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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"

32720 results found.

  1. EP250827a: Gemini-South redshift z = 1.613
  2. EP250827a: Global MASTER-Net observations report
  3. EP250827a: Las Cumbres independent detection of the optical counterpart
  4. EP250827a: Gemini-South optical counterpart detection
  5. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  6. Fermi GRB 250826A: Global MASTER-Net observations report
  7. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  8. EP250821a: Gemini GMOS Redshift Confirmation
  9. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  10. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  11. Fermi GRB 250824B: Global MASTER-Net observations report
  12. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  13. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  14. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  15. GRB 250823A: Swift-BAT refined analysis
  16. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  17. GRB 250821B: AstroSat CZTI detection
  18. GRB 250819A: AstroSat CZTI detection
  19. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  20. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  21. GRB 250821B: Insight-HXMT detection
  22. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  23. EP250821a: MeerKAT radio counterpart
  24. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  25. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  26. GRB 250823A: COLIBRÍ optical observations
  27. GRB 250823A: SVOM/VT optical observation
  28. GRB 250823A: Swift/UVOT Detection
  29. GRB 250823A: NOT optical observations
  30. LIGO/Virgo/KAGRA S250818k: CFH/MegaCam follow-up observation for AT2025ulz
  31. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  32. GRB 250823A: Fermi GBM Observation
  33. GRB 250818B: MeerKAT Detection
  34. GRB 250823A: LCOGT Optical Detection
  35. GRB 250823A: BOOTES6/DPRT early optical detection
  36. GRB 250823A: Liverpool Telescope optical detection
  37. Konus-Wind detection of GRB 250821B
  38. LIGO/Virgo/KAGRA S250818k: Rebrightening detected with Gemini/GMOS
  39. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  40. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  41. LIGO/Virgo/KAGRA S250818k: PRIME nIR observations of AT2025ulz
  42. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  43. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  44. LIGO/Virgo/Kagra S250818k: STEP/T80N upper limits on 2025ulz
  45. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  46. GRB 250806A: Gemini observations of host galaxy candidate
  47. IPN triangulation of GRB 250821B (long/bright)
  48. GRB 250821A: Kilonova-Catcher optical upper limits
  49. EP250821a: Swift/XRT counterpart fading
  50. GRB 250812A: SVOM/ECLAIRs refined analysis
  51. GRB 250821A: Swift-BAT refined analysis
  52. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  53. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  54. EP250821a: Swift/UVOT further observations.
  55. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  56. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  57. GRB 250821A: VLT/FORS2 Optical Observation
  58. GRB 250821A: GECAM-B detection
  59. GRB 250821B: SVOM/GRM observation
  60. EP250821a: SVOM/VT optical observation
  61. Fermi GRB 250821B: Global MASTER-Net observations report
  62. GRB 250821A: NOT z-band upper limit
  63. GRB 250821A: KAIT optical upper limit
  64. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  65. Swift GRB 250821A: Global MASTER-Net observations report
  66. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  67. LIGO/Virgo/KAGRA S250818k : Tautenburg observations, upper limits
  68. GRB 250821A: Swift/UVOT Upper Limits
  69. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  70. EP250821a: Swift XRT and UVOT counterpart detection
  71. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  72. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  73. GRB 250821A: LCOGT Optical Upper Limits
  74. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  75. LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
  76. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  77. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  78. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  79. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  80. GRB 250818B: 10 GHz VLA detection
  81. LIGO/Virgo/KAGRA S250818k: Pan-STARRS grizy-band imaging and photometry of AT2025ulz
  82. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  83. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  84. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  85. GRB 250814A: Swift/UVOT Upper Limits
  86. GRB 250813B: Swift/UVOT Upper Limit
  87. IPN triangulation of GRB 250816A (short)
  88. IPN triangulation of GRB 250814C (short)
  89. IPN triangulation of GRB 250804B (short)
  90. GRB 250818B: FTW optical and NIR observations show reddening of the counterpart
  91. GRB 250818B: Kilonova-Catcher optical afterglow detection
  92. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  93. GRB 250818B: Liverpool Telescope optical detections
  94. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  95. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  96. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  97. GRB 250818A: AstroSat CZTI detection
  98. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  99. LIGO/Virgo/KAGRA S250818k: Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  100. GRB 250818B: Swift/UVOT Detection

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