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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"

23603 results found.

  1. GRB 250818A: Swift-BAT refined analysis
  2. Fermi trigger No 776849714: Global MASTER-Net observations report
  3. GRB 250818B: KAIT optical observations
  4. GRB 250818A: Swift/UVOT Upper Limits
  5. LIGO/Virgo/KAGRA S250818k: Candidates from the Zwicky Transient Facility
  6. GRB 250813B: SVOM/ECLAIRs refined analysis
  7. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  8. GRB 250814A: Further GRAWITA TNG NIR observations
  9. GRB 250818B: Swift-XRT afterglow detection
  10. GRB 250818B: GOTO optical counterpart candidate
  11. GRB 250818A: Swift detection of a burst
  12. sb25081602: Swift-XRT observations
  13. Fermi GRB 250814B: Global MASTER-Net observations report
  14. GRB 250814A: Swift-BAT refined analysis
  15. GRB 250815A: Fermi GBM Final Localization
  16. GRB 250813B: Liverpool Telescope optical upper limits
  17. GRB 250814A: Further COLIBRÍ optical upper limit
  18. GRB 250814A: GRAWITA TNG NIR observations
  19. GRB 250812A: SVOM/VT optical continued observation
  20. GRB250814A: TRT optical upper limits
  21. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  22. GRB 250813B: SVOM/GRM observation
  23. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  24. GRB 250814A: KAIT optical upper limit
  25. GRB 250814A: Swift-XRT refined Analysis
  26. GRB 250813B: Fermi GBM Observation
  27. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  28. Swift GRB250814.32: Global MASTER-Net observations report
  29. GRB 250814A: J-band upper limit from WINTER
  30. Subject GRB 250813B: SVOM/MXT refined analysis
  31. GRB 250814A: COLIBRÍ optical upper limit
  32. GRB 250813A: AstroSat CZTI detection
  33. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  34. GRB 250814A: DDOTI Optical Upper Limit
  35. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  36. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  37. GRB 250813B: Ondrejov D50 fast decay
  38. GRB 250813B: Ondrejov D50 optical afterglow detection
  39. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  40. EP250812a: Nickel optical upper limit
  41. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  42. GRB 250812A: NTT spectroscopic redshift z = 2.57
  43. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  44. EP250812a: NOT, NTT, and GS observations
  45. GRB 250812A: Swift/UVOT Detection
  46. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  47. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  48. GRB 250812A: EP-FXT counterpart detection
  49. GRB 250807B: Swift-BAT refined analysis
  50. EP 250812a: GOTO optical upper limit
  51. GRB 250812A: Kilonova-Catcher optical afterglow detection
  52. EP250812a: Swift-XRT counterpart detection
  53. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  54. EP250812a: Einstein Probe detection of an X-ray transient
  55. GRB 250812A: SVOM/VT optical afterglow confirmation
  56. GRB 250812A: TRT likely optical counterpart detection
  57. GRB 250809A: Swift-BAT refined analysis
  58. GRB 250807A: Swift-BAT refined analysis
  59. GRB 250809A: Swift/UVOT Detection
  60. GRB 250702B: Chandra X-ray Detection
  61. GRB 250808A: VLT X-shooter candidate counterpart
  62. GRB 250809A: Swift detection of a gamma ray burst
  63. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  64. GRB 250808A: Swift-XRT candidate counterpart detection
  65. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  66. Konus-Wind detection of GRB 250807A
  67. GRB 250807B: Kilonova-Catcher optical afterglow detection
  68. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  69. GRB 250806A: SVOM/MXT refined analysis
  70. GRB 250807A: AstroSat CZTI detection of bright long burst
  71. GRB 250807B: Swift-XRT refined Analysis
  72. GRB 250807B: NTT optical observations
  73. EP 250807.979: GOTO optical upper limit
  74. EP250807a: COLIBRÍ optical upper limit
  75. EP250806a: Upper limit from Fermi-GBM Observations
  76. GRB 250807B: Swift detection of a burst with an optical counterpart.
  77. GRB 250805A: Kilonova-Catcher optical upper limits
  78. GRB 250805A: Swift/UVOT Upper Limits
  79. EP#01709198415/EP250806a: Swift-XRT observations
  80. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  81. GRB 250806A: J-band upper limit from WINTER
  82. GRB 250805A: Swift-BAT refined analysis
  83. GRB 250806A: KAIT optical upper limit
  84. EP250806a: COLIBRÍ optical upper limit
  85. GRB 250806A: Kilonova-Catcher optical upper limits
  86. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  87. GRB 250805A: ESO/VLT observations
  88. GRB 250805A: Swift-XRT refined Analysis
  89. GRB 250804B: Swift-XRT observations
  90. GRB 250804C: AstroSat CZTI detection of a long burst
  91. GRB 250805A: TRT optical upper limits
  92. GRB 250805A: Swift detection of a burst
  93. EP250802a: Global MASTER-Net observations report
  94. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  95. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  96. GRB 250702B: SMA observations
  97. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  98. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  99. EP250730a: COLIBRÍ optical upper limit
  100. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm

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