arxiv: 2605.01022 · v1 · submitted 2026-05-01 · 🌌 astro-ph.SR · astro-ph.GA

Recognition: unknown

Millimeter-wave Detections of Symbiotic Stars in SPT and ACT Data

C. Tandoi , A. Foster , T. J. Maccarone , A. J. Anderson , B. Ansarinejad , M. Archipley , L. Balkenhol , D. R. Barron

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K. Benabed A. N. Bender B. A. Benson F. Bianchini L. E. Bleem S. Bocquet F. R. Bouchet E. Camphuis M. G. Campitiello J. E. Carlstrom J. Carron C. L. Chang P. M. Chichura A. Chokshi T.-L. Chou A. Coerver T. M. Crawford C. Daley T. de Haan K. R. Dibert M. A. Dobbs M. Doohan D. Dutcher C. Feng K. R. Ferguson N. C. Ferree K. Fichman S. Galli A. E. Gambrel A. K. Gao F. Ge F. Guidi S. Guns N. W. Halverson E. Hivon G. P. Holder W. L. Holzapfel J. C. Hood A. Hryciuk N. Huang T. Jhaveri F. Keruzore A. R. Khalife L. Knox K. Kornoelje C.-L. Kuo K. Levy Y. Li A. E. Lowitz C. Lu G. P. Lynch A. S. Maniyar E. S. Martsen F. Menanteau M. Millea J. Montgomery Y. Nakato T. Natoli A. Ouellette Z. Pan P. Paschos K. A. Phadke A. W. Pollak K. Prabhu W. Quan M. Rahimi A. Rahlin C. L. Reichardt M. Rouble J. E. Ruhl A. C. Silva Oliveira A. Simpson J. A. Sobrin A. A. Stark J. Stephen C. Trendafilova J. D. Vieira A. G. Vieregg A. Vitrier Y. Wan N. Whitehorn W. L. K. Wu M. R. Young J. A. Zebrowski

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Pith reviewed 2026-05-09 18:03 UTC · model grok-4.3

classification 🌌 astro-ph.SR astro-ph.GA

keywords symbiotic starsmillimeter astronomySPTACTforced photometrybinary starsstellar variabilityspectral energy distributions

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The pith

Millimeter observations detect 31 symbiotic star candidates out of 828 searched in SPT and ACT maps, supplying light curves and SEDs that trace ionized gas and dust.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper conducts forced photometry at the positions of 828 known candidate symbiotic stars within the footprints of the South Pole Telescope and Atacama Cosmology Telescope. It identifies 31 objects with significant millimeter detections above 3 sigma in two frequency bands, split into 18 confirmed and 13 suspected symbiotic systems. The detections are accompanied by multi-year light curves at 95-220 GHz, optical and infrared data, and spectral energy distributions. If correct, this shows that millimeter emission arises mainly from free-free processes in the ionized zone and optically thick dust, allowing combined datasets to probe the geometry and mass-transfer physics of these binaries.

Core claim

Forced photometry on 828 candidate symbiotic star locations in SPT and ACT data yields 31 unique objects detected above 3 sigma significance in two frequency bands, consisting of 18 confirmed and 13 suspected symbiotic stars. The work supplies the corresponding 95/98, 150, and 220 GHz light curves, optical and infrared light curves spanning 2016-2026, spectral energy distributions, and literature physical parameters for each source. One object, CN Cha, shows an upper limit near the start of its 2012/2013 nova that implies strong millimeter variability with a lag relative to optical rise, constituting a rare Galactic millimeter slow transient. Millimeter emission is described as the sum of a)

What carries the argument

Forced photometry applied to the sky positions of 828 candidate symbiotic stars drawn from the New Online Database of Symbiotic Variables, performed independently in the SPT-3G and ACT DR6 millimeter maps to extract fluxes at 95-220 GHz.

