---
OA_place: publisher
OA_type: hybrid
PlanS_conform: '1'
_id: '20588'
abstract:
- lang: eng
text: 'In this second paper on our variability survey of central stars of planetary
nebulae (CSPNe) using the Zwicky Transient Facility (ZTF), we report 11 long-timescale
variables with variability timescales ranging from months to years. We also present
preliminary analyses based on spectroscopic and/or photometric follow-up observations
for six of them. Among them is NGC 6833, which shows a 980 days periodic variability
with strange characteristics: “triangle-shaped” brightening in r, i, and WISE
bands but almost coincidental shallow dips in the g-band. The most plausible explanation
is a wide binary with the photometric period being the orbital period. Long-period
near-sinusoidal variability was detected in two other systems, NGC 6905 and Kn
26, with periods of 700 days and 230 days, respectively, making them additional
wide-binary candidates. The latter also shows a short period at 1.18 hr. We then
present CTSS 2 and K 3-5, which show brightening and significant reddening over
the whole ZTF baseline. A stellar model fit to the optical spectrum of CTSS 2
reveals it to be one of the youngest post-AGB CSPNe known. Both show high-density
emission-line cores. We propose these to be late-thermal-pulse candidates, currently
evolving towards the AGB phase. We then present recent HST/COS ultraviolet spectroscopy
of the known wide-binary candidate LoTr 1, showing that the hot star is a spectroscopic
twin of the extremely hot white dwarf in UCAC2 46706450. Similar to this object,
LoTr 1 also has a fast rotating wide subgiant companion. We suggest that the long
photometric period of 11 yr is the binary orbital period. Finally, we briefly
discuss the ZTF light curves of the remaining variables, namely Tan 2, K 3-20,
WHTZ 3, Kn J1857+3931, and IPHAS J1927+0814. With these examples, we present the
effectiveness of the von Neumann statistics and Pearson Skew-based metric space
in searching for long-timescale variables.'
acknowledgement: "This work is based on observations obtained with the Samuel Oschin
Telescope 48 inch and the 60 inch Telescope at the Palomar Observatory as part of
the Zwicky Transient Facility project. ZTF is supported by the National Science
Foundation under grant Nos. AST-1440341 and AST-2034437 and a collaboration including
current partners Caltech, IPAC, the Oskar Klein Center at Stockholm University,
the University of Maryland, University of California, Berkeley, the University of
Wisconsin at Milwaukee, University of Warwick, Ruhr University Bochum, Cornell University,
Northwestern University, and Drexel University. Operations are conducted by COO,
IPAC, and UW.\r\n\r\nThis work has made use of data from the European Space Agency
(ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data
Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium).
Funding for the DPAC has been provided by national institutions, in particular,
the institutions participating in the Gaia Multilateral Agreement.\r\n\r\nWe are
grateful to the staffs of Palomar Observatory and the Hobby-Eberly Telescope for
assistance with the observations and data management. The Liverpool Telescope is
operated on the island of La Palma by Liverpool John Moores University in the Spanish
Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias
with financial support from the UK Science and Technology Facilities Council.\r\n\r\nThe
Low-Resolution Spectrograph 2 (LRS2) on HET was developed and funded by the University
of Texas at Austin McDonald Observatory and Department of Astronomy, and by Pennsylvania
State University. We thank the Leibniz-Institut für Astrophysik Potsdam (AIP) and
the Institut für Astrophysik Göttingen (IAG) for their contributions to the construction
of the integral field units. We acknowledge the Texas Advanced Computing Center
(TACC) at The University of Texas at Austin for providing high performance computing,
visualization, and storage resources that have contributed to the results reported
within this paper.\r\n\r\nThe Isaac Newton Telescope is operated on the island of
La Palma by the Isaac Newton Group of Telescopes in the Spanish Observatorio del
Roque de los Muchachos of the Instituto de Astrofísica de Canarias\r\n\r\nS.B. thanks
Frank J. Masci and Zachary P. Vanderbosch for useful discussions and suggestions
regarding solving the issues with ZTF forced photometry on extended sources. S.B.
also thanks Jim Fuller, Charles C. Steidel, Lynne Hillenbrand, and Adolfo Carvalho
for useful discussions on methods and science. S.B. acknowledges financial support
from the Wallace L. W. Sargent Graduate Fellowship during the first year of his
graduate studies at Caltech. N.C. was supported through the Cancer Research UK grant
A24042.\r\n\r\nN.R. is supported by the Deutsche Forschungsgemeinschaft (DFG) through
grant RE3915/2-1.\r\n\r\nD.J. acknowledges support from the Agencia Estatal de Investigación
del Ministerio de Ciencia, Innovación y Universidades (MICIU/AEI) under grant “Nebulosas
planetarias como clave para comprender la evolución de estrellas binarias” and the
European Regional Development Fund (ERDF) with reference PID-2022-136653NA-I00 (DOI:10.13039/501100011033).
