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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"

28270 results found.

  1. GRB 250830B: Swift-XRT afterglow detection
  2. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  3. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  4. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  5. GRB 250902A: SVOM/GRM observation
  6. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  7. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  8. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  9. GRB 250901A: SVOM/VT optical afterglow with VHF data
  10. GRB 250901A: Swift-XRT afterglow detection
  11. EP250901a: Swift-XRT observations
  12. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  13. GRB 250901A: LCO optical upper limit
  14. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  15. EP250827b: Gemini Spectroscopy of AT 2025wkm
  16. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  17. EP250831a: NOT optical observations and tentative afterglow candidate
  18. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  19. GRB 250901A: SVOM detection of a burst
  20. EP250901a: Mephisto optical upper limits
  21. GRB 250830C: GECAM-B detection
  22. EP250901a: Einstein Probe detection of an X-ray transient
  23. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  24. EP250831a: Swift-XRT observations
  25. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  26. EP250831a: EP-WXT detection of a fast X-ray transient
  27. GRB 250831A: Swift-XRT counterpart detection
  28. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  29. GRB 250831A: SVOM/VT upper limit with VHF data
  30. GRB 250831A: SVOM detection of a soft burst
  31. GRB 250830B: Swift-XRT observations
  32. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  33. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  34. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  35. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  36. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  37. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  38. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  39. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  40. GRB 250830B: MAXI/GSC detection
  41. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  42. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  43. GRB 250828B: Swift-BAT refined analysis
  44. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  45. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  46. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  47. EP250828a: Optical counterpart detection with Kinder observations
  48. EP250828a: Liverpool Telescope upper limits
  49. EP250828a: Global MASTER-Net observations report
  50. EP-WXT trigger 01709200800 : KAIT optical observations
  51. EP250828a: KAIT optical upper limit
  52. EP250827a: Swift/UVOT Detection
  53. EP250828a: NOT optical counterpart confirmation
  54. EP250828a: SVOM/VT optical candidate
  55. EP250828a: Seimei/TriCCS optical counterpart detection
  56. EP250828a: Optical upper limit with Kinder observations
  57. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  58. EP250827a: LCO observations show fading optical counterpart
  59. EP250828a: Einstein Probe detection of an X-ray transient
  60. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  61. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  62. EP250827a: confirmation of optical rebrightening with LCO
  63. GRB 250826A: SVOM/GRM observation
  64. EP250827A: An optical rebrightening was detected by LCO.
  65. EP250827a: Swift-XRT counterpart detection
  66. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  67. EP250827a: TRT optical observations
  68. EP250827a: Gemini-South redshift z = 1.613
  69. EP250827a: Einstein Probe detection of an X-ray transient
  70. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  71. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  72. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  73. Fermi GRB 250824B: Global MASTER-Net observations report
  74. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  75. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  76. GRB 250823A: Swift-BAT refined analysis
  77. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  78. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  79. GRB 250823A: Swift-XRT refined Analysis
  80. EP250821a: MeerKAT radio counterpart
  81. GRB 250823A: COLIBRÍ optical observations
  82. GRB 250823A: SVOM/VT optical observation
  83. GRB 250823A: Swift/UVOT Detection
  84. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  85. GRB 250823A: Fermi GBM Observation
  86. GRB 250823A: Enhanced Swift-XRT position
  87. GRB 250823A: LCOGT Optical Detection
  88. GRB 250823A: Swift detection of a burst
  89. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  90. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  91. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  92. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  93. GRB 250806A: Gemini observations of host galaxy candidate
  94. GRB 250821A: Kilonova-Catcher optical upper limits
  95. EP250821a: Swift/XRT counterpart fading
  96. GRB 250821A: Swift-BAT refined analysis
  97. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  98. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  99. GRB 250821A: VLT/FORS2 Optical Observation
  100. GRB 250821B: SVOM/GRM observation

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