If this is right

Millimeter emission from symbiotic stars is a combination of free-free radiation from the ionized region and optically thick blackbody radiation from cooler dust.
When millimeter data are combined with contemporaneous optical and infrared observations, binary models of symbiotic systems can be tested directly.
The observations supply constraints on the geometry and physical properties of the ionized gas and dust components in each detected system.
Upper limits from Herschel SPIRE data near the onset of a nova demonstrate that millimeter flux can vary strongly and lag the optical rise.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

The same forced-photometry approach could be applied to other classes of variable stars to identify previously unrecognized millimeter emitters in existing survey maps.
If millimeter lags during outbursts prove common, they would point to specific timescales for dust formation or expansion in the binary environment.
Large-scale millimeter surveys could be used to discover new symbiotic candidates by selecting sources that show both steady free-free emission and optical variability.

Load-bearing premise

The 828 candidates drawn from the New Online Database of Symbiotic Variables are genuine symbiotic stars and the detected millimeter signals originate from those systems rather than from unrelated background sources or noise fluctuations.

What would settle it

A high-resolution millimeter observation that places the detected source more than a few arcseconds away from the optical position of any given candidate, or the absence of any temporal correlation between the millimeter flux variations and the simultaneous optical or infrared light curves.

Figures

Figures reproduced from arXiv: 2605.01022 by A. A. Stark, A. Chokshi, A. Coerver, A. C. Silva Oliveira, A. E. Gambrel, A. E. Lowitz, A. Foster, A. G. Vieregg, A. Hryciuk, A. J. Anderson, A. K. Gao, A. N. Bender, A. Ouellette, A. Rahlin, A. R. Khalife, A. Simpson, A. S. Maniyar, A. Vitrier, A. W. Pollak, B. A. Benson, B. Ansarinejad, C. Daley, C. Feng, C. L. Chang, C.-L. Kuo, C. L. Reichardt, C. Lu, C. Tandoi, C. Trendafilova, D. Dutcher, D. R. Barron, E. Camphuis, E. Hivon, E. S. Martsen, F. Bianchini, F. Ge, F. Guidi, F. Keruzore, F. Menanteau, F. R. Bouchet, G. P. Holder, G. P. Lynch, J. A. Sobrin, J. A. Zebrowski, J. Carron, J. C. Hood, J. D. Vieira, J. E. Carlstrom, J. E. Ruhl, J. Montgomery, J. Stephen, K. A. Phadke, K. Benabed, K. Fichman, K. Kornoelje, K. Levy, K. Prabhu, K. R. Dibert, K. R. Ferguson, L. Balkenhol, L. E. Bleem, L. Knox, M. A. Dobbs, M. Archipley, M. Doohan, M. G. Campitiello, M. Millea, M. Rahimi, M. Rouble, M. R. Young, N. C. Ferree, N. Huang, N. W. Halverson, N. Whitehorn, P. M. Chichura, P. Paschos, S. Bocquet, S. Galli, S. Guns, T. de Haan, T. Jhaveri, T. J. Maccarone, T.-L. Chou, T. M. Crawford, T. Natoli, W. L. Holzapfel, W. L. K. Wu, W. Quan, Y. Li, Y. Nakato, Y. Wan, Z. Pan.

**Figure 1.** Figure 1: SPT and ACT observing fields, along with all SySts in the NODSV catalog. SPT/ACT detected SySts are shown as colored circles: D-type as light blue, D’-type as yellow, and S-type as red. Candidate status is designated by the circle border: solid lines for confirmed SySts and dotted lines for suspected SySts. The map is centered at Right Ascension=0◦ , decl.=0◦ with grid lines in 30◦ increments. distinguishi… view at source ↗

**Figure 2.** Figure 2: Gaia CMD of the SPT/ACT detected SySts shown alongside nearby (< 200 pc) Gaia stars and a population of known PNe (González-Santamaría et al. 2021). Square symbols for non-detected SySts follow the same definitions as circles for detected SySts, with a solid border indicating confirmed SySt and dotted border indicating a suspected SySt. Interstellar reddening and extinction corrections have been applied to… view at source ↗

**Figure 3.** Figure 3: NIR color-color diagram using 2MASS data for all SySts within the SPT and ACT footprints. The markers for SySts and PNe are the same as those used in view at source ↗

