[{"department":[{"_id":"IlCa"}],"citation":{"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. <i>Publications of the Astronomical Society of the Pacific</i>. IOP Publishing. <a href=\"https://doi.org/10.1088/1538-3873/ae051e\">https://doi.org/10.1088/1538-3873/ae051e</a>","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.” <i>Publications of the Astronomical Society of the Pacific</i>, vol. 137, no. 10, 104206, IOP Publishing, 2025, doi:<a href=\"https://doi.org/10.1088/1538-3873/ae051e\">10.1088/1538-3873/ae051e</a>.","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. <i>Publications of the Astronomical Society of the Pacific</i>. 2025;137(10). doi:<a href=\"https://doi.org/10.1088/1538-3873/ae051e\">10.1088/1538-3873/ae051e</a>","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).","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.","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.” <i>Publications of the Astronomical Society of the Pacific</i>. IOP Publishing, 2025. <a href=\"https://doi.org/10.1088/1538-3873/ae051e\">https://doi.org/10.1088/1538-3873/ae051e</a>.","ieee":"S. Bhattacharjee <i>et al.</i>, “Variability of central stars of planetary nebulae with the Zwicky Transient Facility. II. Long-timescale variables including wide binary and late thermal pulse candidates,” <i>Publications of the Astronomical Society of the Pacific</i>, vol. 137, no. 10. IOP Publishing, 2025."},"publication_identifier":{"issn":["1538-3873"]},"external_id":{"isi":["001595690000001"],"arxiv":["2502.18651"]},"has_accepted_license":"1","OA_place":"publisher","language":[{"iso":"eng"}],"OA_type":"hybrid","issue":"10","_id":"20588","article_processing_charge":"Yes (in subscription journal)","date_updated":"2025-12-01T15:13:50Z","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","file_date_updated":"2025-11-04T08:26:39Z","intvolume":"       137","publication":"Publications of the Astronomical Society of the Pacific","tmp":{"short":"CC BY (4.0)","legal_code_url":"https://creativecommons.org/licenses/by/4.0/legalcode","name":"Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)","image":"/images/cc_by.png"},"isi":1,"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.","publisher":"IOP Publishing","publication_status":"published","date_published":"2025-10-01T00:00:00Z","volume":137,"oa_version":"Published Version","scopus_import":"1","day":"01","year":"2025","doi":"10.1088/1538-3873/ae051e","author":[{"full_name":"Bhattacharjee, Soumyadeep","last_name":"Bhattacharjee","first_name":"Soumyadeep"},{"first_name":"Nicole","last_name":"Reindl","full_name":"Reindl, Nicole"},{"full_name":"Bond, Howard E.","first_name":"Howard E.","last_name":"Bond"},{"last_name":"Werner","first_name":"Klaus","full_name":"Werner, Klaus"},{"full_name":"Zeimann, Gregory R.","first_name":"Gregory R.","last_name":"Zeimann"},{"full_name":"Jones, David","first_name":"David","last_name":"Jones"},{"first_name":"Kareem","last_name":"El-Badry","full_name":"El-Badry, Kareem"},{"last_name":"Mackensen","first_name":"Nina","full_name":"Mackensen, Nina"},{"last_name":"Chornay","first_name":"Nicholas","full_name":"Chornay, Nicholas"},{"first_name":"S. R.","last_name":"Kulkarni","full_name":"Kulkarni, S. R."},{"orcid":"0000-0002-4770-5388","first_name":"Ilaria","last_name":"Caiazzo","id":"8ae5b6e7-2a03-11ee-914d-b58ed7a3b47d","full_name":"Caiazzo, Ilaria"},{"full_name":"Van Roestel, Jan","first_name":"Jan","last_name":"Van Roestel"},{"last_name":"Rodriguez","first_name":"Antonio C.","full_name":"Rodriguez, Antonio C."},{"last_name":"Prince","first_name":"Thomas A.","full_name":"Prince, Thomas A."},{"full_name":"Rusholme, Ben","last_name":"Rusholme","first_name":"Ben"},{"first_name":"Russ R.","last_name":"Laher","full_name":"Laher, Russ R."},{"last_name":"Smith","first_name":"Roger","full_name":"Smith, Roger"}],"article_type":"original","article_number":"104206","PlanS_conform":"1","ddc":["520"],"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","month":"10","date_created":"2025-11-02T23:01:34Z","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."