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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"

28261 results found.

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

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