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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"

27350 results found.

  1. GRB 250813B: Swift/UVOT Upper Limit
  2. IPN triangulation of GRB 250816A (short)
  3. IPN triangulation of GRB 250814C (short)
  4. IPN triangulation of GRB 250804B (short)
  5. GRB 250818B: Kilonova-Catcher optical afterglow detection
  6. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  7. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  8. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  9. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  10. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  11. GRB 250818B: Swift/UVOT Detection
  12. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  13. GRB 250818B: SAO RAS optical observations
  14. GRB 250818A: Swift-XRT refined Analysis
  15. GRB 250818B: EP-FXT counterpart detection
  16. GRB 250818A: Swift-BAT refined analysis
  17. GRB 250818B: KAIT optical observations
  18. GRB 250818A: Swift/UVOT Upper Limits
  19. LIGO/Virgo/KAGRA S250818t: Updated Sky localization
  20. GRB 250818A: Enhanced Swift-XRT position
  21. GRB 250813B: SVOM/ECLAIRs refined analysis
  22. GRB 250818A: Fermi GBM Observation
  23. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  24. GRB 250814A: Further GRAWITA TNG NIR observations
  25. GRB 250818B: Swift-XRT afterglow detection
  26. GRB 250818B: SVOM detection of a short burst
  27. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  28. GRB 250818A: Swift detection of a burst
  29. sb25081602: Swift-XRT observations
  30. GRB 250816A: SVOM/GRM observation of a short burst
  31. GRB 250814A: Swift-BAT refined analysis
  32. GRB 250813B: Liverpool Telescope optical upper limits
  33. GRB 250814A: Further COLIBRÍ optical upper limit
  34. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  35. GRB 250814A: GRAWITA TNG NIR observations
  36. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  37. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  38. GRB250814A: TRT optical upper limits
  39. GRB 250814B: SVOM/GRM observation
  40. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  41. GRB 250813B: SVOM/GRM observation
  42. GRB 250814A: P200/WIRC observations of the afterglow candidate
  43. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  44. GRB 250814A: KAIT optical upper limit
  45. GRB 250814A: Swift-XRT refined Analysis
  46. GRB 240814A: Fermi GBM Observation
  47. GRB 250814A: Possible afterglow candidate from P200/WIRC
  48. GRB 250813B: Fermi GBM Observation
  49. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  50. GRB 250814A: J-band upper limit from WINTER
  51. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  52. GRB 250813B: NOT observations of the optical afterglow
  53. GRB 250814A: COLIBRÍ optical upper limit
  54. GRB 250813A: AstroSat CZTI detection
  55. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  56. GRB 250814A: DDOTI Optical Upper Limit
  57. GRB 250813B: EP-FXT counterpart detection
  58. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  59. GRB 250813B: Swift-XRT afterglow detection
  60. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  61. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  62. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  63. GRB 250813B: SVOM detection of a bright long burst
  64. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  65. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  66. EP250812a: Nickel optical upper limit
  67. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  68. EP250812a: NOT, NTT, and GS observations
  69. GRB 250812A: Swift/UVOT Detection
  70. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  71. EP250812a: Liverpool Telescope upper limits
  72. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  73. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  74. GRB 250812A: EP-FXT counterpart detection
  75. GRB 250807B: Swift-BAT refined analysis
  76. EP 250812a: GOTO optical upper limit
  77. GRB 250812A: Kilonova-Catcher optical afterglow detection
  78. EP250812a: Swift-XRT counterpart detection
  79. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  80. EP250812a: Einstein Probe detection of an X-ray transient
  81. GRB 250812A: Swift-XRT afterglow detection
  82. GRB 250812A: TRT likely optical counterpart detection
  83. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  84. GRB 250809A: Swift-BAT refined analysis
  85. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  86. GRB 250807A: Swift-BAT refined analysis
  87. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  88. GRB 250809A: Swift/UVOT Detection
  89. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  90. Corrected Swift-XRT Refined Analysis of GRB 250809A
  91. GRB 250809A: Swift-XRT refined Analysis
  92. GRB 250809A: LCOGT Optical Upper Limits
  93. GRB 250808A: VLT X-shooter candidate counterpart
  94. GRB 250809A: Swift detection of a gamma ray burst
  95. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  96. GRB 250808A: Fermi GBM Observation
  97. GRB 250808A: Swift-XRT candidate counterpart detection
  98. GRB 250807B: Swift/UVOT Detection
  99. GRB 250807B: Kilonova-Catcher optical afterglow detection
  100. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube

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