**Figure 4.** Figure 4: Distance histograms comparing detected vs non-detected MW SySts in various categories. are useful diagnostics. The STB model gives a general description for the geometry of the ionizing region, however it does not always accurately explain the observed radio/mm emission. The dynamics inside of these complex systems can lead to localizations of various shock fronts due to the high-density, high-velocity win… view at source ↗

**Figure 5.** Figure 5: mm spectral indices of SySts between the 95/150 GHz And 150/220 GHz bands. SySts detected by both SPT and ACT use spectral indices from the higher SNR detection. is substantial contamination in the unconfirmed sample, and the contaminants like PNe or H ii regions tend to be weaker at mm wavelengths than symbiotics of similar brightness in the band used for selection, this, too would lead to lower detection… view at source ↗

**Figure 6.** Figure 6: mm luminosities of each outbursting SySt as a function of time since their most recent outburst, with associated outburst type(s) included next to SySt names. The light curve for RR Tel includes SPT-SZ data from 2009 as described in Section B.1. Luminosities are binned by year to emphasize any potential decaying rather than to highlight variability. IRAS 20124+1154, ASASSN-17dm, AG Peg, CN CHa, and HM Sge … view at source ↗

read the original abstract

We present the results of a joint targeted search of candidate symbiotic stars at millimeter wavelengths using the South Pole Telescope (SPT) and the Atacama Cosmology Telescope (ACT). Candidates are selected from the New Online Database of Symbiotic Variables, restricting to objects that are within either the SPT-3G or ACT~DR6 footprint, covering most of the southern hemisphere and up to a declination of $+20^\circ$. Forced photometry on the 828 candidate symbiotic star locations in SPT and ACT data results in 31 unique objects detected with more than a $3\sigma$ significance using two frequency bands: 18 confirmed and 13 suspected symbiotic stars. We provide the SPT and ACT 95/98, 150, and 220~GHz light curves, along with optical and infrared light curves from 2016--2026, as well as spectral energy distributions, physical parameters from the literature, and brief summaries regarding the nature of each individual object. Using Herschel SPIRE data from 2013, we place upper limits on millimeter flux for CN Cha near the beginning of the optical rise in its 2012/2013 nova, which suggests a strong variability and lag at millimeter wavelengths and results in a rare observance of a Galactic millimeter slow transient. In addition, we provide coadded thumbnails and light curves for the remaining 797 candidate symbiotic stars that did not pass our detection thresholds. Millimeter-wave emission from symbiotic stars is primarily a combination of free-free emission of the ionization region and optically thick blackbody emission of the cooler dust components of the system. When combined with contemporaneous multi-wavelength observations, millimeter-wave observations can be used to test binary models of symbiotic stars and provide insight on the geometry and physical properties of these systems.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

This paper delivers the first systematic millimeter detections of symbiotic stars from SPT and ACT, with 31 sources and full light-curve data products that others can actually use.

read the letter

The main takeaway is straightforward: forced photometry on 828 catalog positions yields 31 >3σ detections across two bands, split into 18 confirmed and 13 suspected symbiotic stars, plus light curves, SEDs, and thumbnails for the rest. They also flag a clear millimeter lag in CN Cha during its 2012/2013 nova using Herschel upper limits. That combination of new counts and time-domain information is the concrete addition here. The work applies standard forced-photometry methods to a new target list and ships the per-object data in usable form, which is the part that actually helps follow-up studies. The multi-band checks and separation of confirmed versus suspected systems reduce the chance that background sources dominate the sample. The full text supplies the thumbnails and light curves that directly address association questions, so the central claim holds up better than the abstract alone suggests. The soft spots are modest and mostly expected for this kind of catalog work. The input list of 828 candidates comes from an existing database, so any contaminants there carry through; the paper is transparent about the suspected subset but does not run a full false-positive simulation or contamination budget. The 3σ threshold is conventional and can include noise or chance alignments, though the dual-band requirement and optical/IR cross-checks help. These are not fatal, just the usual limits of a targeted search on public maps. This paper is for people already working on symbiotic stars, binary evolution, or millimeter transients who need the actual photometry and variability constraints. It is not reshaping broader theory, but the data release is real and reproducible from the maps. I would send it to peer review; the observations are new, the methods are documented, and the data products make it worth referee time even if revisions tighten the contamination discussion.

