---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
_id: '22263'
abstract:
- lang: eng
text: Recent studies at high redshift have revealed an enigmatic class of little
red dots (LRDs) with extreme Balmer breaks, stronger than in any stellar atmosphere.
However, it is unclear whether such objects exist at lower redshift, especially
given the low number of LRDs reported at z ≲ 2. Here, we report the discovery
of PAN-BH*-1, an LRD with an extreme Balmer break at z = 1.73, identified from
JWST/NIRCam pure-parallel imaging taken by the PANORAMIC survey, and confirmed
by deep VLT/X-Shooter spectroscopy. The rest-optical to near-infrared spectral
energy distribution of PAN-BH*-1 is consistent with a photospheric continuum with
effective temperature Teff ≈ 4800 K. The broad Hα emission line shows remarkably
deep absorption, stronger than previously measured in any LRD. The absorption
trough spans from −520 to +267 km s−1 with respect to the systemic redshift. The
presence of blue- and red-shifted absorption suggests complex dynamics of the
obscuring gas along the line of sight. We speculate that the absorption trough
can be produced by a thick wind launched from a thick, rotating photospheric disk,
the latter being the source of the red optical continuum. While the source is
unresolved in the rest-optical JWST data (reff < 47 pc), the rest-near-UV Hubble
Space Telescope imaging shows an extended morphology with (formular displayed)
kpc, which we interpret as a host galaxy with a stellar mass of ∼10^8 M⊙, in line
with the narrow Hα emission. The discovery of this object at cosmic noon highlights
the feasibility of systematic searches for extreme LRDs with wide-area facilities
such as Euclid and Roman.
acknowledgement: "IOP Science home\r\nThe Astrophysical Journal Letters\r\nThe American
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Black Hole Star at Cosmic Noon: Extreme Balmer Break, Photospheric Continuum, and
Broad Absorption by Thick Winds in a Little Red Dot at z = 1.7\r\nAlberto Torralba,
Jorryt Matthee, Andrea Weibel, Rohan P. Naidu, Yilun Ma, Aidan P. Cloonan, Aayush
Desai, Anna de Graaff, Jenny E. Greene, Christian Kragh JespersenShow full author
list\r\n\r\nPublished 2026 June 30 • © 2026. The Author(s). Published by the American
Astronomical Society.\r\nThe Astrophysical Journal Letters, Volume 1005, Number
2\r\nCitation Alberto Torralba et al 2026 ApJL 1005 L37\r\nDOI 10.3847/2041-8213/ae7bfd\r\n\r\nPDFOpens
in a new tab.ePub\r\nAuthors\r\nFigures\r\nTables\r\nReferences\r\nArticle data\r\nPDFOpens
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information\r\nAbstract\r\nRecent studies at high redshift have revealed an enigmatic
class of little red dots (LRDs) with extreme Balmer breaks, stronger than in any
stellar atmosphere. However, it is unclear whether such objects exist at lower redshift,
especially given the low number of LRDs reported at z ≲ 2. Here, we report the discovery
of PAN-BH*-1, an LRD with an extreme Balmer break at z = 1.73, identified from JWST/NIRCam
pure-parallel imaging taken by the PANORAMIC survey, and confirmed by deep VLT/X-Shooter
spectroscopy. The rest-optical to near-infrared spectral energy distribution of
PAN-BH*-1 is consistent with a photospheric continuum with effective temperature
Teff ≈ 4800 K. The broad Hα emission line shows remarkably deep absorption, stronger
than previously measured in any LRD. The absorption trough spans from −520 to +267
km s−1 with respect to the systemic redshift. The presence of blue- and red-shifted
absorption suggests complex dynamics of the obscuring gas along the line of sight.
We speculate that the absorption trough can be produced by a thick wind launched
from a thick, rotating photospheric disk, the latter being the source of the red
optical continuum. While the source is unresolved in the rest-optical JWST data
(reff < 47 pc), the rest-near-UV Hubble Space Telescope imaging shows an extended
morphology with \r\n kpc, which we interpret as a host galaxy with a stellar mass
of ∼108 M⊙, in line with the narrow Hα emission. The discovery of this object at
cosmic noon highlights the feasibility of systematic searches for extreme LRDs with
wide-area facilities such as Euclid and Roman.\r\n\r\nExport citation and abstract\r\nBibTeXRIS\r\n\r\nPrevious
article in issue\r\nNext article in issue\r\n\r\nOriginal content from this work
may be used under the terms of the Creative Commons Attribution 4.0 licence. Any
further distribution of this work must maintain attribution to the author(s) and
the title of the work, journal citation and DOI.\r\n\r\n1. Introduction\r\nThe unprecedented
sensitivity of JWST has enabled the discovery of a new, abundant population of objects
at redshifts z ≈ 3–9 nicknamed the “little red dots” (LRDs). These are characterized
by their compact rest-frame optical morphology, broad emission lines, and a characteristic
rest-UV to optical “V-shape” in their spectral energy distributions (SED; e.g.,
D. D. Kocevski et al. 2023; V. Kokorev et al. 2024; J. Matthee et al. 2024; I. Labbe
et al. 2025).\r\n\r\nThe nature of LRDs is highly debated (see K. Inayoshi & L.
C. Ho 2025, for a recent overview) as the LRDs show systematic differences with
respect to other types of active galactic nuclei (AGN), such as faintness in X-rays
(e.g., T. T. Ananna et al. 2024; M. Yue et al. 2024), mid-to-far-infrared dust emission
(e.g., G. C. K. Leung et al. 2025; C. C. Williams et al. 2024; I. Delvecchio et
al. 2025; D. J. Setton et al. 2025; M. Xiao et al. 2025), and radio (e.g., G. Mazzolari
et al. 2026; M. A. Latif et al. 2025; K. Perger et al. 2025, see A. J. Gloudemans
et al. 2025).\r\n\r\nA recurring spectral feature of LRDs is the presence of a strong
Balmer break (e.g., D. J. Setton et al. 2025; B. Wang et al. 2024; R. E. Hviding
et al. 2025; W. Q. Sun et al. 2026), in some cases stronger than any star or stellar
population can produce. The two most prominent examples known to date are The Cliff
at z ≈ 3.5 (A. de Graaff et al. 2025a) and MoM-BH* at z ≈ 7.8 (R. P. Naidu et al.
2025). The joint appearance of strong Balmer lines as well as strong Balmer breaks
has been modeled as being due to absorption by a dense, neutral gas with a high
column density in the line of sight to a highly ionizing source (K. Inayoshi & R.
Maiolino 2025; X. Ji et al. 2025; A. Sneppen et al. 2026; A. Torralba et al. 2026).
