The current Call for Proposals is for HST Cycle 34. 0 Assigned ID: 6942 ----- Attempting Submission 1 (Thu Jan 08 21:08:32 GMT 2026) ----- this is an XMM/HST proposal. I was instructed to slect cycle 33 Unsupported characters were found in Observing Description and replaced with |*| POS TARG OUTSIDE OF APERTURE NO ORIENT POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE NO ORIENT POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE NO ORIENT POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE NO ORIENT POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE NO ORIENT POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE NO ORIENT POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE NO ORIENT POS TARG OUTSIDE OF APERTURE POS TARG OUTSIDE OF APERTURE NO ORIENT POS TARG OUTSIDE OF APERTURE With respect to the original text in the proposal, we removed the FLATS for defringing because we realized fringes are not an issue in the wavelength covered by these observations. We slightly increased the exposure time of the MAMA observations, since we realized there was some extra time available in the first orbit. 447644107 ----- Attempting Submission 1 (Wed Feb 04 22:51:58 GMT 2026) ----- we believe that the warnings can be ignored but please let us know if there are any concerns. Thanks! True Seyfert 2 galaxies are active nuclei with no optical/UV/IR broad emission lines that are simultaneously unabsorbed in X-rays and variable, demonstrating a direct view of the inner nucleus. The detection of optical and UV broad lines in the prototypical Seyfert 2 galaxy NGC 3147 in narrow-slit HST spectra has however questioned the very existence of the population as a whole. We propose here a joint XMM-Newton and HST program on one of the best remaining true Seyfert 2 candidates - NGC 3660 - with the goals of (I) searching for a broad, so far undetected, Halpha emission line using narrow-slit HST spectroscopy, and (II) deriveing a high quality intrinsic nuclear SED using quasi-simultaneous observations. The program has the potential of settling once and for all the debate on the existence of true Seyfert 2 galaxies in general. In order to achieve our goals, we request narrow-slit optical spectra around H|*| using STIS/CCD and the G750M grating and optical/UV imaging with STIS/NUV-MAMA. We will use the 52x0.1 arcsec slit to reduce host galaxy contamination by a factor of |*| 10 with respect to ground based observations and to increase the contrast of any broad line component against both the stellar continuum and the superimposed narrow lines, which are mostly produced in the extended (kpc-scale) narrow line region (0.1|*| |*| 25 pc at z = 0.012). We replicate the highly successful strategy that led to the discovery of a broad H|*| in NGC 3147 (right panel of Fig. 1) by our team. The pointing will be aimed at the host galaxy photocenter. A target acquisition image with the F28X50LP will be taken to allow recentering on the brightest region, where we expect the AGN to be located, with exposure of 60 s, appropriate for the expected surface brightness of |*| 15 mag arcsec|*|2. To avoid missing the AGN at the center of the galaxy nucleus, we will obtain 5 spectra, as done for NGC 3147 (GO15225, PI: Bianchi). The first will be centered at the location derived following the acquisition image. The following will be taken with a POS-TARG of (+0.1,0.0), (+0.2,0.0), (-0.1,0.0), (-0.2,0.0). We performed accurate S/N simulations using the STIS ETC. The stellar continuum within the 0.1|*| slit is expected to be F|*| |*| 2 |*| 10|*|16 erg cm|*|2 s|*|1 |*|A|*|1, using the information derived from ground based spectra. The resulting S/N is 11 per resolution element. The broad emission line is expected to have a flux F(H|*|) |*| 1 |*| 10|*|13 erg cm|*|2 s|*|1 and FWHM|*|3000-6000 km s|*|1 (Bianchi et al 2012). Assuming a FWHM of 5000 km s|*|1, we expect a S/N of 37 at the peak. We use the 52x01E1 aperture to mitigate CTE losses and two CR-SPLIT images at each slit position to eliminate cosmic rays. As for the SED measurements, we will utilize the STIS/NUV-MAMA with the F25SFR2 filter, centered at 2320 |*|A to obtain imaging in the UV. Two dithered exposures will be obtained with a total exposure time of 300 sec, reaching a point source S/N of 17 for a flux of F|*| |*| 1 |*| 10|*|17 erg cm|*|2 s|*|1 |*|A|*|1. The acquisition image will instead provide a measurement of the AGN continuum at |*| 7000|*|A. Using the HST APT, our program can be completed within 4 HST orbits N/A Supermassive Black Holes and Active Galaxies 6 false false false false false false false true SECONDARY XMM_NEWTON 098108 false SUPPORTED GALAXY NUCLEUS SEYFERT YES This object was generated by the targetselector and retrieved from the SIMBAD database. SIMBAD listed proper motion for this target. When retrieving targets with PM from SIMBAD, APT requests the coordinates be calculated with an epoch of the year 2000. Do not modify this epoch. Always review coordinates using the Target Confirmation tool, which graphically displays the PM. J2000 J2000 STIS/CCD Spectroscopic No No G750M 6581 STIS/NUV-MAMA Imaging No No F25SRF2 POS-TARG DITHER 0.567 LINE false false 2 26.6 STIS-SPIRAL-DITH 1 false 1770152144965 The scheduling data was generated by CASM 34.0. CASM was run in Phase II mode. /private/var/folders/l_/5v2qhxc17r9gmt251m6xf_r80003jg/T/OPVisit1111863935627178944.xml (Tic-Visit :proposal-id 18225 :visit-id "01" :proposal-version -1 :trans-version "20250929" :date "03-Feb-2026 15:55:44.0" :trans-errors '(:WARNINGS 16 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 4 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 397216 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 18225 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 18225 :visit-id "01" :orbit-number 1 :pcs-time 380 :si-vis-utilization 2510 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2977 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18225 :visit-id "01" :orbit-number 2 :pcs-time 380 :si-vis-utilization 2587 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2977 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18225 :visit-id "01" :orbit-number 3 :pcs-time 380 :si-vis-utilization 2541 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2977 :pcs-gap 0 ) (Tic-Orbit :proposal-id 18225 :visit-id "01" :orbit-number 4 :pcs-time 380 :si-vis-utilization 2570 :al-overhead-at-end 0 :internal-dur-at-end 439 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2977 :pcs-gap 0 ) true 4 0