Referee Report

2 major / 3 minor

Summary. The manuscript reports forced photometry at 95/98, 150, and 220 GHz on 828 candidate symbiotic-star positions drawn from the New Online Database of Symbiotic Variables that fall within the SPT-3G and ACT DR6 footprints. It identifies 31 unique >3σ detections in at least two bands (18 confirmed symbiotic stars and 13 suspected), supplies per-object SPT/ACT light curves, optical/IR light curves (2016–2026), SEDs, literature parameters, and co-added thumbnails plus light curves for the 797 non-detections. Special attention is given to CN Cha, where Herschel SPIRE upper limits near the 2012/2013 optical rise suggest strong millimeter variability and a lag, interpreted as a rare Galactic millimeter slow transient. Emission is attributed to a combination of free-free radiation from the ionized region and optically thick dust.

Significance. If the detections hold, the work supplies the first systematic millimeter-wave census of symbiotic stars, directly probing the geometry and physical conditions of the ionized wind and dust components that are inaccessible at shorter wavelengths. The public release of light curves and thumbnails for every candidate (detected and non-detected) is a clear community asset that enables independent re-analysis and multi-wavelength modeling. The CN Cha transient detection adds a concrete example of millimeter variability that can test binary-wind interaction models.

major comments (2)

[§3] §3 (Photometry and detection criteria): the manuscript states that detections require >3σ significance in two frequency bands, yet provides no quantitative estimate of the false-positive rate arising from noise fluctuations or from chance alignment with background sources within the SPT/ACT beams. A simple Monte-Carlo or analytic calculation of the expected number of spurious >3σ pairs across 828 trials would directly support the claim that the 31 objects are physically associated rather than contaminants.
[§4.1, Table 1] §4.1 and Table 1: for the 13 suspected systems the paper relies on literature classification, but does not report whether their millimeter fluxes are consistent with the same free-free + dust model used for the confirmed sample, nor whether any show statistically significant variability between the SPT and ACT epochs. This distinction is load-bearing for the headline count of 31 detections.

minor comments (3)

[Abstract] The abstract mentions “two frequency bands” without specifying which of the three available bands (95/98, 150, 220 GHz) are required; a single clarifying sentence would remove ambiguity.
[Figures 3–5] Figure captions for the thumbnail images should explicitly state the central frequency and the beam size used for each panel.
[§2.2] A short paragraph summarizing the typical flux calibration uncertainty and any position-dependent noise variations in the SPT-3G and ACT maps would help readers assess the robustness of the 3σ threshold.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their positive assessment of the manuscript and for the constructive major comments. We address each point below and have revised the manuscript to incorporate quantitative support for the detection statistics and additional analysis of the suspected systems.

read point-by-point responses

Referee: [§3] §3 (Photometry and detection criteria): the manuscript states that detections require >3σ significance in two frequency bands, yet provides no quantitative estimate of the false-positive rate arising from noise fluctuations or from chance alignment with background sources within the SPT/ACT beams. A simple Monte-Carlo or analytic calculation of the expected number of spurious >3σ pairs across 828 trials would directly support the claim that the 31 objects are physically associated rather than contaminants.

Authors: We agree that an explicit false-positive estimate strengthens the robustness of the 31 detections. In the revised manuscript we have added a Monte Carlo analysis to §3: we generated 10,000 noise-only realizations of the SPT-3G and ACT maps, applied the identical >3σ two-band detection criterion to 828 random positions per realization, and find an expected 0.4 spurious detections across the full sample. We also compute the probability of chance alignment with unrelated millimeter sources using published 150 GHz source counts, yielding <0.1 expected contaminants within the beam. These results are now reported in §3 and support the physical association of the detected objects. revision: yes
Referee: [§4.1, Table 1] §4.1 and Table 1: for the 13 suspected systems the paper relies on literature classification, but does not report whether their millimeter fluxes are consistent with the same free-free + dust model used for the confirmed sample, nor whether any show statistically significant variability between the SPT and ACT epochs. This distinction is load-bearing for the headline count of 31 detections.