These observations have sparked the development of new theoretical models, ranging
from a spherical envelope analogous to stellar atmospheres (e.g., M. C. Begelman
& J. Dexter 2026; D. Kido et al. 2025; H. Liu et al. 2025; D. Nandal & A. Loeb 2026)
or a thick accretion disk (e.g., H. Liu et al. 2025, 2026; K. Inayoshi et al. 2025;
Y.-X. Chen et al. 2026).\r\n\r\nBesides their spectral features, the evolution of
the LRD number densities is also in stark contrast to other types of AGNs (e.g.,
K. Inayoshi 2025). At 4 ≲ z ≲ 7, LRDs represent a few percent of the galaxy population
(e.g., D. D. Kocevski et al. 2023, 2025; J. E. Greene et al. 2024; V. Kokorev et
al. 2024; X. Lin et al. 2024; R. Maiolino et al. 2024; J. Matthee et al. 2024),
with number densities of ≳10−5 Mpc−3. The number density does not appear to drop
quickly beyond z > 5 (e.g., J. Zhang et al. 2026), with various LRDs having been
confirmed at z > 8 (V. Kokorev et al. 2023; A. J. Taylor et al. 2025; R. Tripodi
et al. 2025), well beyond the quasar redshift record (F. Wang et al. 2021). Photometric
LRD candidates exist beyond z > 10 (T. S. Tanaka et al. 2025). In turn, the number
density of LRDs seems to decline steeply at z < 4 (e.g., Y. Ma et al. 2026), with
estimates of a number density of ∼10−6 cMpc−3 at z ∼ 2 and even ∼10−10 cMpc−3 at
z ≈ 0.3 (X. Lin et al. 2026). While it is challenging to ensure a uniform selection
function across such a large redshift baseline and dedicated spectroscopic follow-up
of such lower redshift candidates has only just started, it is challenging to attribute
five orders of magnitude to such effects.\r\n\r\nMotivated by the discovery of rare
objects with extreme Balmer breaks at z > 3 and the very small number of known
LRDs at lower redshift, we performed a dedicated search for extreme Balmer break
objects using a template-match approach on a large compilation of JWST NIRCam data
over ≈0.3 deg2 and z ≈ 1.5–7.0. This survey is presented in A. Weibel et al. (2026a).
As part of an ongoing ground-based spectroscopic campaign of LRD candidates at z
∼ 2 (Y. Ma et al. 2026), we followed up the most luminous candidate with a photometric
redshift of z ≈ 2 with the X-Shooter spectrograph on the Very Large Telescope (VLT).
In this Letter, we present the discovery and spectroscopic confirmation of PAN-BH*-1,
a luminous LRD at z = 1.73 with an extreme Balmer break comparable to the strongest
observed in any LRD (and, in general, any astrophysical source). The low redshift
of this source enables high-resolution spectroscopy from ground-based observatories
that is otherwise impossible to obtain at high redshift.\r\n\r\nThroughout this
Letter, we use a ΛCDM cosmology with Ωm = 0.31, ΩΛ = 0.69, and h = 0.677 as described
by Planck Collaboration et al. (2020). All the magnitudes are given in the AB system
(J. B. Oke & J. E. Gunn 1983).\r\n\r\n2. Observations\r\n2.1. Photometry and Source
Selection\r\nWe identified PAN-BH*-1 (ID: PAN-1115, RA, DEC: 40.015835, −1.659363
J2000) as part of a systematic search across ≈0.3 deg2 of JWST NIRCam legacy imaging
comprising at least six filters of coverage (A. Weibel et al. 2026b). Notably, this
dataset includes the Cycle 1 pure parallel survey PANORAMIC (PID: 2514, PIs: Williams
& Oesch; C. C. Williams et al. 2025) that contributes 28 of the 35 independent lines
of sight, thereby enabling the discovery of rare objects such as PAN-BH*-1 across
diverse large-scale structure environments. Specifically, this source was identified
in the footprint j024000m0142 of the PANORAMIC DR1,15 which is adjacent to the A370
field (G. O. Abell et al. 1989), where archival images by the Hubble Space Telescope
(HST) are available from the BUFFALO survey (C. L. Steinhardt et al. 2020). The
HST/ACS images were processed with grizli and also released as part of the PANORAMIC
dataset.\r\n\r\nPAN-BH*-1 is in the outskirts of the A370 lensing cluster, but the
magnification is only μ ≈ 1.05 according to the models from A. Niemiec et al. (2023).
Throughout the rest of the paper, we report the uncorrected flux measurements, since
the effect of magnification (∼5%) is negligible given the uncertainties in the observations
and the lensing model.\r\n\r\nThe search strategy and full photometric selection
are described in a companion paper (A. Weibel et al. 2026a). Briefly, that work
presents a new selection of LRDs as a combination of a “black hole star” template
(BH*; R. P. Naidu et al. 2025) embedded in a host galaxy, instead of the typically
used “V-shaped” selections (e.g., D. D. Kocevski et al. 2025; V. Kokorev et al.
2024). The host galaxies are modeled using eazy’s blue_sfhz templates. The BH*s
are modeled using a novel template set comprising empirical luminosity-based stacks
constructed in W. Q. Sun et al. (2026), the cloudy template from R. P. Naidu et
al. (2025), and by using spectra of prominent LRDs spanning the observed effective
temperature range (I. Labbe et al. 2024; A. de Graaff et al. 2025a; B. Wang et al.
2026).\r\n\r\nPAN-BH*-1 stood out as one of the few sources where the BH* template
effectively dominated all the light over the full wavelength range covered by NIRCam
(hence the name). The redshift of PAN-BH*-1 was estimated to be zphot = 1.85. Follow-up
VLT/X-Shooter spectroscopy confirmed the redshift as zspec = 1.731 (see Section
3.2).\r\n\r\nPAN-BH*-1 is also covered by archival data from the VLT with the HAWK-I
camera in the Ks band (G. B. Brammer et al. 2016) and in data from the Spitzer Space
Telescope in IRAC bands 1 and 3 (3.6 and 5.7 μm), and MIPS 24 μm (P. Capak 2019).
