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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"

15985 results found.

  1. GRB260914A: MAO/AZT-22 optical observations
  2. GRB 260924A: Near-infrared detection with MDM/MIRAGE
  3. GRB 260924A: COLIBRÍ optical observations
  4. GRB 260925A: Swift/UVOT Upper Limits
  5. GRB 260924A: Optical follow-up observations with Kinder
  6. GRB 260925A: COLIBRÍ optical upper limits
  7. GRB 260925A: FRAM-Auger optical limit
  8. GRB 260924A: Ondrejov D50 optical afterglow detection
  9. GRB 260924A: SVOM/GRM observation
  10. GRB 260924A: 2.2m CAHA spectroscopic redshift z = 3.51
  11. GRB 260924A: J-band observations by the SYSU 80 cm infrared telescope
  12. GRB 260924A: GROWTH-India Telescope optical observations
  13. GRB 260921A: SVOM/GRM observation
  14. GRB 260922A: COLIBRÍ Confirmation of the Optical Counterpart
  15. GRB 260924A: Fermi GRB Observation
  16. GRB 260920A: SVOM/GRM observation
  17. GRB 260924A: NOT optical counterpart confirmation
  18. GRB 260924A: detection of a bright optical afterglow by the 1.5m OSN telescope
  19. GRB 260922A: Ondrejov D50 optical limit
  20. GRB 260922A: J-band upper limit with WINTER
  21. GRB 260922A: Swift/UVOT Upper Limits
  22. GRB 260922A: COLIBRÍ Optical Counterpart Candidate (correction to GCN 45698)
  23. GRB 260922A: COLIBRÍ optical upper limits
  24. GRB 260922A: SVOM/C-GFT optical upper limit
  25. GRB 260921A: Fermi GBM Observation
  26. EP260920b: 2.2m CAHA optical afterglow detection and 10.4m GTC redshift confirmation
  27. Swift GRB 260921A: MASTER OT J094129.58+025052.5 possible optical counterpart detection with host galaxy (z=1.3)
  28. EP260920b: VLT/X-shooter spectroscopic redshift z = 3.582
  29. EP260920b: SVOM/VT optical observation
  30. EP260920b: COLIBRÍ optical observations
  31. EP260920b: LCO optical counterpart detection
  32. EP260920a: NOT early time optical upper limits
  33. EP260920a: NOT optical upper limits
  34. EP260920a: SVOM/VT optical upper limits
  35. EP260920a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  36. EP260920a: COLIBRÍ optical upper limits
  37. EP260920a: Update of the LCO optical counterpart candidate
  38. EP260920a: LCO optical counterpart candidate
  39. GRB 260915A: VLT optical and near-infrared upper limits
  40. EP260917a: SVOM/VT optical upper limits
  41. GRB 260918A: SVOM/C-GFT optical upper limits
  42. GRB 260918A: SVOM/VT optical upper limits
  43. GRB 260917B: Mondy optical upper limit
  44. GRB 260917B: EP-FXT follow-up observation
  45. EP260917a: COLIBRÍ optical upper limits
  46. GRB 260918A: LCO optical upper limits
  47. GRB 260918A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  48. GRB 260917B: FRAM-Auger optical limits
  49. GRB 260917B: WINTER J-band observations
  50. GRB 260917B: SVOM/VT optical observations
  51. GRB 260917B: LCO optical observation
  52. GRB 260917B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  53. GRB 260914A: 2.2m CAHA optical afterglow detection and 10.4m GTC redshift confirmation
  54. GRB 260914A: Mondy and TShAO optical observations
  55. GRB 260915A: SVOM/C-GFT optical upper limits
  56. GRB 260915A: EP-FXT follow-up observation
  57. GRB 260915A: SVOM/VT refined early optical upper limits
  58. GRB 260915A: REM optical/NIR observations
  59. GRB 260914A: REM optical/NIR observations
  60. GRB 260914A: VLT/X-shooter observations and redshift confirmation
  61. GRB 260915A: SVOM/VT optical upper limits
  62. GRB 260915A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  63. GRB 260914A: VLT/X-shooter spectroscopic redshift z = 0.778
  64. GRB 260915A: 10.4m GTC deep optical limits
  65. GRB 260915A: NOT optical upper limit
  66. GRB 260915A: SVOM/VT optical upper limits from VHF data
  67. GRB 260915A: LCO optical upper limits
  68. GRB 260914A: EP-FXT follow-up observation
  69. GRB 260914A: LCO optical observation
  70. GRB 260914A: SVOM/C-GFT optical observations
  71. GRB 260914A: SVOM/VT optical counterpart confirmation
  72. GRB 260914A: SVOM/VT optical observation from VHF data
  73. GRB 260914A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  74. GRB 260913A: SVOM/C-GFT optical upper limit
  75. GRB 260909A: OSN 1.5m, CAHA 2.2m and GTC 10.4m optical upper limits
  76. GRB 260907A: SVOM/GRM observation
  77. GRB 260909A: CrAO and AbAO optical upper limits
  78. GRB 260910B: GOTO tentative optical counterpart candidates
  79. GRB 260909A: KAIT optical upper limit
  80. GRB 260903A: Swift-XRT observations
  81. EP260806a: VLA+ALMA radio detections
  82. GRB 260909A: VLT optical and near-infrared upper limits
  83. EP Alert 260909.53: Global MASTER-Net observations report
  84. GRB 260909A: EP-FXT follow-up observation
  85. GRB 260909A: SVOM/VT optical upper limits
  86. GRB 260909A: Mondy optical observations and afterglow candidate
  87. GRB 260909A: Xinglong 2.16m optical upper limit
  88. GRB 260909A: SVOM/C-GFT optical upper limit
  89. Fermi trigger No 810554827: Global MASTER-Net observations report
  90. EP Alert 260908.60: Global MASTER-Net observations report
  91. Fermi GRB 260907B: Global MASTER-Net observations report
  92. GRB 260903A: SAO RAS optical upper limit
  93. Fermi GRB 260907A: Global MASTER-Net observations report
  94. EP Alert 260905.11: Global MASTER-Net observations report
  95. GRB 260903A: J-band upper limit with WINTER
  96. EP Alert 260903.47: Global MASTER-Net observations report
  97. GRB260903A: Liverpool Telescope optical observations
  98. GRB 260903A: SAO RAS optical observations
  99. EP260903a: EP-WXT detection of a fast X-ray transient
  100. EP Alert 260903.62: Global MASTER-Net observations report

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