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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"

27324 results found.

  1. sb25081602: Swift-XRT observations
  2. GRB 250816A: SVOM/GRM observation of a short burst
  3. GRB 250814A: Swift-BAT refined analysis
  4. GRB 250813B: Liverpool Telescope optical upper limits
  5. GRB 250814A: Further COLIBRÍ optical upper limit
  6. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  7. GRB 250814A: GRAWITA TNG NIR observations
  8. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  9. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  10. GRB250814A: TRT optical upper limits
  11. GRB 250814B: SVOM/GRM observation
  12. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  13. GRB 250813B: SVOM/GRM observation
  14. GRB 250814A: P200/WIRC observations of the afterglow candidate
  15. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  16. GRB 250814A: KAIT optical upper limit
  17. GRB 250814A: Swift-XRT refined Analysis
  18. GRB 240814A: Fermi GBM Observation
  19. GRB 250814A: Possible afterglow candidate from P200/WIRC
  20. GRB 250813B: Fermi GBM Observation
  21. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  22. GRB 250814A: J-band upper limit from WINTER
  23. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  24. GRB 250813B: NOT observations of the optical afterglow
  25. GRB 250814A: COLIBRÍ optical upper limit
  26. GRB 250813A: AstroSat CZTI detection
  27. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  28. GRB 250814A: DDOTI Optical Upper Limit
  29. GRB 250813B: EP-FXT counterpart detection
  30. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  31. GRB 250813B: Swift-XRT afterglow detection
  32. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  33. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  34. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  35. GRB 250813B: SVOM detection of a bright long burst
  36. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  37. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  38. EP250812a: Nickel optical upper limit
  39. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  40. EP250812a: NOT, NTT, and GS observations
  41. GRB 250812A: Swift/UVOT Detection
  42. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  43. EP250812a: Liverpool Telescope upper limits
  44. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  45. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  46. GRB 250812A: EP-FXT counterpart detection
  47. GRB 250807B: Swift-BAT refined analysis
  48. EP 250812a: GOTO optical upper limit
  49. GRB 250812A: Kilonova-Catcher optical afterglow detection
  50. EP250812a: Swift-XRT counterpart detection
  51. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  52. EP250812a: Einstein Probe detection of an X-ray transient
  53. GRB 250812A: Swift-XRT afterglow detection
  54. GRB 250812A: TRT likely optical counterpart detection
  55. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  56. GRB 250809A: Swift-BAT refined analysis
  57. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  58. GRB 250807A: Swift-BAT refined analysis
  59. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  60. GRB 250809A: Swift/UVOT Detection
  61. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  62. Corrected Swift-XRT Refined Analysis of GRB 250809A
  63. GRB 250809A: Swift-XRT refined Analysis
  64. GRB 250809A: LCOGT Optical Upper Limits
  65. GRB 250808A: VLT X-shooter candidate counterpart
  66. GRB 250809A: Swift detection of a gamma ray burst
  67. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  68. GRB 250808A: Fermi GBM Observation
  69. GRB 250808A: Swift-XRT candidate counterpart detection
  70. GRB 250807B: Swift/UVOT Detection
  71. GRB 250807B: Kilonova-Catcher optical afterglow detection
  72. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  73. GRB 250807A: Swift/UVOT Detection
  74. GRB 250807A: Swift-XRT refined Analysis
  75. GRB 250806A: SVOM/MXT refined analysis
  76. EP250807a: NTT z-band optical upper limit
  77. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  78. GRB 250807A: SVOM/GRM observation
  79. GRB 250807A: AstroSat CZTI detection of bright long burst
  80. GRB 250807B: Swift-XRT refined Analysis
  81. EP250807a: EP-WXT detection of a fast X-ray transient
  82. EP 250807.979: GOTO optical upper limit
  83. EP250807a: COLIBRÍ optical upper limit
  84. EP250806a: Upper limit from Fermi-GBM Observations
  85. GRB 250807B: Enhanced Swift-XRT position
  86. GRB 250807A: Enhanced Swift-XRT position
  87. IceCube-Cascade 250804A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 250807B: Swift detection of a burst with an optical counterpart.
  89. GRB 250805A: Kilonova-Catcher optical upper limits
  90. GRB 250805A: Swift/UVOT Upper Limits
  91. GRB 250806A: Swift/UVOT U-band detection
  92. EP250806a: Liverpool telescope optical upper limit
  93. GRB 250807A: Swift detection of a burst with an optical counterpart
  94. EP250802a: EP-FXT follow-up observation
  95. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  96. EP250806a: SVOM /VT optical candidate
  97. GRB 250806A: J-band upper limit from WINTER
  98. GRB 250805A: Swift-BAT refined analysis
  99. GRB 250806A: KAIT optical upper limit
  100. GRB 250806A: Swift-XRT counterpart detection

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