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

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