mathrm{keV}$) with reliable stellar counterparts. We selected 107 X-ray sources located within the red giant branch of the color-magnitude diagram, many of which are verified long-period variables. These sources exhibit high X-ray luminosities ($L_{\mathrm{X}} \approx 10^{31}$--$10^{33}\,\mathrm{erg~s^{-1}}$), significantly exceeding the typical coronal saturation levels of single giants. Their X-ray spectra are notably harder than those of quiescent stellar coronae, with plasma temperatures reaching up to $kT \approx 6\,\mathrm{keV}$ and a prominent emission feature at $\sim 6.7\,\mathrm{keV}$. The combination of high $L_{\mathrm{X}}$, hard spectra, and intense Fe XXV emission identifies this population as accretion-powered binaries associated with late-type giants. Our analysis demonstrates that this population contributes $\sim 20\%$ of the total GRXE continuum and $\sim 40\%$ of its iron line emission, providing a key component to resolving the Galactic X-ray background puzzle.

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arXiv2026

An energetic dirty fireball detected in soft X-rays

The collapse of massive stars drives explosions that power relativistic fireballs. If only a small amount of matter is entrained, such clean fireballs can expand with Lorentz factors $Γ> 100$, accounting for gamma-ray bursts (GRBs). It has been hypothesized that energetic explosions with more baryon contamination, dubbed ``dirty fireballs'', may exist in nature, but they have not been observed. Here we report the observation of an extragalactic fast X-ray transient, EP241113a, detected by Einstein Probe. Compared to GRBs, it has a similar isotropic energy of $1.4\times 10^{51}$ erg, but significantly lower spectral peak energy. Theoretical modeling of its early X-ray afterglow suggests a relativistic jet with a low Lorentz factor of $Γ\sim 20$ aligned close to the line-of-sight, signifying the prototype of a dirty fireball.

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arXiv2026

A search for optical counterparts in quiescent black hole X-ray transients

Dynamical mass measurements of compact stars in X-ray transients demand the detection of optical/near infrared counterparts in quiescence. Out of the 73 black-hole candidates in X-ray transients, optical and near-infrared quiescent counterparts have only been identified for 34 objects. We present ULTRACAM photometric observations of nine candidate black hole X-ray transients with no reported counterparts in quiescence, complemented with data from the public surveys DECaPS and Pan-STARRS. In addition, we analyze photometry of three sources (SWIFT J1539.2-6227, XTE J1817-330 and XTE J1818-245) obtained during their discovery outburst. The data provide the first optical identifications and precise astrometry of four targets (MAXI J1348-630, SWIFT J1539.2-6227, XTE J1726-476 and XTE J1817-330) plus $3σ$ lower limits to the quiescent optical magnitudes for an additional five (MAXI J0637-430, 4U 1755-338, MAXI J1803-298, XTE J1818-245 and MAXI J1828-249). Of these five, 4U 1755-338 was found to be active during our ULTRACAM observations and we use our images to derive refined astrometric coordinates. We use the photometric magnitudes and colors to place preliminary constraints on the orbital periods and spectral types of the companion stars. Finding charts of all the targets are also provided to facilitate future follow-up studies. Finally, we present updated astrometry for XTE J1650-500 using archival FORS2 images.

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arXiv2026

Ubiquitous yet forgotten: broad absorptions in the optical spectra of low-mass X-ray binaries

Optical outburst spectra of low-mass X-ray binaries enable studies of extreme accretion and ejection phenomena. While some of their spectroscopic features have been analysed in detail, the appearance of broad absorptions in the optical regime has been traditionally neglected. In this work, we introduce the first population study dedicated to these features with the aim to understand their fundamental properties and discuss them in the context of their origin. We complement the study with a spectroscopic database of six low-mass X-ray binaries during outburst, in order to assess their evolution. We find that broad absorptions are ubiquitous, with the majority of black hole low-mass X-ray binaries exhibiting them in spite of a typically scarce outburst coverage. Their detection does not depend on the orbital inclination or the compact object nature, but they seem favoured in systems with orbital periods shorter than < 11 h. They predominantly occur in the hydrogen Balmer series, being stronger at shorter wavelengths, and they are detected across all X-ray states. We find that the normalised depth of these broad absorptions is anti-correlated with the system luminosity, and that they show constant line ratios over the whole sample. Based on these properties, we favour a scenario where BAs arise from a stable, optically thick layer of the accretion disc, below the hotter chromosphere-like region producing the emission line components. Our study is consistent with the continuous presence of broad absorptions during the whole outburst, with their visibility being conditioned by the emission lines filling the broad absorption profile and veiling by the X-ray reprocessed continuum.