D.J. also acknowledges support from the Agencia Estatal de Investigación del Ministerio
de Ciencia, Innovación y Universidades (MICIU/AEI) under grant “Revolucionando el
conocimiento de la evolución de estrellas poco masivas” and the the European Union
NextGenerationEU/PRTR with reference CNS2023-143910 (DOI:10.13039/501100011033).\r\n\r\nWe
have used Python packages Numpy (Harris et al. 2020), SciPy (Virtanen et al. 2020),
Matplotlib (Hunter 2007), Pandas (pandas development team 2020), Astropy (Astropy
Collaboration et al. 2013, 2018), and Astroquery (Ginsburg et al. 2019) at various
stages of this research."
article_number: '104206'
article_processing_charge: Yes (in subscription journal)
article_type: original
arxiv: 1
author:
- first_name: Soumyadeep
full_name: Bhattacharjee, Soumyadeep
last_name: Bhattacharjee
- first_name: Nicole
full_name: Reindl, Nicole
last_name: Reindl
- first_name: Howard E.
full_name: Bond, Howard E.
last_name: Bond
- first_name: Klaus
full_name: Werner, Klaus
last_name: Werner
- first_name: Gregory R.
full_name: Zeimann, Gregory R.
last_name: Zeimann
- first_name: David
full_name: Jones, David
last_name: Jones
- first_name: Kareem
full_name: El-Badry, Kareem
last_name: El-Badry
- first_name: Nina
full_name: Mackensen, Nina
last_name: Mackensen
- first_name: Nicholas
full_name: Chornay, Nicholas
last_name: Chornay
- first_name: S. R.
full_name: Kulkarni, S. R.
last_name: Kulkarni
- first_name: Ilaria
full_name: Caiazzo, Ilaria
id: 8ae5b6e7-2a03-11ee-914d-b58ed7a3b47d
last_name: Caiazzo
orcid: 0000-0002-4770-5388
- first_name: Jan
full_name: Van Roestel, Jan
last_name: Van Roestel
- first_name: Antonio C.
full_name: Rodriguez, Antonio C.
last_name: Rodriguez
- first_name: Thomas A.
full_name: Prince, Thomas A.
last_name: Prince
- first_name: Ben
full_name: Rusholme, Ben
last_name: Rusholme
- first_name: Russ R.
full_name: Laher, Russ R.
last_name: Laher
- first_name: Roger
full_name: Smith, Roger
last_name: Smith
citation:
ama: Bhattacharjee S, Reindl N, Bond HE, et al. Variability of central stars of
planetary nebulae with the Zwicky Transient Facility. II. Long-timescale variables
including wide binary and late thermal pulse candidates. Publications of the
Astronomical Society of the Pacific. 2025;137(10). doi:10.1088/1538-3873/ae051e
apa: Bhattacharjee, S., Reindl, N., Bond, H. E., Werner, K., Zeimann, G. R., Jones,
D., … Smith, R. (2025). Variability of central stars of planetary nebulae with
the Zwicky Transient Facility. II. Long-timescale variables including wide binary
and late thermal pulse candidates. Publications of the Astronomical Society
of the Pacific. IOP Publishing. https://doi.org/10.1088/1538-3873/ae051e
chicago: Bhattacharjee, Soumyadeep, Nicole Reindl, Howard E. Bond, Klaus Werner,
Gregory R. Zeimann, David Jones, Kareem El-Badry, et al. “Variability of Central
Stars of Planetary Nebulae with the Zwicky Transient Facility. II. Long-Timescale
Variables Including Wide Binary and Late Thermal Pulse Candidates.” Publications
of the Astronomical Society of the Pacific. IOP Publishing, 2025. https://doi.org/10.1088/1538-3873/ae051e.
ieee: S. Bhattacharjee et al., “Variability of central stars of planetary
nebulae with the Zwicky Transient Facility. II. Long-timescale variables including
wide binary and late thermal pulse candidates,” Publications of the Astronomical
Society of the Pacific, vol. 137, no. 10. IOP Publishing, 2025.