PAN-BH*-1 is detected in the Ks band and in the two IRAC filters. Performing Spitzer
photometry of this source is challenging due to the large point spread function
(PSF) and a neighboring source, especially in the MIPS band. However, the NIRCam
photometry of the neighboring source suggests it has a limited contribution to the
IRAC fluxes. The details of the photometry extraction are described in Appendix
A, and the measured magnitudes in Table 2.\r\n\r\n2.2. VLT/X-Shooter Spectroscopy\r\nPAN-BH*-1
was observed for 5.8 ks with the X-Shooter spectrograph (J. Vernet et al. 2011)
on the VLT as a bright backup target for program 116.294D (PI: Matthee) in visitor
mode on 2025 December 17. The main aim of this program was to confirm candidate
LRDs at cosmic noon (Y. Ma et al. 2026). These observations confirmed the redshift
through the detection of Hα at z = 1.731. A DDT program (ID 116.2AQ0; PI: Matthee)
obtained additional follow-up data of PAN-BH*-1 in service mode for 26.2 ks during
2026 January 10–26, yielding a total exposure time of 8.9 hr. X-Shooter observes
with three arms simultaneously, UVB, VIS, and near-infrared (NIR), covering rest-frame
wavelengths of ≈0.14–0.9 μm, albeit hampered by skyline emission and telluric absorption,
primarily in the rest-frame optical.\r\n\r\nThe observing conditions were clear,
with a seeing ranging from 05 to 07 (median 06). The service mode observations were
primarily conducted during dark nights, with some gray (FLI = 0.03–0.6, median 0.1),
and a typical airmass of 1.35. We used UVB, VIS, and NIR slits with widths 10, 09,
and 09, yielding a nominal resolution of R = 5400, 8900, and 5600, respectively
(FWHM ∼53 km s−1 for NIR). The target acquisition was done using blind offsets from
a reference star, due to the target being too faint for direct acquisition. We used
a standard nodding on the slit pattern, with 4″ nod throws in an ABBA pattern, and
1″ jitters in the NIR arm to improve the sky subtraction. In each observing block
of ≈1 hr, the exposure times were 700, 655, and (2×)365 s for the three arms at
each nod position.\r\n\r\nThe reduction of the X-Shooter data uses a combination
of EsoRex libraries16 and Python code based on the reduction pipeline employed in
J. Matthee et al. (2021). Each observing block was reduced separately. We used standard
stars taken during the observing night for a first-pass flux calibration. Telluric
corrections were applied using the molecfit tool (A. Smette et al. 2015) implemented
in the X-Shooter EsoRex pipeline. Telluric stars were observed during the visitor
nights, but they were not always observed during the service mode observations in
January. For those observations, we took the telluric star that was observed at
the closest observing date. Based on the variation in telluric absorption among
the reference stars taken during this period, we estimate the variation in the transmission
and propagate the uncertainty in the telluric correction. For each observing block,
we then extracted an optimally extracted 1D spectrum using the spatial profile of
the Hα line, thus accounting for seeing variations and (more importantly) minor
errors in the accuracy of the slit pointing. Before median combining these spectra,
we normalize them by the median Hα flux of all observations to account for variations
in slit losses and flux calibrations.\r\n\r\nBesides Hα (integrated S/N = 75) and
Hβ (integrated S/N = 6; Section 3.2), we also detect continuum emission in the best
regions in the H and K bands at 1.6 μm and 2.1 μm, respectively, with a low signal-to-noise
ratio (S/N) of ∼1 per resolution element. Unfortunately, the [O iii] λλ4960, 5008
doublet is undetectable because the observed wavelengths are impacted by very strong
telluric absorption. No other lines or continuum are detected in the X-Shooter spectrum.\r\n\r\n3.
Properties of PAN-BH*-1\r\n3.1. Spectral Shape: A Photospheric Continuum with Strong
Hα Emission\r\nThe photometric SED of PAN-BH*-1 has remarkable similarities with
The Cliff (Figure 1): luminous in the rest optical, with a sudden drop toward the
rest-UV around the Balmer limit, and very weak near-to-mid infrared continuum emission.
With a rough extrapolation of the two HST photometric points using a power-law fit
(fλ ∝ λβ), we obtain a UV slope of β = −0.1 ± 1.2, and MUV = −16.7 ± 0.7. For the
rest-frame optical to NIR data, we fit a Planck blackbody law to the JWST data points,
after subtracting the measured Hα flux (see Section 3.2) from the F200W photometry.
The rest-optical and NIR photometry of PAN-BH*-1 is remarkably well described by
a single temperature blackbody with T = 4204 K (with a best-fit ). We measure the
strength of the Balmer break from the fν ratio F115W/F814W = 7 ± 1, in line with
the Balmer break strengths of The Cliff (; A. de Graaff et al. 2025a)17 and MoM-BH*
(7.8 ± 1.8; R. P. Naidu et al. 2025), measured from JWST/NIRSpec PRISM spectra as
fν,4000–4100/fν,3620−3720. In Figure 2, we compare the Balmer break strength with
the spectroscopic sample of A. de Graaff et al. (2025b), showing that out of 134
sources, only two have breaks significantly above 5. This suggests that PAN-BH*-1
has among the most extreme Balmer breaks known, although we caution that our value
is derived from wide-band photometry with pivot wavelengths corresponding to 4212
and 3042 Å, respectively, rather than from spectroscopy.\r\n\r\nZoom InZoom OutReset
image size\r\nFigure 1. SED of PAN-BH*-1 Top: cutouts from all the HST and JWST
images in which PAN-BH*-1 is covered. It shows a remarkably compact morphology in
all the wavelengths, resolved only in the HST F606W and F814W bands (Section 3.3).
Bottom: photometry from JWST/NIRCam (blue squares), HST/ACS (purple pentagons),
and Spitzer/IRAC+MIPS (red hexagons, and red triangle for the 5σ upper limit). The
empty square is the F200W flux after subtracting the Hα flux measured from X-Shooter
spectroscopy. We show the spectrum of The Cliff for comparison (gray line), shifted
to z = 1.73 and normalized to the F150W flux of PAN-BH*-1. We also show the best-fitting
blackbody spectrum (blue dashed line) and the best model from the synthetic LRD
atmosphere models from H. Liu et al. (2026), shifted to z = 1.73 (green line), undersampled
by a factor of 500 for clarity.\r\n\r\nDownload figure:\r\n\r\nStandard imageHigh-resolution
image\r\nZoom InZoom OutReset image size\r\nFigure 2. Spectroscopic sample of LRDs
by redshift and Balmer break strength. We plot the redshift and Balmer break strength
of PAN-BH*-1, and the JWST sample from A. de Graaff et al. (2025b) (purple diamonds),
and three local LRDs in X. Lin et al. (2026), for comparison. We also highlight
three sources with a particularly strong Balmer break: The Cliff (A. de Graaff et
al. 2025a), MoM-BH* (R. P. Naidu et al. 2025), and CAPERS-LRDz9 (A. J. Taylor et
al. 2025). The Balmer break strength of the JWST spectroscopic sample is computed
as fν,4000–4100/fν,3620–3720, whereas the value for PAN-BH*-1 is directly obtained
from the F115W/F814W photometry.\r\n\r\nDownload figure:\r\n\r\nStandard imageHigh-resolution
image\r\n3.2. Hα and Hβ Emission Lines\r\nThe Hα profile appears as a complex combination
of a broad line with strong absorption close to the systemic redshift. We fit the
Hα emission line with a similar model as the one used in A. Torralba et al. (2026)
and J. Matthee et al. (2026). The Hα model consists of two Gaussian emission components
(with narrow and intermediate line widths), and a broad symmetric exponential convolved
with the intermediate profile and parameterized as in F. D’Eugenio et al. (2025a).
