Pub Date : 2026-01-30DOI: 10.1051/0004-6361/202557649
A. Choplin, L. Siess, S. Goriely, P. Eggenberger, F. D. Moyano
Context. The intermediate neutron-capture process (i-process) can occur during proton ingestion events (PIEs), which may take place in the early evolutionary phases of asymptotic giant branch (AGB) stars.Aims. We investigate the impact of rotational and magnetic mixing on i-process nucleosynthesis in low-metallicity, low-mass AGB stars.Methods. We computed AGB models with [Fe/H] = −2.5 and −1.7 and initial masses of 1 and 1.5 M⊙ using the STAREVOL code, including a network of 1160 nuclei coupled to transport equations. Rotating models incorporate a calibrated Tayler-Spruit (TS) dynamo to account for core rotation rates inferred from asteroseismic observations of solar-metallicity sub-giants and giants. Initial rotation velocities of 0, 30, and 90 km s−1 were considered, along with varying assumptions for magnetic mixing.Results. Rotation without magnetic fields strongly suppresses the i-process due to the production of primary 14N, which is subsequently converted into 22Ne – a potent neutron poison during the PIE. Including magnetic fields via the TS dynamo restores the models close to their non-rotating counterparts: strong core-envelope coupling suppresses shear mixing and prevents primary 14N synthesis, yielding i-process nucleosynthesis similar to non-rotating models. We also find that rotational mixing during the AGB phase is insufficient to affect the occurrence of PIEs.Conclusions. Proton ingestion event-driven nucleosynthesis proceeds similarly in asteroseismic-calibrated magnetic rotating AGB stars and non-rotating stars, producing identical abundance patterns.
上下文。中间中子捕获过程（i-process）可能发生在质子摄取事件（pie）中，这可能发生在渐近巨支（AGB）恒星的早期演化阶段。我们研究了旋转和磁性混合对低金属丰度、低质量AGB星i-过程核合成的影响。我们使用STAREVOL代码计算了[Fe/H] = - 2.5和- 1.7，初始质量为1和1.5 M⊙的AGB模型，包括一个由1160个核组成的网络，耦合到输运方程。旋转模型包括一个校准的泰勒-斯普雷特（TS）发电机，以解释从太阳金属丰度次巨星和巨星的星震观测推断出的核心旋转速率。考虑了0、30和90 km s−1的初始旋转速度，以及对磁混合的不同假设。没有磁场的旋转强烈地抑制了i过程，因为产生了初级14N，随后在PIE过程中转化为22Ne——一种强大的中子毒素。通过TS发电机加入磁场使模型恢复到接近非旋转模型的状态：强核包膜耦合抑制剪切混合并阻止初级14N合成，产生类似于非旋转模型的i-过程核合成。我们还发现，AGB阶段的旋转混合不足以影响pie的发生。质子摄取事件驱动的核合成在星震校准的磁旋转AGB恒星和非旋转恒星中进行类似，产生相同的丰度模式。
{"title":"The intermediate neutron capture process","authors":"A. Choplin, L. Siess, S. Goriely, P. Eggenberger, F. D. Moyano","doi":"10.1051/0004-6361/202557649","DOIUrl":"https://doi.org/10.1051/0004-6361/202557649","url":null,"abstract":"<i>Context.<i/> The intermediate neutron-capture process (i-process) can occur during proton ingestion events (PIEs), which may take place in the early evolutionary phases of asymptotic giant branch (AGB) stars.<i>Aims.<i/> We investigate the impact of rotational and magnetic mixing on i-process nucleosynthesis in low-metallicity, low-mass AGB stars.<i>Methods.<i/> We computed AGB models with [Fe/H] = −2.5 and −1.7 and initial masses of 1 and 1.5 <i>M<i/><sub>⊙<sub/> using the STAREVOL code, including a network of 1160 nuclei coupled to transport equations. Rotating models incorporate a calibrated Tayler-Spruit (TS) dynamo to account for core rotation rates inferred from asteroseismic observations of solar-metallicity sub-giants and giants. Initial rotation velocities of 0, 30, and 90 km s<sup>−1<sup/> were considered, along with varying assumptions for magnetic mixing.<i>Results.<i/> Rotation without magnetic fields strongly suppresses the i-process due to the production of primary <sup>14<sup/>N, which is subsequently converted into <sup>22<sup/>Ne – a potent neutron poison during the PIE. Including magnetic fields via the TS dynamo restores the models close to their non-rotating counterparts: strong core-envelope coupling suppresses shear mixing and prevents primary <sup>14<sup/>N synthesis, yielding i-process nucleosynthesis similar to non-rotating models. We also find that rotational mixing during the AGB phase is insufficient to affect the occurrence of PIEs.<i>Conclusions.<i/> Proton ingestion event-driven nucleosynthesis proceeds similarly in asteroseismic-calibrated magnetic rotating AGB stars and non-rotating stars, producing identical abundance patterns.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"290 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146098082","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-30DOI: 10.1051/0004-6361/202558482
Wenjie Zhang
In this Letter, we report the detection of soft X-ray time lags – i.e., variability in the softer photons lagging behind that in the harder photons – in seven XMM–Newton observations of the tidal disruption event (TDE) candidate AT2021ehb. We find correlated variability between the soft (0.3–0.7 keV) and hard (0.9–10 keV) bands on ∼104 s timescales, and measure a soft lag of ∼500 s. This behavior is broadly consistent with the disk–corona reverberation scenario established in active galactic nuclei (AGNs). Together with the previously reported strong hard X-ray emission and broad Fe K line, our results suggest the presence of a compact corona and prominent relativistic disk reflection in AT2021ehb. The unusually high blackbody temperature (peaking at ∼200 eV) is difficult to reconcile with thermal emission from a standard accretion disk around a ∼107M⊙ black hole, and may instead be analogous to the soft excess commonly observed in AGNs, whose physical origin remains debated. Finally, the measured lags offer a possible explanation for the rapid X-ray flux decline that occurred only three days after the peak, pointing to a scenario in which the corona cools following a sudden loss of the magnetic support required to sustain it.