ista: Bhattacharjee S, Reindl N, Bond HE, Werner K, Zeimann GR, Jones D, El-Badry
K, Mackensen N, Chornay N, Kulkarni SR, Caiazzo I, Van Roestel J, Rodriguez AC,
Prince TA, Rusholme B, Laher RR, Smith R. 2025. Variability of central stars of
planetary nebulae with the Zwicky Transient Facility. II. Long-timescale variables
including wide binary and late thermal pulse candidates. Publications of the Astronomical
Society of the Pacific. 137(10), 104206.
mla: Bhattacharjee, Soumyadeep, et al. “Variability of Central Stars of Planetary
Nebulae with the Zwicky Transient Facility. II. Long-Timescale Variables Including
Wide Binary and Late Thermal Pulse Candidates.” Publications of the Astronomical
Society of the Pacific, vol. 137, no. 10, 104206, IOP Publishing, 2025, doi:10.1088/1538-3873/ae051e.
short: S. Bhattacharjee, N. Reindl, H.E. Bond, K. Werner, G.R. Zeimann, D. Jones,
K. El-Badry, N. Mackensen, N. Chornay, S.R. Kulkarni, I. Caiazzo, J. Van Roestel,
A.C. Rodriguez, T.A. Prince, B. Rusholme, R.R. Laher, R. Smith, Publications of
the Astronomical Society of the Pacific 137 (2025).
date_created: 2025-11-02T23:01:34Z
date_published: 2025-10-01T00:00:00Z
date_updated: 2025-12-01T15:13:50Z
day: '01'
ddc:
- '520'
department:
- _id: IlCa
doi: 10.1088/1538-3873/ae051e
external_id:
arxiv:
- '2502.18651'
isi:
- '001595690000001'
file:
- access_level: open_access
checksum: cc7d00c349d48458accb0d3df67e4879
content_type: application/pdf
creator: dernst
date_created: 2025-11-04T08:26:39Z
date_updated: 2025-11-04T08:26:39Z
file_id: '20599'
file_name: 2025_PASP_BhattacharjeeS.pdf
file_size: 12677603
relation: main_file
success: 1
file_date_updated: 2025-11-04T08:26:39Z
has_accepted_license: '1'
intvolume: ' 137'
isi: 1
issue: '10'
language:
- iso: eng
license: https://creativecommons.org/licenses/by/4.0/
month: '10'
oa: 1
oa_version: Published Version
publication: Publications of the Astronomical Society of the Pacific
publication_identifier:
issn:
- 1538-3873
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
scopus_import: '1'
status: public
title: Variability of central stars of planetary nebulae with the Zwicky Transient
Facility. II. Long-timescale variables including wide binary and late thermal pulse
candidates
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: 137
year: '2025'
...
---
OA_place: publisher
OA_type: hybrid
PlanS_conform: '1'
_id: '21241'
abstract:
- lang: eng
text: White dwarfs (WDs) showing transits from orbiting planetary debris provide
significant insights into the structure and dynamics of debris disks, which are
eventually accreted to produce metal pollution. This is a rare class of objects
with only eight published systems. In this work, we perform a systematic search
for such systems within 500 pc in the Gaia-eDR3 catalog of WDs using the light
curves from the Zwicky Transient Facility (ZTF) and present six new candidates.
Our selection process targets the top 1% most photometrically variable sources
identified using a combined variability metric from ZTF and Gaia eDR3 photometry,
boosted by a metric space we define using von Neumann statistics and Pearson-Skew
as a novel discovery tool to identify these systems. This is followed by optical
spectroscopic observations of visually selected variables to confirm metal pollution.
Four of the six systems show long-timescale photometric variability spanning several
months to years, resulting either from long-term evolution of transit activity
or dust and debris clouds at wide orbits. Among them, WD J1013–0427 shows an indication
of reddening during the long-duration dip. Interpreting this as dust extinction
makes it the first system to indicate an abundance of dust grains with radius
≲0.3 μm in the occulting material. The same object also shows metal emission lines
that map an optically thick eccentric gas disk orbiting within the star’s Roche
limit. For each candidate, we infer the abundances of the photospheric metals
and estimate accretion rates. We show that transiting debris systems tend to have
higher inferred accretion rates compared to the general population of metal-polluted
WDs. Growing the number of these systems will further illuminate such comparative
properties in the near future. Separately, we also serendipitously discovered
an AM Canis Venaticorum showing a very long-duration outburst—only the fourth
such system to be known.
acknowledgement: "This work is based on observations obtained with the Samuel Oschin
Telescope 48 inch and the 60 inch Telescope at the Palomar Observatory as part of
the Zwicky Transient Facility project. Z.T.F. is supported by the National Science
Foundation under grants No. AST-1440341 and AST-2034437 and a collaboration including
current partners Caltech, IPAC, the Oskar Klein Center at Stockholm University,
the University of Maryland, University of California, Berkeley, the University of
Wisconsin at Milwaukee, University of Warwick, Ruhr University Bochum, Cornell University,
Northwestern University, and Drexel University. Operations are conducted by COO,
IPAC, and UW.\r\n\r\nThis work has made use of data from the European Space Agency
(ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data
Processing and Analysis Consortium (DPAC; https://www.cosmos.esa.int/web/gaia/dpac/consortium).
