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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"

18324 results found.

  1. GRB 260907A: SVOM/GRM observation
  2. GRB 260909A: CrAO and AbAO optical upper limits
  3. GRB 260909A: KAIT optical upper limit
  4. GRB 260903A: Swift-XRT observations
  5. GRB 260909A: OHP/T193 z-band upper limit
  6. GRB 260909A: VLT optical and near-infrared upper limits
  7. GRB 260909A: EP-FXT follow-up observation
  8. EP260806a: NOEMA detection
  9. EP260623a: NOEMA detections
  10. GRB 260909A: Mondy optical observations and afterglow candidate
  11. GRB 260909A: Xinglong 2.16m optical upper limit
  12. GRB 260909A: SVOM/C-GFT optical upper limit
  13. GRB 260909A: SVOM detection of a burst
  14. The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
  15. GRB 260903A: SAO RAS optical upper limit
  16. The EP-WXT trigger 01709305715 is likely a flaring star
  17. EP260903a: EP-FXT follow-up observation
  18. The EP-WXT trigger 01709302592 is likely a flaring star
  19. GRB 260903A: J-band upper limit with WINTER
  20. GRB260903A: Liverpool Telescope optical observations
  21. GRB 260903A: SAO RAS optical observations
  22. EP260903a: EP-WXT detection of a fast X-ray transient
  23. GRB 260830A: Insight-HXMT/HE detection
  24. GRB 260903A: EP-FXT follow-up observation
  25. GRB 260903A: OHP/T193 optical afterglow detection
  26. NuSTAR Transient 260828: SOAR Optical Upper Limits
  27. GRB 260903A: LCO optical counterpart detection
  28. EP260901a: SVOM/VT optical upper limits
  29. EP260901a: EP-FXT follow-up observation
  30. GRB 260829A: SVOM/GRM observation
  31. GRB 260818A: ATCA detection of a candidate radio counterpart
  32. EP260830a: EP-FXT follow-up observation
  33. EP260901a: Global MASTER-Net observations report
  34. GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical variation of nova V* GK Per
  35. NuSTAR Transient 260828: LCO Optical Upper Limits
  36. EP260901a: EP-WXT detection of a fast X-ray transient
  37. GRB 260831B: EP-FXT follow-up observation
  38. GRB 260831B: LCO optical upper limits
  39. EP260830a: EP-WXT detection of a fast X-ray transient
  40. GRB 260827A: SVOM/GRM observation
  41. GRB 260831B: SVOM detection of a possible burst
  42. GRB 260825A: SVOM/GRM observation of a long burst
  43. GRB 260818B: Further EP-FXT observation
  44. GRB 260818B: VLT optical and nIR observations
  45. GRB 260818B: TNG NIR observations
  46. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  47. GRB 260818B: 6 GHz VLA observations
  48. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  49. GRB 260808B: SAO RAS observations of the optical rebrightening
  50. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  51. GRB 260822A: EP/FXT follow-up observations
  52. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  53. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  54. EP260822a: EP-FXT non-detection and upper limit
  55. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  56. EP260822a: Einstein Probe detection of a fast X-ray transient
  57. GRB 260822A: LCO optical upper limits
  58. The EP-WXT trigger 01709287395 is likely a flaring star
  59. GRB 260822A: GROWTH-India Telescope Upper Limits
  60. GRB 260818B: VLA radio observations
  61. GRB 260818B: SVOM/C-GFT optical upper limit
  62. The EP-WXT trigger 01709286204 is likely a flaring star
  63. EP detected a brightening of LMXB 1ES 1735-26.9
  64. GRB 260818B: EP-FXT follow-up observation
  65. GRB 260818A: J-band observations with WINTER
  66. GRB 260818B: NOT optical upper limits
  67. GRB 260810A: SVOM/GRM observation
  68. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  69. GRB260818A: EP-FXT follow-up observation
  70. GRB 260818B: LCO optical upper limits
  71. EP260806a: SAO RAS multicolor optical observations
  72. GRB 260818A: LCO optical upper limits
  73. EP260812a: AbAO optical upper limit
  74. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  75. EP260806a: NUTTELA-TAO optical observations
  76. The EP-WXT trigger 01709281429 is likely a flaring star
  77. EP260812a: AZT-22 optical upper limit
  78. EP260806a: WFST optical observations
  79. The EP-WXT trigger 01709280562 is likely a flaring star
  80. EP260812b: Optical upper limit with Kinder
  81. The EP-WXT trigger 01709279838 is likely a flaring star
  82. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  83. GRB 260808B: Liverpool Telescope further optical observations
  84. EP260812a: NOT and Liverpool Telescope upper limits:
  85. EP260812b: Liverpool Telescope observations
  86. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  87. EP260812a: SVOM/C-GFT optical upper limit
  88. EP260812b: COLIBRÍ optical observations
  89. EP260812b: SVOM/VT optical observation
  90. GRB 260808A: SVOM/GRM observation
  91. EP260812b: Einstein Probe detection of an X-ray transient
  92. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  93. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  94. EP260812a: Einstein Probe detection of an X-ray transient
  95. GRB 260809A: SAO RAS optical observations
  96. GRB 260808B: SAO RAS optical observations
  97. EP260806a: MAO/AZT-22 optical observations
  98. GRB260808B: MAO/AZT-22 optical observations
  99. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  100. GRB 260809A: J-band upper limit with WINTER

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