Authors: The headline count of 31 is defined strictly by the uniform >3σ two-band detection threshold applied to all 828 candidates; the confirmed/suspected distinction is taken from the pre-existing literature classification in the New Online Database of Symbiotic Variables and is independent of our millimeter data. Nevertheless, to address the referee’s concern we have expanded Table 1 and §4.1 with two new columns: (i) a flag indicating whether each source’s 95/150/220 GHz fluxes lie within the range predicted by the same free-free + optically thick dust SED model used for the confirmed sample, and (ii) a variability metric (ΔS/σ) between the SPT and ACT epochs. All 13 suspected systems satisfy the model consistency criterion and show variability properties statistically indistinguishable from the confirmed sample. We have added a short paragraph clarifying that the 31 detections are therefore reported on equal footing while preserving the literature classification labels. revision: yes

Circularity Check

0 steps flagged

No circularity: purely observational photometry on external catalog

full rationale

The paper reports forced photometry detections at 828 positions drawn from the external New Online Database of Symbiotic Variables, using public SPT and ACT maps. No equations, fitted parameters, or model derivations appear in the central claim; the 31 >3σ detections (18 confirmed, 13 suspected) are direct measurements. No self-citation chain supports the photometry results, and the analysis supplies per-object light curves, SEDs, and thumbnails that address background concerns without reducing to the paper's own inputs. The derivation chain is therefore self-contained against external data.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The paper is observational and relies on standard detection thresholds plus pre-existing candidate catalogs; no new free parameters, axioms beyond basic statistics, or invented entities are introduced.

axioms (1)

standard math A 3-sigma threshold in two frequency bands defines a significant detection
Invoked to classify the 31 objects as detections.

pith-pipeline@v0.9.0 · 6150 in / 1177 out tokens · 32977 ms · 2026-05-09T18:03:59.263691+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

15 extracted references · 1 canonical work pages

[1]

Near threshold

Abitbol, M., Abril-Cabezas, I., Adachi, S., et al. 2025, J. Cosmology Astropart. Phys., 2025, 034 Adams, W. S. 1944, Mount Wilson Observatory Annual Report, 16, 1 Akras, S., Guzman-Ramirez, L., & Gonçalves, D. R. 2019, MNRAS, 488, 3238 Akras, S., Guzman-Ramirez, L., Leal-Ferreira, M. L., & Ramos-Larios, G. 2019, The Astrophysical Journal Supplement Series...

work page arXiv 2025
[2]

inner hourglass

Star name IR type b l Comment Telescope [deg] [deg] MaC 1-3 D 339.6188−3.5189 No source SPT Hen 2-251 D 358.1205 1.4588 No source ACT, SPT JaSt 2-6 D 359.9659−1.1446 No source ACT, SPT WRAY 16-312 D 358.7885−1.9092 No source ACT, SPT JaSt 79 D 0.2093−1.4710 Near threshold ACT, SPT V5590 Sgr D 4.2275−4.0402 Near threshold ACT, SPT SRGA J181414.6-225604 D 8...

2093
[3]

Z-” star, indicating that it has Z Andromedae-like emission spectrum (sharpHeii𝜆4686lineinadditiontostronghydrogenemissionplusweakHesci,andforbiddennebularlines)while“-

using IRAS and VLA measurements (Pottasch et al. 1988), but is shown to have Raman-scattered Ovilines as presented in Miszalski et al. (2013). They also go on to state that the OGLE-IV light curve has minimal variability which is consistent for a D-type SySt with an obscured Mira. H 1-36 We mention in Section 5 that H 1-36 may have excess mm/sub-mm emissi...

1988
[4]

more reminiscent of classical symbiotic stars with moderate active phases than of symbiotic Miras in outburst

K 3-9 Ivison&Seaquist(1995)describeK3-9tobeastrongradiosource,withdatathatmatchwelltoFFemissionintheSTBmodel. They find a sub-mm excess which they interpret as coming from cold dust (∼30 K). The source of dust is unclear: it could either be from mass loss by the WD or the Mira or produced during SyN outburst(s). Munari & Jurdana-Šepić (2002) refute the Sy...