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arXiv2025

Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake: Time-domain astronomy

We outline the science case for a 30-40 m optical/infrared telescope in the Northern Hemisphere, optimised for transformative time-domain astronomy in the 2040s. Upcoming multi-wavelength and multi-messenger facilities will reveal fast, faint, rapidly evolving Northern transients whose earliest phases carry decisive diagnostics. A Northern ELT with rapid response, broad wavelength coverage, high time resolution, polarimetric capabilities, and diffraction-limited imaging is essential to capture these phases and secure deep spectroscopy and photometry as transients fade. These capabilities will enable recovery of key physical information and detailed characterisation of transient environments, while also enabling unprecedented studies of accretion phenomena at all scales. Among potential sites, La Palma uniquely combines atmospheric stability, complementary longitude to ESO's ELT, protected dark skies, and robust infrastructure to host this facility.

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arXiv2025

Unveiling the nature of the Einstein Probe transient EP 241021a

We present a multi-wavelength analysis of the fast X-ray transient EP 241021a, discovered by the Wide-field X-ray Telescope aboard the \emph{Einstein Probe} satellite on 2024 October 21. The event was not detected in gamma-rays. Follow-up observations from $\sim$1.5 to 100 days post-trigger were obtained across X-ray, UV, optical, near-infrared, and radio bands with ground- and space-based facilities. The redshift is constrained to $z = 0.7485$ from prominent optical spectral features. The optical light curve shows complex evolution: an initial $\sim t^{-0.7}$ decay, followed by a rapid re-brightening peaking at day 7.7 with $\sim t^{-1.7}$ decay, and a third phase peaking near day 19 with $\sim t^{-1.3}$ decay. The spectral energy distribution (SED) and its temporal evolution are consistent with a mix of non-thermal and thermal components. Early optical-to-X-ray spectral indices agree with optically thin synchrotron emission, while steepening of the optical SED after $\sim$20 days indicates either a shift in emission mechanism or the emergence of an additional component. Although broad-lined absorption features are absent, comparisons with type Ic-BL supernovae suggest a SN contribution at late times, suggesting a collapsar origin for EP 241021a. The likely SN in EP 241021a appears to require an additional energy source beyond $^{56}$Ni decay. These results support the view that some fast X-ray transients detected by the \emph{Einstein Probe} arise from massive stellar explosions.

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arXiv2025

EP250207b is not a collapsar fast X-ray transient. Is it due to a compact object merger?

Fast X-ray Transients (FXTs) are short-lived extra-galactic X-ray sources. Recent progress through multi-wavelength follow-up of Einstein Probe discovered FXTs has shown that several are related to collapsars, which can also produce gamma-ray bursts (GRBs). In this paper we investigate the nature of the FXT EP250207b. The VLT/MUSE spectra of a nearby (15.9 kpc in projection) lenticular galaxy reveal no signs of recent star formation. If this galaxy is indeed the host, EP250207b lies at a redshift of z=0.082, implying a peak observed absolute magnitude for the optical counterpart of M_r=-14.5. At the time when supernovae (SNe) would peak, it is substantially fainter than all SN types. These results are inconsistent with a collapsar origin for EP250207b. The properties favour a binary compact object merger driven origin. The X-ray, optical and radio observations are compared with predictions of several types of extra-galactic transients, including afterglow and kilonova models. The data can be fit with a slightly off-axis viewing angle afterglow. However, the late-time (~30 day) optical/NIR counterpart is too bright for the afterglow and also for conventional kilonova models. This could be remedied if that late emission is due to a globular cluster or the core of a (tidally disrupted) dwarf galaxy. If confirmed, this would be the first case where the multi-wavelength properties of an FXT are found to be consistent with a compact object merger origin, increasing the parallels between FXTs and GRBs. We finally discuss if the source could originate in a higher redshift host galaxy.

