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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. Konus-Wind detection of GRB 250716A
  2. GRB 250716A: Swift-XRT afterglow detection
  3. GRB 250717B: Fermi GBM Final Real-time Localization
  4. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  5. GRB 250717A: Fermi GBM Final Real-time Localization
  6. GRB 250716A: Swift ToO observations
  7. GRB 250716A: GOTO tentative optical counterpart candidate
  8. GRB 250716A: Fermi GBM Observation
  9. GRB 250714A: SVOM/GRM observation
  10. Fermi GRB 250716A: Global MASTER-Net observations report
  11. GRB 250716A: Fermi GBM Final Real-time Localization
  12. Fermi GRB 250715A: Global MASTER-Net observations report
  13. GRB 250715A: Fermi GBM Final Real-time Localization
  14. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  15. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  16. GRB 250713A: Mephisto optical upper limits
  17. Fermi GRB 250714A: Global MASTER-Net observations report
  18. GRB 250713A: SVOM/VT optical upper limit
  19. GRB 250713A: NOT optical upper limits
  20. GRB 250713A: OHP/T193 upper limit
  21. GRB 250713A: SVOM/C-GFT upper limit
  22. GRB 250714A: Fermi GBM Final Real-time Localization
  23. GRB 250706B/C: 7DT Follow-up Observations
  24. GRB 250713A: Swift-XRT observations
  25. GRB 250713A: EP-FXT counterpart detection
  26. EP250711a: COLIBRÍ continuous optical observations
  27. GRB 250706A: Swift-BAT refined analysis
  28. GRB 250702F: Swift-BAT refined analysis
  29. GRB 250628A: Swift-BAT refined analysis
  30. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  31. GRB 250713A: JinShan optical upper limits
  32. GRB 250713A: SVOM detection of a long burst
  33. EP250711a: Global MASTER-Net observations report
  34. GRB 250711A: DDOTI Optical Upper Limit
  35. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  36. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  37. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  38. GRB 250711A: SVOM/GRM observation
  39. EP250711a: NOT optical counterpart candidate
  40. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  41. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  42. Fermi GRB 250711A: Global MASTER-Net observations report
  43. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  44. GRB 250704A: GRANDMA observations
  45. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  46. GRB 250711A: Fermi GBM Final Real-time Localization
  47. GRB 250704A: SVOM/ECLAIRs refined analysis
  48. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  49. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  50. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  51. GRB 250702B,D,E / EP250702a: ALMA detection
  52. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  53. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  54. IceCube-250708A: No Candidates from WINTER
  55. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  56. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  57. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  58. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  59. GRB 250709A: Fermi GBM Final Localization
  60. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  61. GRB 250706B/C: Insight-HXMT detection
  62. EP/WXT 01709181970: GOTO observations confirm stellar variability
  63. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  64. EP250704a/GRB 250704B: 10 GHz VLA detection
  65. The EP-WXT trigger 01709181970 is likely a flaring star
  66. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  67. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  68. IceCube-250706A: No Candidates from WINTER
  69. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  70. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  71. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  72. GRB 250704B / EP250704a: VLA radio detection
  73. Fermi GRB 250708A: Global MASTER-Net observations report
  74. IceCube-250708A: Global MASTER-Net observations report
  75. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  76. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  77. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  78. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  79. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  80. EP250704a/GRB250704B : HCT optical and NIR upper limits
  81. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  82. GRB 250708A: Fermi GBM Final Real-time Localization
  83. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  84. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  85. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  86. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  87. GRB 250702F: radio detection with the VLA
  88. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  89. IceCube-250706A: EP-FXT follow-up observations
  90. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  91. GRB 250706B/C: Fermi-LAT detection
  92. IceCube-250706A: Global MASTER-Net observations report
  93. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  94. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  95. GRB 250706B: Swift/UVOT Detection
  96. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  97. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  98. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  99. GRB 250702F: GRANDMA observations
  100. GRB 250706A: Swift-XRT refined Analysis

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