Funding for the DPAC has been provided by national institutions, in particular,
the institutions participating in the Gaia Multilateral Agreement. This publication
makes use of data products from the Wide-field Infrared Survey Explorer, which is
a joint project of the University of California, Los Angeles, and the Jet Propulsion
Laboratory/California Institute of Technology, funded by the National Aeronautics
and Space Administration.\r\n\r\nThis research has made use of the VizieR catalog
access tool, CDS, Strasbourg, France https://vizier.cds.unistra.fr/. The original
description of the VizieR service was published in Ochsenbein et al. (2000).\r\n\r\nWe
are grateful to the staffs of Palomar and Keck Observatory for assistance with the
observations and data management.\r\n\r\nThe authors thank the anonymous referee
for very extensive and useful comments which improved the presentation of the paper
significantly. S.B. acknowledges the support from the Kishore Vaigyanik Protsahan
Yojana (KVPY) scheme of the Department of Science and Technology, Government of
India (a former fellowship program for undergraduate studies in basic science) during
his undergraduate studies at IISc. S.B. thanks the Summer Undergraduate Research
Fellowship (SURF) at Caltech and Shrinivas R. Kulkarni for hosting him as a summer
research student in 2022. S.B. acknowledges the financial support from the Wallace
L. W. Sargent Graduate Fellowship during the first year of his graduate studies
at Caltech. P.E.T. received funding from the European Research Council under the
European Union’s Horizon 2020 research and innovation program number 101002408.
S.X. 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. J.A.G. is supported by the National Science Foundation Graduate
Research Fellowship Program under grant No. 2234657. This material is based upon
work supported by the National Aeronautics and Space Administration under grant
No. 80NSSC23K1068 issued through the Science Mission Directorate.\r\n\r\nWe have
used Python packages Numpy (Harris et al. 2020), SciPy (Virtanen et al. 2020), Matplotlib
(Hunter 2007), Pandas (The pandas development team 2020), Astropy (Astropy Collaboration
et al. 2013, 2018), and Astroquery (Ginsburg et al. 2019) at various stages of this
research."
article_number: '074202'
article_processing_charge: Yes (in subscription journal)
article_type: original
arxiv: 1
author:
- first_name: 'Soumyadeep '
full_name: 'Bhattacharjee, Soumyadeep '
last_name: Bhattacharjee
- first_name: Zachary P.
full_name: Vanderbosch, Zachary P.
last_name: Vanderbosch
- first_name: Mark A.
full_name: Hollands, Mark A.
last_name: Hollands
- first_name: Pier-Emmanuel
full_name: Tremblay, Pier-Emmanuel
last_name: Tremblay
- first_name: Siyi
full_name: Xu, Siyi
last_name: Xu
- first_name: Joseph A.
full_name: Guidry, Joseph A.
last_name: Guidry
- first_name: J.J.
full_name: Hermes, J.J.
last_name: Hermes
- first_name: Ilaria
full_name: Caiazzo, Ilaria
id: 8ae5b6e7-2a03-11ee-914d-b58ed7a3b47d
last_name: Caiazzo
orcid: 0000-0002-4770-5388
- first_name: Antonio C.
full_name: Rodriguez, Antonio C.
last_name: Rodriguez
- first_name: Jan
full_name: van Roestel, Jan
last_name: van Roestel
- first_name: 'Kareem '
full_name: 'El-Badry, Kareem '
last_name: El-Badry
- first_name: Andrew J.
full_name: Drake, Andrew J.
last_name: Drake
- first_name: Benjamin R.
full_name: Roulston, Benjamin R.
last_name: Roulston
- first_name: Reed
full_name: Riddle, Reed
last_name: Riddle
- first_name: Ben
full_name: Rusholme, Ben
last_name: Rusholme
- first_name: Steven L.
full_name: Groom, Steven L.