{"title":"Discovery of a soft X-ray lag in the tidal disruption event AT2021ehb","authors":"Wenjie Zhang","doi":"10.1051/0004-6361/202558482","DOIUrl":"https://doi.org/10.1051/0004-6361/202558482","url":null,"abstract":"In this Letter, we report the detection of soft X-ray time lags – i.e., variability in the softer photons lagging behind that in the harder photons – in seven <i>XMM–Newton<i/> observations of the tidal disruption event (TDE) candidate AT2021ehb. We find correlated variability between the soft (0.3–0.7 keV) and hard (0.9–10 keV) bands on ∼10<sup>4<sup/> s timescales, and measure a soft lag of ∼500 s. This behavior is broadly consistent with the disk–corona reverberation scenario established in active galactic nuclei (AGNs). Together with the previously reported strong hard X-ray emission and broad Fe K line, our results suggest the presence of a compact corona and prominent relativistic disk reflection in AT2021ehb. The unusually high blackbody temperature (peaking at ∼200 eV) is difficult to reconcile with thermal emission from a standard accretion disk around a ∼10<sup>7<sup/> <i>M<i/><sub>⊙<sub/> black hole, and may instead be analogous to the soft excess commonly observed in AGNs, whose physical origin remains debated. Finally, the measured lags offer a possible explanation for the rapid X-ray flux decline that occurred only three days after the peak, pointing to a scenario in which the corona cools following a sudden loss of the magnetic support required to sustain it.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"81 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146098078","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1051/0004-6361/202557127
Q. Kral, J. Wang, J. Kammerer, S. Lacour, M. Malin, T. Winterhalder, B. Charnay, C. Perrot, P. Huet, R. Abuter, A. Amorim, W. O. Balmer, M. Benisty, J.-P. Berger, H. Beust, S. Blunt, A. Boccaletti, M. Bonnefoy, H. Bonnet, M. S. Bordoni, G. Bourdarot, W. Brandner, F. Cantalloube, P. Caselli, G. Chauvin, A. Chavez, A. Chomez, E. Choquet, V. Christiaens, Y. Clénet, V. Coudé du Foresto, A. Cridland, R. Davies, R. Dembet, J. Dexter, A. Drescher, G. Duvert, A. Eckart, F. Eisenhauer, N. M. Förster Schreiber, P. Garcia, R. Garcia Lopez, T. Gardner, E. Gendron, R. Genzel, S. Gillessen, J. H. Girard, S. Grant, X. Haubois, Th. Henning, S. Hinkley, S. Hippler, M. Houllé, Z. Hubert, L. Jocou, M. Keppler, P. Kervella, L. Kreidberg, N. T. Kurtovic, A.-M. Lagrange, V. Lapeyrère, J.-B. Le Bouquin, D. Lutz, A.-L. Maire, F. Mang, G.-D. Marleau, A. Mérand, P. Mollière, J. D. Monnier, C. Mordasini, D. Mouillet, E. Nasedkin, M. Nowak, T. Ott, G. P. P. L. Otten, C. Paladini, T. Paumard, K. Perraut, G. Perrin, O. Pfuhl, N. Pourré, L. Pueyo, D. C. Ribeiro, E. Rickman, Z. Rustamkulov, J. Shangguan, T. Shimizu, D. Sing, J. Stadler, T. Stolker, O. Straub, C. Straubmeier, E. Sturm, L. J. Tacconi, A. Vigan, F. Vincent, S. D. von Fellenberg, F. Widmann, J. Woillez, S. Yazici, K. Abd El Dayem, N. Aimar, A. Berdeu, C. Correia, D. Defrère, M. Fabricius, H. Feuchtgruber, A. Foschi, S. F. Hönig, S. Joharle, R. Laugier, O. Lai, J. Leftley, B. Lopez, F. Millour, M. Montargès, N. Morujão, H. Nowacki, J. Osorno, R. Petrov, P. O. Petrucci, S. Rabien, S. Robbe-Dubois, M. Sadun Bordoni, J. Sánchez Bermúdez, D. Santos, J. Sauter, J. Scigliuto, F. Soulez, M. Subroweit, C. Sykes
Context. This study presents the first application of high-precision astrometry to search for exomoons around substellar companions, as this field remains largely unexplored.Aims. We investigate whether the orbital motion of the companion HD 206893 B exhibits astrometric residuals consistent with the gravitational influence of an exomoon or binary planet.Methods. Using the VLTI/GRAVITY instrument, we monitored the astrometric positions of HD 206893 B and c on short (days to months) and long (yearly) timescales. This enabled us to isolate potential residual wobbles in the motion of component B attributable to an orbiting moon.Results. Our analysis reveals tentative astrometric residuals in the HD 206893 B orbit. If interpreted as an exomoon signature, these residuals correspond to a candidate (HD 206893 B I) with an orbital period of approximately 0.76 years and a mass of ~0.4 Jupiter masses. However, the origin of these residuals remains ambiguous and could be due to systematics. Complementing the astrometry, our analysis of GRAVITY R = 4000 spectroscopy for HD 206893 B confirms a clear detection of water, but no CO was found using cross-correlation. We also found that AF Lep b, and β Pic b are the best short-term candidates to look for moons with GRAVITY+.Conclusions. Our observations demonstrate the transformative potential of high-precision astrometry in the search for exomoons and proves the feasibility of the technique to detect moons with masses lower than Jupiter and potentially down to less than Neptune in optimistic cases. Crucially, further high-precision astrometric observations with VLTI/GRAVITY are essential to verify the reality and nature of this signal and apply this technique to a range of planetary systems.
