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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').
Advanced Search

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"

28261 results found.

  1. GRB 250901A: Swift-XRT afterglow detection
  2. EP250901a: Swift-XRT observations
  3. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  4. GRB 250901A: LCO optical upper limit
  5. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  6. EP250827b: Gemini Spectroscopy of AT 2025wkm
  7. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  8. EP250831a: NOT optical observations and tentative afterglow candidate
  9. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  10. GRB 250901A: SVOM detection of a burst
  11. EP250901a: Mephisto optical upper limits
  12. GRB 250830C: GECAM-B detection
  13. EP250901a: Einstein Probe detection of an X-ray transient
  14. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  15. EP250831a: Swift-XRT observations
  16. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  17. EP250831a: EP-WXT detection of a fast X-ray transient
  18. GRB 250831A: Swift-XRT counterpart detection
  19. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  20. GRB 250831A: SVOM/VT upper limit with VHF data
  21. GRB 250831A: SVOM detection of a soft burst
  22. GRB 250830B: Swift-XRT observations
  23. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  24. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  25. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  26. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  27. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  28. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  29. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  30. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  31. GRB 250830B: MAXI/GSC detection
  32. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  33. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  34. GRB 250828B: Swift-BAT refined analysis
  35. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  36. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  37. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  38. EP250828a: Optical counterpart detection with Kinder observations
  39. EP250828a: Liverpool Telescope upper limits
  40. EP250828a: Global MASTER-Net observations report
  41. EP-WXT trigger 01709200800 : KAIT optical observations
  42. EP250828a: KAIT optical upper limit
  43. EP250827a: Swift/UVOT Detection
  44. EP250828a: NOT optical counterpart confirmation
  45. EP250828a: SVOM/VT optical candidate
  46. EP250828a: Seimei/TriCCS optical counterpart detection
  47. EP250828a: Optical upper limit with Kinder observations
  48. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  49. EP250827a: LCO observations show fading optical counterpart
  50. EP250828a: Einstein Probe detection of an X-ray transient
  51. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  52. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  53. EP250827a: confirmation of optical rebrightening with LCO
  54. GRB 250826A: SVOM/GRM observation
  55. EP250827A: An optical rebrightening was detected by LCO.
  56. EP250827a: Swift-XRT counterpart detection
  57. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  58. EP250827a: TRT optical observations
  59. EP250827a: Gemini-South redshift z = 1.613
  60. EP250827a: Einstein Probe detection of an X-ray transient
  61. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  62. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  63. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  64. Fermi GRB 250824B: Global MASTER-Net observations report
  65. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  66. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  67. GRB 250823A: Swift-BAT refined analysis
  68. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  69. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  70. GRB 250823A: Swift-XRT refined Analysis
  71. EP250821a: MeerKAT radio counterpart
  72. GRB 250823A: COLIBRÍ optical observations
  73. GRB 250823A: SVOM/VT optical observation
  74. GRB 250823A: Swift/UVOT Detection
  75. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  76. GRB 250823A: Fermi GBM Observation
  77. GRB 250823A: Enhanced Swift-XRT position
  78. GRB 250823A: LCOGT Optical Detection
  79. GRB 250823A: Swift detection of a burst
  80. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  81. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  82. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  83. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  84. GRB 250806A: Gemini observations of host galaxy candidate
  85. GRB 250821A: Kilonova-Catcher optical upper limits
  86. EP250821a: Swift/XRT counterpart fading
  87. GRB 250821A: Swift-BAT refined analysis
  88. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  89. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  90. GRB 250821A: VLT/FORS2 Optical Observation
  91. GRB 250821B: SVOM/GRM observation
  92. EP250821a: SVOM/VT optical observation
  93. GRB 250821A: NOT z-band upper limit
  94. GRB 250821A: KAIT optical upper limit
  95. GRB 250821A: Swift-XRT refined Analysis
  96. GRB 250821B: Fermi GBM Detection
  97. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  98. GRB 250821A: Enhanced Swift-XRT position
  99. GRB 250821A: Swift/UVOT Upper Limits
  100. EP250821a: Rapidly fading optical source detected in Las Cumbres followup

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