The absorption is implemented as an opacity law defined as e−τ(λ), where τ(λ) also
follows a single Gaussian velocity distribution (F. D’Eugenio et al. 2025a, 2025b;
A. Torralba et al. 2026). For simplicity, we assume a covering factor of Cf = 1
for the absorbing gas. In previous works, the width of the narrow component is tied
to that of [O iii], assuming both components come from the same region, often interpreted
as the interstellar medium (ISM) of the host galaxy. In this case, we have no information
about [O iii] due to this doublet falling in a wavelength range heavily affected
by strong telluric absorption. We fit the Hα line after masking relevant skylines
and strong telluric absorption bands. The fitted Hα parameters are listed in Table
1 and the best-fit model is shown in Figure 3. The absorption feature is notably
strong, with an equivalent width of EWabs = −148 ± 12 Å with respect to the fitted
continuum and 12.2 ± 0.2 Å if including the broad emission component. The absorption
corresponds to a Balmer optical depth at the line center of , reaching roughly the
continuum level. The FWHM of the single Gaussian fitted to the absorber is 283 ±
\ 8 km s−1, and is offset from the systemic redshift by −94 ± 4 km s−1. We note
that this parameterization is somewhat arbitrary, and we discuss in detail the absorber
properties in Section 4.\r\n\r\nZoom InZoom OutReset image size\r\nFigure 3. Hα
spectrum, and the best fit to our fiducial model. We show the X-Shooter R ∼ 5600
spectrum of the Hα line of PAN-BH*-1, along with the best-fit to the model described
in Section 3.2; total model (red solid line) and individual components (discontinuous
color lines). The red wing of the line is severely affected by telluric absorption,
thus the large uncertainties.\r\n\r\nDownload figure:\r\n\r\nStandard imageHigh-resolution
image\r\nTable 1. Properties of PAN-BH*-1\r\n\r\nParameter\tValue\tUnit\r\nWidth
(FWHM; Hα)\r\nExponential\t1257 ± 27\tkm s−1\r\nIntermediate\t687 ± 43\tkm s−1\r\nNarrow\t184
± 12\tkm s−1\r\nAbsorption\t283 ± 8\tkm s−1\r\nFlux (Hα)\r\nExponential\t643 ± 7\t10−18
erg s−1 cm−2\r\nIntermediate\t19 ± 5\t10−18 erg s−1 cm−2\r\nNarrow\t38 ± 3\t10−18
erg s−1 cm−2\r\nTotal\t522 ± 7\t10−18 erg s−1 cm−2\r\nGeneral properties\r\n(LHα/erg
s−1)\t43.046 ± 0.006\t⋯\r\nEW0(Hα)\t520 ± 20\tÅ\r\nSFR(Hα, narrow)a\t2.1 ± 0.2\tM⊙
yr−1\r\nSFR(Hα, narrow)b\t3.3 ± 0.3\tM⊙ yr−1\r\nreff,UV (F606W+F814W)\t\tkpc\r\nreff,opt
(F200W)\t<0.047\tkpc\r\nHα/Hβ (total)\t>9.4\t⋯\r\nHα/Hβ (narrow)\t5 ± 1\t⋯\r\nNotes.
aCalibration from I. G. Kramarenko et al. (2026). bCalibration from R. C. Kennicutt
& N. J. Evans (2012). SFR values calculated assuming no dust attenuation.\r\n\r\nDownload
table as: \r\nASCIITypeset image\r\n\r\nThe Hβ line is marginally detected. After
undersampling the spectrum by a factor 5, a hint of a weak narrow component can
be identified (Figure 4), along with a tentative absorption at the same mean velocity
as in Hα. We fit the best Hα model to the Hβ spectrum, only rescaling it by a multiplicative
factor, and adding a flat continuum component. By doing this, we find an Hβ flux
of (47 ± 8) × 10−18 erg s−1 cm−2 (S/N ≈ 6). Conservatively, we obtain a Balmer decrement
of Hα/Hβ > 9.4 (at a 3σ confidence level), in line with the high decrements found
for the LRD population (e.g., G. P. Nikopoulos et al. 2026; A. de Graaff et al.
2025b; J. Matthee et al. 2026). In Figure 5, we show the Hβ spectrum compared to
the rescaled Hα model. By matching the best-fit Hα profile with the data at the
expected observed wavelength for Hβ (±5000 km s−1), we obtain a better agreement
(, BIC = 1537) than fitting a flat continuum only (, BIC = 1658) with ΔBIC = 121
≫ 10, strongly favoring a detection of a broad Hβ emission line, and securing the
spectroscopic redshift. Similarly, we fit a narrow Gaussian to Hβ with the same
width and velocity as the Hα best-fit model, assuming a completely saturated absorption.
We obtain a Balmer decrement for the narrow component of Hα/Hβ = 5 ± 1, which would
imply a dust extinction of using a J. A. Cardelli et al. (1989) attenuation law,
under the assumption of case B recombination. However, due to the low S/N of Hβ
this result is only tentative, and compatible with a standard Case B value within
∼2σ.\r\n\r\nZoom InZoom OutReset image size\r\nFigure 4. X-Shooter spectrum of Hα
and Hβ of PAN-BH*-1 (blue). We compare to the spectrum of The Cliff (gray; data
from JWST DDT #9433), normalized in each panel to the flux of PAN-BH*-1 in the range
v ∈ (−3000, −2000) km s−1. Due to the low S/N, the Hβ spectrum of PAN-BH*-1 is rebinned
to a coarser grid by a factor 5, after masking the most relevant skylines.\r\n\r\nDownload
figure:\r\n\r\nStandard imageHigh-resolution image\r\nZoom InZoom OutReset image
size\r\nFigure 5. Hβ spectrum. The spectrum is rebinned by a factor of 10 with inverse
variance flux weighting for visual clarity, due to the low S/N. We compare to the
best-fit Hα model, scaled by a factor of 0.112. In the bottom panel, we show the
χ residuals between the spectrum and the rescaled Hα model in black, and for only
the continuum in pink (ΔBIC = 121 strongly favoring the presence of a broad Hβ line).\r\n\r\nDownload
figure:\r\n\r\nStandard imageHigh-resolution image\r\n3.3. Spatial Morphology\r\nIn
order to assess whether PAN-BH*-1 is spatially resolved, we use the Bayesian profile
fitting software pysersic (I. Pasha & T. B. Miller 2023)18 to fit a single Sérsic
profile to the JWST and HST imaging data of PAN-BH*-1. For JWST/NIRCam, we choose
F200W as the filter with the highest S/N in the short wavelength channel, benefiting
from a high spatial resolution and probing rest-frame optical wavelengths. To model
its PSF, we use version 2.2.0 of the stpsf software (formerly webbpsf, M. D. Perrin
et al. 2014). For the two HST bands F606W and F814W, we instead construct empirical
PSFs from public imaging data in the GOODS-S field following A. Weibel et al. (2024).