{"title":"Exomoon search with VLTI/GRAVITY around the substellar companion HD 206893 B","authors":"Q. Kral, J. Wang, J. Kammerer, S. Lacour, M. Malin, T. Winterhalder, B. Charnay, C. Perrot, P. Huet, R. Abuter, A. Amorim, W. O. Balmer, M. Benisty, J.-P. Berger, H. Beust, S. Blunt, A. Boccaletti, M. Bonnefoy, H. Bonnet, M. S. Bordoni, G. Bourdarot, W. Brandner, F. Cantalloube, P. Caselli, G. Chauvin, A. Chavez, A. Chomez, E. Choquet, V. Christiaens, Y. Clénet, V. Coudé du Foresto, A. Cridland, R. Davies, R. Dembet, J. Dexter, A. Drescher, G. Duvert, A. Eckart, F. Eisenhauer, N. M. Förster Schreiber, P. Garcia, R. Garcia Lopez, T. Gardner, E. Gendron, R. Genzel, S. Gillessen, J. H. Girard, S. Grant, X. Haubois, Th. Henning, S. Hinkley, S. Hippler, M. Houllé, Z. Hubert, L. Jocou, M. Keppler, P. Kervella, L. Kreidberg, N. T. Kurtovic, A.-M. Lagrange, V. Lapeyrère, J.-B. Le Bouquin, D. Lutz, A.-L. Maire, F. Mang, G.-D. Marleau, A. Mérand, P. Mollière, J. D. Monnier, C. Mordasini, D. Mouillet, E. Nasedkin, M. Nowak, T. Ott, G. P. P. L. Otten, C. Paladini, T. Paumard, K. Perraut, G. Perrin, O. Pfuhl, N. Pourré, L. Pueyo, D. C. Ribeiro, E. Rickman, Z. Rustamkulov, J. Shangguan, T. Shimizu, D. Sing, J. Stadler, T. Stolker, O. Straub, C. Straubmeier, E. Sturm, L. J. Tacconi, A. Vigan, F. Vincent, S. D. von Fellenberg, F. Widmann, J. Woillez, S. Yazici, K. Abd El Dayem, N. Aimar, A. Berdeu, C. Correia, D. Defrère, M. Fabricius, H. Feuchtgruber, A. Foschi, S. F. Hönig, S. Joharle, R. Laugier, O. Lai, J. Leftley, B. Lopez, F. Millour, M. Montargès, N. Morujão, H. Nowacki, J. Osorno, R. Petrov, P. O. Petrucci, S. Rabien, S. Robbe-Dubois, M. Sadun Bordoni, J. Sánchez Bermúdez, D. Santos, J. Sauter, J. Scigliuto, F. Soulez, M. Subroweit, C. Sykes","doi":"10.1051/0004-6361/202557127","DOIUrl":"https://doi.org/10.1051/0004-6361/202557127","url":null,"abstract":"<i>Context<i/>. This study presents the first application of high-precision astrometry to search for exomoons around substellar companions, as this field remains largely unexplored.<i>Aims<i/>. We investigate whether the orbital motion of the companion HD 206893 B exhibits astrometric residuals consistent with the gravitational influence of an exomoon or binary planet.<i>Methods<i/>. Using the VLTI/GRAVITY instrument, we monitored the astrometric positions of HD 206893 B and c on short (days to months) and long (yearly) timescales. This enabled us to isolate potential residual wobbles in the motion of component B attributable to an orbiting moon.<i>Results<i/>. Our analysis reveals tentative astrometric residuals in the HD 206893 B orbit. If interpreted as an exomoon signature, these residuals correspond to a candidate (HD 206893 B I) with an orbital period of approximately 0.76 years and a mass of ~0.4 Jupiter masses. However, the origin of these residuals remains ambiguous and could be due to systematics. Complementing the astrometry, our analysis of GRAVITY <i>R<i/> = 4000 spectroscopy for HD 206893 B confirms a clear detection of water, but no CO was found using cross-correlation. We also found that AF Lep b, and <i>β<i/> Pic b are the best short-term candidates to look for moons with GRAVITY+.<i>Conclusions<i/>. Our observations demonstrate the transformative potential of high-precision astrometry in the search for exomoons and proves the feasibility of the technique to detect moons with masses lower than Jupiter and potentially down to less than Neptune in optimistic cases. Crucially, further high-precision astrometric observations with VLTI/GRAVITY are essential to verify the reality and nature of this signal and apply this technique to a range of planetary systems.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"2 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146073390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1051/0004-6361/202558046
I. A. Zinchenko, J. M. Vílchez, C. Kehrig, P. Papaderos, J. E. Méndez-Delgado
We present new precise measurements of the electron temperatures and oxygen abundances in the southeast knot of I Zw 18, one of the most metal poor blue compact dwarf galaxies known. We used spectroscopic data from the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1). For the first time in I Zw 18, we directly measured the electron temperature in the low-ionization zone using the rarely detected [O II]λλ7320,7330 doublet. We also detected the [O III]λ4363 and [S III]λ6312 auroral lines, which are associated with high- and intermediate-ionization zones, respectively. We derived Te([O III]) = 21 200 ± 860 K, Te([O II]) = 16 170 ± 950 K, and Te([S III]) = 17 290±1750, which highlights a significant temperature difference between the ionization zones. Using these direct temperature measurements, we determined a total oxygen abundance of 12+log(O/H) = 7.066 ± 0.046, log(N/O) = –1.509 ± 0.097, and log(S/O) = –1.558 ± 0.041. Our results extend the calibration of t2 − t3 relations to the highest temperatures and provide important anchor points for the temperature structure of extremely metal-poor H II regions, including high-redshift galaxies, for which direct temperature measurements are especially challenging.
