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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').
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"

21206 results found.

  1. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  2. EP250905b: EP-WXT detection of a fast X-ray transient
  3. EP250905a: FTW one optical and multiple NIR counterpart candidates
  4. EP250905a: JinShan likely optical counterpart detection
  5. GRB 250905A: Swift/UVOT Upper Limits
  6. GRB 250901A - SVOM/ECLAIRs refined analysis
  7. EP250905a: Einstein Probe detection of an X-ray transient
  8. GRB250904A: Liverpool Telescope upper limits
  9. GRB 250905A: Enhanced Swift-XRT position
  10. GRB 250904A: Swift/UVOT Detection
  11. GRB 250903A: Swift/UVOT detection
  12. EP detected a brightening of LMXB 1ES 1735-26.9
  13. GRB 250905A: KAIT optical upper limit
  14. GRB 250905A: Swift detection of a burst
  15. GRB 250904A: Enhanced Swift-XRT position
  16. GRB 250904A: TRT optical counterpart detection
  17. GRB 250904A: Swift detection of a burst
  18. GRB 250902A: VZLUSAT-2 detection
  19. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  20. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  21. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  22. GRB 250830C: VZLUSAT-2 detection
  23. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  24. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  25. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  26. GRB 250903A: LCO optical observation
  27. GRB 250903A: LCO optical afterglow detection
  28. GRB 250903A: SVOM/VT optical confirmation with VHF data
  29. EP250901a: Mondy, Assy and SAO RAS optical limits
  30. GRB 250903A: TRT optical counterpart detection
  31. GRB 250902B: AstroSat CZTI detection
  32. GRB 250903A: SVOM detection of a burst
  33. EP250903a: TRT optical observations
  34. EP250903a: Einstein Probe detection of an X-ray transient
  35. EP 250827B: Detection of supernova counterpart by LCO.
  36. GRB 250902B: SVOM/GRM observation
  37. EP250827b: SVOM/VT observation of AT 2025wkm
  38. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  39. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  40. GRB 250901A: Swift/UVOT Upper Limit
  41. GRB 250830B: Swift-XRT afterglow detection
  42. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  43. GRB 250902A: SVOM/GRM observation
  44. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  45. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  46. GRB 250901A: EP-FXT follow-up observation
  47. GRB 250901A: SVOM/VT optical afterglow with VHF data
  48. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  49. GRB 250901A: LCO optical upper limit
  50. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  51. EP250831a: NOT optical observations and tentative afterglow candidate
  52. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  53. GRB 250901A: SVOM detection of a burst
  54. EP250901a: Mephisto optical upper limits
  55. GRB 250830C: AstroSat CZTI detection of a long burst
  56. EP250901a: Einstein Probe detection of an X-ray transient
  57. IceCube Alert 250831.75: Global MASTER-Net observations report
  58. EP250831a: EP-WXT detection of a fast X-ray transient
  59. GRB 250831A: Swift-XRT counterpart detection
  60. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  61. GRB 250831A: SVOM/VT upper limit with VHF data
  62. GRB 250831A: SVOM detection of a soft burst
  63. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  64. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  65. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  66. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  67. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  68. GRB 250828B: Swift-BAT refined analysis
  69. EP250821a: SOAR observations
  70. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  71. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  72. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  73. GRB 250808B: SVOM detection of a burst through offline search
  74. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  75. EP250828a: Optical counterpart detection with Kinder observations
  76. EP250828a: Liverpool Telescope upper limits
  77. EP-WXT trigger 01709200800 : KAIT optical observations
  78. EP250828a: KAIT optical upper limit
  79. EP250827a: Swift/UVOT Detection
  80. EP250828a: NOT optical counterpart confirmation
  81. EP250828a: SVOM/VT optical candidate
  82. EP250828a: Seimei/TriCCS optical counterpart detection
  83. EP250828a: Optical upper limit with Kinder observations
  84. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  85. EP250828a: Einstein Probe detection of an X-ray transient
  86. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  87. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  88. EP250827a: confirmation of optical rebrightening with LCO
  89. EP250827a: GOTO observation of the optical afterglow
  90. GRB 250826A: SVOM/GRM observation
  91. EP250827A: An optical rebrightening was detected by LCO.
  92. EP250827a: TRT optical observations
  93. EP250827a: BOOTES-7 early optical dectection
  94. EP250827a: Las Cumbres independent detection of the optical counterpart
  95. EP250827a: Einstein Probe detection of an X-ray transient
  96. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  97. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  98. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  99. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  100. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate

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