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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"

25713 results found.

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

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