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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"

19802 results found.

  1. IceCube-250905A: Upper limits from a search for additional neutrino events in IceCube
  2. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  3. EP250905a: Liverpool Telescope i-band upper limits
  4. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  5. EP250905a: Liverpool Telescope observations
  6. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  7. EP250905b: EP-WXT detection of a fast X-ray transient
  8. EP250905a: JinShan likely optical counterpart detection
  9. GRB 250905A: Swift/UVOT Upper Limits
  10. GRB 250901A - SVOM/ECLAIRs refined analysis
  11. EP250905a: Einstein Probe detection of an X-ray transient
  12. GRB250904A: Liverpool Telescope upper limits
  13. GRB 250905A: Enhanced Swift-XRT position
  14. GRB 250904A: Swift/UVOT Detection
  15. GRB 250903A: Swift/UVOT detection
  16. EP detected a brightening of LMXB 1ES 1735-26.9
  17. GRB 250905A: KAIT optical upper limit
  18. GRB 250905A: Swift detection of a burst
  19. GRB 250904A: Enhanced Swift-XRT position
  20. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  21. GRB 250904A: TRT optical counterpart detection
  22. GRB 250904A: Swift detection of a burst
  23. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  24. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  25. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  26. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  27. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  28. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  29. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  30. GRB 250903A: LCO optical observation
  31. GRB 250903A: LCO optical afterglow detection
  32. GRB 250903A: SVOM/VT optical confirmation with VHF data
  33. EP250901a: Mondy, Assy and SAO RAS optical limits
  34. GRB 250903A: TRT optical counterpart detection
  35. GRB 250903A: SVOM detection of a burst
  36. EP250903a: TRT optical observations
  37. EP250903a: Einstein Probe detection of an X-ray transient
  38. EP 250827B: Detection of supernova counterpart by LCO.
  39. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  40. GRB 250902B: SVOM/GRM observation
  41. EP250827b: SVOM/VT observation of AT 2025wkm
  42. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  43. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  44. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  45. GRB 250901A: Swift/UVOT Upper Limit
  46. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  47. GRB 250830B: Swift-XRT afterglow detection
  48. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  49. GRB 250902A: SVOM/GRM observation
  50. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  51. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  52. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  53. GRB 250901A: SVOM/VT optical afterglow with VHF data
  54. GRB 250901A: Swift-XRT afterglow detection
  55. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  56. GRB 250901A: LCO optical upper limit
  57. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  58. EP250831a: NOT optical observations and tentative afterglow candidate
  59. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  60. GRB 250901A: SVOM detection of a burst
  61. EP250901a: Mephisto optical upper limits
  62. GRB 250830C: AstroSat CZTI detection of a long burst
  63. EP250901a: Einstein Probe detection of an X-ray transient
  64. EP250831a: EP-WXT detection of a fast X-ray transient
  65. GRB 250831A: Swift-XRT counterpart detection
  66. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  67. GRB 250831A: SVOM/VT upper limit with VHF data
  68. GRB 250831A: SVOM detection of a soft burst
  69. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  70. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  71. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  72. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  73. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  74. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  75. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  76. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  77. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  78. GRB 250808B: SVOM detection of a burst through offline search
  79. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  80. EP250828a: Optical counterpart detection with Kinder observations
  81. EP250828a: Liverpool Telescope upper limits
  82. EP-WXT trigger 01709200800 : KAIT optical observations
  83. EP250828a: KAIT optical upper limit
  84. EP250827a: Swift/UVOT Detection
  85. EP250828a: NOT optical counterpart confirmation
  86. EP250828a: SVOM/VT optical candidate
  87. EP250828a: Seimei/TriCCS optical counterpart detection
  88. EP250828a: Optical upper limit with Kinder observations
  89. EP250828a: Einstein Probe detection of an X-ray transient
  90. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  91. GRID detection of GRB 250824A
  92. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  93. EP250827a: confirmation of optical rebrightening with LCO
  94. GRB 250826A: SVOM/GRM observation
  95. EP250827A: An optical rebrightening was detected by LCO.
  96. EP250827a: TRT optical observations
  97. EP250827a: Einstein Probe detection of an X-ray transient
  98. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  99. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  100. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz

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