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Rapid Release Areahere we provide images/ finding charts and tables for new transients that may happen to fall within ChaMPlane survey coverage. Sep, 7, 2011 (ATel #3634)
Pre-outburst optical/NIR observations of the field around the
accreting millisecond X-ray pulsar IGR J17498-2921
M. van den Berg (Utrecht, CfA), J. Grindlay, P. Zhao, J. Hong,
M. Servillat (CfA)
We report on pre-outburst optical (VRIHalpha) and near-infrared (NIR;
JHKs) imaging observations of the field containing the newly
discovered transient accreting milli-second X-ray pulsar IGR
J17498-2921 (ATel #3551). The observations were done with the Mosaic
(optical) and ISPI (NIR) cameras on the CTIO-4m Blanco telescope as
part of our X-ray and optical/NIR Bulge Latitude Survey.
The optical images were taken on 2008 May 10. The astrometric
calibration has an uncertainty of ~0.1" in each coordinate. The R
(1200 sec total exposure time), I (540 sec), and Halpha (4500 sec)
images show a source at RA(J2000)=17h 49m 55.34s, Dec(J2000)=-29d 19m
19.7s. At an offset of 0.16", this is consistent with the Chandra
position. The Mosaic source lies 0.79" from the proposed optical
counterpart found in Sloan i' images from the 2m Faulkes Telescope
South taken during the ongoing outburst (ATel #3622). Given the error
on the Faulkes position (0.3"), and the absence of other sources in
the Mosaic and Faulkes images within 1.8" of the Chandra position, we
consider our Mosaic source and the proposed optical counterpart to be
the same. We note that the finding charts of ATel #3622 suggest that
the proposed counterpart is closer to the Chandra position than 0.79",
so we suspect that there may be a mistake in the reported
position. The magnitudes of our Mosaic source are R=23.2(2),
I=21.06(5), and Halpha-R=0.4(3). The values in brackets give the
internal errors of the PSF-photometry routine, while photometric
calibration errors are on the order of 0.1 mag (Zhao et al. 2005, ApJS
161, 429). We have used the transformation equations in Jordi et
al. 2006, A&A, 460, 339 to convert our I magnitude to the Sloan i'
band, which gives i'=21.9(2). This is consistent with the magnitude of
i'=22.5(7) in ATel #3622. As the true counterpart is expected to show
a large difference between the outburst and pre-outburst optical
magnitudes, it is likely that the proposed counterpart is a chance
alignment. The distance estimate for the X-ray pulsar (7.6 kpc; ATel
#3568) and column density derived from the X-ray spectrum (3e22 cm-2;
ATel #3555) also suggest that the optical source is an unassociated
foreground source.
At an offset of 0.16", the astrometric match found in pre-outburst NIR
images reported in ATel #3562 is consistent with a source in our ISPI
images from 2008 July 31 found at RA(J2000)=17h 49m 55.34s,
Dec(J2000)=-29d 19m 19.6s (error 0.13" in each coordinate). With
J=17.3(1), H=15.7(1), and Ks=15.0(1) the ISPI magnitudes are
consistent with the values from ATel #3562.
Finding charts of the field:
Aug, 5, 2011 (ATel #3529)IR counterpart candidates to the transient Swift J174535.5-285921 - UPDATE M. Servillat, J. Grindlay, P. Zhao, J. Hong, B. Allen (CfA), M. van den Berg (U. Utrecht), S. Laycock (UMass Lowell) Due to a correction of the coordinates (ATEL #3525) of the recent Galactic Center X-ray transient Swift J174535.5-285921 (ATEL #3472), we performed again the search for Ks-band near-infrared counterparts we reported in ATEL #3481 using images of the field we obtained with ISPI at CTIO 4m from 2005 to 2009, and 3 images obtained with PANIC at Magellan 6.5m (seeing 0.4-0.6") in 2004-06, 2007-08 and 2010-07 (the 2004 dataset is described in more detail by Laycock et al. 2005, ApJL, 634, L53). We found no long-term variables or astrometric candidates among our ISPI images. For the PANIC images, 2 candidates are consistent with the reported position of the transient Swift J174535.5-285921 (ATEL #3472), and one to the matching Chandra X-ray source CXOGC J174535.6-285928 (Muno et al. 2009, ApJS, 181, 110). IR CXOGC RA Dec K04 K07 K10 -- --------------- ------------ ------------ ----- ----- ----- S1 transient 17:45:35.774 -28:59:28.75 14.58 14.60 14.64 S2 transient 17:45:35.710 -28:59:29.71 15.06 15.14 15.32 S3 174535.6-285928 17:45:35.662 -28:59:28.99 14.57 14.56 14.68 Magnitudes are in the 2MASS system with an rms of ~0.2 mag, and absolute astrometry errors <0.2". Ks-band magnitudes are listed above for each star corresponding to the 3 PANIC observation epochs. Images are provided below. Note that the source CXOGC J174535.4-285925 at the corner of each image was previously considered a match to the Swift UVOT enhanced position (see ATEL #3481 reproduced below). Jul, 10, 2011 (ATel #3481)IR counterpart candidates to the transient Swift J174535.5-285921 M. Servillat, J. Grindlay, P. Zhao, J. Hong, B. Allen (CfA), M. van den Berg (U. Utrecht), S. Laycock (UMass Lowell) Following the recent detection of the new Galactic Center X-ray transient Swift J174535.5-285921 (ATEL #3472) and the search for potential near- infrared counterparts leading to magnitudes limits (ATEL #3476), we searched our catalog of Ks-band sources and long term variables in the 10'x10' field centered on Sgr A* (Servillat et al. in prep). We obtained yearly images of the field with ISPI at CTIO 4m from 2005 to 2009, and 3 images with PANIC at Magellan 6.5m (seeing 0.4-0.6") in 2004-06, 2007-08 and 2010-07 (the 2004 dataset is described in more details by Laycock et al. 2005, ApJL, 634, L53). We found no long-term variables in the Swift XRT-UVOT enhanced position error circle and no ISPI counterpart (similarly to ATEL #3476), but we found 3 counterpart candidates in our PANIC images to the 2 matching Chandra sources, CXOGC174535.5-285920 and CXOGC174535.4-285925 (Muno et al. 2009, ApJS 181, 110). IR CXOGC RA Dec K04 K07 K10 -- --------------- ----------- ----------- ----- ----- ----- A 174535.5-285920 17:45:35.54 -28:59:19.9 16.80 16.93 17.01 B 174535.5-285920 17:45:35.53 -28:59:20.3 16.89 C 174535.4-285925 17:45:35.44 -28:59:25.4 15.49 15.66 15.61 Magnitudes are in the 2MASS system with an rms of ~0.2 mag, the astrometry error is lower than 0.2". We give 3 K-band magnitudes corresponding to the 3 PANIC observation epochs. Source B magnitudes K07 and K10 are not available due to a slightly worse seeing at those epochs and confusion with source A, but the source seems to be present and constant in the images shown below. Observations are needed in the next week to test if one of these 3 sources, or any of the other IR sources in the Swift error circle, has brightened. Crowding in this region makes the use of large telescopes with an infrared camera required. Sept, 21, 2006IGR J17497-2821: Additional Optical Counterpart Identifications S. Laycock, P. Zhao, M. van den Berg, J. Grindlay, J. Hong We looked for counterparts for the new Integral/Swift transient IGR J17497-2821 toward the Galactic Bulge on a set of very deep (limiting Vmag~24) optical images taken in 2003 with the CTIO 4m + MOSAIC imager, as part of the ChaMPlane survey. |