{"title":"First direct electron temperature measurement in [O II] zone in I Zw 18","authors":"I. A. Zinchenko, J. M. Vílchez, C. Kehrig, P. Papaderos, J. E. Méndez-Delgado","doi":"10.1051/0004-6361/202558046","DOIUrl":"https://doi.org/10.1051/0004-6361/202558046","url":null,"abstract":"We present new precise measurements of the electron temperatures and oxygen abundances in the southeast knot of I Zw 18, one of the most metal poor blue compact dwarf galaxies known. We used spectroscopic data from the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1). For the first time in I Zw 18, we directly measured the electron temperature in the low-ionization zone using the rarely detected [O II]<i>λλ<i/>7320,7330 doublet. We also detected the [O III]<i>λ<i/>4363 and [S III]<i>λ<i/>6312 auroral lines, which are associated with high- and intermediate-ionization zones, respectively. We derived T<sub><i>e<i/><sub/>([O III]) = 21 200 ± 860 K, T<sub><i>e<i/><sub/>([O II]) = 16 170 ± 950 K, and T<sub><i>e<i/><sub/>([S III]) = 17 290±1750, which highlights a significant temperature difference between the ionization zones. Using these direct temperature measurements, we determined a total oxygen abundance of 12+log(O/H) = 7.066 ± 0.046, log(N/O) = –1.509 ± 0.097, and log(S/O) = –1.558 ± 0.041. Our results extend the calibration of <i>t<i/><sub>2<sub/> − <i>t<i/><sub>3<sub/> relations to the highest temperatures and provide important anchor points for the temperature structure of extremely metal-poor H II regions, including high-redshift galaxies, for which direct temperature measurements are especially challenging.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"43 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146073388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1051/0004-6361/202555798
M. Archipley, A. Hryciuk, L. E. Bleem, K. Kornoelje, M. Klein, A. J. Anderson, B. Ansarinejad, M. Aravena, L. Balkenhol, P. S. Barry, K. Benabed, A. N. Bender, B. A. Benson, F. Bianchini, S. Bocquet, F. R. Bouchet, E. Camphuis, M. G. Campitiello, J. E. Carlstrom, J. Cathey, C. L. Chang, S. C. Chapman, P. Chaubal, P. M. Chichura, A. Chokshi, T.-L. Chou, A. Coerver, T. M. Crawford, C. Daley, T. de Haan, R. P. Deane, K. R. Dibert, M. A. Dobbs, M. Doohan, A. Doussot, D. Dutcher, W. Everett, C. Feng, K. R. Ferguson, K. Fichman, B. Floyd, A. Foster, S. Galli, A. E. Gambrel, R. W. Gardner, F. Ge, N. Goeckner-Wald, A. Gonzalez, S. Grandis, T. R. Greve, R. Gualtieri, F. Guidi, S. Guns, N. W. Halverson, R. Hill, E. Hivon, G. P. Holder, W. L. Holzapfel, J. C. Hood, N. Huang, F. Kéruzoré, A. R. Khalife, L. Knox, M. Korman, C.-L. Kuo, K. Levy, A. E. Lowitz, C. Lu, G. P. Lynch, A. Maniyar, E. S. Martsen, F. Menanteau, M. Millea, J. Montgomery, Y. Nakato, T. Natoli, G. I. Noble, Y. Omori, A. Ouellette, Z. Pan, K. A. Phadke, A. W. Pollak, K. Prabhu, W. Quan, S. Raghunathan, M. Rahimi, A. Rahlin, C. L. Reichardt, C. Reuter, M. Rouble, J. E. Ruhl, E. Schiappucci, A. Simpson, J. A. Sobrin, B. Stalder, A. A. Stark, N. Sulzenauer, C. Tandoi, B. Thorne, C. Trendafilova, C. Umilta, J. D. Vieira, A. Vitrier, D. Vizgan, Y. Wan, A. Weiß, N. Whitehorn, W. L. K. Wu, M. R. Young, J. A. Zebrowski, D. Zhou
Context. The South Pole Telescope third-generation camera (SPT-3G) has observed over 10 000 square degrees of sky at 95, 150, and 220 GHz (3.3, 2.0, 1.4 mm, respectively) and will significantly overlap the ongoing 14 000 square-degree Euclid Wide Survey. The Euclid collaboration recently released Euclid Deep Field South (EDF-S) observations of 23 square degrees at wide field depths in the first quick data release (Q1).Aims. With the goal of releasing complementary millimeter-wave data and encouraging legacy science, we performed dedicated observations of a 57-square-degree field overlapping the EDF-S.Methods. The observing time totaled 20 days, and we reached noise depths of 4.3, 3.8, and 13.2 μK-arcmin at 95, 150, and 220 GHz, respectively.Results. In this work we present the temperature maps and two catalogs constructed from these data. The emissive source catalog contains 601 objects (334 inside EDF-S) with 54% synchrotron-dominated sources and 46% thermal dust emission-dominated sources. The 5σ detection thresholds are 1.7, 2.0, and 6.5 mJy in the three bands. The cluster catalog contains 217 cluster candidates (121 inside EDF-S) with median mass M500c = 2.12 × 1014M⊙/h70 and median redshift z = 0.70, corresponding to an order-of-magnitude improvement in cluster density over previous tSZ-selected catalogs in this region (3.81 clusters per square degree).Conclusions. The overlap between SPT and Euclid data will enable a range of multiwavelength studies of the aforementioned source populations. This work serves as the first step toward joint projects between SPT and Euclid and provides a rich dataset containing information on galaxies, clusters, and their environments.
