---
OA_place: publisher
OA_type: diamond
_id: '19931'
abstract:
- lang: eng
  text: JWST observations have uncovered a new population of red, compact objects
    at high redshifts dubbed “little red dots” (LRDs), which typically show broad
    emission lines and are thought to be dusty active galactic nuclei (AGNs). Some
    of their other features, however, challenge the AGN explanation, such as prominent
    Balmer breaks and extremely faint or even missing metal high-ionization lines,
    X-ray, or radio emission, including in deep stacks. Time variability is another
    robust test of AGN activity. Here, we exploit the z = 7.045 multiply imaged LRD
    A2744-QSO1, which offers a particularly unique test of variability due to lensing-induced
    time delays between the three images spanning 22 yr (2.7 yr in the rest-frame),
    to investigate its photometric and spectroscopic variability. We find the equivalent
    widths (EWs) of the broad Hα and Hβ lines, which are independent of magnification
    and other systematics, to exhibit significant variations, of up to 18 ± 3% for
    Hα and up to 22 ± 8% in Hβ, on a timescale of 875 d (2.4 yr) in the rest-frame.
    This suggests that A2744-QSO1 is indeed an AGN. We find no significant photometric
    variability beyond the limiting systematic uncertainties, so it currently cannot
    be determined whether the EW variations are due to line-flux or continuum variability.
    These results are consistent with a typical damped random walk variability model
    for an AGN such as A2744-QSO1 (MBH = 4 × 107 M⊙) given the sparse sampling of
    the light curve with the available data. Our results therefore support the AGN
    interpretation of this LRD, and highlight the need for further photometric and
    spectroscopic monitoring in order to build a detailed and reliable light curve.
acknowledgement: 'We would like to thank Xihan Ji, Hannah Übler, and Roberto Maiolino,
  for cordial and useful discussions. The BGU lensing group acknowledges support by
  grant No. 2020750 from the United States-Israel Binational Science Foundation (BSF)
  and grant No. 2109066 from the United States National Science Foundation (NSF),
  and by the Israel Science Foundation Grant No. 864/23. P.D. warmly thanks the European
  Commission’s and University of Groningen’s CO-FUND Rosalind Franklin program. This
  work is based on observations obtained with the NASA/ESA/CSA JWST, namely programs
  GO-2756, -2561, -2883, -3538, -4111, and -3516, retrieved from the Mikulski Archive
  for Space Telescopes (MAST) at the Space Telescope Science Institute (STScI). STScI
  is operated by the Association of Universities for Research in Astronomy, Inc. under
  NASA contract NAS 5-26555. The spectroscopy products presented herein, from JWST
  program GO-2561, were retrieved from the Dawn JWST Archive (DJA). DJA is an initiative
  of the Cosmic Dawn Center (DAWN), which is funded by the Danish National Research
  Foundation under grant DNRF140. The data used in this work may be retrieved from
  the MAST archive at: http://dx.doi.org/10.17909/p7t7-te67. This work also makes
  use of the Center for Computational Astrophysics at the Flatiron Institute which
  is supported by the Simons Foundation. Support for JWST programs GO-2561, -4111,
  and -3516 was provided by NASA through grants from STScI. This research made use
  of Astropy, (http://www.astropy.org) a community-developed core Python package for
  Astronomy (Astropy Collaboration 2013, 2018) and Photutils, an Astropy package for
  detection and photometry of astronomical sources (Bradley et al. 2024), as well
  as the packages NumPy (van der Walt et al. 2011), SciPy (Virtanen et al. 2020),
  Matplotlib (Hunter 2007), and the MAAT Astronomy and Astrophysics tools for MATLAB
  (Ofek 2014).'
article_number: A227
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Lukas J.
  full_name: Furtak, Lukas J.
  last_name: Furtak
- first_name: Amy R.
  full_name: Secunda, Amy R.
  last_name: Secunda
- first_name: Jenny E.
  full_name: Greene, Jenny E.
  last_name: Greene
- first_name: Adi
  full_name: Zitrin, Adi
  last_name: Zitrin
- first_name: Ivo
  full_name: Labbé, Ivo
  last_name: Labbé
- first_name: Miriam
  full_name: Golubchik, Miriam
  last_name: Golubchik
- first_name: Rachel
  full_name: Bezanson, Rachel
  last_name: Bezanson
- first_name: Vasily
  full_name: Kokorev, Vasily
  last_name: Kokorev
- first_name: Hakim
  full_name: Atek, Hakim
  last_name: Atek
- first_name: Gabriel B.
  full_name: Brammer, Gabriel B.
  last_name: Brammer
- first_name: Iryna
  full_name: Chemerynska, Iryna
  last_name: Chemerynska
- first_name: Sam E.
  full_name: Cutler, Sam E.
  last_name: Cutler
- first_name: Pratika
  full_name: Dayal, Pratika
  last_name: Dayal
- first_name: Robert
  full_name: Feldmann, Robert
  last_name: Feldmann
- first_name: Seiji
  full_name: Fujimoto, Seiji
  last_name: Fujimoto
- first_name: Karl
  full_name: Glazebrook, Karl
  last_name: Glazebrook
- first_name: Joel
  full_name: Leja, Joel
  last_name: Leja
- first_name: Yilun
  full_name: Ma, Yilun
  last_name: Ma
- 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: Erica J.
