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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"

31633 results found.

  1. EP250302a: SPI-ACS/INTEGRAL Upper Limit
  2. GRB 250327B: CrAO and SAO RAS Optical Observations
  3. GRB 250327B: OHP/T193 spectroscopic observations and redshift confirmation
  4. GRB 250327B: further optical observations by LCOGT
  5. EP250315a: Pan-STARRS r and i-band imaging and photometry
  6. GRB 250327b: Liverpool Telescope optical observations
  7. GRB 250322A: GRANDMA/TNOT optical upper limits
  8. LIGO/Virgo/KAGRA S250328ae: Updated Sky localization
  9. GRB 250327A: SVOM/VT upper limits on the XRT position
  10. LIGO/Virgo/KAGRA S250328ae: Identification of a GW compact binary merger candidate
  11. GRB 250327B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  12. GRB 250327B: Las Cumbres optical counterpart detection
  13. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  14. GRB 250327B: 1.6m Mephisto optical observations
  15. GRB 250327B: NOT spectroscopic redshift z = 3.035
  16. GRB 250327B: GOTO optical counterpart detection
  17. GRB 250327B: SVOM/VT optically bright counterpart
  18. GRB 250327B: SAO RAS optical candidate
  19. FRB 20250316A: Gemini Imaging and Spectroscopy of the Sub-arcsecond Localization Region of FRB 20250316A
  20. GRB 250327A: J-band observations with WINTER
  21. GRB 250327A: SVOM/VT optical candidate
  22. FRB 20250316A: Pan-STARRS r and i-band imaging and photometry
  23. GRB 250327A: Fermi GBM observation
  24. Fermi GRB 250327A: Global MASTER-Net observations report
  25. Swift GRB 250327A: Global MASTER-Net observations report
  26. GRB 250327A: DDOTI Optical Observations
  27. GRB 250327A: COLIBRÍ optical upper limit
  28. GRB 250327A: Swift detection of a burst
  29. LIGO/Virgo/KAGRA S250326y: Updated Sky localization
  30. Konus-Wind detection of GRB 250322A (short)
  31. IPN triangulation of GRB 250322B
  32. LIGO/Virgo/KAGRA S250326y: Identification of a GW compact binary merger candidate
  33. EP250321a: Mondy AZT-33IK Continued Optical Observations
  34. GRB 250322A: third epoch of NOT optical observations
  35. GRB 250322A: Swift-BAT refined analysis
  36. GRB 250321B: ISON-Kitab RC-36 Optical Upper Limit
  37. FRB 250316A: NOT optical upper limit for the X ray source EP J120944.2+585060
  38. GRB 250322A: further NOT optical observations
  39. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  40. GRB 250322A: Swift/UVOT Upper Limits
  41. GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
  42. FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
  43. GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
  44. EP250321a: TNOT Observation of Optical Counterpart
  45. FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
  46. GRB 250322A: Gemini-North redshift of candidate host galaxy
  47. EP250304a: VLT/MUSE spectroscopic observation of its associated supernova SN 2025fhm
  48. GRB 250322A: AstroSat CZTI detection of a short burst
  49. GRB250322A: STEP/T80S optical limits
  50. GRB 250322A: Gemini-South optical observations
  51. GRB 250322A: VLT optical observations
  52. GRB 250322A: VLT near-infrared observations
  53. FRB 250316A: DDOTI Continued Optical Observations
  54. GRB 250322A: NOT optical upper limits
  55. GRB 250321B: SVOM/COLIBRÍ (F-GFT) follow-up observations
  56. FRB 20250316A: Kinder optical upper limits of the Einstein Probe candidate X-ray source EP J120944.2+585060
  57. GRB 250322A: MASTER optical observation
  58. EP250321a: Liverpool Telescope optical follow-up
  59. EP250321a: Mondy AZT-33IK Optical Observations
  60. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  61. EP250321a: KAIT optical observations
  62. EP250321A: COLIBRÍ Continuing Optical Observations
  63. GRB 250225B: GECAM-A detection
  64. GRB 250312A: GECAM-A detection
  65. GRB 250321B: Swift ToO observations
  66. EP250321a: WFST optical observations
  67. GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
  68. GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
  69. GRB 250320B: Fermi GBM Observation
  70. EP250321a: Xinglong 216 decaying optical observations
  71. GRB 250321A: Swift-BAT refined analysis
  72. GRB 250320B: Fermi-LAT detection
  73. EP250321a: SVOM/VT optical observation
  74. EP 250321A: Optical counterpart detection by LCO.
  75. EP250321a: Kinder optical follow-up observations
  76. GRB 250321A: Swift/UVOT Upper Limits
  77. GRB 250320B: SVOM/GRM observation of a long burst
  78. EP250321a: LCO optical counterpart detection
  79. EP250321a: Swift-XRT detection of an X-ray source
  80. EP250321A: COLIBRÍ Optical Observations
  81. EP250321a: VLT/X-shooter redshift z = 4.368
  82. GRB 250320B: AstroSat CZTI detection
  83. EP250321a: REM optical/NIR afterglow detection
  84. Fermi GRB 250320B: Global MASTER-Net observations report
  85. EP250321a: TRT optical counterpart detection
  86. EP250321a: Global MASTER-Net observations report
  87. Swift GRB 250321A: Global MASTER-Net observations report
  88. Fermi GRB 250321A: Global MASTER-Net observations report
  89. GRB 250321A: GOTO optical upper limits
  90. GRB 250321A: Swift-XRT localisation
  91. GRB 250314A: Keck/NIRC2 J-band upper limit
  92. EP250226a/GRB 250226A: KAIT optical observations
  93. GRB 250321A: Fermi GBM Observation
  94. GRB 250309B: Proof-of-concept for Joint ZTF+EP Experiment
  95. GRB 250317B: Mondy AZT-33IK Continued Optical Observations
  96. Fermi GRB 250319B: Global MASTER-Net observations report
  97. GRB 250313A: GRBAlpha detection
  98. LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
  99. GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
  100. LIGO/Virgo/KAGRA S250319bu: Updated Sky localization

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