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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 250715A: Fermi GBM Final Real-time Localization
  2. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  3. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  4. GRB 250713A: Mephisto optical upper limits
  5. Fermi GRB 250714A: Global MASTER-Net observations report
  6. GRB 250713A: SVOM/VT optical upper limit
  7. GRB 250713A: NOT optical upper limits
  8. GRB 250713A: OHP/T193 upper limit
  9. GRB 250713A: SVOM/C-GFT upper limit
  10. GRB 250714A: Fermi GBM Final Real-time Localization
  11. GRB 250706B/C: 7DT Follow-up Observations
  12. GRB 250713A: Swift-XRT observations
  13. GRB 250713A: EP-FXT counterpart detection
  14. EP250711a: COLIBRÍ continuous optical observations
  15. GRB 250706A: Swift-BAT refined analysis
  16. GRB 250702F: Swift-BAT refined analysis
  17. GRB 250628A: Swift-BAT refined analysis
  18. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  19. GRB 250713A: JinShan optical upper limits
  20. GRB 250713A: SVOM detection of a short burst
  21. EP250711a: Global MASTER-Net observations report
  22. GRB 250711A: DDOTI Optical Upper Limit
  23. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  24. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  25. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  26. GRB 250711A: SVOM/GRM observation
  27. EP250711a: NOT optical counterpart candidate
  28. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  29. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  30. Fermi GRB 250711A: Global MASTER-Net observations report
  31. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  32. GRB 250704A: GRANDMA observations
  33. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  34. GRB 250711A: Fermi GBM Final Real-time Localization
  35. GRB 250704A: SVOM/ECLAIRs refined analysis
  36. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  37. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  38. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  39. GRB 250702B,D,E / EP250702a: ALMA detection
  40. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  41. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  42. IceCube-250708A: No Candidates from WINTER
  43. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  44. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  45. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  46. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  47. GRB 250709A: Fermi GBM Final Localization
  48. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  49. GRB 250706B/C: Insight-HXMT detection
  50. EP/WXT 01709181970: GOTO observations confirm stellar variability
  51. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  52. EP250704a/GRB 250704B: 10 GHz VLA detection
  53. The EP-WXT trigger 01709181970 is likely a flaring star
  54. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  55. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  56. IceCube-250706A: No Candidates from WINTER
  57. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  58. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  59. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  60. GRB 250704B / EP250704a: VLA radio detection
  61. Fermi GRB 250708A: Global MASTER-Net observations report
  62. IceCube-250708A: Global MASTER-Net observations report
  63. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  64. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  65. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  66. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  67. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  68. EP250704a/GRB250704B : HCT optical and NIR upper limits
  69. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  70. GRB 250708A: Fermi GBM Final Real-time Localization
  71. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  72. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  73. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  74. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  75. GRB 250702F: radio detection with the VLA
  76. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  77. IceCube-250706A: EP-FXT follow-up observations
  78. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  79. GRB 250706B/C: Fermi-LAT detection
  80. IceCube-250706A: Global MASTER-Net observations report
  81. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  82. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  83. GRB 250706B: Swift/UVOT Detection
  84. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  85. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  86. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  87. GRB 250702F: GRANDMA observations
  88. GRB 250706A: Swift-XRT refined Analysis
  89. GRB 250706B: refined SVOM/MXT data analysis
  90. GRB 250706A: Swift/UVOT Upper Limits
  91. GRB 250706B: REM optical observations
  92. GRB 250706A: REM optical/NIR observations
  93. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  94. IceCube-250416A: DDOTI Optical Upper Limit
  95. IceCube-250706A: COLIBRÍ optical upper limits
  96. Swift GRB 250706A: Global MASTER-Net observations report
  97. GRB 250706A: JinShan optical upper limits
  98. GRB 250706A: SAO RAS optical observations
  99. EP250704A: NOWT Detection
  100. GRB 250706A: SVOM/C-GFT upper limit in eary phase

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