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arXiv2025

The orbital period and inclination of the neutron star X-ray transient MAXI J1807+132

The neutron star X-ray transient MAXI J1807+132 has undergone outbursts in 2017, 2019, and 2023. We conducted an $R$-band time series photometry campaign using the Isaac Newton Telescope during the 2022 quiescent state. We detected a periodic variation in the light curve, consistent with ellipsoidal modulation, which allowed us to determine an orbital period of $P_{\rm orb} = 4.258 \pm 0.008$ hr. By modelling the light curve, we obtained a binary inclination of $ i = 72\pm5 \, °$ and a mass ratio $q = 0.24^{+0.19}_{-0.14}$ ($68$ per cent confidence level). Furthermore, our analysis supports an early M-dwarf companion that contributes between 30 and 50 per cent to the total flux in the $R$-band. We extend the previously established absolute magnitude versus orbital period correlation for black hole X-ray transients to neutron star systems. We applied the correlation to MAXI J1807+132, estimating its distance as $6.3 \pm 0.7$ kpc and its height above the Galactic plane to be $1.6 \pm 0.2$ kpc.

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arXiv2025

Characterising the short-orbital period X-ray transient Swift J1910.2-0546

SwiftJ1910.2-0546 is a Galactic X-ray transient discovered during a bright outburst in 2012. We use time-series optical photometry and spectroscopy to estimate the orbital period, characterise the donor star, determine the interstellar extinction, distance, and system geometry, and constrain the component masses. Multi-site r-band and clear-filter light curves and WHT/ACAM spectra from the 2012 outburst are combined with time-series spectroscopy from GTC/OSIRIS and VLT/FORS2 in quiescence. Period searches are conducted using generalised Lomb-Scargle, phase-dispersion minimisation, and analysis-of-variance algorithms. Diffuse interstellar bands constrain E(B-V), while empirical correlations involving H$α$ yield estimates of K2, q, and i. We detect a double-humped modulation with a period of $0.0941\pm0.0007$d ($2.26\pm0.02$h) during the outburst. Its morphology is consistent with an early superhump, suggesting that the true orbital period may be slightly shorter than 4.52h. The H$α$ radial velocity curves do not yield a definitive orbital period. In quiescence, TiO bands indicate an M3-M3.5 donor contributing 70% of the red continuum. Diffuse interstellar bands give E(B-V)=$0.60\pm0.05$ and N_H=$(3.9\pm1.3)$x10$^{21}$cm$^{-2}$, placing the system at a distance of 2.8-4.0 kpc. The H$α$ line width in quiescence (FWHM_0 =$990\pm45$km/s), via a FWHM-K_2 calibration, provides an estimate of K_2, while its double peaked profile gives q and i. Adopting the resulting K_2=$230\pm17$km/s and q=$0.032\pm0.010$, and two orbital period scenarios (2.25 and 4.50h), Monte Carlo sampling returns a compact object mass M_1=8-11M_sun and an inclination i=13-18 deg for plausible donor masses (M_2=0.25-0.35M_sun). We favour an orbital period of 4.5h. Further phase-resolved spectroscopy and photometry during quiescence are needed to better determine its fundamental parameters.

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arXiv2025

EP 250108a/SN 2025kg: Observations of the most nearby Broad-Line Type Ic Supernova following an Einstein Probe Fast X-ray Transient

With a small sample of fast X-ray transients (FXTs) with multi-wavelength counterparts discovered to date, the progenitors of FXTs and their connections to gamma-ray bursts (GRBs) and supernovae (SNe) remain ambiguous. Here, we present photometric and spectroscopic observations of SN 2025kg, the supernova counterpart to the FXT EP 250108a. At $z=0.17641$, this is the closest known SN discovered following an Einstein Probe (EP) FXT. We show that SN 2025kg's optical spectra reveal the hallmark features of a broad-lined Type Ic SN. Its light curve evolution and expansion velocities are also comparable to those of GRB-SNe, including SN 1998bw, and several past FXT SNe. We present JWST/NIRSpec spectroscopy taken around SN 2025kg's maximum light, and find weak absorption due to He I $λ1.0830, λ2.0581$ $μ$m and a broad, unidentified feature at $\sim$ 4-4.5 $μ$m. Further, we observe clear evidence for broadened H$α$ in optical data at 42.5 days that is not detected at other epochs, indicating interaction with hydrogen-rich material. From its light curve, we derive a $^{56}$Ni mass of 0.2 - 0.6 $M_{\odot}$. Together with our companion paper (Eyles-Ferris et al. 2025), our broadband data of EP 250108a/SN 2025kg are consistent with a trapped or low energy ($\lesssim 10^{51}$ ergs) jet-driven explosion from a collapsar with a zero-age main sequence mass of 15-30 $M_{\odot}$. Finally, we show that the sample of EP FXT SNe support past rate estimates that low-luminosity jets seen through FXTs are more common than successful (GRB) jets, and that similar FXT-like signatures are likely present in at least a few percent of the brightest Ic-BL SNe.

