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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"

20490 results found.

  1. Fermi GRB 250821B: Global MASTER-Net observations report
  2. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  3. Swift GRB 250821A: Global MASTER-Net observations report
  4. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  5. LIGO/Virgo/KAGRA S250818k : Tautenburg observations, upper limits
  6. GRB 250821A: Swift/UVOT Upper Limits
  7. EP250821a: Swift XRT and UVOT counterpart detection
  8. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  9. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  10. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  11. LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
  12. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  13. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  14. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  15. GRB 250818B: 10 GHz VLA detection
  16. LIGO/Virgo/KAGRA S250818k: Pan-STARRS grizy-band imaging and photometry of AT2025ulz
  17. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  18. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  19. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  20. GRB 250814A: Swift/UVOT Upper Limits
  21. GRB 250813B: Swift/UVOT Upper Limit
  22. GRB 250818B: FTW optical and NIR observations show reddening of the counterpart
  23. GRB 250818B: Kilonova-Catcher optical afterglow detection
  24. GRB 250818B: Liverpool Telescope optical detections
  25. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  26. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  27. LIGO/Virgo/KAGRA S250818k: Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  28. GRB 250818B: Swift/UVOT Detection
  29. LIGO/Virgo/KAGRA S250818k: FTW Fast reddening of AT 2025ulz
  30. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  31. GRB 250818B: TRT Optical Observation
  32. Fermi GRB 250816A: Global MASTER-Net observations report
  33. GRB 250818B: SAO RAS optical observations
  34. Swift GRB 250818A: Global MASTER-Net observations report
  35. GRB 250818B: NOT optical observations
  36. LIGO/Virgo/KAGRA S250818k: FTW optical and NIR observations of AT 2025ulz
  37. Fermi trigger No 776849714: Global MASTER-Net observations report
  38. GRB 250818B: KAIT optical observations
  39. GRB 250818A: Swift/UVOT Upper Limits
  40. LIGO/Virgo/KAGRA S250818k: Candidates from the Zwicky Transient Facility
  41. GRB 250813B: SVOM/ECLAIRs refined analysis
  42. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  43. GRB 250818B: SVOM/VT optical observation
  44. GRB 250814A: Further GRAWITA TNG NIR observations
  45. GRB 250818B: Swift-XRT afterglow detection
  46. GRB 250818B: GOTO optical counterpart candidate
  47. sb25081602: Swift-XRT observations
  48. Fermi GRB 250814B: Global MASTER-Net observations report
  49. GRB 250813B: Liverpool Telescope optical upper limits
  50. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  51. GRB 250814A: GRAWITA TNG NIR observations
  52. GRB 250812A: SVOM/VT optical continued observation
  53. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  54. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  55. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  56. GRB 250814A: P200/WIRC observations of the afterglow candidate
  57. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  58. GRB 250814A: Possible afterglow candidate from P200/WIRC
  59. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  60. Fermi trigger No 776818276: Global MASTER-Net observations report
  61. Swift GRB250814.32: Global MASTER-Net observations report
  62. GRB 250814A: J-band upper limit from WINTER
  63. GRB 250813B: NOT observations of the optical afterglow
  64. GRB 250813B: SVOM/VT optical observations
  65. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  66. GRB 250814A: DDOTI Optical Upper Limit
  67. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  68. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  69. GRB 250813B: Ondrejov D50 fast decay
  70. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  71. EP250812a: Nickel optical upper limit
  72. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  73. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  74. EP250812a: NOT, NTT, and GS observations
  75. GRB 250812A: Swift/UVOT Detection
  76. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  77. EP250812a: SVOM/VT optical counterpart
  78. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  79. IceCube Alert 250813.14: Global MASTER-Net observations report
  80. GRB 250812A: Swift ToO observations
  81. EP 250812a: GOTO optical upper limit
  82. GRB 250812A: Kilonova-Catcher optical afterglow detection
  83. EP250812a: Swift-XRT counterpart detection
  84. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  85. GRB 250812A: SVOM/VT optical afterglow confirmation
  86. GRB 250812A: Swift-XRT afterglow detection
  87. GRB 250812A: TRT likely optical counterpart detection
  88. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  89. GRB 250809A: Swift/UVOT Detection
  90. GRB 250702B: Chandra X-ray Detection
  91. EP250807a: Global MASTER-Net observations report
  92. Fermi GRB 250808A: Global MASTER-Net observations report
  93. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  94. GRB 250808A: Swift-XRT candidate counterpart detection
  95. GRB 250807A: SVOM/VT optical continued observation
  96. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  97. GRB 250807B: Swift/UVOT Detection
  98. GRB 250807B: Kilonova-Catcher optical afterglow detection
  99. GRB 250807A: Swift/UVOT Detection
  100. EP250807a: NTT z-band optical upper limit

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