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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"

23601 results found.

  1. GRB 250818B: KAIT optical observations
  2. GRB 250818A: Swift/UVOT Upper Limits
  3. LIGO/Virgo/KAGRA S250818k: Candidates from the Zwicky Transient Facility
  4. GRB 250813B: SVOM/ECLAIRs refined analysis
  5. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  6. GRB 250814A: Further GRAWITA TNG NIR observations
  7. GRB 250818B: Swift-XRT afterglow detection
  8. GRB 250818B: GOTO optical counterpart candidate
  9. GRB 250818A: Swift detection of a burst
  10. sb25081602: Swift-XRT observations
  11. Fermi GRB 250814B: Global MASTER-Net observations report
  12. GRB 250814A: Swift-BAT refined analysis
  13. GRB 250815A: Fermi GBM Final Localization
  14. GRB 250813B: Liverpool Telescope optical upper limits
  15. GRB 250814A: Further COLIBRÍ optical upper limit
  16. GRB 250814A: GRAWITA TNG NIR observations
  17. GRB 250812A: SVOM/VT optical continued observation
  18. GRB250814A: TRT optical upper limits
  19. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  20. GRB 250813B: SVOM/GRM observation
  21. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  22. GRB 250814A: KAIT optical upper limit
  23. GRB 250814A: Swift-XRT refined Analysis
  24. GRB 250813B: Fermi GBM Observation
  25. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  26. Swift GRB250814.32: Global MASTER-Net observations report
  27. GRB 250814A: J-band upper limit from WINTER
  28. Subject GRB 250813B: SVOM/MXT refined analysis
  29. GRB 250814A: COLIBRÍ optical upper limit
  30. GRB 250813A: AstroSat CZTI detection
  31. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  32. GRB 250814A: DDOTI Optical Upper Limit
  33. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  34. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  35. GRB 250813B: Ondrejov D50 fast decay
  36. GRB 250813B: Ondrejov D50 optical afterglow detection
  37. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  38. EP250812a: Nickel optical upper limit
  39. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  40. GRB 250812A: NTT spectroscopic redshift z = 2.57
  41. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  42. EP250812a: NOT, NTT, and GS observations
  43. GRB 250812A: Swift/UVOT Detection
  44. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  45. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  46. GRB 250812A: EP-FXT counterpart detection
  47. GRB 250807B: Swift-BAT refined analysis
  48. EP 250812a: GOTO optical upper limit
  49. GRB 250812A: Kilonova-Catcher optical afterglow detection
  50. EP250812a: Swift-XRT counterpart detection
  51. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  52. EP250812a: Einstein Probe detection of an X-ray transient
  53. GRB 250812A: SVOM/VT optical afterglow confirmation
  54. GRB 250812A: TRT likely optical counterpart detection
  55. GRB 250809A: Swift-BAT refined analysis
  56. GRB 250807A: Swift-BAT refined analysis
  57. GRB 250809A: Swift/UVOT Detection
  58. GRB 250702B: Chandra X-ray Detection
  59. GRB 250808A: VLT X-shooter candidate counterpart
  60. GRB 250809A: Swift detection of a gamma ray burst
  61. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  62. GRB 250808A: Swift-XRT candidate counterpart detection
  63. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  64. Konus-Wind detection of GRB 250807A
  65. GRB 250807B: Kilonova-Catcher optical afterglow detection
  66. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  67. GRB 250806A: SVOM/MXT refined analysis
  68. GRB 250807A: AstroSat CZTI detection of bright long burst
  69. GRB 250807B: Swift-XRT refined Analysis
  70. GRB 250807B: NTT optical observations
  71. EP 250807.979: GOTO optical upper limit
  72. EP250807a: COLIBRÍ optical upper limit
  73. EP250806a: Upper limit from Fermi-GBM Observations
  74. GRB 250807B: Swift detection of a burst with an optical counterpart.
  75. GRB 250805A: Kilonova-Catcher optical upper limits
  76. GRB 250805A: Swift/UVOT Upper Limits
  77. EP#01709198415/EP250806a: Swift-XRT observations
  78. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  79. GRB 250806A: J-band upper limit from WINTER
  80. GRB 250805A: Swift-BAT refined analysis
  81. GRB 250806A: KAIT optical upper limit
  82. EP250806a: COLIBRÍ optical upper limit
  83. GRB 250806A: Kilonova-Catcher optical upper limits
  84. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  85. GRB 250805A: ESO/VLT observations
  86. GRB 250805A: Swift-XRT refined Analysis
  87. GRB 250804B: Swift-XRT observations
  88. GRB 250804C: AstroSat CZTI detection of a long burst
  89. GRB 250805A: TRT optical upper limits
  90. GRB 250805A: Swift detection of a burst
  91. EP250802a: Global MASTER-Net observations report
  92. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  93. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  94. GRB 250702B: SMA observations
  95. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  96. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  97. EP250730a: COLIBRÍ optical upper limit
  98. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  99. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  100. GRB 250725A: AstroSat CZTI detection

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