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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"

28060 results found.

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

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