---
DOAJ_listed: '1'
OA_place: publisher
OA_type: gold
_id: '21709'
abstract:
- lang: eng
text: 'JWST’s “little red dots” (LRDs) are increasingly interpreted as active galactic
nuclei (AGN) obscured by dense thermalized gas rather than dust as evidenced by
their X-ray weakness, blackbody-like continua, and Balmer line profiles. Key questions
are how LRDs connect to standard UV-luminous AGN, whether transitional phases
exist, and whether they are observable. We present the “X-ray dot” (XRD), a compact
source at z = 3.28 observed by the NIRSpec Wide Guaranteed Time Observation survey.
The XRD exhibits LRD hallmarks: a blackbody-like (Teff ≃ 6400 K) red continuum,
a faint but blue rest-UV excess, falling mid-IR emission, and broad Balmer lines
(FWHM ∼ 2700–3200 km s−1). Unlike LRDs, however, it is remarkably X-ray luminous
(L2−10 keV = 1044.18 erg s−1) and has a continuum inflection that is blueward
of the Balmer limit. We find that the red rest-optical and blue mid-IR continuum
cannot be reproduced by standard dust-attenuated AGN models without invoking extremely
steep extinction curves, nor can the weak mid-IR emission be reconciled with well-established
X-ray–torus scaling relations. We therefore consider an alternative scenario:
the XRD may be an LRD in transition, where the gas envelope dominates the optical
continuum but optically thin sight lines allow X-rays to escape. The XRD may thus
provide a physical link between LRDs and standard AGN, offering direct evidence
that LRDs are powered by supermassive black holes and providing insight into their
accretion properties.'
acknowledgement: "We would like to thank the anonymous reviewer for their constructive
comments, which improved the final manuscript.\r\n\r\nWe thank Bernd Husemann for
his critical contributions to the NIRSpec Wide GTO survey, and in particular his
help in selecting high-priority X-ray-luminous targets.\r\n\r\nR.E.H. acknowledges
support by the German Aerospace Center (DLR) and the Federal Ministry for Economic
Affairs and Energy (BMWi) through program 50OR2403 “RUBIES.” A.d.G. acknowledges
support from a Clay Fellowship awarded by the Smithsonian Astrophysical Observatory.
A.J.B. acknowledges funding from the “FirstGalaxies” Advanced grant from the European
Research Council (ERC) under the European Union’s Horizon 2020 research and innovation
program (grant agreement No. 789056). R.P.N. thanks Neil Pappalardo and Jane Pappalardo
for their generous support of the MIT Pappalardo Fellowships in Physics. Support
for this work was provided by the Brinson Foundation through a Brinson Prize Fellowship
grant. H.Ü. acknowledges funding by the European Union (ERC APEX, 101164796). Views
and opinions expressed are, however, those of the authors only and do not necessarily
reflect those of the European Union or the European Research Council Executive Agency.
Neither the European Union nor the granting authority can be held responsible for
them. G.V. acknowledges support from European Union’s HE ERC Starting grant No.
101040227—WINGS. B.W. acknowledges support provided by NASA through Hubble Fellowship
grant HST-HF2-51592.001 awarded by the Space Telescope Science Institute, which
is operated by the Association of Universities for Research in Astronomy, In., for
NASA, under the contract NAS 5-26555.\r\n\r\nThe data products presented herein
were retrieved from the Dawn JWST Archive (DJA). DJA is an initiative of the Cosmic
Dawn Center (DAWN).\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
Nos. GTO-1213. The data described here may be obtained from the MAST archive at
DOI: 10.17909/qffz-b324.\r\n\r\nThis Letter employs a list of Chandra datasets,
obtained by the Chandra X-ray Observatory, contained in DOI: 10.25574/cdc.540.\r\n\r\nThis
work is based on observations taken by the 3D-HST Treasury Program (GO 12177 and
12328) with the NASA/ESA HST, which is operated by the Association of Universities
for Research in Astronomy, Inc., under NASA contract NAS5-26555.\r\n\r\nThis work
makes use of color palettes created by Martin Krzywinski designed for colorblindness.
The color palettes and more information can be found at http://mkweb.bcgsc.ca/colorblind/.\r\n\r\nFacilities:
CXO - Chandra X-ray Observatory satellite (ACIS), HST - Hubble Space Telescope satellite
(ACS, WFC3) - , CFHT - Canada-France-Hawaii Telescope (WIRCam), JWST - James Webb
Space Telescope (NIRSpec), Spitzer - Spitzer Space Telescope satellite (IRAC, MIPS)
- , JCMT - James Clerk Maxwell Telescope (SCUBA).\r\n\r\nSoftware: Astropy (Astropy
Collaboration et al. 2013, 2018, 2022), dust_attenuation, dust_extinction (K. Gordon
2024), jax (J. Bradbury et al. 2018), LaTeX (L. Lamport 1994), Matplotlib (J. D.
