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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. EP250711a: Global MASTER-Net observations report
  2. GRB 250711A: DDOTI Optical Upper Limit
  3. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  4. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  5. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  6. GRB 250711A: SVOM/GRM observation
  7. EP250711a: NOT optical counterpart candidate
  8. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  9. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  10. Fermi GRB 250711A: Global MASTER-Net observations report
  11. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  12. GRB 250704A: GRANDMA observations
  13. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  14. GRB 250711A: Fermi GBM Final Real-time Localization
  15. GRB 250704A: SVOM/ECLAIRs refined analysis
  16. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  17. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  18. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  19. GRB 250702B,D,E / EP250702a: ALMA detection
  20. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  21. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  22. IceCube-250708A: No Candidates from WINTER
  23. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  24. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  25. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  26. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  27. GRB 250709A: Fermi GBM Final Localization
  28. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  29. GRB 250706B/C: Insight-HXMT detection
  30. EP/WXT 01709181970: GOTO observations confirm stellar variability
  31. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  32. EP250704a/GRB 250704B: 10 GHz VLA detection
  33. The EP-WXT trigger 01709181970 is likely a flaring star
  34. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  35. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  36. IceCube-250706A: No Candidates from WINTER
  37. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  38. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  39. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  40. GRB 250704B / EP250704a: VLA radio detection
  41. Fermi GRB 250708A: Global MASTER-Net observations report
  42. IceCube-250708A: Global MASTER-Net observations report
  43. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  44. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  45. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  46. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  47. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  48. EP250704a/GRB250704B : HCT optical and NIR upper limits
  49. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  50. GRB 250708A: Fermi GBM Final Real-time Localization
  51. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  52. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  53. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  54. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  55. GRB 250702F: radio detection with the VLA
  56. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  57. IceCube-250706A: EP-FXT follow-up observations
  58. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  59. GRB 250706B/C: Fermi-LAT detection
  60. IceCube-250706A: Global MASTER-Net observations report
  61. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  62. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  63. GRB 250706B: Swift/UVOT Detection
  64. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  65. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  66. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  67. GRB 250702F: GRANDMA observations
  68. GRB 250706A: Swift-XRT refined Analysis
  69. GRB 250706B: refined SVOM/MXT data analysis
  70. GRB 250706A: Swift/UVOT Upper Limits
  71. GRB 250706B: REM optical observations
  72. GRB 250706A: REM optical/NIR observations
  73. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  74. IceCube-250416A: DDOTI Optical Upper Limit
  75. IceCube-250706A: COLIBRÍ optical upper limits
  76. Swift GRB 250706A: Global MASTER-Net observations report
  77. GRB 250706A: JinShan optical upper limits
  78. GRB 250706A: SAO RAS optical observations
  79. EP250704A: NOWT Detection
  80. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  81. The EP-WXT trigger 01709181580 is likely a flaring star
  82. GRB250706B: Swift-XRT counterpart detection
  83. GRB 250706B: iTelescope optical observations
  84. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  85. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  86. GRB 250706B: SVOM/VT optical observation
  87. GRB 250706B: TRT bright optical counterpart detection
  88. GRB 250706A: GROWTH-India Telescope optical upper limit
  89. GRB 250706B: SVOM detection of a long burst
  90. GRB 250706A: Swift detection of a burst
  91. GRB 250704B: Swift-XRT refined Analysis
  92. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  93. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  94. GRB 250703A: EIRSAT-1 GMOD Detection
  95. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  96. GRB 250704B: Swift/UVOT Upper Limits
  97. GRB 250704A: Swift/UVOT Detection
  98. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  99. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  100. GRB 250704B: Insight-HXMT detection

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