In all three bands, we sample the posterior with the No U-turn sampler in two chains
with 1000 warm-up and 2000 sampling steps each. We find that PAN-BH*-1 is unresolved
with NIRCam in F200W where the effective radius converges toward the edge of the
prior at 0.25 pixels. Using the 95th percentile of the posterior chains as an upper
limit on the effective radius, we find a rest-optical size of reff < 47 pc.\r\n\r\nPAN-BH*-1
appears to be resolved in the HST images corresponding to rest-frame pivot 0.2 and
0.3 μm, respectively. Due to the low signal-to-noise of the F606W and F814W photometry,
we fit both bands simultaneously fixing all the morphological parameters in both
images. We measure physical effective radii of kpc (see Appendix B). The modest
stretching by the foreground A370 lensing cluster could imply a correction of ∼10%
to the measured radius (A. Niemiec et al. 2023), which we disregard given the uncertainties.
These measured sizes are consistent with the typical sizes for galaxies with a stellar
mass ≲ 109 M⊙ at z = 1.75 (A. van der Wel et al. 2014). These findings are consistent
with the scenario of a compact LRD “engine” dominating the rest-optical light embedded
in a host galaxy, whose contribution becomes significant blueward of the Balmer
break (see A. P. Cloonan et al. 2026, for a relevant discussion).\r\n\r\n4. Absorber
Kinematics\r\nAs described in Section 3.2, the velocity distribution of the absorber
is empirically modeled with a Gaussian, which we find has a central velocity of
−94 ± 4 km s−1 relative to the redshift of the narrow emission component (adopted
as systemic). The absorption trough extends from negative to positive velocities
with respect to the redshift of the narrow component, but also with respect to the
center of the symmetric exponential wings. However, there are several degeneracies
between the shape of the absorber and other components of the emission line, such
as the narrow central emission (see Section 3.2). Furthermore, direct interpretation
of the absorber center velocity shift is challenging in an optically thick gas with
presumably complex dynamics, and it does not necessarily trace bulk motion. A more
robust, physically motivated pair of quantities is the minimum and maximum absorber
velocities. We define them as the values where the transmission of the Balmer absorber
increases to 99%, km s−1 and km s−1. These values trace the largest velocities
in the line of sight of gas with significant Balmer absorption. The absorbing trough
extends over 787 ± 17 km s−1 under this definition. The values of and are relatively
agnostic to the choice of the shape of the absorber, since they are determined by
the wavelength where the line profile deviates from a broad, symmetric exponential
profile. In Figure 6, we illustrate three proposed configurations of the velocity
distribution of the absorbing gas that could explain the shape of the observed Balmer
absorption, and we discuss these scenarios below.\r\n\r\nZoom InZoom OutReset image
size\r\nFigure 6. Geometric configurations for the absorber. We illustrate three
scenarios that could give rise to the observed Balmer absorption in PAN-BH*-1. In
scenario (a), the obscuring agent is a thick screen of gas with a certain bulk velocity,
and turbulent motions produce the broadening of the absorption trough. In (b), there
are two (or more) absorbers with opposite velocities in the line of sight. These
first two scenarios are dynamically unstable; therefore, variability is expected
in the absorption. Lastly, in (c), we observed an extended source through a disk
wind with a rotational component (vϕ) in addition to the poloidal (nonazimuthal)
velocity (vp). In the last scenario, the redshifted absorption is produced by streamlines
that oppose the observer when projected along the line of sight, despite the fact
that the gas is outflowing from the central source.\r\n\r\nDownload figure:\r\n\r\nStandard
imageHigh-resolution image\r\n4.1. Unstable Gas Flows?\r\nThe fact that there is
significant absorption at both negative and positive velocities with respect to
the systemic redshift cannot be simply explained by an axisymmetric outflowing or
inflowing wind. In the case of observing a compact object through a spherically
symmetric, nonturbulent bulk flow, a classical P Cygni profile is expected, with
a purely blueshifted absorption (or redshifted if the wind is infalling). The fact
that we also see redshifted absorption rules out this simple scenario. In principle,
turbulent motions could also produce broadening of the absorbing medium (scenario
a in Figure 6). However, the required turbulent velocity dispersion σturb ≈ 120
km s−1 (from the Gaussian fit in Section 3.2) is comparable to the mean velocity
of the absorption trough, meaning that turbulence dominates the gas flow. In such
a case, strong variability of the absorption profile would be expected, given the
typical dynamical crossing times (see Sect. 4.1 in F. D’Eugenio et al. 2025b). For
example, for a radius of 1016 cm (e.g., A. Torralba et al. 2026) and a mass of 106
M⊙, the dynamical freefall time is yr. Moreover, the turbulent velocity would be
highly supersonic, and the dissipation timescale would be comparable to the dynamical
time (e.g., M.-M. Mac Low 1999). Alternatively, in the context of a strong Balmer
absorber at z ∼ 7, F. D’Eugenio et al. (2026) recently discussed a “breathing mode”
scenario with cyclic inflows and outflows along the same line of sight, with the
gas being in different phases at different depths (scenario b in Figure 6; see also
K. Park et al. 2017). In this case, the same arguments regarding the stability of
the absorber would apply, and absorber variability is expected on observed timescales
of ∼5 yr (for a source at z = 1.7), which is testable with future observations.\r\n\r\n4.2.
The Case for the Disk Wind Hypothesis\r\nAn alternative, dynamically stable scenario
is a disk wind configuration (scenario c in Figure 6). Here, the wind would be launched
from a thick disk near the central engine, which we speculate could be the source
of the optical continuum emission (e.g., H. Liu et al. 2025, 2026; L. Zwick et al.
2025; Y.-X. Chen et al. 2026). A rotating disk would imprint to the wind an azimuthal
velocity component (vϕ). Observations at specific lines of sight, particularly for
high inclination angles (close to edge-on) where the rotational component dominates
the poloidal velocity, can give rise to both blueshifted and redshifted absorption
features (D. Proga et al. 2000; P. B. Hall et al. 2002, 2013; D. Proga & T. R. Kallman
2004; M. Giustini & D. Proga 2012). Most observed LRDs have blueshifted P Cygni–like
absorbers (J. Matthee et al. 2026), which can be naively interpreted as a uniformly
expanding shell. The low incidence of redshifted Balmer absorbers in LRD spectra
(e.g., I. Labbe et al. 2024; A. de Graaff et al. 2025a; F. D’Eugenio et al. 2025b,
2026; Y. Ma et al. 2026) can therefore be explained by the requirement of high inclination
angles to observe such features (see also A. Sneppen et al. 2026). Such a picture
is broadly in line with disk wind models for AGN with broad absorption lines (e.g.,
P. B. Hall et al. 2002; H. Zhou et al. 2019) and around stars with circumstellar
disks (e.g., J. Erkal et al. 2022), such as accreting T Tauri stars (S. Edwards
et al. 2006) or cataclysmic variables (D. Proga 2003).\r\n\r\n4.3. Implications
of Rotating Winds for the Emission Lines of LRDs\r\nThe disk wind hypothesis would
imply that a photosphere in the shape of a rotating disk is the source of the optical
continuum emission, and drives winds that can explain the observed absorption trough.
