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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"

19808 results found.

  1. GRB 250903A: Swift-XRT afterglow detection
  2. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  3. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  4. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  5. EP250905a: Liverpool Telescope i-band upper limits
  6. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  7. EP250905a: Liverpool Telescope observations
  8. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  9. EP250905b: EP-WXT detection of a fast X-ray transient
  10. EP250905a: JinShan likely optical counterpart detection
  11. GRB 250905A: Swift/UVOT Upper Limits
  12. GRB 250901A - SVOM/ECLAIRs refined analysis
  13. EP250905a: Einstein Probe detection of an X-ray transient
  14. GRB250904A: Liverpool Telescope upper limits
  15. GRB 250905A: Enhanced Swift-XRT position
  16. GRB 250904A: Swift/UVOT Detection
  17. GRB 250903A: Swift/UVOT detection
  18. EP detected a brightening of LMXB 1ES 1735-26.9
  19. GRB 250905A: KAIT optical upper limit
  20. GRB 250905A: Swift detection of a burst
  21. GRB 250904A: Enhanced Swift-XRT position
  22. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  23. GRB 250904A: TRT optical counterpart detection
  24. GRB 250904A: Swift detection of a burst
  25. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  26. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  27. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  28. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  29. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  30. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  31. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  32. GRB 250903A: LCO optical observation
  33. GRB 250903A: LCO optical afterglow detection
  34. GRB 250903A: SVOM/VT optical confirmation with VHF data
  35. EP250901a: Mondy, Assy and SAO RAS optical limits
  36. GRB 250903A: TRT optical counterpart detection
  37. GRB 250903A: SVOM detection of a burst
  38. EP250903a: TRT optical observations
  39. EP250903a: Einstein Probe detection of an X-ray transient
  40. EP 250827B: Detection of supernova counterpart by LCO.
  41. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  42. GRB 250902B: SVOM/GRM observation
  43. EP250827b: SVOM/VT observation of AT 2025wkm
  44. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  45. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  46. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  47. GRB 250901A: Swift/UVOT Upper Limit
  48. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  49. GRB 250830B: Swift-XRT afterglow detection
  50. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  51. GRB 250902A: SVOM/GRM observation
  52. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  53. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  54. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  55. GRB 250901A: SVOM/VT optical afterglow with VHF data
  56. GRB 250901A: Swift-XRT afterglow detection
  57. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  58. GRB 250901A: LCO optical upper limit
  59. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  60. EP250831a: NOT optical observations and tentative afterglow candidate
  61. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  62. GRB 250901A: SVOM detection of a burst
  63. EP250901a: Mephisto optical upper limits
  64. GRB 250830C: AstroSat CZTI detection of a long burst
  65. EP250901a: Einstein Probe detection of an X-ray transient
  66. EP250831a: EP-WXT detection of a fast X-ray transient
  67. GRB 250831A: Swift-XRT counterpart detection
  68. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  69. GRB 250831A: SVOM/VT upper limit with VHF data
  70. GRB 250831A: SVOM detection of a soft burst
  71. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  72. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  73. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  74. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  75. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  76. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  77. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  79. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  80. GRB 250808B: SVOM detection of a burst through offline search
  81. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  82. EP250828a: Optical counterpart detection with Kinder observations
  83. EP250828a: Liverpool Telescope upper limits
  84. EP-WXT trigger 01709200800 : KAIT optical observations
  85. EP250828a: KAIT optical upper limit
  86. EP250827a: Swift/UVOT Detection
  87. EP250828a: NOT optical counterpart confirmation
  88. EP250828a: SVOM/VT optical candidate
  89. EP250828a: Seimei/TriCCS optical counterpart detection
  90. EP250828a: Optical upper limit with Kinder observations
  91. EP250828a: Einstein Probe detection of an X-ray transient
  92. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  93. GRID detection of GRB 250824A
  94. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  95. EP250827a: confirmation of optical rebrightening with LCO
  96. GRB 250826A: SVOM/GRM observation
  97. EP250827A: An optical rebrightening was detected by LCO.
  98. EP250827a: TRT optical observations
  99. EP250827a: Einstein Probe detection of an X-ray transient
  100. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate

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