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arXiv2025

A Halpha metric for identifying dormant black holes in X-ray transients

Dormant black holes (BHs) in X-ray transients can be identified by the presence of broad Ha emission lines from quiescent accretion discs. Unfortunately, short-period cataclysmic variables (CVs) can also produce broad Ha lines, especially when viewed at high inclinations, and are thus a major source of contamination. Here we compare the full width at half maximum (FWHM) and equivalent width (EW) of the Ha line in a sample of 20 quiescent BH transients and 354 CVs (305 from SDSS I to IV) with secure orbital periods (Porb) and find that: (1) FWHM and EW values decrease with Porb, and (2) for a given Porb both parameters are typically larger in BH transients than in CVs. We also compile spectral types for 17 low-mass companions in BH transients from the literature and derive an empirical Porb-Teff calibration. Using this, we conclude that the decrease in EW with Porb is mostly driven by the dilution of the Ha flux by the donor star continuum, which dominates the r-band spectrum for Porb>~0.2 d. At shorter periods, the larger contribution of the disc to the total r-band flux introduces significant scatter in the EWs due to the changing visibility of the disc projected area with binary inclination. On the other hand, the larger EWs observed in BHs can be explained by their extreme mass ratios (which limit the fractional contribution of the companion to the total flux) and the absence of a white dwarf component (important at Porb<~0.085 d). Finally, we present a tentative metric, based on Ha FWHM and EW information, and provide optimal cuts to select ~80 % of the BH X-ray transients, while rejecting ~78 % of the CVs in our sample. Such a metric, combined with other multi-frequency diagnostics, can help detect new dormant BH X-ray transients in blind large-scale surveys such as HaWKs and its pathfinder, Mini-HaWKs.

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arXiv2025

Dynamical confirmation of a black hole in the X-ray transient Swift J1727.8-1613

The X-ray transient Swift J1727.8-1613 ended its 10-month discovery outburst on June of 2024, when it reached an optical brightness comparable to pre-discovery magnitudes. With the aim of performing a dynamical study, we launched an optical spectroscopy campaign with the GTC telescope. We detect the companion star and construct its radial velocity curve, yielding a binary orbital period of Porb = 10.8038 +- 0.0010 h and a radial velocity semi-amplitude of K2 = 390 +- 4 km/s. This results in a mass function of f(M1)=2.77 +- 0.09 Msun. Combined with constraints on the binary inclination, it sets a lower limit to the compact object mass of M1 > 3.12 +- 0.10 Msun, dynamically confirming the black hole nature of the accretor. Comparison of the average spectrum in the rest frame of the companion with synthetic stellar templates supports a K4V donor partially veiled (74%) by the accretion disc. A refined distance measurement of 3.7+- 0.3 kpc, together with the astrometric proper motion and the systemic velocity derived from the radial velocity curve (-181 +-4 km/s), supports a natal kick velocity of 220 +40 -50 km/s, at the upper end of the observed distribution.

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arXiv2025

Revisiting the fundamental parameters for the black hole X-ray transient Swift J1753.5-0127

We present time-resolved Gran Telescopio Canarias optical spectroscopy and William Herschel Telescope $i$-band photometry of the X-ray transient SWIFT J1753.5-0127 in quiescence. The $i$-band light curve is dominated by flickering with an amplitude of $\sim 0.5$ mag and shows no evidence of the ellipsoidal modulation of the companion star. The telluric-corrected average spectrum, on the other hand, reveals the presence of weak (strongly veiled) TiO bands at $7055$ Ȧ and $7589$ Ȧ. We used them for a spectral classification, finding an M4-5 V companion star. However, as velocity shifts are not clearly detected in the individual spectra, we turned the analysis to the double-peaked H$α$ emission line from the accretion disc. By exploiting the empirical correlations established for quiescent X-ray transients between the line morphology and fundamental binary parameters, we estimated the radial velocity semi-amplitude of the companion $K_2 = 820 \pm 36$ km s$^{-1}$, a mass ratio $q = 0.023 \pm 0.006$ and an inclination $i = 79 \pm 5$ deg. Moreover, an orbital period of $3.26 \pm 0.02$ h was measured from the modulation of the centroid velocities and the double-peak trough depth of the H$α$ profile. These quantities yielded a mass function $f(M_1) = 7.8 \pm 1.0$ M$_\odot$ and black hole and companion star masses of $M_1 = 8.8 \pm 1.3$ M$_\odot$ and $M_2 = 0.20 \pm 0.06$ M$_\odot$, respectively. The companion star mass is in line with the spectral classification obtained from the relative depth of the TiO bands. Based on the mean quiescent magnitude ($i = 21.4 \pm 0.1$), orbital period, and interstellar extinction, we estimate the distance to the source to be $3.9 \pm 0.7$ kpc and a Galactic plane elevation of $0.8 \pm 0.2$ kpc, supporting the case for a large natal kick.

