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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"

20391 results found.

  1. GRB 250823A: LCOGT Optical Detection
  2. GRB 250823A: Swift detection of a burst
  3. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  4. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  5. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  6. GRB 250806A: Gemini observations of host galaxy candidate
  7. GRB 250821A: Kilonova-Catcher optical upper limits
  8. GRB 250812A: SVOM/ECLAIRs refined analysis
  9. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  10. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  11. GRB 250821A: VLT/FORS2 Optical Observation
  12. GRB 250821B: SVOM/GRM observation
  13. EP250821a: SVOM/VT optical observation
  14. GRB 250821A: NOT z-band upper limit
  15. GRB 250821A: KAIT optical upper limit
  16. GRB 250821A: Swift-XRT refined Analysis
  17. GRB 250821A: Enhanced Swift-XRT position
  18. GRB 250821A: Swift/UVOT Upper Limits
  19. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  20. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  21. GRB 250821A: LCOGT Optical Upper Limits
  22. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  23. LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
  24. GRB 250821A: Swift detection of a burst
  25. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  26. EP250821a: Einstein Probe detection of an X-ray transient
  27. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  28. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  29. GRB 250818B: 10 GHz VLA detection
  30. LIGO/Virgo/KAGRA S250818k: Pan-STARRS grizy-band imaging and photometry of AT2025ulz
  31. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  32. GRB 250814A: Swift/UVOT Upper Limits
  33. GRB 250813B: Swift/UVOT Upper Limit
  34. IPN triangulation of GRB 250816A (short)
  35. IPN triangulation of GRB 250814C (short)
  36. IPN triangulation of GRB 250804B (short)
  37. GRB 250818B: Kilonova-Catcher optical afterglow detection
  38. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  39. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  40. GRB 250818B: Swift/UVOT Detection
  41. GRB 250818B: SAO RAS optical observations
  42. GRB 250818B: KAIT optical observations
  43. GRB 250818A: Swift/UVOT Upper Limits
  44. GRB 250818A: Enhanced Swift-XRT position
  45. GRB 250813B: SVOM/ECLAIRs refined analysis
  46. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  47. GRB 250814A: Further GRAWITA TNG NIR observations
  48. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  49. GRB 250818A: Swift detection of a burst
  50. GRB 250816A: SVOM/GRM observation of a short burst
  51. GRB 250813B: Liverpool Telescope optical upper limits
  52. GRB 250814A: Further COLIBRÍ optical upper limit
  53. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  54. GRB 250814A: GRAWITA TNG NIR observations
  55. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  56. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  57. GRB250814A: TRT optical upper limits
  58. GRB 250814B: SVOM/GRM observation
  59. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  60. GRB 250814A: P200/WIRC observations of the afterglow candidate
  61. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  62. GRB 250814A: KAIT optical upper limit
  63. GRB 250814A: Swift-XRT refined Analysis
  64. GRB 250814A: Possible afterglow candidate from P200/WIRC
  65. GRB 250813B: Fermi GBM Observation
  66. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  67. GRB 250814A: J-band upper limit from WINTER
  68. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  69. GRB 250813B: NOT observations of the optical afterglow
  70. GRB 250814A: COLIBRÍ optical upper limit
  71. GRB 250813A: AstroSat CZTI detection
  72. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  73. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  74. GRB 250814A: DDOTI Optical Upper Limit
  75. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  76. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  77. GRB 250813B: SVOM/COLIBRÍ (FM-GFT) optical observations
  78. GRB 250813B: SVOM detection of a bright long burst (Correction for GCN 41352).
  79. GRB 250813B: SVOM detection of a bright long burst
  80. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  81. EP250812a: Nickel optical upper limit
  82. EP250812a: NOT, NTT, and GS observations
  83. GRB 250812A: Swift/UVOT Detection
  84. EP250812a: COLIBRÍ detection of the VT candidate and evidence of flattening
  85. EP250812a: Liverpool Telescope upper limits
  86. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  87. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  88. EP 250812a: GOTO optical upper limit
  89. GRB 250812A: Kilonova-Catcher optical afterglow detection
  90. EP250812a: Swift-XRT counterpart detection
  91. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  92. EP250812a: Einstein Probe detection of an X-ray transient
  93. GRB 250812A: Swift-XRT afterglow detection
  94. GRB 250812A: TRT likely optical counterpart detection
  95. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  96. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  97. GRB 250809A: Swift/UVOT Detection
  98. GRB 250809A: Swift-XRT refined Analysis
  99. GRB 250809A: LCOGT Optical Upper Limits
  100. GRB 250808A: VLT X-shooter candidate counterpart

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