  full_name: Nelson, Erica J.
  last_name: Nelson
- first_name: Pascal A.
  full_name: Oesch, Pascal A.
  last_name: Oesch
- first_name: Richard
  full_name: Pan, Richard
  last_name: Pan
- first_name: Sedona H.
  full_name: Price, Sedona H.
  last_name: Price
- first_name: Katherine A.
  full_name: Suess, Katherine A.
  last_name: Suess
- first_name: Bingjie
  full_name: Wang, Bingjie
  last_name: Wang
- first_name: John R.
  full_name: Weaver, John R.
  last_name: Weaver
- first_name: Katherine E.
  full_name: Whitaker, Katherine E.
  last_name: Whitaker
citation:
  ama: Furtak LJ, Secunda AR, Greene JE, et al. Investigating photometric and spectroscopic
    variability in the multiply imaged little red dot A2744-QSO1. <i>Astronomy &#38;
    Astrophysics</i>. 2025;698. doi:<a href="https://doi.org/10.1051/0004-6361/202554110">10.1051/0004-6361/202554110</a>
  apa: Furtak, L. J., Secunda, A. R., Greene, J. E., Zitrin, A., Labbé, I., Golubchik,
    M., … Whitaker, K. E. (2025). Investigating photometric and spectroscopic variability
    in the multiply imaged little red dot A2744-QSO1. <i>Astronomy &#38; Astrophysics</i>.
    EDP Sciences. <a href="https://doi.org/10.1051/0004-6361/202554110">https://doi.org/10.1051/0004-6361/202554110</a>
  chicago: Furtak, Lukas J., Amy R. Secunda, Jenny E. Greene, Adi Zitrin, Ivo Labbé,
    Miriam Golubchik, Rachel Bezanson, et al. “Investigating Photometric and Spectroscopic
    Variability in the Multiply Imaged Little Red Dot A2744-QSO1.” <i>Astronomy &#38;
    Astrophysics</i>. EDP Sciences, 2025. <a href="https://doi.org/10.1051/0004-6361/202554110">https://doi.org/10.1051/0004-6361/202554110</a>.
  ieee: L. J. Furtak <i>et al.</i>, “Investigating photometric and spectroscopic variability
    in the multiply imaged little red dot A2744-QSO1,” <i>Astronomy &#38; Astrophysics</i>,
    vol. 698. EDP Sciences, 2025.
  ista: Furtak LJ, Secunda AR, Greene JE, Zitrin A, Labbé I, Golubchik M, Bezanson
    R, Kokorev V, Atek H, Brammer GB, Chemerynska I, Cutler SE, Dayal P, Feldmann
    R, Fujimoto S, Glazebrook K, Leja J, Ma Y, Matthee JJ, Naidu RP, Nelson EJ, Oesch
    PA, Pan R, Price SH, Suess KA, Wang B, Weaver JR, Whitaker KE. 2025. Investigating
    photometric and spectroscopic variability in the multiply imaged little red dot
    A2744-QSO1. Astronomy &#38; Astrophysics. 698, A227.
  mla: Furtak, Lukas J., et al. “Investigating Photometric and Spectroscopic Variability
    in the Multiply Imaged Little Red Dot A2744-QSO1.” <i>Astronomy &#38; Astrophysics</i>,
    vol. 698, A227, EDP Sciences, 2025, doi:<a href="https://doi.org/10.1051/0004-6361/202554110">10.1051/0004-6361/202554110</a>.
  short: L.J. Furtak, A.R. Secunda, J.E. Greene, A. Zitrin, I. Labbé, M. Golubchik,
    R. Bezanson, V. Kokorev, H. Atek, G.B. Brammer, I. Chemerynska, S.E. Cutler, P.
    Dayal, R. Feldmann, S. Fujimoto, K. Glazebrook, J. Leja, Y. Ma, J.J. Matthee,
    R.P. Naidu, E.J. Nelson, P.A. Oesch, R. Pan, S.H. Price, K.A. Suess, B. Wang,
    J.R. Weaver, K.E. Whitaker, Astronomy &#38; Astrophysics 698 (2025).
date_created: 2025-06-29T22:01:16Z
date_published: 2025-06-01T00:00:00Z
date_updated: 2026-02-16T12:11:22Z
day: '01'
ddc:
- '520'
department:
- _id: JoMa
doi: 10.1051/0004-6361/202554110
external_id:
  arxiv:
  - '2502.07875'
  isi:
  - '001510826300017'
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  date_created: 2025-06-30T08:44:24Z
  date_updated: 2025-06-30T08:44:24Z
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has_accepted_license: '1'
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language:
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month: '06'
oa: 1
oa_version: Published Version
publication: Astronomy & Astrophysics
publication_identifier:
  eissn:
  - 1432-0746
  issn:
  - 0004-6361
publication_status: published
publisher: EDP Sciences
quality_controlled: '1'
scopus_import: '1'
status: public
title: Investigating photometric and spectroscopic variability in the multiply imaged
  little red dot A2744-QSO1
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: 698
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