{"title":"Millimeter-wave observations of Euclid Deep Field South using the South Pole Telescope","authors":"M. Archipley, A. Hryciuk, L. E. Bleem, K. Kornoelje, M. Klein, A. J. Anderson, B. Ansarinejad, M. Aravena, L. Balkenhol, P. S. Barry, K. Benabed, A. N. Bender, B. A. Benson, F. Bianchini, S. Bocquet, F. R. Bouchet, E. Camphuis, M. G. Campitiello, J. E. Carlstrom, J. Cathey, C. L. Chang, S. C. Chapman, P. Chaubal, P. M. Chichura, A. Chokshi, T.-L. Chou, A. Coerver, T. M. Crawford, C. Daley, T. de Haan, R. P. Deane, K. R. Dibert, M. A. Dobbs, M. Doohan, A. Doussot, D. Dutcher, W. Everett, C. Feng, K. R. Ferguson, K. Fichman, B. Floyd, A. Foster, S. Galli, A. E. Gambrel, R. W. Gardner, F. Ge, N. Goeckner-Wald, A. Gonzalez, S. Grandis, T. R. Greve, R. Gualtieri, F. Guidi, S. Guns, N. W. Halverson, R. Hill, E. Hivon, G. P. Holder, W. L. Holzapfel, J. C. Hood, N. Huang, F. Kéruzoré, A. R. Khalife, L. Knox, M. Korman, C.-L. Kuo, K. Levy, A. E. Lowitz, C. Lu, G. P. Lynch, A. Maniyar, E. S. Martsen, F. Menanteau, M. Millea, J. Montgomery, Y. Nakato, T. Natoli, G. I. Noble, Y. Omori, A. Ouellette, Z. Pan, K. A. Phadke, A. W. Pollak, K. Prabhu, W. Quan, S. Raghunathan, M. Rahimi, A. Rahlin, C. L. Reichardt, C. Reuter, M. Rouble, J. E. Ruhl, E. Schiappucci, A. Simpson, J. A. Sobrin, B. Stalder, A. A. Stark, N. Sulzenauer, C. Tandoi, B. Thorne, C. Trendafilova, C. Umilta, J. D. Vieira, A. Vitrier, D. Vizgan, Y. Wan, A. Weiß, N. Whitehorn, W. L. K. Wu, M. R. Young, J. A. Zebrowski, D. Zhou","doi":"10.1051/0004-6361/202555798","DOIUrl":"https://doi.org/10.1051/0004-6361/202555798","url":null,"abstract":"<i>Context<i/>. The South Pole Telescope third-generation camera (SPT-3G) has observed over 10 000 square degrees of sky at 95, 150, and 220 GHz (3.3, 2.0, 1.4 mm, respectively) and will significantly overlap the ongoing 14 000 square-degree <i>Euclid<i/> Wide Survey. The <i>Euclid<i/> collaboration recently released <i>Euclid<i/> Deep Field South (EDF-S) observations of 23 square degrees at wide field depths in the first quick data release (Q1).<i>Aims<i/>. With the goal of releasing complementary millimeter-wave data and encouraging legacy science, we performed dedicated observations of a 57-square-degree field overlapping the EDF-S.<i>Methods<i/>. The observing time totaled 20 days, and we reached noise depths of 4.3, 3.8, and 13.2 μK-arcmin at 95, 150, and 220 GHz, respectively.<i>Results<i/>. In this work we present the temperature maps and two catalogs constructed from these data. The emissive source catalog contains 601 objects (334 inside EDF-S) with 54% synchrotron-dominated sources and 46% thermal dust emission-dominated sources. The 5σ detection thresholds are 1.7, 2.0, and 6.5 mJy in the three bands. The cluster catalog contains 217 cluster candidates (121 inside EDF-S) with median mass <i>M<i/><sub>500c<sub/> = 2.12 × 10<sup>14<sup/> <i>M<i/><sub>⊙<sub/><i>/h<i/><sub>70<sub/> and median redshift <i>z<i/> = 0.70, corresponding to an order-of-magnitude improvement in cluster density over previous tSZ-selected catalogs in this region (3.81 clusters per square degree).<i>Conclusions<i/>. The overlap between SPT and <i>Euclid<i/> data will enable a range of multiwavelength studies of the aforementioned source populations. This work serves as the first step toward joint projects between SPT and <i>Euclid<i/> and provides a rich dataset containing information on galaxies, clusters, and their environments.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"281 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146073389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1051/0004-6361/202558345
B. Mosser, M. Takata, C. Pinçon, M. S. Cunha, M. Vrard, K. Belkacem, S. Deheuvels, M. Matteuzzi
Context. Dipole mixed modes observed in the oscillation pattern of red giant stars probe the radiative regions in the stellar core.Aims. Oscillation spectra of helium-core-burning stars sometimes show extra peaks that remain unexplained by the dipole mixed-mode pattern expected from the coupling of a radiative cavity in the stellar core and a pressure cavity in the stellar envelope.Methods. We use the asymptotic expansion developed for a multi-cavity star in order to characterize these extra peaks.Results. The analytical resonance condition of the multi-cavity gravito-acoustic modes, with two inner gravity cavities and an outer pressure cavity, helps us explain that the apparent extra peaks are dipole mixed modes that follow the three-cavity oscillation pattern. The derivation of the two asymptotic period spacings associated with the two distinct regions in the radiative core provides an estimate of the full radiative cavity.Conclusions. Our results provide new constraints for analyzing the overshoot or mixing in the core of helium-core-burning stars. An important structure discontinuity inside the radiative core may explain the larger than expected observed period spacings.
