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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

28042 results found.

  1. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  2. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  3. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  4. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  5. GRB 250818B: Swift/UVOT Detection
  6. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  7. GRB 250818B: SAO RAS optical observations
  8. GRB 250818A: Swift-XRT refined Analysis
  9. GRB 250818B: EP-FXT counterpart detection
  10. GRB 250818A: Swift-BAT refined analysis
  11. GRB 250818B: KAIT optical observations
  12. GRB 250818A: Swift/UVOT Upper Limits
  13. LIGO/Virgo/KAGRA S250818t: Updated Sky localization
  14. GRB 250818A: Enhanced Swift-XRT position
  15. GRB 250813B: SVOM/ECLAIRs refined analysis
  16. GRB 250818A: Fermi GBM Observation
  17. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  18. GRB 250814A: Further GRAWITA TNG NIR observations
  19. GRB 250818B: Swift-XRT afterglow detection
  20. GRB 250818B: SVOM detection of a short burst
  21. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  22. GRB 250818A: Swift detection of a burst
  23. sb25081602: Swift-XRT observations
  24. GRB 250816A: SVOM/GRM observation of a short burst
  25. GRB 250814A: Swift-BAT refined analysis
  26. GRB 250813B: Liverpool Telescope optical upper limits
  27. GRB 250814A: Further COLIBRÍ optical upper limit
  28. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  29. GRB 250814A: GRAWITA TNG NIR observations
  30. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  31. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  32. GRB250814A: TRT optical upper limits
  33. GRB 250814B: SVOM/GRM observation
  34. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  35. GRB 250813B: SVOM/GRM observation
  36. GRB 250814A: P200/WIRC observations of the afterglow candidate
  37. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  38. GRB 250814A: KAIT optical upper limit
  39. GRB 250814A: Swift-XRT refined Analysis
  40. GRB 240814A: Fermi GBM Observation
  41. GRB 250814A: Possible afterglow candidate from P200/WIRC
  42. GRB 250813B: Fermi GBM Observation
  43. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  44. GRB 250814A: J-band upper limit from WINTER
  45. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  46. GRB 250813B: NOT observations of the optical afterglow
  47. GRB 250814A: COLIBRÍ optical upper limit
  48. GRB 250813A: AstroSat CZTI detection
  49. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  50. GRB 250814A: DDOTI Optical Upper Limit
  51. GRB 250813B: EP-FXT counterpart detection
  52. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  53. GRB 250813B: Swift-XRT afterglow detection
  54. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  55. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  56. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  57. GRB 250813B: SVOM detection of a bright long burst
  58. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  59. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  60. EP250812a: Nickel optical upper limit
  61. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  62. EP250812a: NOT, NTT, and GS observations
  63. GRB 250812A: Swift/UVOT Detection
  64. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  65. EP250812a: Liverpool Telescope upper limits
  66. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  67. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  68. GRB 250812A: EP-FXT counterpart detection
  69. GRB 250807B: Swift-BAT refined analysis
  70. EP 250812a: GOTO optical upper limit
  71. GRB 250812A: Kilonova-Catcher optical afterglow detection
  72. EP250812a: Swift-XRT counterpart detection
  73. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  74. EP250812a: Einstein Probe detection of an X-ray transient
  75. GRB 250812A: Swift-XRT afterglow detection
  76. GRB 250812A: TRT likely optical counterpart detection
  77. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  78. GRB 250809A: Swift-BAT refined analysis
  79. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  80. GRB 250807A: Swift-BAT refined analysis
  81. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  82. GRB 250809A: Swift/UVOT Detection
  83. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  84. Corrected Swift-XRT Refined Analysis of GRB 250809A
  85. GRB 250809A: Swift-XRT refined Analysis
  86. GRB 250809A: LCOGT Optical Upper Limits
  87. GRB 250808A: VLT X-shooter candidate counterpart
  88. GRB 250809A: Swift detection of a gamma ray burst
  89. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  90. GRB 250808A: Fermi GBM Observation
  91. GRB 250808A: Swift-XRT candidate counterpart detection
  92. GRB 250807B: Swift/UVOT Detection
  93. GRB 250807B: Kilonova-Catcher optical afterglow detection
  94. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  95. GRB 250807A: Swift/UVOT Detection
  96. GRB 250807A: Swift-XRT refined Analysis
  97. GRB 250806A: SVOM/MXT refined analysis
  98. EP250807a: NTT z-band optical upper limit
  99. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  100. GRB 250807A: SVOM/GRM observation

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