Hunter 2007), NumPy (T. E. Oliphant 2006; S. van der Walt et al. 2011; C. R. Harris
et al. 2020), NumPyro (D. Phan et al. 2019), scipy (P. Virtanen et al. 2020), sedpy
(B. Johnson & J. Leja 2017), specutils (Astropy-Specutils Development Team 2019),
unite (R. E. Hviding 2025)."
article_number: L18
article_processing_charge: Yes
article_type: original
arxiv: 1
author:
- first_name: Raphael E.
full_name: Hviding, Raphael E.
last_name: Hviding
- first_name: Anna
full_name: De Graaff, Anna
last_name: De Graaff
- first_name: Hanpu
full_name: Liu, Hanpu
last_name: Liu
- first_name: Andy D.
full_name: Goulding, Andy D.
last_name: Goulding
- first_name: Yilun
full_name: Ma, Yilun
last_name: Ma
- first_name: Jenny E.
full_name: Greene, Jenny E.
last_name: Greene
- first_name: Leindert A.
full_name: Boogaard, Leindert A.
last_name: Boogaard
- first_name: Andrew J.
full_name: Bunker, Andrew J.
last_name: Bunker
- first_name: Nikko J.
full_name: Cleri, Nikko J.
last_name: Cleri
- first_name: Marijn
full_name: Franx, Marijn
last_name: Franx
- first_name: Michaela
full_name: Hirschmann, Michaela
last_name: Hirschmann
- first_name: Joel
full_name: Leja, Joel
last_name: Leja
- 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: Rohan P.
full_name: Naidu, Rohan P.
last_name: Naidu
- first_name: David J.
full_name: Setton, David J.
last_name: Setton
- first_name: Hannah
full_name: Übler, Hannah
last_name: Übler
- first_name: Giacomo
full_name: Venturi, Giacomo
last_name: Venturi
- first_name: Bingjie
full_name: Wang, Bingjie
last_name: Wang
citation:
ama: 'Hviding RE, De Graaff A, Liu H, et al. The X-ray dot: Exotic dust or a late-stage
Little Red Dot? The Astrophysical Journal Letters. 2026;1000(1). doi:10.3847/2041-8213/ae4c88'
apa: 'Hviding, R. E., De Graaff, A., Liu, H., Goulding, A. D., Ma, Y., Greene, J.
E., … Wang, B. (2026). The X-ray dot: Exotic dust or a late-stage Little Red Dot?
The Astrophysical Journal Letters. IOP Publishing. https://doi.org/10.3847/2041-8213/ae4c88'
chicago: 'Hviding, Raphael E., Anna De Graaff, Hanpu Liu, Andy D. Goulding, Yilun
Ma, Jenny E. Greene, Leindert A. Boogaard, et al. “The X-Ray Dot: Exotic Dust
or a Late-Stage Little Red Dot?” The Astrophysical Journal Letters. IOP
Publishing, 2026. https://doi.org/10.3847/2041-8213/ae4c88.'
ieee: 'R. E. Hviding et al., “The X-ray dot: Exotic dust or a late-stage
Little Red Dot?,” The Astrophysical Journal Letters, vol. 1000, no. 1.
IOP Publishing, 2026.'
ista: 'Hviding RE, De Graaff A, Liu H, Goulding AD, Ma Y, Greene JE, Boogaard LA,
Bunker AJ, Cleri NJ, Franx M, Hirschmann M, Leja J, Matthee JJ, Naidu RP, Setton
DJ, Übler H, Venturi G, Wang B. 2026. The X-ray dot: Exotic dust or a late-stage
Little Red Dot? The Astrophysical Journal Letters. 1000(1), L18.'
mla: 'Hviding, Raphael E., et al. “The X-Ray Dot: Exotic Dust or a Late-Stage Little
Red Dot?” The Astrophysical Journal Letters, vol. 1000, no. 1, L18, IOP
Publishing, 2026, doi:10.3847/2041-8213/ae4c88.'
short: R.E. Hviding, A. De Graaff, H. Liu, A.D. Goulding, Y. Ma, J.E. Greene, L.A.
Boogaard, A.J. Bunker, N.J. Cleri, M. Franx, M. Hirschmann, J. Leja, J.J. Matthee,
R.P. Naidu, D.J. Setton, H. Übler, G. Venturi, B. Wang, The Astrophysical Journal
Letters 1000 (2026).
date_created: 2026-04-12T22:01:48Z
date_published: 2026-03-20T00:00:00Z
date_updated: 2026-05-04T07:13:07Z
day: '20'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.3847/2041-8213/ae4c88
external_id:
arxiv:
- '2601.09778'
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has_accepted_license: '1'
intvolume: ' 1000'
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language:
- iso: eng
license: https://creativecommons.org/licenses/by/4.0/
month: '03'
oa: 1
oa_version: Published Version
publication: The Astrophysical Journal Letters
publication_identifier:
eissn:
- 2041-8213
issn:
- 2041-8205
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
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title: 'The X-ray dot: Exotic dust or a late-stage Little Red Dot?'
tmp:
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legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
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type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
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