{"title":"Extra modes in helium-core-burning stars probing an infra core cavity","authors":"B. Mosser, M. Takata, C. Pinçon, M. S. Cunha, M. Vrard, K. Belkacem, S. Deheuvels, M. Matteuzzi","doi":"10.1051/0004-6361/202558345","DOIUrl":"https://doi.org/10.1051/0004-6361/202558345","url":null,"abstract":"<i>Context.<i/> Dipole mixed modes observed in the oscillation pattern of red giant stars probe the radiative regions in the stellar core.<i>Aims.<i/> Oscillation spectra of helium-core-burning stars sometimes show extra peaks that remain unexplained by the dipole mixed-mode pattern expected from the coupling of a radiative cavity in the stellar core and a pressure cavity in the stellar envelope.<i>Methods.<i/> We use the asymptotic expansion developed for a multi-cavity star in order to characterize these extra peaks.<i>Results.<i/> The analytical resonance condition of the multi-cavity gravito-acoustic modes, with two inner gravity cavities and an outer pressure cavity, helps us explain that the apparent extra peaks are dipole mixed modes that follow the three-cavity oscillation pattern. The derivation of the two asymptotic period spacings associated with the two distinct regions in the radiative core provides an estimate of the full radiative cavity.<i>Conclusions.<i/> Our results provide new constraints for analyzing the overshoot or mixing in the core of helium-core-burning stars. An important structure discontinuity inside the radiative core may explain the larger than expected observed period spacings.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"8 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146073391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1051/0004-6361/202556814
A. Crespo Gómez, L. Colina, P. G. Pérez-González, J. Álvarez-Márquez, M. García-Marín, A. Alonso-Herrero, M. Annunziatella, A. Bik, S. Bosman, A. J. Bunker, A. Labiano, D. Langeroodi, P. Rinaldi, G. Östlin, L. Boogaard, S. Gillman, G. Barro, S. L. Finkelstein, G. C. K. Leung
We present new MIRI F560W, F770W, and F1000W imaging of the galaxy GN-z11 at a redshift of 10.603. We report a significant detection (14σ) in the F560W and F770W images, and a marginal detection (3.2σ) in the F1000W filter. The new MIRI observations cover the optical-red spectral range and significantly extend previous NIRCam wavelength coverage from rest-frame 0.38 μm up to 0.86 μm. In this work, we analyse the spectral energy distribution (SED) combining this new MIRI imaging data with archival NIRSpec/Prism and MRS spectroscopy, and NIRCam imaging, i.e. covering the rest-frame 0.12–0.86 μm. New constraints such as the equivalent widths of the strong optical lines ([O III]λ5008, Hβ and Hα) and the continuum emission at rest-frame 0.48 μm, 0.66 μm, and 0.86 μm, free of emission line contributions, are presented. The continuum emission shows a flat energy distribution, in fν, up to 0.5 μm, compatible with the presence of a mixed stellar population of young (4 ± 1 Myr) and mature (63 ± 23 Myr) stars that also account for the [O III], Hβ, and Hα emission lines. The continuum at rest-frame 0.66 μm shows a 36 ± 3% flux excess above the predicted flux for a mixed stellar population, pointing to the presence of an additional source contributing at these wavelengths. This excess increases to 91 ± 28% at rest-frame 0.86 μm, although with a large uncertainty due to the marginal detection in the F1000W filter. We consider that hot dust emission in the dusty torus around a type 2 active galactic nucleus (AGN) could be responsible for the observed excess. Alternatively, this excess could be due to hot dust emission or a photoluminiscence dust process (Extended Red Emission, ERE) under the extreme UV radiation field, as is observed in local metal-poor galaxies and in young compact starbursts. The presence of a type 1 AGN is not supported by the observed SED as the hot dust emission in luminous high-z quasi-stellar objects (QSOs) contributes at wavelengths above rest-frame 1 μm, and an additional ad hoc red source would be required to explain the observed flux excess at 0.66 and 0.86 μm. Additional deep MIRI imaging covering the rest-frame near-IR is needed to confirm the flux detection at 10 μm, and to discriminate between the different hot dust emission in the extreme starburst and AGN scenarios.
{"title":"MIRI spectrophotometry of GN-z11: Detection and nature of an optical red continuum component","authors":"A. Crespo Gómez, L. Colina, P. G. Pérez-González, J. Álvarez-Márquez, M. García-Marín, A. Alonso-Herrero, M. Annunziatella, A. Bik, S. Bosman, A. J. Bunker, A. Labiano, D. Langeroodi, P. Rinaldi, G. Östlin, L. Boogaard, S. Gillman, G. Barro, S. L. Finkelstein, G. C. K. Leung","doi":"10.1051/0004-6361/202556814","DOIUrl":"https://doi.org/10.1051/0004-6361/202556814","url":null,"abstract":"We present new MIRI F560W, F770W, and F1000W imaging of the galaxy GN-z11 at a redshift of 10.603. We report a significant detection (14<i>σ<i/>) in the F560W and F770W images, and a marginal detection (3.2<i>σ<i/>) in the F1000W filter. The new MIRI observations cover the optical-red spectral range and significantly extend previous NIRCam wavelength coverage from rest-frame 0.38 μm up to 0.86 μm. In this work, we analyse the spectral energy distribution (SED) combining this new MIRI imaging data with archival NIRSpec/Prism and MRS spectroscopy, and NIRCam imaging, i.e. covering the rest-frame 0.12–0.86 μm. New constraints such as the equivalent widths of the strong optical lines ([O III]<i>λ<i/>5008, H<i>β<i/> and H<i>α<i/>) and the continuum emission at rest-frame 0.48 μm, 0.66 μm, and 0.86 μm, free of emission line contributions, are presented. The continuum emission shows a flat energy distribution, in <i>f<i/><sub><i>ν<i/><sub/>, up to 0.5 μm, compatible with the presence of a mixed stellar population of young (4 ± 1 Myr) and mature (63 ± 23 Myr) stars that also account for the [O III], H<i>β<i/>, and H<i>α<i/> emission lines. The continuum at rest-frame 0.66 μm shows a 36 ± 3% flux excess above the predicted flux for a mixed stellar population, pointing to the presence of an additional source contributing at these wavelengths. This excess increases to 91 ± 28% at rest-frame 0.86 μm, although with a large uncertainty due to the marginal detection in the F1000W filter. We consider that hot dust emission in the dusty torus around a type 2 active galactic nucleus (AGN) could be responsible for the observed excess. Alternatively, this excess could be due to hot dust emission or a photoluminiscence dust process (Extended Red Emission, ERE) under the extreme UV radiation field, as is observed in local metal-poor galaxies and in young compact starbursts. The presence of a type 1 AGN is not supported by the observed SED as the hot dust emission in luminous high-<i>z<i/> quasi-stellar objects (QSOs) contributes at wavelengths above rest-frame 1 μm, and an additional ad hoc red source would be required to explain the observed flux excess at 0.66 and 0.86 μm. Additional deep MIRI imaging covering the rest-frame near-IR is needed to confirm the flux detection at 10 μm, and to discriminate between the different hot dust emission in the extreme starburst and AGN scenarios.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"74 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146073387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-28DOI: 10.1051/0004-6361/202557986
