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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').
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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"

26361 results found.

  1. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  2. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  3. GRB 250821A: LCOGT Optical Upper Limits
  4. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  5. GRB 250821A: Swift detection of a burst
  6. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  7. EP250821a: Einstein Probe detection of an X-ray transient
  8. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  9. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  10. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  11. GRB 250814A: Swift/UVOT Upper Limits
  12. GRB 250813B: Swift/UVOT Upper Limit
  13. IPN triangulation of GRB 250816A (short)
  14. IPN triangulation of GRB 250814C (short)
  15. IPN triangulation of GRB 250804B (short)
  16. GRB 250818B: Kilonova-Catcher optical afterglow detection
  17. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  18. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  19. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  20. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  21. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  22. GRB 250818B: Swift/UVOT Detection
  23. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  24. GRB 250818B: SAO RAS optical observations
  25. GRB 250818A: Swift-XRT refined Analysis
  26. GRB 250818B: EP-FXT counterpart detection
  27. GRB 250818A: Swift-BAT refined analysis
  28. GRB 250818B: KAIT optical observations
  29. GRB 250818A: Swift/UVOT Upper Limits
  30. LIGO/Virgo/KAGRA S250818t: Updated Sky localization
  31. GRB 250818A: Enhanced Swift-XRT position
  32. GRB 250813B: SVOM/ECLAIRs refined analysis
  33. GRB 250818A: Fermi GBM Observation
  34. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  35. GRB 250814A: Further GRAWITA TNG NIR observations
  36. GRB 250818B: Swift-XRT afterglow detection
  37. GRB 250818B: SVOM detection of a short burst
  38. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  39. GRB 250818A: Swift detection of a burst
  40. sb25081602: Swift-XRT observations
  41. GRB 250816A: SVOM/GRM observation of a short burst
  42. GRB 250814A: Swift-BAT refined analysis
  43. GRB 250813B: Liverpool Telescope optical upper limits
  44. GRB 250814A: Further COLIBRÍ optical upper limit
  45. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  46. GRB 250814A: GRAWITA TNG NIR observations
  47. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  48. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  49. GRB250814A: TRT optical upper limits
  50. GRB 250814B: SVOM/GRM observation
  51. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  52. GRB 250813B: SVOM/GRM observation
  53. GRB 250814A: P200/WIRC observations of the afterglow candidate
  54. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  55. GRB 250814A: KAIT optical upper limit
  56. GRB 250814A: Swift-XRT refined Analysis
  57. GRB 240814A: Fermi GBM Observation
  58. GRB 250814A: Possible afterglow candidate from P200/WIRC
  59. GRB 250813B: Fermi GBM Observation
  60. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  61. GRB 250814A: J-band upper limit from WINTER
  62. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  63. GRB 250813B: NOT observations of the optical afterglow
  64. GRB 250814A: COLIBRÍ optical upper limit
  65. GRB 250813A: AstroSat CZTI detection
  66. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  67. GRB 250814A: DDOTI Optical Upper Limit
  68. GRB 250813B: EP-FXT counterpart detection
  69. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  70. GRB 250813B: Swift-XRT afterglow detection
  71. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  72. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  73. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  74. GRB 250813B: SVOM detection of a bright long burst
  75. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  76. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  77. EP250812a: Nickel optical upper limit
  78. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  79. EP250812a: NOT, NTT, and GS observations
  80. GRB 250812A: Swift/UVOT Detection
  81. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  82. EP250812a: Liverpool Telescope upper limits
  83. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  84. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  85. GRB 250812A: EP-FXT counterpart detection
  86. GRB 250807B: Swift-BAT refined analysis
  87. EP 250812a: GOTO optical upper limit
  88. GRB 250812A: Kilonova-Catcher optical afterglow detection
  89. EP250812a: Swift-XRT counterpart detection
  90. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  91. EP250812a: Einstein Probe detection of an X-ray transient
  92. GRB 250812A: Swift-XRT afterglow detection
  93. GRB 250812A: TRT likely optical counterpart detection
  94. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  95. GRB 250809A: Swift-BAT refined analysis
  96. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  97. GRB 250807A: Swift-BAT refined analysis
  98. LIGO/Virgo/KAGRA S250810ck: Updated Sky localization and EM Bright Classification
  99. GRB 250809A: Swift/UVOT Detection
  100. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate

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