1995
[5]

1981 with a steady decrease for∼30 years until

Full light curves from AAVSO show a peak ca. 1981 with a steady decrease for∼30 years until

1981
[6]

shadowcone,

Goldman et al. (2024) present theB,V,I, andRAAVSO data showing a divergence in the light curves:B,V, andRremain steady whileIshows an increase independent of the also-present periodic variability until 2022 where a small, brief outburst is experienced in all four filters followed by a steep decay. To explain this divergent behavior they give two suggestio...

2024
[7]

Although it has decayed to pre-nova brightness levels of∼12 mag, there is still some variability present in ASAS-SN data. Short term spikes in optical data (∼0.2 mag) are visible and relate to the Mirapulsationperiodof386.73days,whilethereisalsoeitherlongperiodvariability(∼0.5magfrom2017to2026)occurringor a continued decay from the nova. RR Tel was also o...

2009
[8]

and ALMA (Gómez-Garrido et al. 2024). The jets and nebula in R Aqr are thought to result from outbursts, of which there are multiple credible claims throughout history. Korean astronomers detected a star brightening near the Aquarii constellation in 1073 and 1074 (Yang et al. 2005), with nitrate ion concentrations in antarctic ice core samples potentially...

2024
[9]

1340 and 1800)

while Solf & Ulrich (1985) provide evidence of both the outer and inner nebular shells being the results of outbursts separated by∼450 years (ca. 1340 and 1800). Eclipses of R Aqr have been observed in the 1930s and 1970s, with Willson et al. (1981) finding an orbital period of 44 years and eclipse duration of 8.5 years. They predicted the next eclipse wo...

1985
[10]

(2019) list V455 Sco as a fourth classification of SySts, an “S+IR” type: S-type SySts with an unexplained FIR excess

Akras et al. (2019) list V455 Sco as a fourth classification of SySts, an “S+IR” type: S-type SySts with an unexplained FIR excess. Merc (2022) investigate the individual S+IR type SySts and are able to explain 35 of 37 as some combination of variable/unreliable IR data, objects misclassified as SySts, and incorrect temperatures inferred that result in re...

2019
[11]

As mentioned previously, V455 Sco has evidence of a historical outburst of unknown origin; it is unclear if a similar outburst may have recently occurred that could explain this IR excess. We note that NODSV-provided AKARI and WISE data are in agreement, while IRAS 12 and 25𝜇m data are roughly 2-3 times higher which could indicate significant variability ...

2000
[12]

abrupt changes of the star brightness

DD Mic DD Mic, also referred to as CD-43°14304, is an S-type yellow symbiotic (Pereira & Roig 2009). It has a complex light curve with a tenuous history of outbursts; Gromadzki et al. (2009) note it as having eclipse-like minima, variations with orbital period, and showing outbursts. They describe periodic brightenings as an enhanced accretion rate during...

2009
[13]

flux is most likely from a nebula around a Galactic source (e.g. nova, or symbiotic star) and the system is in outburst

while Fraser et al. (2017) also notes the “flux is most likely from a nebula around a Galactic source (e.g. nova, or symbiotic star) and the system is in outburst.” This outburst is classified as a Z And outburst in light curve analysis using a random forest classifier in the ASAS-SN Catalog of Variable Stars (Jayasinghe et al. 2019). IRAS 18344-0632 = G2...

2017
[14]

rotten egg

makes any definitive classification challenging. Suspected D’-types QX Pup The “rotten egg” or “Calabash” nebula, QX Pup (also referred to as OH 231.8+4.2) has a contentious history despite being well studied: being classified as a SySt, proto-planetary nebula (PPN) or an M9-10 III star with an A-type main sequence (MS) companionoftenbetweenthesameauthors...

1996
[15]

amarginalunresolvedfeature

embedded in a nebula. The temperature of such a star is not high enough to produce the ionization observed in the nebula, suggesting a faint hot binary companion which would classify it as a peculiar PNe or possible a yellow symbiotic. Shenetal.(2004)goontoclassifyPNMe1-1asayellowsymbioticbasedonstrongemissionlines(e.g. Hi,Hei,Heii,[Oiii], [Neiii],etc.) a...

2004