Z. Roumeliotis, L. Matrà, G. M. Kennedy, S. Marino, K. Y. L. Su, D. J. Wilner, M. C. Wyatt, A. P. Jackson
Context. Giant impacts between planetary embryos are a natural step in the terrestrial planet formation process and are expected to create disks of warm debris in the terrestrial regions of their stars. Understanding the gas and dust debris produced in giant impacts is vital for comprehending and constraining models of planetary collisions.Aims. We reveal the distribution of millimeter (mm) grains in the giant impact debris disk of HD 172555 for the first time, using new ALMA 0.87 mm observations at ∼80 mas (2.3 au) resolution.Methods. We modeled the interferometric visibilities to obtain basic spatial properties of the disk and compared these data to the disk’s dust and gas distributions at other wavelengths.Results. We detected the star and dust emission from an inclined disk out to ∼9 au and down to 2.3 au (on-sky) from the central star, with no significant asymmetry in the dust distribution. The radiative transfer modeling of the visibilities indicates the disk surface density distribution of mm grains most likely peaks around ∼5 au, while the width inferred remains model-dependent at the S/N of the data. We highlighted an outward radial offset of the small grains traced by scattered light observations compared to the mm grains, which could be explained by the combined effect of gas drag and radiation pressure in the presence of large enough gas densities. Furthermore, our SED modeling implies a size distribution slope for the mm grains consistent with the expectation of collisional evolution and flatter than inferred for the micron-sized grains, implying a break in the grain size distribution and confirming an overabundance of small grains.
{"title":"Resolving the terrestrial planet-forming region of HD 172555 with ALMA","authors":"Z. Roumeliotis, L. Matrà, G. M. Kennedy, S. Marino, K. Y. L. Su, D. J. Wilner, M. C. Wyatt, A. P. Jackson","doi":"10.1051/0004-6361/202557986","DOIUrl":"https://doi.org/10.1051/0004-6361/202557986","url":null,"abstract":"<i>Context<i/>. Giant impacts between planetary embryos are a natural step in the terrestrial planet formation process and are expected to create disks of warm debris in the terrestrial regions of their stars. Understanding the gas and dust debris produced in giant impacts is vital for comprehending and constraining models of planetary collisions.<i>Aims<i/>. We reveal the distribution of millimeter (mm) grains in the giant impact debris disk of HD 172555 for the first time, using new ALMA 0.87 mm observations at ∼80 mas (2.3 au) resolution.<i>Methods<i/>. We modeled the interferometric visibilities to obtain basic spatial properties of the disk and compared these data to the disk’s dust and gas distributions at other wavelengths.<i>Results<i/>. We detected the star and dust emission from an inclined disk out to ∼9 au and down to 2.3 au (on-sky) from the central star, with no significant asymmetry in the dust distribution. The radiative transfer modeling of the visibilities indicates the disk surface density distribution of mm grains most likely peaks around ∼5 au, while the width inferred remains model-dependent at the S/N of the data. We highlighted an outward radial offset of the small grains traced by scattered light observations compared to the mm grains, which could be explained by the combined effect of gas drag and radiation pressure in the presence of large enough gas densities. Furthermore, our SED modeling implies a size distribution slope for the mm grains consistent with the expectation of collisional evolution and flatter than inferred for the micron-sized grains, implying a break in the grain size distribution and confirming an overabundance of small grains.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"120 8 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146070548","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-27DOI: 10.1051/0004-6361/202557949
F. Mattig, B. N. Barlow, D. Liu, M. Dorsch, S. Geier, M. Pritzkuleit, H. Dawson, B. Wang, V. Schaffenroth, T. Kupfer, C. Derbyshire, S. Barocci-Faul
Context. Massive short-period binaries involving hot subdwarf stars (sdO/Bs) are rare but very relevant to constraining pathways for binary star evolution. Moreover, some of the most promising candidate progenitor systems leading to Type Ia supernovae (SNe Ia) involve sdO/Bs. LAMOST J065816.72+094343.1 has been identified to be such a candidate system.Aims. To explore the nature and evolutionary future of LAMOST J065816.72+094343.1, we complemented archival spectroscopic data with additional time series spectra as well as high-resolution spectroscopy of the object. After combining these with photometric data, we determined the orbital parameters of the system and the mass of the companion.Methods. We solved the orbit of the system by analyzing 68 low- and medium-resolution spectra using state-of-the-art mixed local thermodynamic equilibrium (LTE) and non-LTE model atmospheres. Additionally, we gathered nine high-resolution spectra to determine atmospheric parameters and the projected rotational velocity of the sdOB. The inclination angle of the system was constrained assuming tidal synchronization of the sdOB, which was verified via analysis of the ellipsoidal variations in the TESS light curve.Results. We determine LAMOST J065816.72+094343.1 to be a binary consisting of a massive 0.82 ± 0.17 M⊙ sdOB component with a unseen companion. Due to the companion’s mass being very close to the Chandrasekhar mass limit and high for a white dwarf, it is unclear whether the compact companion is a white dwarf or a neutron star. We find the system to be in a close orbit, with a period of P = 0.31955193 d and an inclination angle of . While the exact nature of the companion remains unknown, we determine the system to either lead to a SN Ia or an intermediate mass binary pulsar, potentially after a phase as an intermediate-mass X-ray binary.