last_name: Groom
- first_name: Roger
full_name: Smith, Roger
last_name: Smith
- first_name: Odette
full_name: Toloza, Odette
last_name: Toloza
citation:
ama: 'Bhattacharjee S, Vanderbosch ZP, Hollands MA, et al. A ZTF search for circumstellar
debris transits in White Dwarfs: Six new candidates, one with gas disk emission,
identified in a novel metric space. Publications of the Astronomical Society
of the Pacific. 2025;137(7). doi:10.1088/1538-3873/ade0ea'
apa: 'Bhattacharjee, S., Vanderbosch, Z. P., Hollands, M. A., Tremblay, P.-E., Xu,
S., Guidry, J. A., … Toloza, O. (2025). A ZTF search for circumstellar debris
transits in White Dwarfs: Six new candidates, one with gas disk emission, identified
in a novel metric space. Publications of the Astronomical Society of the Pacific.
IOP Publishing. https://doi.org/10.1088/1538-3873/ade0ea'
chicago: 'Bhattacharjee, Soumyadeep , Zachary P. Vanderbosch, Mark A. Hollands,
Pier-Emmanuel Tremblay, Siyi Xu, Joseph A. Guidry, J.J. Hermes, et al. “A ZTF
Search for Circumstellar Debris Transits in White Dwarfs: Six New Candidates,
One with Gas Disk Emission, Identified in a Novel Metric Space.” Publications
of the Astronomical Society of the Pacific. IOP Publishing, 2025. https://doi.org/10.1088/1538-3873/ade0ea.'
ieee: 'S. Bhattacharjee et al., “A ZTF search for circumstellar debris transits
in White Dwarfs: Six new candidates, one with gas disk emission, identified in
a novel metric space,” Publications of the Astronomical Society of the Pacific,
vol. 137, no. 7. IOP Publishing, 2025.'
ista: 'Bhattacharjee S, Vanderbosch ZP, Hollands MA, Tremblay P-E, Xu S, Guidry
JA, Hermes JJ, Caiazzo I, Rodriguez AC, van Roestel J, El-Badry K, Drake AJ, Roulston
BR, Riddle R, Rusholme B, Groom SL, Smith R, Toloza O. 2025. A ZTF search for
circumstellar debris transits in White Dwarfs: Six new candidates, one with gas
disk emission, identified in a novel metric space. Publications of the Astronomical
Society of the Pacific. 137(7), 074202.'
mla: 'Bhattacharjee, Soumyadeep, et al. “A ZTF Search for Circumstellar Debris Transits
in White Dwarfs: Six New Candidates, One with Gas Disk Emission, Identified in
a Novel Metric Space.” Publications of the Astronomical Society of the Pacific,
vol. 137, no. 7, 074202, IOP Publishing, 2025, doi:10.1088/1538-3873/ade0ea.'
short: S. Bhattacharjee, Z.P. Vanderbosch, M.A. Hollands, P.-E. Tremblay, S. Xu,
J.A. Guidry, J.J. Hermes, I. Caiazzo, A.C. Rodriguez, J. van Roestel, K. El-Badry,
A.J. Drake, B.R. Roulston, R. Riddle, B. Rusholme, S.L. Groom, R. Smith, O. Toloza,
Publications of the Astronomical Society of the Pacific 137 (2025).
date_created: 2026-02-16T15:10:51Z
date_published: 2025-07-09T00:00:00Z
date_updated: 2026-02-17T11:35:53Z
day: '09'
ddc:
- '520'
department:
- _id: IlCa
doi: 10.1088/1538-3873/ade0ea
external_id:
arxiv:
- '2502.05502'
file:
- access_level: open_access
checksum: 237eddc36e3823b3092fab6aa5bc8655
content_type: application/pdf
creator: dernst
date_created: 2026-02-17T11:30:29Z
date_updated: 2026-02-17T11:30:29Z
file_id: '21289'
file_name: 2025_PASP_Bhattacharjee.pdf
file_size: 8900420
relation: main_file
success: 1
file_date_updated: 2026-02-17T11:30:29Z
has_accepted_license: '1'
intvolume: ' 137'
issue: '7'
language:
- iso: eng
license: https://creativecommons.org/licenses/by/3.0/
month: '07'
oa: 1
oa_version: Published Version
publication: Publications of the Astronomical Society of the Pacific
publication_identifier:
issn:
- 1538-3873
publication_status: published
publisher: IOP Publishing
quality_controlled: '1'
status: public
title: 'A ZTF search for circumstellar debris transits in White Dwarfs: Six new candidates,
one with gas disk emission, identified in a novel metric space'
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/3.0/legalcode
name: Creative Commons Attribution 3.0 Unported (CC BY 3.0)
short: CC BY (3.0)
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 137
year: '2025'
...