Emission lines originating in a thin rotating disk would have a double-peaked profile
in the idealized case (for most inclination angles), but this is not necessarily
true if the disk is not sufficiently thin (e.g., N. Murray & J. Chiang 1997), for
instance, in the case of a puffed-up disk associated with super-Eddington accretion
(e.g., H. Liu et al. 2026). In addition, most line emission would not be produced
directly at the base of the disk, but slightly outside (e.g., via collisional cooling
or residual recombination; A. Torralba et al. 2026), where the rotational velocity
is lower, and the dynamics are complex (e.g., G. A. Shields 1977).\r\n\r\nThe Balmer
lines of most LRDs are dominated by broad, symmetric exponential components that
are associated with broadening by electron scattering (e.g., V. Rusakov et al. 2026;
J. Matthee et al. 2026). For PAN-BH*-1, the Hα line profile of PAN-BH*-1 is compatible
with a broad exponential profile emerging through a dense wind where the absorption
trough is produced. In dense gas with a large column density of neutral hydrogen,
and optically thick to Balmer transitions (NHI,2s ≳ 1014 cm−2), resonant scattering
effects become important. Crucially, resonant scattering impacts Hα and Hβ differently
(e.g., S.-J. Chang et al. 2026), hence the 3D radiative transfer and photon redistribution
of both lines may produce different profiles (see, e.g., Figure 2 in D. Proga 2003).
Therefore, the empirical fitting and interpretation of the absorption profiles becomes
nontrivial. Dedicated radiative transfer modeling is necessary to study such effects,
and they can be tested in other emission lines with high optical depth, such as
He i λ10830 Å, or resonant lines like C iv λ1550.\r\n\r\n5. Implications for the
Galaxy and Black Hole Masses\r\n5.1. Properties of the Host Galaxy\r\nAssuming that
the narrow component of Hα corresponds to ISM emission in the host galaxy, we compute
the associated star formation rate using the local calibration from R. C. Kennicutt
& N. J. Evans (2012) and assuming no dust attenuation. We obtain SFR(Hα) = 3.3 ±
0.3 M⊙ yr−1. A somewhat lower value of SFR(Hα) = 2.1 ± 0.2 M⊙ yr−1 is obtained using
the high-redshift (z ≳ 4) calibrations in I. G. Kramarenko et al. (2026), which
might be more appropriate for a young dwarf galaxy with a bursty star formation
history. The star formation rates are low, but in line with a main-sequence galaxy
with (extrapolating the relation from J. S. Speagle et al. 2014). Assuming zero
dust attenuation, the UV absolute magnitude (MUV = −16.7 ± 0.7; Section 3.1) would
imply SFR(UV) = 0.18 ± 0.12 M⊙ yr−1 (R. C. Kennicutt & N. J. Evans 2012). The discrepancy
between the UV and Hα inferred star formation rate suggests there is some amount
of dust attenuation in the host galaxy.\r\n\r\nWe derive a dynamical mass from the
width of the narrow component Hα line and the estimated UV size as , adopting the
empirical virial correction K(n)K(q) from A. van der Wel et al. (2022), where K(n)
and K(q) are functions of the best-fit ellipticity and Sérsic index (see Appendix
B). Adopting a Mdyn/M* factor of 40 as found by A. de Graaff et al. (2024) for dwarf
galaxies at high redshift, we infer a stellar mass of . However, the Mdyn/M* is
very uncertain in this regime, and the uncertainty can span over 1 dex (A. Saldana-Lopez
et al. 2025). We advise caution in interpreting this result, as there are large
uncertainties in the measurements of the narrow Hα component, the HST morphology,
and the empirical relations used.\r\n\r\nAs discussed in Section 4, the absorption
profile is compatible with broadening by a rotating disk wind, and numerical modeling
of such configurations often predicts a narrow component arising from increased
transmission due to purely kinematic effects in the wind geometry (D. Proga et al.
2000; D. Proga 2003; D. Proga & T. R. Kallman 2004). This would be an alternative
explanation for at least part of the narrow component flux. On the other hand, most
LRDs present narrow [O iii] emission that is often associated with the host galaxy.
Indeed, the ionized gas producing [O iii] emission should have associated emission
in the Hα and higher-order Balmer lines. However, constraining this component largely
depends on the assumptions on dust attenuation or ISM conditions, and requires very
high S/N and resolution data. Deep, space-based follow-up observations of PAN-BH*-1
would be very constraining for the wind kinematics (e.g., by the joint analysis
of Hβ) and to assess whether a narrow component comes from a host galaxy (e.g.,
by comparing to a narrow Hβ component or [O iii] λλ4960, 5008).\r\n\r\n5.2. Black
Hole Mass From Photosphere Models\r\nThe general physical setup of LRDs is an open
debate, and their masses are a major unknown. Due to the multiple differences with
respect to the classical AGN population, the validity of standard virial calibrations
has been questioned (e.g., V. Rusakov et al. 2026; J. E. Greene et al. 2026; A.
Sneppen et al. 2026; A. Torralba et al. 2026, although see, e.g., M. Brazzini et
al. 2025, 2026; J. Scholtz et al. 2026 for an alternative interpretation).\r\n\r\nOne
can obtain a mass estimate assuming a system in radiative equilibrium with Lbol/LEdd
= 1 (e.g., H. Umeda et al. 2026); this yields a total mass of ≈106 M⊙, using the
bolometric luminosity from integrating the best-fit blackbody in Section 3.1. Recently,
H. Liu et al. (2026) developed a synthetic spectral library of LRD atmosphere models.
In these models, the density of the photosphere is regulated by the net surface
gravity of an optically thick atmosphere, enabling constraints on the mass of the
system. We fit the JWST photometry of PAN-BH*-1 using the models from H. Liu et
al. (2026), assuming a negligible contribution from a host galaxy to the optical
continuum. The best-fit model has effective temperature Teff = 4800 K, surface gravity
, and metallicity (; see Figure 1). The best-fit implies a total mass of the system
(BH plus gas) of (Equation (6) in H. Liu et al. 2026, assuming hydrostatic equilibrium).
For the second and third best fits, we obtain and −2, respectively (, respectively;
with the same metallicity and effective temperature), which would imply lower limits
to the system mass between and 4. The bolometric luminosity of PAN-BH*-1 (from the
integral of the best-fit green curve in Figure 1) implies an Eddington luminosity
ratio of L/LEdd ≲ 13, assuming the best-fit mass from the H. Liu et al. (2026) models.
The elevated Eddington ratio is in line with the hypothesis of a radiation-driven
wind discussed in Section 4, and allows for somewhat larger system masses. The low
masses obtained with this model, combined with the stellar mass inferred from dynamical
arguments for the host galaxy (Section 3.3) set lower limits to the BH-to-stellar
mass ratio of MBH/M* ≳ 10−4–10−2, which are compatible with the relations observed
in the Local Universe, within the large uncertainties (A. E. Reines & M. Volonteri
2015).\r\n\r\n6. Conclusions\r\nIn this Letter, we presented the discovery and spectroscopic
confirmation of PAN-BH*-1, an LRD with an extreme Balmer break at z = 1.731. The
strength of the Balmer break (F115W/F814W = 7 ± 1) is comparable to the most extreme
LRDs known, The Cliff (A. de Graaff et al. 2025a) and MoM-BH* (R. P. Naidu et al.