{"title":"The massive hot subdwarf binary LAMOST J065816.72+094343.1","authors":"F. Mattig, B. N. Barlow, D. Liu, M. Dorsch, S. Geier, M. Pritzkuleit, H. Dawson, B. Wang, V. Schaffenroth, T. Kupfer, C. Derbyshire, S. Barocci-Faul","doi":"10.1051/0004-6361/202557949","DOIUrl":"https://doi.org/10.1051/0004-6361/202557949","url":null,"abstract":"<i>Context.<i/> Massive short-period binaries involving hot subdwarf stars (sdO/Bs) are rare but very relevant to constraining pathways for binary star evolution. Moreover, some of the most promising candidate progenitor systems leading to Type Ia supernovae (SNe Ia) involve sdO/Bs. LAMOST J065816.72+094343.1 has been identified to be such a candidate system.<i>Aims.<i/> To explore the nature and evolutionary future of LAMOST J065816.72+094343.1, we complemented archival spectroscopic data with additional time series spectra as well as high-resolution spectroscopy of the object. After combining these with photometric data, we determined the orbital parameters of the system and the mass of the companion.<i>Methods.<i/> We solved the orbit of the system by analyzing 68 low- and medium-resolution spectra using state-of-the-art mixed local thermodynamic equilibrium (LTE) and non-LTE model atmospheres. Additionally, we gathered nine high-resolution spectra to determine atmospheric parameters and the projected rotational velocity of the sdOB. The inclination angle of the system was constrained assuming tidal synchronization of the sdOB, which was verified via analysis of the ellipsoidal variations in the TESS light curve.<i>Results.<i/> We determine LAMOST J065816.72+094343.1 to be a binary consisting of a massive 0.82 ± 0.17 M<sub>⊙<sub/> sdOB component with a unseen companion. Due to the companion’s mass being very close to the Chandrasekhar mass limit and high for a white dwarf, it is unclear whether the compact companion is a white dwarf or a neutron star. We find the system to be in a close orbit, with a period of <i>P<i/> = 0.31955193 d and an inclination angle of . While the exact nature of the companion remains unknown, we determine the system to either lead to a SN Ia or an intermediate mass binary pulsar, potentially after a phase as an intermediate-mass X-ray binary.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146057096","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-27DOI: 10.1051/0004-6361/202558202
M. M. Bennedik, B. Stelzer, H. Isaacson, A. Binks, M. Caramazza, F. Haberl
As the only known unambiguous star in a Maunder minimum-like chromospheric activity state, the properties of HD 166620 can provide valuable insight into the behaviour of the Sun during the historic extended low-states of its activity cycle. The coronal X-ray activity of HD 166620 has so far only been probed with a ROSAT/HRI observation in 1996, near the chromospheric activity maximum before the star entered its grand minimum around 2004. We conducted a deep XMM-Newton observation of HD 166620 during its chromospheric Ca II H&K activity grand minimum to achieve a better understanding of its magnetic activity. We detected HD 166620 with an X-ray luminosity of , corresponding to and an X-ray surface flux of . With respect to the earlier ROSAT observation, the X-ray brightness of HD 166620 has decreased by a factor of 2.5 during its Maunder minimum-like state. To place its X-ray properties into context, we constructed an X-ray sample of late-type stars within 10 pc of the Sun. The activity of HD 166620 is below the levels of all other K dwarfs in the 10 pc sample. The corona of HD 166620 during its grand minimum emits at the level of the solar background corona, which implies that it has no large active magnetic structures. Along with long-term Ca II H&K monitoring of HD 166620, this result provides evidence that the solar activity during the Maunder minimum was not reduced significantly below the levels seen during its present-day cycle minima. The similar X-ray surface flux of HD 166620 and the modern quiet Sun, and also their Rossby number near the critical value of spin-down models, suggest a connection between the regime of weakened magnetic braking and the occurrence of Maunder minimum states.
HD 166620是目前已知唯一一颗处于类似蒙德极小期色球活动状态的明确恒星，它的特性可以为了解太阳在历史上延长的低活动周期中的行为提供有价值的见解。到目前为止，HD 166620的日冕x射线活动仅在1996年通过ROSAT/HRI观测进行了探测，在2004年左右进入最小值之前，接近色球活动的最大值。我们在hd166620的色球Ca II H&K活动极小期对其进行了深入的xmm -牛顿观测，以更好地了解其磁活动。我们探测到HD 166620的x射线光度为，对应的x射线表面通量为。相对于早期的ROSAT观测，HD 166620的x射线亮度在其蒙德最小值状态期间下降了2.5倍。为了了解它的x射线特性，我们在距离太阳10%的范围内构建了一个晚期恒星的x射线样本。HD 166620的活动水平低于10%样本中所有其他K矮星的水平。HD 166620在其极小期的日冕辐射水平相当于太阳背景日冕，这意味着它没有大型的活动磁结构。结合对hd166620的长期Ca II H&K监测，这一结果提供了证据，证明蒙德极小期的太阳活动并没有明显减少到低于当前周期极小期的水平。HD 166620的x射线表面通量与现代安静太阳相似，而且它们的罗斯比数接近自旋下降模型的临界值，这表明磁制动减弱的状态与蒙德最小状态的发生之间存在联系。
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