}],"type":"journal_article","oa":1,"file":[{"relation":"main_file","access_level":"open_access","creator":"dernst","date_updated":"2025-11-04T08:26:39Z","checksum":"cc7d00c349d48458accb0d3df67e4879","file_size":12677603,"file_id":"20599","file_name":"2025_PASP_BhattacharjeeS.pdf","date_created":"2025-11-04T08:26:39Z","content_type":"application/pdf","success":1}],"status":"public","quality_controlled":"1","arxiv":1},{"issue":"7","date_updated":"2026-02-17T11:35:53Z","article_processing_charge":"Yes (in subscription journal)","_id":"21241","external_id":{"arxiv":["2502.05502"]},"citation":{"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.” <i>Publications of the Astronomical Society of the Pacific</i>, vol. 137, no. 7, 074202, IOP Publishing, 2025, doi:<a href=\"https://doi.org/10.1088/1538-3873/ade0ea\">10.1088/1538-3873/ade0ea</a>.","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. <i>Publications of the Astronomical Society of the Pacific</i>. 2025;137(7). doi:<a href=\"https://doi.org/10.1088/1538-3873/ade0ea\">10.1088/1538-3873/ade0ea</a>","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).","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.","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. <i>Publications of the Astronomical Society of the Pacific</i>. IOP Publishing. <a href=\"https://doi.org/10.1088/1538-3873/ade0ea\">https://doi.org/10.1088/1538-3873/ade0ea</a>","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.” <i>Publications of the Astronomical Society of the Pacific</i>. IOP Publishing, 2025. <a href=\"https://doi.org/10.1088/1538-3873/ade0ea\">https://doi.org/10.1088/1538-3873/ade0ea</a>.","ieee":"S. Bhattacharjee <i>et al.</i>, “A ZTF search for circumstellar debris transits in White Dwarfs: Six new candidates, one with gas disk emission, identified in a novel metric space,” <i>Publications of the Astronomical Society of the Pacific</i>, vol. 137, no. 7. IOP Publishing, 2025."},"publication_identifier":{"issn":["1538-3873"]},"department":[{"_id":"IlCa"}],"OA_place":"publisher","language":[{"iso":"eng"}],"OA_type":"hybrid","has_accepted_license":"1","publication_status":"published","publisher":"IOP Publishing","oa_version":"Published Version","date_published":"2025-07-09T00:00:00Z","volume":137,"publication":"Publications of the Astronomical Society of the Pacific","license":"https://creativecommons.org/licenses/by/3.0/","intvolume":"       137","file_date_updated":"2026-02-17T11:30:29Z","user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","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.","tmp":{"name":"Creative Commons Attribution 3.0 Unported (CC BY 3.0)","image":"/images/cc_by.png","short":"CC BY (3.0)","legal_code_url":"https://creativecommons.org/licenses/by/3.0/legalcode"},"ddc":["520"],"PlanS_conform":"1","month":"07","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","author":[{"first_name":"Soumyadeep ","last_name":"Bhattacharjee","full_name":"Bhattacharjee, Soumyadeep "},{"first_name":"Zachary P.","last_name":"Vanderbosch","full_name":"Vanderbosch, Zachary P."},{"full_name":"Hollands, Mark A.","last_name":"Hollands","first_name":"Mark A."},{"full_name":"Tremblay, Pier-Emmanuel","last_name":"Tremblay","first_name":"Pier-Emmanuel"},{"full_name":"Xu, Siyi","first_name":"Siyi","last_name":"Xu"},{"full_name":"Guidry, Joseph A.","last_name":"Guidry","first_name":"Joseph A."},{"first_name":"J.J.","last_name":"Hermes","full_name":"Hermes, J.J."},{"last_name":"Caiazzo","first_name":"Ilaria","orcid":"0000-0002-4770-5388","full_name":"Caiazzo, Ilaria","id":"8ae5b6e7-2a03-11ee-914d-b58ed7a3b47d"},{"first_name":"Antonio C.","last_name":"Rodriguez","full_name":"Rodriguez, Antonio C."},{"first_name":"Jan","last_name":"van Roestel","full_name":"van Roestel, Jan"},{"first_name":"Kareem ","last_name":"El-Badry","full_name":"El-Badry, Kareem "},{"first_name":"Andrew J.","last_name":"Drake","full_name":"Drake, Andrew J."},{"first_name":"Benjamin R.","last_name":"Roulston","full_name":"Roulston, Benjamin R."},{"last_name":"Riddle","first_name":"Reed","full_name":"Riddle, Reed"},{"full_name":"Rusholme, Ben","last_name":"Rusholme","first_name":"Ben"},{"full_name":"Groom, Steven L.","last_name":"Groom","first_name":"Steven L."},{"last_name":"Smith","first_name":"Roger","full_name":"Smith, Roger"},{"full_name":"Toloza, Odette","first_name":"Odette","last_name":"Toloza"}],"year":"2025","doi":"10.1088/1538-3873/ade0ea","day":"09","article_number":"074202","article_type":"original","quality_controlled":"1","arxiv":1,"status":"public","abstract":[{"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.","lang":"eng"}],"date_created":"2026-02-16T15:10:51Z","oa":1,"file":[{"file_id":"21289","file_size":8900420,"checksum":"237eddc36e3823b3092fab6aa5bc8655","date_updated":"2026-02-17T11:30:29Z","access_level":"open_access","creator":"dernst","relation":"main_file","success":1,"date_created":"2026-02-17T11:30:29Z","content_type":"application/pdf","file_name":"2025_PASP_Bhattacharjee.pdf"}],"type":"journal_article"}]