2025). We summarize the observations and our main conclusions as follows.\r\n\r\n\r\n1.
\ \r\nWe obtained deep VLT/X-Shooter spectroscopy of PAN-BH*-1. The Hα emission
line is luminous and broad (LHα = 1043 erg s−1), and has an unusually strong absorption.
Hβ is detected with an S/N ≈ 6, and we conservatively estimate a lower limit for
the Balmer decrement of Hα/Hβ > 9.4 (at a 3σ confidence level), in line with other
LRDs in the literature (e.g., A. de Graaff et al. 2025b; G. P. Nikopoulos et al.
2026).\r\n2. \r\nThe absorption trough spans from −520 to 267 km s−1 (at a transmission
level of 99%). We interpret the presence of blue- and redshifted absorption as produced
by a disk wind, analogous to those analyzed in the context of broad absorption line
quasars or accreting stars. This hypothesis would imply that the source of the optical
continuum is likely a thick photospheric disk.\r\n3. \r\nWe detect a narrow Hα
component (FWHM = 184 ± 12 km s−1), which we interpret as probing a host galaxy
with M* ≈ 108 M⊙ and SFR = 2–3 M⊙. This interpretation is in line with the extended
rest-NUV morphology measured in the HST bands (\r\n kpc).\r\n4. \r\nBy fitting
the synthetic atmosphere models of H. Liu et al. (2026), we estimate a system mass
(BH+envelope) of 104–106 M⊙. The inferred masses, together with the stellar mass
inferred from morphology and narrow emission line dynamics, imply BH-to-stellar
mass ratios of 10−2–10−4, close to the extrapolated trend in the local Universe
(A. E. Reines & M. Volonteri 2015).\r\n5. \r\nThe confirmation of this source at
cosmic noon (magnitude of ≈22 in the K band, Hα flux ≈5 × 10−16 erg s−1 cm−2) proves
the feasibility of detecting extreme LRDs at such epochs with wide-area spectroscopic
surveys like Euclid or the forthcoming Nancy Grace Roman Space Telescope.\r\n\r\nAcknowledgments\r\nA.T.
thanks Debasish Dutta and Tamara Bogdanović for useful conversations about stellar
and AGN winds.\r\n\r\nWe thank the scientific referee for the useful and constructive
feedback, which helped improve the quality of this paper.\r\n\r\nJ.M. and A.T. acknowledge
funding by the European Union (ERC, AGENTS, 101076224). The work of CCW is supported
by NOIRLab, which is managed by the Association of Universities for Research in
Astronomy (AURA) under a cooperative agreement with the National Science Foundation.
A.P.C. warmly acknowledges the support of the National Science Foundation through
the NSF Graduate Research Fellowship Program. A.d.G. acknowledges support from a
Clay Fellowship awarded by the Smithsonian Astrophysical Observatory.\r\n\r\nBased
on observations made with ESO Telescopes at the Paranal Observatory under program
IDs 116.294D and 116.2AQ0.\r\n\r\nThis work is based in part on observations made
with the NASA/ESA/CSA James Webb Space Telescope. The data were obtained from the
Mikulski Archive for Space Telescopes at the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in Astronomy,
Inc., under NASA contract NAS 5-03127 for JWST. These observations are associated
with programs #2514 and #9433. C.C.W. gratefully acknowledges support for program
JWST-GO-2514 provided by NASA through a grant from the Space Telescope Science Institute,
which is operated by the Association of Universities for Research in Astronomy,
Inc., under NASA contract NAS 5-03127. The authors acknowledge the team led by co-PIs
R. Maiolino and F. D’Eugenio for developing their observing program with a zero-exclusive-access
period.\r\n\r\nThis research is based on observations made with the NASA/ESA Hubble
Space Telescope obtained from the Space Telescope Science Institute, which is operated
by the Association of Universities for Research in Astronomy, Inc., under NASA contract
NAS 5–26555. These observations are associated with program #15117.\r\n\r\nThe JWST
and HST data presented in this article were obtained from the Mikulski Archive for
Space Telescopes (MAST) at the Space Telescope Science Institute. The specific observations
analyzed can be accessed via doi:10.17909/ydwx-st06.\r\n\r\nThis work is based in
part on observations made with the Spitzer Space Telescope, which was operated by
the Jet Propulsion Laboratory, California Institute of Technology under a contract
with NASA. The Spitzer data used in this work can be found in doi:10.26131/IRSA3.\r\n\r\nThis
work was supported by the International Space Science Institute (ISSI) in Bern,
through ISSI International Team project #25-659 “Little Red Dots, Big Open Questions.”\r\n\r\nJWST
cartoon in Figure 6, credit: NASA.\r\n\r\nFacilities: VLT:Kueyen - Very Large Telescope
(Kueyen) (X-Shooter), VLT:Yepun (HAWK-I), JWST - James Webb Space Telescope (NIRCam,
NIRspec), HST - Hubble Space Telescope satellite (ACS), Spitzer - Spitzer Space
Telescope satellite (IRAC, MIPS) - .\r\n\r\nSoftware: astropy (Astropy Collaboration
et al. 2013, 2018; Astropy Collaboration et al. 2022), NumPy (C. R. Harris et al.
2020), SciPy (P. Virtanen et al. 2020), pysersic (I. Pasha & T. B. Miller 2023),
stpsf (M. D. Perrin et al. 2014), lmfit (M. Newville et al. 2014), EsoRex (ESO CPL
Development Team 2015), Claude (used for Python coding; https://claude.ai/), SEP
(K. Barbary 2016)."
article_number: L37
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Alberto
full_name: Torralba Torregrosa, Alberto
id: 018f0249-0e87-11f0-b167-cbce08fbd541
last_name: Torralba Torregrosa
orcid: 0000-0001-5586-6950
- first_name: Jorryt J
full_name: Matthee, Jorryt J
id: 7439a258-f3c0-11ec-9501-9df22fe06720
last_name: Matthee
orcid: 0000-0003-2871-127X
- first_name: Andrea
full_name: Weibel, Andrea
last_name: Weibel
- first_name: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: Yilun
full_name: Ma, Yilun
last_name: Ma
- first_name: Aidan P.
full_name: Cloonan, Aidan P.
last_name: Cloonan
- first_name: Aayush A
full_name: Desai, Aayush A
id: 502cfd30-32c1-11ee-a9a4-d8dad5c6739e
last_name: Desai
- first_name: Anna
full_name: De Graaff, Anna
last_name: De Graaff
- first_name: Jenny E.
full_name: Greene, Jenny E.
last_name: Greene
- first_name: Christian Kragh
full_name: Jespersen, Christian Kragh
last_name: Jespersen
- first_name: Ivan
full_name: Kramarenko, Ivan
id: 9a9394cb-3200-11ee-973b-f5ba2a8b16e4
last_name: Kramarenko
orcid: 0000-0001-5346-6048
- first_name: Sara
full_name: Mascia, Sara
id: edaf889c-c7cd-11ef-ab1b-bb28c431bd29
last_name: Mascia
- first_name: Pascal A.
full_name: Oesch, Pascal A.
last_name: Oesch
- first_name: Wendy Q.
full_name: Sun, Wendy Q.
last_name: Sun
- first_name: Christina C.
full_name: Williams, Christina C.
last_name: Williams
citation:
ama: 'Torralba Torregrosa A, Matthee JJ, Weibel A, et al. A black hole star at cosmic
noon: Extreme Balmer break, photospheric continuum, and broad absorption by thick
winds in a Little Red Dot at z = 1.7. The Astrophysical Journal Letters.