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arXiv2025

State-dependent signatures of jets and winds in the optical and infrared spectrum of the black hole transient GX 339$-$4

GX 339$-$4 is one of the prototypical black hole X-ray transients, exhibiting recurrent outbursts that allow detailed studies of black hole accretion and ejection phenomena. In this work we present four epochs of optical and near-infrared spectroscopy obtained with X-shooter at the Very Large Telescope. The dataset includes two hard state spectra, collected during the 2013 and 2015 outbursts, and two soft state spectra observed during the 2021 outburst. Strong Balmer, Paschen, He I and He II emission lines are consistently observed in all spectra, while Brackett transitions and the Bowen blend are only prominent in the soft state. Although P-Cygni profiles are not identified, the presence of wind signatures, such as extended emission wings, flat-top and asymmetric red-skewed profiles, is consistently observed through most emission lines, suggesting the presence of wind-type ejecta. These features are particularly evident in the hard state, but they are also observed in the soft state, especially in the near-infrared. This strengthens the case for state-independent winds in black hole transients and increases the evidence for wind signatures in low-to-intermediate orbital inclination systems. We also study the spectral energy distribution, which provides evidence for the presence of synchrotron emission during the hard state. The jet significantly affects the near-infrared continuum, greatly diluting the emission features produced in the accretion flow. The simultaneous identification of both jet and wind signatures during the hard state reinforces the idea of a complex outflow scenario, in which different types of ejecta coexist.

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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.

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arXiv2024

Soft X-ray prompt emission from a high-redshift gamma-ray burst EP240315a

Long gamma-ray bursts (GRBs) are believed to originate from core collapse of massive stars. High-redshift GRBs can probe the star formation and reionization history of the early universe, but their detection remains rare. Here we report the detection of a GRB triggered in the 0.5--4 keV band by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated as EP240315a, whose bright peak was also detected by the Swift Burst Alert Telescope and Konus-Wind through off-line analyses. At a redshift of $z=4.859$, EP240315a showed a much longer and more complicated light curve in the soft X-ray band than in gamma-rays. Benefiting from a large field-of-view ($\sim$3600 deg$^2$) and a high sensitivity, EP-WXT captured the earlier engine activation and extended late engine activity through a continuous detection. With a peak X-ray flux at the faint end of previously known high-$z$ GRBs, the detection of EP240315a demonstrates the great potential for EP to study the early universe via GRBs.

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arXiv2024

Evidence for inflows and outflows in the nearby black hole transient Swift J1727.8-162

We present 20 epochs of optical spectroscopy obtained with the GTC-10.4m telescope across the bright discovery outburst of the black hole candidate Swift J1727.8-162. The spectra cover the main accretion states and are characterised by the presence of hydrogen and helium emission lines, commonly observed in these objects. They show complex profiles, including double-peaks, but also blue-shifted absorptions (with blue-edge velocities of 1150 km/s), broad emission wings and flat-top profiles, which are usual signatures of accretion disc winds. Moreover, red-shifted absorptions accompanied by blue emission excesses suggest the presence of inflows in at least two epochs, although a disc origin cannot be ruled out. Using pre-outburst imaging from Pan-STARRS, we identify a candidate quiescent optical counterpart with a magnitude of g = 20.8. This implies an outburst optical amplitude of DV = 7.7, supporting an estimated orbital period of 7.6 h, which favours an early K-type companion star. Employing various empirical methods we derive a distance to the source of d = 2.7 +- 0.3 kpc, corresponding to a Galactic Plane elevation of z = 0.48 +- 0.05 kpc. Based on these findings, we propose that Swift J1727.8-162 is a nearby black hole X-ray transient that exhibited complex signatures of optical inflows and outflows throughout its discovery outburst.

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