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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. GRB 250713A: NOT optical upper limits
  2. GRB 250713A: OHP/T193 upper limit
  3. GRB 250713A: SVOM/C-GFT upper limit
  4. GRB 250714A: Fermi GBM Final Real-time Localization
  5. GRB 250706B/C: 7DT Follow-up Observations
  6. GRB 250713A: Swift-XRT observations
  7. GRB 250713A: EP-FXT counterpart detection
  8. EP250711a: COLIBRÍ continuous optical observations
  9. GRB 250706A: Swift-BAT refined analysis
  10. GRB 250702F: Swift-BAT refined analysis
  11. GRB 250628A: Swift-BAT refined analysis
  12. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  13. GRB 250713A: JinShan optical upper limits
  14. GRB 250713A: SVOM detection of a long burst
  15. EP250711a: Global MASTER-Net observations report
  16. GRB 250711A: DDOTI Optical Upper Limit
  17. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  18. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  19. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  20. GRB 250711A: SVOM/GRM observation
  21. EP250711a: NOT optical counterpart candidate
  22. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  23. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  24. Fermi GRB 250711A: Global MASTER-Net observations report
  25. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  26. GRB 250704A: GRANDMA observations
  27. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  28. GRB 250711A: Fermi GBM Final Real-time Localization
  29. GRB 250704A: SVOM/ECLAIRs refined analysis
  30. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  31. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  32. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  33. GRB 250702B,D,E / EP250702a: ALMA detection
  34. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  35. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  36. IceCube-250708A: No Candidates from WINTER
  37. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  38. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  39. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  40. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  41. GRB 250709A: Fermi GBM Final Localization
  42. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  43. GRB 250706B/C: Insight-HXMT detection
  44. EP/WXT 01709181970: GOTO observations confirm stellar variability
  45. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  46. EP250704a/GRB 250704B: 10 GHz VLA detection
  47. The EP-WXT trigger 01709181970 is likely a flaring star
  48. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  49. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  50. IceCube-250706A: No Candidates from WINTER
  51. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  52. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  53. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  54. GRB 250704B / EP250704a: VLA radio detection
  55. Fermi GRB 250708A: Global MASTER-Net observations report
  56. IceCube-250708A: Global MASTER-Net observations report
  57. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  58. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  59. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  60. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  61. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  62. EP250704a/GRB250704B : HCT optical and NIR upper limits
  63. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  64. GRB 250708A: Fermi GBM Final Real-time Localization
  65. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  66. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  67. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  68. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  69. GRB 250702F: radio detection with the VLA
  70. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  71. IceCube-250706A: EP-FXT follow-up observations
  72. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  73. GRB 250706B/C: Fermi-LAT detection
  74. IceCube-250706A: Global MASTER-Net observations report
  75. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  76. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  77. GRB 250706B: Swift/UVOT Detection
  78. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  79. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  80. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  81. GRB 250702F: GRANDMA observations
  82. GRB 250706A: Swift-XRT refined Analysis
  83. GRB 250706B: refined SVOM/MXT data analysis
  84. GRB 250706A: Swift/UVOT Upper Limits
  85. GRB 250706B: REM optical observations
  86. GRB 250706A: REM optical/NIR observations
  87. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  88. IceCube-250416A: DDOTI Optical Upper Limit
  89. IceCube-250706A: COLIBRÍ optical upper limits
  90. Swift GRB 250706A: Global MASTER-Net observations report
  91. GRB 250706A: JinShan optical upper limits
  92. GRB 250706A: SAO RAS optical observations
  93. EP250704A: NOWT Detection
  94. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  95. The EP-WXT trigger 01709181580 is likely a flaring star
  96. GRB250706B: Swift-XRT counterpart detection
  97. GRB 250706B: iTelescope optical observations
  98. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  99. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  100. GRB 250706B: SVOM/VT optical observation

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