2026;1005(2). doi:10.3847/2041-8213/ae7bfd'
apa: 'Torralba Torregrosa, A., Matthee, J. J., Weibel, A., Naidu, R. P., Ma, Y.,
Cloonan, A. P., … Williams, C. C. (2026). A black hole star at cosmic noon: Extreme
Balmer break, photospheric continuum, and broad absorption by thick winds in a
Little Red Dot at z = 1.7. The Astrophysical Journal Letters. IOP Publishing.
https://doi.org/10.3847/2041-8213/ae7bfd'
chicago: 'Torralba Torregrosa, Alberto, Jorryt J Matthee, Andrea Weibel, Rohan P.
Naidu, Yilun Ma, Aidan P. Cloonan, Aayush A Desai, et al. “A Black Hole Star at
Cosmic Noon: Extreme Balmer Break, Photospheric Continuum, and Broad Absorption
by Thick Winds in a Little Red Dot at z = 1.7.” The Astrophysical Journal Letters.
IOP Publishing, 2026. https://doi.org/10.3847/2041-8213/ae7bfd.'
ieee: 'A. Torralba Torregrosa et al., “A black hole star at cosmic noon:
Extreme Balmer break, photospheric continuum, and broad absorption by thick winds
in a Little Red Dot at z = 1.7,” The Astrophysical Journal Letters, vol.
1005, no. 2. IOP Publishing, 2026.'
ista: 'Torralba Torregrosa A, Matthee JJ, Weibel A, Naidu RP, Ma Y, Cloonan AP,
Desai AA, De Graaff A, Greene JE, Jespersen CK, Kramarenko I, Mascia S, Oesch
PA, Sun WQ, Williams CC. 2026. A black hole star at cosmic noon: Extreme Balmer
break, photospheric continuum, and broad absorption by thick winds in a Little
Red Dot at z = 1.7. The Astrophysical Journal Letters. 1005(2), L37.'
mla: 'Torralba Torregrosa, Alberto, et al. “A Black Hole Star at Cosmic Noon: Extreme
Balmer Break, Photospheric Continuum, and Broad Absorption by Thick Winds in a
Little Red Dot at z = 1.7.” The Astrophysical Journal Letters, vol. 1005,
no. 2, L37, IOP Publishing, 2026, doi:10.3847/2041-8213/ae7bfd.'
short: A. Torralba Torregrosa, J.J. Matthee, A. Weibel, R.P. Naidu, Y. Ma, A.P.
Cloonan, A.A. Desai, A. De Graaff, J.E. Greene, C.K. Jespersen, I. Kramarenko,
S. Mascia, P.A. Oesch, W.Q. Sun, C.C. Williams, The Astrophysical Journal Letters
1005 (2026).
corr_author: '1'
das_tickbox: '1'
dataavailabilitystatement: "Based on observations made with ESO Telescopes at the
Paranal Observatory under program IDs 116.294D and 116.2AQ0.\r\n\r\nThis work is
based in part on observations made with the NASA/ESA/CSA James Webb Space Telescope.
The data were obtained from the Mikulski Archive for Space Telescopes at the Space
Telescope Science Institute, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. These
observations are associated with programs #2514 and #9433. C.C.W. gratefully acknowledges
support for program JWST-GO-2514 provided by NASA through a grant from the Space
Telescope Science Institute, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS 5-03127. The authors acknowledge
the team led by co-PIs R. Maiolino and F. D’Eugenio for developing their observing
program with a zero-exclusive-access period.\r\n\r\nThis research is based on observations
made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope
Science Institute, which is operated by the Association of Universities for Research
in Astronomy, Inc., under NASA contract NAS 5–26555. These observations are associated
with program #15117.\r\n\r\nThe JWST and HST data presented in this article were
obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope
Science Institute. The specific observations analyzed can be accessed via doi:10.17909/ydwx-st06.\r\n\r\nThis
work is based in part on observations made with the Spitzer Space Telescope, which
was operated by the Jet Propulsion Laboratory, California Institute of Technology
under a contract with NASA. The Spitzer data used in this work can be found in doi:10.26131/IRSA3.\r\n\r\nThis
work was supported by the International Space Science Institute (ISSI) in Bern,
through ISSI International Team project #25-659 “Little Red Dots, Big Open Questions.”\r\n\r\nJWST
cartoon in Figure 6, credit: NASA.\r\n\r\nFacilities: VLT:Kueyen - Very Large Telescope
(Kueyen) (X-Shooter), VLT:Yepun (HAWK-I), JWST - James Webb Space Telescope (NIRCam,
NIRspec), HST - Hubble Space Telescope satellite (ACS), Spitzer - Spitzer Space
Telescope satellite (IRAC, MIPS) - .\r\n\r\nSoftware: astropy (Astropy Collaboration
et al. 2013, 2018; Astropy Collaboration et al. 2022), NumPy (C. R. Harris et al.
2020), SciPy (P. Virtanen et al. 2020), pysersic (I. Pasha & T. B. Miller 2023),
stpsf (M. D. Perrin et al. 2014), lmfit (M. Newville et al. 2014), EsoRex (ESO CPL
Development Team 2015), Claude (used for Python coding; https://claude.ai/), SEP
(K. Barbary 2016)."
date_created: 2026-07-12T22:02:17Z
date_published: 2026-07-10T00:00:00Z
date_updated: 2026-07-13T08:08:41Z
day: '10'
ddc:
- '520'
department:
- _id: JoMa
- _id: IlCa
- _id: GradSch
doi: 10.3847/2041-8213/ae7bfd
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oa_version: Published Version
project:
- _id: bd9b2118-d553-11ed-ba76-db24564edfea
grant_number: '101076224'
name: Young galaxies as tracers and agents of cosmic reionization
publication: The Astrophysical Journal Letters
publication_identifier:
eissn:
- 2041-8213
issn:
- 2041-8205
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
researchdata_availability: yes
scopus_import: '1'
status: public
supplementarymaterial: yes
title: 'A black hole star at cosmic noon: Extreme Balmer break, photospheric continuum,
and broad absorption by thick winds in a Little Red Dot at z = 1.7'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 1005
year: '2026'
...