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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28275 results found.

  1. EP250821a: Swift/XRT counterpart fading
  2. GRB 250821A: Swift-BAT refined analysis
  3. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  4. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  5. GRB 250821A: VLT/FORS2 Optical Observation
  6. GRB 250821B: SVOM/GRM observation
  7. EP250821a: SVOM/VT optical observation
  8. GRB 250821A: NOT z-band upper limit
  9. GRB 250821A: KAIT optical upper limit
  10. GRB 250821A: Swift-XRT refined Analysis
  11. GRB 250821B: Fermi GBM Detection
  12. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  13. GRB 250821A: Enhanced Swift-XRT position
  14. GRB 250821A: Swift/UVOT Upper Limits
  15. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  16. EP250821a: Swift XRT and UVOT counterpart detection
  17. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  18. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  19. GRB 250821A: LCOGT Optical Upper Limits
  20. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  21. GRB 250821A: Swift detection of a burst
  22. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  23. EP250821a: Einstein Probe detection of an X-ray transient
  24. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  25. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  26. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  27. GRB 250814A: Swift/UVOT Upper Limits
  28. GRB 250813B: Swift/UVOT Upper Limit
  29. IPN triangulation of GRB 250816A (short)
  30. IPN triangulation of GRB 250814C (short)
  31. IPN triangulation of GRB 250804B (short)
  32. GRB 250818B: Kilonova-Catcher optical afterglow detection
  33. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  34. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  35. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  36. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  37. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  38. GRB 250818B: Swift/UVOT Detection
  39. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  40. GRB 250818B: SAO RAS optical observations
  41. GRB 250818A: Swift-XRT refined Analysis
  42. GRB 250818B: EP-FXT counterpart detection
  43. GRB 250818A: Swift-BAT refined analysis
  44. GRB 250818B: KAIT optical observations
  45. GRB 250818A: Swift/UVOT Upper Limits
  46. LIGO/Virgo/KAGRA S250818t: Updated Sky localization
  47. GRB 250818A: Enhanced Swift-XRT position
  48. GRB 250813B: SVOM/ECLAIRs refined analysis
  49. GRB 250818A: Fermi GBM Observation
  50. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  51. GRB 250814A: Further GRAWITA TNG NIR observations
  52. GRB 250818B: Swift-XRT afterglow detection
  53. GRB 250818B: SVOM detection of a short burst
  54. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  55. GRB 250818A: Swift detection of a burst
  56. sb25081602: Swift-XRT observations
  57. GRB 250816A: SVOM/GRM observation of a short burst
  58. GRB 250814A: Swift-BAT refined analysis
  59. GRB 250813B: Liverpool Telescope optical upper limits
  60. GRB 250814A: Further COLIBRÍ optical upper limit
  61. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  62. GRB 250814A: GRAWITA TNG NIR observations
  63. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  64. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  65. GRB250814A: TRT optical upper limits
  66. GRB 250814B: SVOM/GRM observation
  67. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  68. GRB 250813B: SVOM/GRM observation
  69. GRB 250814A: P200/WIRC observations of the afterglow candidate
  70. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  71. GRB 250814A: KAIT optical upper limit
  72. GRB 250814A: Swift-XRT refined Analysis
  73. GRB 240814A: Fermi GBM Observation
  74. GRB 250814A: Possible afterglow candidate from P200/WIRC
  75. GRB 250813B: Fermi GBM Observation
  76. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  77. GRB 250814A: J-band upper limit from WINTER
  78. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  79. GRB 250813B: NOT observations of the optical afterglow
  80. GRB 250814A: COLIBRÍ optical upper limit
  81. GRB 250813A: AstroSat CZTI detection
  82. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  83. GRB 250814A: DDOTI Optical Upper Limit
  84. GRB 250813B: EP-FXT counterpart detection
  85. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  86. GRB 250813B: Swift-XRT afterglow detection
  87. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  88. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  89. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  90. GRB 250813B: SVOM detection of a bright long burst
  91. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  92. LIGO/Virgo/KAGRA S250813k: Updated Sky localization
  93. EP250812a: Nickel optical upper limit
  94. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  95. EP250812a: NOT, NTT, and GS observations
  96. GRB 250812A: Swift/UVOT Detection
  97. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  98. EP250812a: Liverpool Telescope upper limits
  99. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  100. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate

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