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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"

32531 results found.

  1. EP240703a/GRB 240703A: TRT and JinShan decaying optical afterglow candidate
  2. IPN triangulation of GRB 240627A
  3. GRB 240619A: Host galaxy redshift from VLT/X-shooter
  4. LIGO/Virgo/KAGRA S240422ed: Updated significance estimate
  5. The first three GRBs detected by SVOM: X-ray Upper Limits from EP-WXT
  6. Konus-Wind detection of GRB 240703A (a counterpart of EP240703a)
  7. EP240702a: Swift/XRT upper limit
  8. EP240702a: GSP optical upper limit
  9. Fermi GRB 240702A: Global MASTER-Net observations report
  10. GRB 240627A: CALET Gamma-Ray Burst Monitor detection
  11. LIGO/Virgo/KAGRA S240630t: Updated Sky localization
  12. LIGO/Virgo/KAGRA S240629by: Updated Sky localization
  13. LIGO/Virgo/KAGRA S240630t: Identification of a GW compact binary merger candidate
  14. LIGO/Virgo/KAGRA S240629by: Upper limits from Fermi-GBM Observations
  15. LIGO/Virgo/KAGRA S240629by: Coverage and upper limits from MAXI/GSC observations
  16. Fermi GRB 240629A: Global MASTER-Net observations report
  17. Fermi Gamma-ray Burst Monitor trigger 741288821/240628732 is not a GRB
  18. LIGO/Virgo/KAGRA S240629by: Identification of a GW compact binary merger candidate
  19. IPN triangulation of GRB 240619C
  20. GRB 240627A: NuSTAR Detection of the long GRB
  21. GRB 240615A: SAI CMO J- band observations
  22. EP240626a: Montarrenti Observatory optical upper limit
  23. LIGO/Virgo/KAGRA S240627by: Identification of a GW compact binary merger candidate
  24. EP240625a: GRANDMA Optical Upper Limits
  25. EP240626a: EP-FXT detection of the X-ray emission
  26. GRB 240624A: Swift-BAT refined analysis
  27. Konus-Wind detection of GRB 240619A
  28. Fermi GRB 240625B: Global MASTER-Net observations report
  29. GRB 240624B: CALET Gamma-Ray Burst Monitor detection
  30. GRB 240625A: Fermi GBM Observation
  31. EP240625a: NOT optical counterpart candidate
  32. EP240625a: EP-FXT detection of the X-ray emission
  33. GRB 240624B: GRBAlpha detection
  34. GRB240624A: Fermi GBM Observation
  35. Swift GRB 240624A: Global MASTER-Net observations report
  36. GRB240615A: Gemini-North observations of the BAT and XRT positions
  37. Fermi GRB 240624A: Global MASTER-Net observations report
  38. GRB240615A: Gemini-North observations of the BAT and XRT positions
  39. GRB 240619A: detection of a radio counterpart with AMI-LA
  40. EP240618a: NOT further optical observations
  41. GRB 240619A: J-band detection with WINTER (duplicate submission of GCN 36739)
  42. GRB 240619A: J-band detection with WINTER
  43. LIGO/Virgo/KAGRA S240622h: Updated Sky localization and Source Classification
  44. EP240618a: NOT optical counterpart candidate
  45. LIGO/Virgo/KAGRA S240621em: Updated Sky localization and Source Classification
  46. GRB 240529A: JinShan optical observations
  47. LIGO/Virgo/KAGRA S240621dy: Updated Sky localization and Source Classification
  48. LIGO/Virgo/KAGRA S240621eb: Updated Sky localization and Source Classification
  49. EP240618a: GSP optical upper limit
  50. LIGO/Virgo/KAGRA S240622h: Identification of a GW compact binary merger candidate
  51. LIGO/Virgo/KAGRA S240621em: Identification of a GW compact binary merger candidate
  52. LIGO/Virgo/KAGRA S240621eb: Identification of a GW compact binary merger candidate
  53. LIGO/Virgo/KAGRA S240621dy: Identification of a GW compact binary merger candidate
  54. IPN triangulation of GRB 240615A (short)
  55. X-ray transient EP240618a: Fermi/GBM non-detection
  56. GRB 240619A: GRBAlpha detection
  57. EP240618a: Swift/XRT upper limit
  58. EP240617a: tentative Swift/XRT detection of the afterglow
  59. GRB 240619A: Swift-XRT probable afterglow detection
  60. GRB 240619A: Swift ToO observations
  61. GRB 240619A: CALET Gamma-Ray Burst Monitor detection
  62. GRB 240619C: NuSTAR automated detection of the GRB
  63. GRB 240619A: Fermi GBM Observation
  64. Fermi GBM Sub-Threshold Detection of GRB 240619C
  65. GRB 240619A: GOTO candidate optical afterglow
  66. EP240618a: Abastumani optical observationsEP240618a
  67. GRB 240615A: NOT optical observations
  68. EP240618a: GRANDMA Optical Upper Limits
  69. EP240618a: TRT optical upper limit
  70. Fermi GRB 240619A: Global MASTER-Net observations report
  71. EP240617a: STEP/T80S optical limits
  72. GRB 240615A: possible transient detection from Wendelstein observations
  73. LIGO/Virgo S240615dg: GRANDMA/FRAM-CTA-N Observations
  74. LIGO/Virgo/KAGRA S240615dg: Updated Sky localization
  75. LIGO/Virgo/KAGRA S240618ah: Updated Sky localization
  76. EP240618a: OHP/T193 MISTRAL i' and Y band upper limits
  77. GRB240615A: 1.3m DFOT optical upper limit
  78. EP240617a is likely a GRB event
  79. LIGO/Virgo/KAGRA S240618ah: Identification of a GW compact binary merger candidate
  80. GRB 240615A: J-band upper limits from WINTER
  81. GRB 240615A: Fermi GBM Observation
  82. LIGO/Virgo/KAGRA S240615ea: Updated Sky localization
  83. GRB 240615A: GECAM detection
  84. X-ray transient EP240414a: Chandra late time observation
  85. GRB 240615A: FLWO-1.2m optical upper limits
  86. Fermi GRB 240616A: Global MASTER-Net observations report
  87. Konus-Wind detection of GRB 240615A (short/hard)
  88. GRB 240615A: GOTO optical upper limits
  89. GRB 240615A: Swift ToO observations
  90. GRB 240615A: Swift/BAT-GUANO arcminute localization of a short burst
  91. LIGO/Virgo/KAGRA S240615ea: Identification of a GW compact binary merger candidate
  92. LIGO/Virgo/KAGRA S240615dg: Identification of a GW compact binary merger candidate
  93. GRB 240603A: VZLUSAT-2 detection
  94. GRB 240612A: GRBAlpha detection
  95. Fermi GRB 240612B: Global MASTER-Net observations report
  96. Fermi GRB 240612A: Global MASTER-Net observations report
  97. GRB 240607A: GECAM detection of a bright long burst
  98. Fermi GRB 240611A: Global MASTER-Net observations report
  99. Konus-Wind detection of GRB 240607A
  100. EXO 0748-676: Swift-BAT refined analysis

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