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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"

37555 results found.

  1. GRB 250815A: Fermi GBM Final Localization
  2. GRB 250813B: Liverpool Telescope optical upper limits
  3. GRB 250814A: Further COLIBRÍ optical upper limit
  4. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  5. GRB 250814A: GRAWITA TNG NIR observations
  6. GRB 250812A: SVOM/VT optical continued observation
  7. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  8. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  9. GRB250814A: TRT optical upper limits
  10. GRB 250814B: SVOM/GRM observation
  11. GRB 250814C: SVOM/GRM observation of a short burst
  12. GRB 250813B: SVOM/GRM observation
  13. GRB 250814A: P200/WIRC observations of the afterglow candidate
  14. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  15. GRB 250814A: KAIT optical upper limit
  16. GRB 250814A: Swift-XRT refined Analysis
  17. GRB 240814A: Fermi GBM Observation
  18. GRB 250814A: Possible afterglow candidate from P200/WIRC
  19. GRB 250813B: Fermi GBM Observation
  20. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  21. Fermi trigger No 776818276: Global MASTER-Net observations report
  22. GRB 250814A: J-band upper limit from WINTER
  23. GRB 250813B: NOT observations of the optical afterglow
  24. GRB 250813B: SVOM/VT optical observations
  25. Subject GRB 250813B: SVOM/MXT refined analysis
  26. GRB 250814A: COLIBRÍ optical upper limit
  27. GRB 250814B: Fermi GBM Final Real-time Localization
  28. GRB 250813A: AstroSat CZTI detection
  29. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  30. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  31. GRB 250814A: DDOTI Optical Upper Limit
  32. GRB 250813B: EP-FXT counterpart detection
  33. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  34. GRB 250813B: Swift-XRT afterglow detection
  35. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  36. GRB 250814A: Fermi GBM Final Real-time Localization
  37. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  38. GRB 250813B: Ondrejov D50 fast decay
  39. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  40. GRB 250813B: Ondrejov D50 optical afterglow detection
  41. GRB 250813B: SVOM detection of a bright long burst
  42. EP250812a: Nickel optical upper limit
  43. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  44. GRB 250812A: NTT spectroscopic redshift z = 2.57
  45. GRB 250812A: Swift/UVOT Detection
  46. GRB 250813A: Fermi GBM Final Localization
  47. IceCube-250813A - IceCube observation of a high-energy neutrino candidate track-like event
  48. GRB 250812A: EP-FXT counterpart detection
  49. GRB 250812A: Swift ToO observations
  50. GRB 250807B: Swift-BAT refined analysis
  51. GRB 250812A: Kilonova-Catcher optical afterglow detection
  52. Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
  53. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  54. GRB 250812A: SVOM/VT optical afterglow confirmation
  55. GRB 250812A: Swift-XRT afterglow detection
  56. GRB 250812A: TRT likely optical counterpart detection
  57. GRB 250812A: SVOM detection of a faint long burst
  58. GRB 250809A: Swift-BAT refined analysis
  59. Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
  60. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  61. GRB 250807A: Swift-BAT refined analysis
  62. GRB 250809A: Swift/UVOT Detection
  63. Corrected Swift-XRT Refined Analysis of GRB 250809A
  64. GRB 250809A: Swift-XRT refined Analysis
  65. GRB 250807B: SVOM/VT optical observation
  66. GRB 250809A: LCOGT Optical Upper Limits
  67. GRB 250702B: Chandra X-ray Detection
  68. Fermi GRB 250808A: Global MASTER-Net observations report
  69. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  70. GRB 250808A: VLT X-shooter candidate counterpart
  71. GRB 250809A: Prompt enhanced Swift-XRT position
  72. GRB 250809A: Swift detection of a gamma ray burst
  73. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  74. GRB 250808A: Fermi GBM Observation
  75. GRB 250808A: Swift-XRT candidate counterpart detection
  76. GRB 250807A: SVOM/VT optical continued observation
  77. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  78. GRB 250808A: SVOM detection of a long burst
  79. GRB 250808A: Fermi GBM Final Real-time Localization
  80. Konus-Wind detection of GRB 250807A
  81. GRB 250807B: Swift/UVOT Detection
  82. GRB 250807B: Kilonova-Catcher optical afterglow detection
  83. GRB 250807A: Swift/UVOT Detection
  84. GRB 250807A: Swift-XRT refined Analysis
  85. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  86. GRB 250806A: SVOM/MXT refined analysis
  87. GRB 250806A: SVOM/ECLAIRs refined analysis
  88. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  89. GRB 250804B: Insight-HXMT detection
  90. GRB 250807A: SVOM/GRM observation
  91. GRB 250807A: AstroSat CZTI detection of bright long burst
  92. GRB 250807B: Swift-XRT refined Analysis
  93. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  94. GRB 250807B: NTT optical observations
  95. GRB 250807A: SVOM/VT optical observation
  96. EP250806a: Upper limit from Fermi-GBM Observations
  97. GRB 250807B: Enhanced Swift-XRT position
  98. GRB 250807A: Enhanced Swift-XRT position
  99. GRB 250807B: Swift detection of a burst with an optical counterpart.
  100. GRB 250805A: Kilonova-Catcher optical upper limits

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